6/25 - 10:30am MDT - Great Faces. Great Places.

Today's blog post title is the South Dakota's state slogan. As you can probably gather by that, we're in South Dakota today! Southwesterly flow aloft at 500 mb (18,000 feet) will be present in the western half of South Dakota, northwest Nebraska, and Eastern Wyoming today as the general pattern we dealt with yesterday continues. While the winds aren't terribly strong, the RAP model is beginning to pick up on an area of enhanced speeds near 30-40 knots around parts of Western South Dakota and Northwestern Nebraska. If this enhanced area verifies there could be some better storms under it.

At the surface right now there are southeasterly winds across this area, but the more easterly of the wind vectors are favoring Western South Dakota right now. We'll see how this develops throughout the day as surface conditions continue to change. We'll want these more easterly wind vectors becuase they'll contribute to low-level wind shear that could possibly lead to rotating storms, should they form.

I say "should they form" because we're still dealing with some very warm temperatures aloft. These warm temperatures aloft, called "the cap", inhibit storm development because rising air parcels can't continue to rise buoyantly if the environmental air around them is warmer than they are. The good news here is that temperatures at the surface today will again be in the 90's to near or above 100 degrees. This will really heat up these surface air parcels so that they might shoot through the cap. All models I've looked at this morning have the cap breaking at some point in the early to mid afternoon, but where exactly this happens is still in question. The 14z RAP model has an interesting hole in the cap at around 4pm near Rapid City, but our current thinking is that the Black Hills near Rapid City will be a focus for storm development because they are a constant source of lift and thus a typical location for storm initiation.

To get some of the heating we'll need for storms to form today, we need to have a plentiful supply of sunshine. Right now we do have a layer of clouds over South Dakota that is inhibiting this right now, but western parts of the state are clearing out and it should hopefully leave us with blue skies later this morning. Storms should form sometime after 3pm this afternoon should things come together as forecast. The main threats will be wind and hail from any storm that forms, but we'll be on the lookout for some rotation in these storms as well. The Storm Prediction Center has a general thunderstorm risk for our target area today, but also mentions a 5% severe wind and hail risk.

Follow me on Twitter and Facebook for the latest updates this afternoon!

6/24 - 11:55pm MDT - An Unexpectedly Great Chase Today!

I can't say that I fully expected to see a great storm today. With all the intense surface heating and warm air aloft coupled with weak upper-level winds, the odds were against us. The great thing is that a storm did indeed form in this environment and it took advantage of every ounce of energy it was given from what it looked like. This storm split into a couple parts at one point and these parts were battling each other out for a while before merging back into one mean storm. This storm did have a few radar scans of rotation and we could certainly see it from the ground for a few minutes as a brief rotating wall cloud formed. A fleeting finger-like funnel danged down for a moment at the peak of the rotation, but it was gone by the time we all pointed it out and raised our cameras to capture it. Something that stuck in the back of my mind is what I posted on the Storm Chasing Adventure Tours Facebook page last night in an update:

Looks like we may be heading north from Denver in the morning! A few storms may try to develop during the afternoon and evening tomorrow where South Dakota, Nebraska, and Wyoming meet.

The intersection of South Dakota, Nebraska, and Wyoming is almost exactly where this storm formed today. Where the three white lines intersect to form a rotated "T" on the upper-right of the radar image to the left is where these state lines come together. My estimate of where we would end up was an educated guess based on data, but I really didn't expect it to come so incredibly close. The other thing about this storm is that it was the only severe storm west of the Mississippi River at the time we were chasing it during the late afternoon. Storms that developed to the south of us in Northeast Colorado just couldn't get strong because it was much too warm both at the surface and aloft.

Check out the video below to see the storm in action and then check out my Flickr or Facebook storm chasing albums for even more views of today's chase:

Tomorrow we'll be heading northward to the Dakotas or Wyoming. The Storm Prediction Center has a 5% risk for severe weather, but we'll be looking at all the data tomorrow morning to see how it all shapes up! Be sure to check back around noon tomorrow on the East Coast for a complete blog update with a discussion on where we're headed.

6/24 - 10:35am MDT - The Chase Begins!

This morning we're heading toward Cheyenne, Wyoming from Denver as we continue to look at weather data coming in. Today's setup still looks marginal by most accounts, but there are a few small features that could cause a few isolated storms to go severe. For one, surface winds out of the east in Wyoming, Northeast Colorado, and Nebraska will generate upslope flow, which is the lift mechanism we need to get storms going.

These winds will also create some shear because they will be interacting with southwesterly winds at 500 mb (18,000 feet). The issue with this is that the faster winds at this level will be further north toward Rapid City, South Dakota instead of where the more favorable surface winds will be just to the south. In any case, the wind direction at 500 mb will be good enough to usher in the wