Showing posts with label model. Show all posts
Showing posts with label model. Show all posts

Sunday, January 20, 2013

1/20 - 2:45pm - Bitter Cold Air is Arriving Soon!

Temperatures in the 30's were common last night in West Tennessee and North Mississippi but temperatures are poised to drop much further than that tonight. A dry and relatively marginal cold front is moving through West Tennessee right now and that cold front is the first of two cold shots for the region. This will put lows down into the mid 20's in West Tennessee and lower to mid 30's in North Mississippi as cold air pours in behind the front. This cold air won't allow temperatures to rise much during the day tomorrow either, with highs in the upper 30's closer to Jackson, TN and closer to 50 down toward the Golden Triangle in Mississippi.

During the day tomorrow the second of two shots of cold air will pour in as another cold front passes by. This one will bring the über cold weather that we'll see on Monday night and Tuesday morning. The winds behind this front will be out of the north, meaning the source region (AKA where the air is coming from) for the cold air we'll see during this time will be in the Upper Midwest where they'll be below zero. While that kind of cold isn't expected, mid to upper teens will be common in West Tennessee with readings closer to 20 or 25 degrees down toward North Mississippi. A low of 16 or 17 degrees in Jackson, TN on Tuesday morning looks pretty reasonable given the intensity of the cold air spilling down. While our neighbors to the north may scoff at this being branded as "bitterly cold" in the South, this is still some incredibly cold air. Pets will certainly need to be inside during this time and people need to be bundled up as much as possible. Limit your time outside on Tuesday morning, if possible, and be sure to cover any exposed skin if you do have to be out. Temperatures during the day on Tuesday will warm to a more reasonable lower 30's in West Tennessee and lower 40's in North Mississippi.

Temperatures will moderate during the week thanks to the return of wind flow from the south. This return flow means more moisture in the air across the region. You might guess that this warmer air and more moisture will eventually lead to rain chances... and you'd be right! A low pressure system and associated upper-level shortwave disturbance will track through near the end of the week, bringing rain chances. There's some disagreement between various models over whether this will start on Thursday or Friday. The GFS model's timeline on this is posted below. My guess at this point is that the timeline you see below will be delayed by about 12 hours, so expect rain chances to creep into the region ahead of this low on Thursday afternoon and continue through the night into Friday.


It's not out of the realm of possibility that a little bit of wintry precipitation may fall on the backside of this system on Friday. If cold air flows in behind a cold front associated with this system fast enough then some of the last few rain showers could mix with or change over to a brief period of snow. The GFS identifies Kentuckiana as being the prime target for this but we all know that model has been trending too warm lately in all the winter weather events we've dealt with. So in my mind, West Tennessee is in a potential area for this mix or snow switchover to occur. We're too early for specifics on this so the forecast will have to be fine-tuned during the week. Stay warm!

Sunday, December 30, 2012

12/30 - 8pm - Anyone Up for a Third Round of Wintry Weather?

With two winter weather events within a week's time in the books for Kentuckiana, it's apparently time for a third! Unfortunately the timing for this one is pretty bad. Just as folks are going home from New Year's parties in the early hours of Tuesday morning we could have snow, sleet, or even freezing rain falling in the region. The good news here is that regardless of what falls from the sky, there won't be much of it. Precipitation amounts will remain light since heavy rain and storms in the South will be stealing our moisture here up north in Kentucky and Indiana during the time of the event. As far as timing goes, a few snow showers will move through tomorrow afternoon as this system begins to move toward us. Going into the evening is when things get tricky.

As a weak area of low pressure continues to approach we'll see some warming aloft out ahead of it. This warming has the potential to turn our falling snow into sleet or even freezing rain. The GFS is leading the charge at the moment on the potential for freezing rain in Louisville as it has a layer above freezing from 4,000 to 7,000 feet at 4am on Tuesday morning that would support freezing rain. The NAM model keeps us all snow with the entire atmosphere being below freezing. Given that the models have overestimated temperatures aloft with the past two snowstorms we've seen lately, I'm inclined to think that Louisville will stay mostly or all snow. Another thing to focus on will be surface temperatures. Should they be just below freezing this snow, sleet, or freezing rain will stick to the roads and make for tricky travel on late Monday night. If they're just above freezing then only expect to see accumulation on the grass and elevated surfaces. We do have a bit of snowcover in Louisville now, so that might lean us more in the direction of below freezing instead of above for this event overnight Monday into Tuesday. We're going to be awfully close to freezing for much of the night regardless. Areas north of the city will likely stay all snow and below freezing while those areas to the south will see a wintry mix and temperatures just above freezing until the early morning hours. National Weather Service offices across the Plains have issued Winter Weather Advisories due to this system, in purple on the image to the left, but uncertainty about precipitation type and amounts in the Ohio Valley has NWS Louisville waiting for more agreement before they issue any advisories.

Like I said before, accumulations are going to be light for this event. The NAM (right) has up to an inch of snow in many areas and the GFS model has been a little more optimistic at times today with 1-3" across the area. Like the last two snow events, I'm thinking that the amount of precipitation being put out on the models will adjust upward a bit as we get closer to time (tonight and tomorrow morning). Given the trends I'm seeing right now I think we'll see 1-2" of snow in portions of Louisville and points northward with up to an inch of snow and mixed precipitation to the south. Once again... grumble grumble grumble... Louisville is right on the line between feast and famine with the snow. Southern Indiana has been the big winner with snow over the past week while folks south of the Ohio River are raising their hands in favor of more. That is, if you're a snow lover of course. So, we'll be looking to see over the next few hours how the models handle the amount of precipitation forecast, and temperatures both aloft and at the surface. Shifts in these could mean some significant changes to the forecast for many areas!

Friday, December 28, 2012

12/28 - 1:30am EST - Kentuckiana Winter Storm Number 2

Wednesday's winter storm didn't give much snow to folks in the Louisville area and instead confined heavy snow to areas of Southern Indiana. While differences in the models did exist over whether Louisville would get any accumulating snow or not, the overall situation was handled pretty well from a forecast standpoint. The highest snow report in NWS Louisville's coverage area was 7.2 inches in Washington County, IN while Louisville received a trace to a half inch.


The next storm on the heels of the last one is less than 24 hours away as a system arrives from the southwest and stays to our southeast as it moves through the region. This will start as some rain for the Louisville area but as colder air filters in we'll switch over to snow during the later evening hours. This exact time for switchover depends on how warm we get during the day tomorrow (lower 40's versus upper 30's makes a difference!) and how fast the cold air comes in. The 0z NAM that came in earlier tonight has about 3" for the city and after comparing this with other models I'm thinking this may be a number we'll see most commonly reported by Saturday morning in Louisville. Higher totals will be possible just a bit further north from Louisville.

But even as I say this there's a small fly in the ointment. The 3z RPM model is in and it has the possibility of 4-6" of snow just due east of the city and a few very small totals like this scattered throughout areas near the Ohio River. This suggests that totals closer to 4" might be more widespread than previously thought. You can click the RPM output on the left for a larger view. We've seen the trend of increasing snow totals today on the models and this run of the RPM just continues this. We'll need to watch for this trend tomorrow morning to see if other models catch on. Right now this isn't really a factor in my forecast since it's just one model. Below is my snow forecast map for the region. Realize that, like the last storm, a small shift in track or more/less cold air will change things for some folks drastically.


Also worth noting is that the Hyrdrometeorological Prediction Center (HPC) has us in a Slight Risk of a 4" snowfall (think of this like the Slight, Moderate, and High severe weather risks) while areas closer to Cincinnati are in a Moderate Risk. Expect to see Winter Weather Advisories being issued tomorrow for portions of Kentuckiana. There may also be a few Winter Storm Watches issued as well depending on if forecast amounts of 4" or more look to be more widespread. You can keep up with the latest on this storm tomorrow by following me on Twitter and Facebook. Good luck, snow lovers!

Friday, December 21, 2012

12/21 - 2pm - I'm Dreaming of a White (Day After) Christmas

How about that snow last night around Kentuckiana? Most places saw a dusting but areas in Southern Indiana near Orange County picked up about 3 inches since a snow band set up there for a few hours during the overnight. Here at my house in Southeast Louisville we picked up a dusting of snow that blew around a bit in the wind. Temperatures today aren't going to make it out of the mid 30's in Louisville today thanks to the cold air behind the front that passed through yesterday. Seems appropriate given that it's the first day of winter!

Temperatures will moderate for the weekend with southerly flow returning but an area of low pressure moving through will bring rain and even warmer temperatures for Christmas Eve. Booooo! Luckily Christmas Day isn't looking like a washout with just a few clouds and highs in the lower 40's. That's a different story further South in Mississippi, Alabama, and Georgia where rain will be setting up.

Now... onto the fun part. Over the past couple of days the forecast models have been jumping onto the idea of an area of low pressure moving from the Gulf states to the western side of the Appalachian Mountains the day after Christmas. This is concerning because this track favors a snow event for Kentuckiana and even some of West Tennessee. You need to be on the north and west side of these low pressure systems if you want to see some snow since that's where the cold air is confined to. The past few systems we've been on the south and east sides of the lows moving though so that has meant thunderstorms and warm weather lately.

The latest 3 runs of the GFS for this particular post-Christmas storm have been fairly consistent with the low track, which is good! The problem has been that there's been trouble determining how much cold air there will be to work with and how strong/large the low moving through will be. These issues have affected how much snow the Louisville area gets. The graphic on the left is a comparison of the last 3 runs of the GFS for December 26th. For entertainment purposes only, the 0z run had just shy of 8" of snow for Louisville, the 6z had about 3", and the 12z had around 2.5". It is still way, way too far out for specific totals and to worry about the cold air issues yet since things will change likely on the models between now and then. I will say though that the 6 and 12z runs seemed to have difficulty keeping the low as a single, compact system once it matured and instead wanted to go with an elongated large low that tries to interact with another low that develops east of the Appalachians. I've seen this kind of thing happen on the GFS earlier this year with the Nor'easters that we had. Eventually, based on what happened with these Nor'easters, these elongated lows should give way to more concentrated, compact lows on the GFS as we get closer to the actual event. This should help to clear up some of the murkiness with the cold air issues too.

The Euro has been fairly consistent with the track of the low as the GFS has been, but has also experienced a few issues of its own like the GFS. Yesterday's 12z run of the Euro had a blockbuster snow event in the Louisville area while the 0z last night backed off on that prospect thanks to, you guessed it, a more elongated low and trouble with cold air. I can't post the precipitation output from the Euro model since it's behind a paywall and copyrighted, but I can at least show you what the 0z run did with the low after it moved through. Lots and lots of cold air will be behind this system if you couldn't tell by the deep blues and purples on the map!

UPDATE 2:20pm - Today's 12z Euro model run is in and it has a blockbuster storm track for snow for us here in Kentuckiana and West Tennessee. That is quite a strong low in East Tennessee on the left-hand map compared to previous runs. Sheesh.

The CMC and the JMA, which are the Canadian and Japanese models, aren't worth showing here right now. The CMC has the storm running off the east coast and the JMA has a nice low track for some snow in Louisville. It's worth noting that this system might disappear all together on the models or make a radical change. It's still too far out for much certainty.

Also, West Tennessee may see snow from this storm should it take the track that we're seeing. It wouldn't be much snow but certainly more than an inch or so isn't out of the realm of possibility, especially in Northwest Tennessee. Once we get closer to time this will become a bit more clear.

The NAO, which is the North Atlantic Oscillation, frankly isn't agreeing that there will be support for this storm. A negative NAO means blocking near Greenland allows for cold air to flow into the Eastern US and stay locked in place. The current forecast is for a positive NAO during this time, but it has been flipping between negative and positive over the past couple of days. This storm doesn't have to have a negative NAO to happen, but it would help to have it for cold air support and for a storm track that rolls up to the northeast. This will, like the aforementioned models, sort itself out over the next few days.

 

Finally, NWS Louisville has been on board with this storm since yesterday. They're being cautious like they should be but mentioning at length the potential for this at 5 days out is something that they don't do very often. Here's their latest statement:

A much more significant weather system will arrive on the 26th. Both the 00z GFS/ECM and ensembles track a strong low pressure system just to the west of the Appalachian spine which may set us up for our first significant snow. If the low pressure system takes its current forecast track, precipitation would enter the area Wed morning with the bulk of precip occurring Wed during the day and then exiting late Wed night or Thurs morning.

Although there is still much uncertainty in the track of this weather system 6 days out, the possibility is there for significant snow based on the low track and anticipated thermal profiles. BUFKIT GFS showed 8 inches at SDF with a little more than 0.5 inch of qpf. The soundings denote a classic heavy snow sounding with subzero and deep isothermal layer super saturated. The synoptic features of interest are a 110 kt jet max entering a the base of a deepening trough.

For now will have 60% pops on the 26th with rain in the morning and then snow in the afternoon and Wed night. Bing Crosby`s I`m dreaming of a White Christmas may happen, just 24 hours later.

Stay tuned for upcoming forecast updates as this weather system may put a kink in holiday travel plans.

 

This will be a fun system to watch over the weekend. Hopefully there's some snow in our future!

 

Monday, November 5, 2012

11/5 - 2:15pm - Quick Shot of Rain on the Way in Mississippi

Showers and a few storms are moving eastward through the I-55 corridor of Central Mississippi right now. The eastern extent of these showers and storms are just about to enter Oktibbeha County and we'll keep them around until we get to midnight or so this evening. Temperatures overnight will get only into the mid 40's thanks to the rain and cloud cover, but get ready for cooler temperatures for election day tomorrow with highs near 60.

An interesting aspect of tonight's rain is that the area of low pressure associated with it will be the same one that will exit off the east coast of Florida and blow up to be a significant Nor'easter by Wednesday. This comes on the heels of Hurricane Sandy causing devastation in the Northeast so folks up there are not looking forward to the one-two punch. This Nor'easter will certainly hamper clean-up efforts but the good news is that it will not be as strong or as long-lived as Sandy.

Full sunshine will return to Mississippi by Wednesday and temperatures will recover well into the 60's to 70 or better by the weekend. We'll be watching a storm system make its way through the middle of the country next weekend that has the potential to impact us on Monday of next week. It's not entirely clear how severe the storms we'll have will be but just keep in the back of your mind that we could be off to a stormy start next week. Check out the video below for your complete forecast for the Golden Triangle area.

Monday, August 27, 2012

8/27 - 9:30pm - Update on Isaac's Expected Gulf Coast Landfall

Tropical Storm Isaac is teetering on the edge of becoming a hurricane this evening with winds of 70 mph as of this writing. The threshold for a Category 1 hurricane is 74 mph. The storm motion has slowed down over the past few hours, now moving northwest at only 10 mph. Issac continues to run into issues that prevent it from rapid intensification, which is certainly good news. The latest issue is a batch of dry air that is currently being pulled into the center of the storm. Without an uninhibited source of moist air the storm cannot form a defined eye or intensify very well. The dry air is why Isaac is lopsided right now with most of the intense winds on the south side.

How long will it be until this dry air is finished working through the storm? Probably a few more hours, possibly lasting into the early morning hours tomorrow if current model forecasts are correct. Speaking of models, the current track from the National Hurricane Center takes Isaac right into the Eastern Louisiana/Mississippi Coast areas late tomorrow night into early Wednesday morning as a weak Category 2 storm with 100 mph winds. With the lack of organization we're seeing right now it may only be a Category 1 at landfall. The latest computer model tracks, the spaghetti plots as you've probably heard about and seen over the past few days, have tightened up on a landfall location somewhere around New Orleans. It's worth noting that some of these models are now trending eastward after a massive amount of successive westward jogs in recent days. It doesn't appear that this landfall will take place further east than Biloxi, Mississippi given the current motion of the storm and model data, but the exact landfall location won't be the big story with this storm.


Storm surge exceedance probabilities
The big story here is how big and how slow this storm is. Sure, there will be some wind damage along the coast as the storm makes landfall, but the large area that Isaac covers means that quite an expansive area along the Gulf Coast will experience other effects from it. Storm surge at or above ten feet is possible in locations from New Orleans to Pascagoula, MS and rainfall amounts over a foot are forecast over much of Central and Southern Mississippi and Eastern Louisiana. Isaac will slow down even more than its current speed once it gets over land so heavy rain will be a good bet across much of the Gulf Coast states until we get into the weekend. Inland flooding will be a problem with the deluge that Isaac with unleash on the region as it crawls northward.

Rainfall through 7pm CDT Saturday
As far as local effects in North Mississippi and West Tennessee, Isaac will bring very heavy rain and winds with gusts in some cases near 40 mph. Starkville, MS may be looking at a six or more inch rainfall scenario through Saturday evening and areas in West Tennessee like Jackson will likely see more than three inches of rain. This highly depends on Isaac's exact track so some areas will see much more rain than others.

With just about any landfalling hurricane you can expect the threat of isolated tornadoes, and Isaac will be no different. The turning of winds with height in a hurricane or tropical storm create favorable wind shear for tornadoes to form in stronger parts of it. Due to this potential threat, the Storm Prediction Center has issued a Slight Risk for most of Mississippi and parts of Louisiana, Alabama, Georgia, and Florida.


So overall we're not looking at Isaac to be a major hurricane at landfall, but the effects from it will be widespread due to it's large size. It's a good thing that folks in a wide area are preparing for this storm since it could be a long haul given the slow motion that's expected from it.

Sunday, August 19, 2012

8/19 - 6pm - Tranquil Weather for the Workweek

Mississippi State University
It's that time of year again when I switch over blog post content to cover Mississippi and West Tennessee in place of the Louisville area. I do this for two reasons: 1) It's difficult to write about the day-to-day goings on of weather back home in Louisville when I'm taking a full college course load at Mississippi State that requires me to keep up with and forecast weather for the Golden Triangle area here in Mississippi and 2) I'm convinced that it is better to forecast for the area which you are currently living in because you're always aware (sometimes painfully) of how accurate your forecast is. If anything significant happens back home in Louisville I'll be sure to include it in my posts here over the next few months, but for now I'll be covering weather down here.

While it was supposed to be a rainy day across the Golden Triangle today we actually saw quite a bit of sunshine and nice weather. A front that has become stationary over Central Mississippi put us in a much drier environment and this has cut off most of the needed moisture for showers and storms to fire up. There's still a chance that a few isolated showers and storms will get going around the region but that's a potential that will be highest during the early morning hours according to the latest short-range guidance.

The trough that's brought us the front and the cooler temperatures this weekend will continue to do so for most of the workweek as it slides slowly eastward. A lack of surface moisture and building surface high pressure will stave off rain chances and even clouds for the most part until we get close to the weekend. Temperatures this week will be gradually rising through the mid 80's for highs until we get to Thursday. By then stronger southerly flow will be bringing in warmer, moister air from the Gulf and get us back to around 90 for highs as we go through the late week and the weekend. Shower and storm chances will be returning by the weekend.

Click image to see a larger view
The tropics have been fairly quiet as of late near the US coastline but there's potential for that to change next week. A disturbed area of weather in the middle of the Atlantic Ocean is on a course that may take it toward the East Coast if the latest computer models are to be believed. It's way too early in the ballgame to discern whether or not this will be a threat to the US since it could curve back out to sea before hitting land or not strengthen into a tropical storm or hurricane. This will be something to keep a close eye on since it could become Tropical Storm Isaac.

Saturday, August 4, 2012

8/4 - 2:30pm - Waking Up to Storms Tomorrow

Scattered storms are firing between Evansville and Louisville right now and are slowly trekking eastward. These aren't expected to become severe but some downpours and lightning are certainly a possibility in Louisville as they continue to develop. The chance for storms in the area should remain with us in Kentuckiana through the early evening.

More storms forming in Illinois and Missouri will be our next focus as they move into Kentuckiana during the early morning hours tomorrow. Some of these could be strong to severe since a trough moving through to our north will be bringing faster winds aloft to the area. This means that damaging winds will be the primary threat from these storms should they hold together for us during the early morning. The 6z NAM model run (right) was pretty bullish on these morning storms but the 12z that just came in was more subdued with their intensity. In either case it looks likely that a lot of folks will wake up to storms early tomorrow morning.

Storms could fire up during the afternoon tomorrow if the morning's storms clear out in time for instability to recover during the afternoon. Another limiting factor for this will be the cold front that will be moving through during the day tomorrow. Storms will fire along and in front of that boundary so its speed will determine who gets storms during the afternoon. Right now it looks like Louisville and areas to the south and east will be in the zone for storms tomorrow afternoon and it's worth noting that their coverage won't be anywhere near this afternoon's and tomorrow morning's storms. Both Kentuckiana and West Tennessee are under a Slight Risk for severe weather tomorrow afternoon as these storms fire up in the heating of the day with the cold front in play. Strong winds will again be the main threat here.

After the front moves through on Sunday temperatures will be in the upper 80's to near 90 for the start of the workweek in Kentuckiana and storm chances will be nonexistent until Thursday.

Thursday, July 26, 2012

7/26 - 1:55pm - Kentuckiana Severe Weather Update

Kentuckiana is right on the edge of what could be a significant severe weather outbreak this evening. Nothing demonstrates this better than the Storm Prediction Center's latest severe weather outlook, which puts us in a Slight Risk but has a 30% severe wind risk running right through the center of Louisville. The reason for this is that faster winds aloft are most prevalent to our north and east so more of a risk area (a Moderate Risk) is needed up there. These winds have the potential to power a large line or cluster of wind-driven storms that could possibly become a derecho just to our north if it sustains itself long enough.

A Severe Thunderstorm WATCH has gone up for areas northeast of Louisville but not including the city. This was needed because severe storms are already affecting areas near Cleveland right now and more will be forming in the near term across Ohio, West Virginia, and Pennsylvania. I suspect a Severe Thunderstorm Watch will be issued for the Louisville area at some point this evening since storms will come through a little later than areas to our north.

Storm timing in Kentuckiana should be after 5pm this evening. The latest High Resolution Rapid Refresh model has storms rolling through the Louisville Metro area at around 7pm but this may vary a bit because this will be highly dependant on where storms fire along outflow boundaries and other surface features. The HRRR suggests that these will be either a broken or continuous line of storms which makes sense given that winds both aloft and near the surface will be from a westerly direction. This also means this could be a wind-driven line of storms so wind damage potential is relatively high here if storms get severe enough. Large hail will be a threat from any of the strongest storms. There may be more than one round of storms this evening in the area through 2 or 3 am since the cold front will not be passing through until that time. This might be a good time to secure your trash cans or any loose articles you have outside your house so that they don't end up in your neighbor's yard...

Sunday, July 15, 2012

7/15 - 7pm CDT - The Heat Returns!

A few showers are ongoing across West Tennnessee right now, but this is quite a bit less than what was expected today. Dry air rotating around a area of high pressure has moved into the region because this high has nudged a bit further westward than originally forecast. This means that a majority of the shower activity has stayed west of the Mississippi River, but a couple thundershowers could still pop up before sunset. These should mostly dissipate before the overnight hours.

Heat and humidity are on their way back as a large ridge of high pressure moves eastward over the next few days. This should surpress storm chances a little bit, but not entirely because temperatures aloft will still be a little cool. This heat at the surface and the slightly cool air aloft should create the typical "summertime pop-up storm" environment that we're used to seeing in the afternoons this time of year. Temperatures underneath this ridge of high pressure should be in the lower to middle 90's in West Tenneessee and middle 90's until Wednesday in Kentuckiana. A front dropping south on Thursday will trigger higher rain chances in both Kentuckiana and West Tenneessee and there could be some slightly cooler temperatures behind the front for Kentuckiana. Things look to remain hot all week long in West Tennessee!

I'm in Jackson, TN right now getting ready for the 10 O'Clock news on WBBJ this evening before going back to Louisville tomorrow. Check out my Hokey Weather Fact from last night's show on the left and be sure to tune in to WBBJ tonight at 10 for a new one!

 

Thursday, July 12, 2012

7/12 - 11:45pm - A Festive Forecast

Tomorrow is the beginning of the Forecastle Festival at Waterfront Park in Louisville. Unfortunately rainfall could be an issue as a stationary boundary begins to move northward from North Mississippi overnight. This boundary will bring even more moisture into the area and a source of lift, the boundary itself, which should bring in some ongoing showers and storms tomorrow morning. The short-range models right now are suggesting that there may be a break in the action after 2pm, which you'll see in the NAM simulated radar image on the right. Disagreement among the models exists over whether the storms will re-fire and make an impact in the area later on in the afternoon. My thoughts on this are that storms may have trouble getting going again in the late afternoon since the morning's activity will be hanging around well into the early afternoon, but that the presence of the frontal boundary will compensate quite a bit for this. Expect then for storms to possibly re-fire and move into the area sometime after 5pm. The good news here for festival goers is that I don't think storm coverage will be quite as high during this second round, so there's a good chance the Waterfront may be able to dodge storms if they remain scattered.

Daily storm chances will continue on Saturday and Sunday as the moisture from the current system sticks around and a bit of upper-level support kicks in thanks to a trough passing through the Great Lakes region. These storm chances will be a bit lower than tomorrow's though because there won't be much of anything to trigger them, like a front, aside from daytime heating in the afternoon. Long story short, bring a rain jacket or poncho if you're going downtown for Forecastle this weekend. Temperatures will top out near 80 tomorrow as the clouds and rain move through, but it will warm into the mid 80's for the weekend in Louisville.

Speaking of this weekend, I'm going to be a busy guy! On Saturday I'm heading down to Jackson, Tennessee to do the Saturday and Sunday evening shifts of weather at WBBJ-TV. This means you'll see me on the 6pm and 10pm newscasts this weekend if you're in the viewing area. It's been almost three months since I've done weather on TV, but I'm very excited to be getting back into it this coming weekend and again on Saturday night next weekend. Be sure to tune in!

Saturday, July 7, 2012

7/7 - 10:30pm - Massive Heat Wave Ends with Storms

Today capped off the longest, hottest stretch of weather in Louisville that most people can remember. Today's 106° high at Louisville International Airport was the hottest it's been since July 14th, 1936 when it got to 107°. That temperature is Louisville's all-time record high and if we didn't have as many clouds as we did this afternoon in the city we would have met or broken it. This ends nine days of 100°+ weather, which is the third-longest stretch of triple digits ever recorded according to NWS Louisville.

Storms that will develop tomorrow will be ushering in cooler temperatures, which is welcome news! The bad part is that some of these storms may be severe due to the incredible amount of energy they'll have at their disposal from all the heat. Temperatures in the mid 90's tomorrow with sunshine and high humidity will power an awful lot of instability, or the tendency for air parcels to rise and create thunderstorms. A cold front sinking down from the north that will be stalling out once it passes just to our south will be the focus for storm chances starting tomorrow in the early afternoon in Louisville and lasting through Monday morning.

The main threats from these storms will be wind and hail, but there could also be a threat for some rotating storms too. While winds don't look favorable for any sort of big tornado problems tomorrow, a couple of these rotating storms may get just enough juice to put down a brief spin-up. EHI values in the adjacent image take into account both instability and helicity, which is a product of wind shear. The elevated values you see are powered mostly by instability and just a little bit of helicity, so again, winds aren't that favorable here. The Louisville area is no stranger to summertime tornadoes as you may remember a series of four of them that touched down in late June of last year.


Given the chances for some severe wind and hail tomorrow, the Storm Prediction Center has issued a 15% Slight Risk area for Kentucky. A better chance for severe weather (30%) exists closer to the East Coast where upper-level winds will be stronger as a trough digs down a bit into that area.

Thursday, June 28, 2012

6/28 - 11:30am MDT - Waking Up in Nebraska

After storms in Northeast Colorado yesterday became contaminated by storms coming off the Front Range, we decided to head east to be ready for today's chase. After waking up in Ogallala, Nebraska this morning we're rested up for a relatively leisurely day without too much driving since we're already pretty much in our target area for the day. The Storm Prediction Center has a general thunderstorm risk out for Western Nebraska, Northeast Colorado, and Northwest Kansas today with a 5% severe wind risk.

The focus today will be a cold front that's slowly moving through the region today. Winds around this frontal boundary may shift out of the east a little bit and that's where we'll position ourselves since the best shear will be where that happens. Dew points will be in the 60's across Central Nebraska this afternoon with slightly lower readings to the west. These surface winds, while weak, and the moisture should be more than enough to get some storms going.

Winds aloft are a little less certain since they may change throughout the day. Early on this morning winds at 500 mb (18,000 feet) were almost westerly across the western half of Nebraska, but already we've seen a shift to the southwest. While not terribly strong, the winds up there could have just enough punch to get storms to become severe. Small embedded shortwaves within the flow may enhance these winds a bit in some areas too. By 6pm MDT tonight the RAP model (right) still has these winds out of the southwest aloft, so that's some good news. The thinking at this point is that the shear won't be high enough to keep storms from merging together and being clustered, but we'll see how that plays out.

Follow me on Twitter and Facebook for constant updates during our chase!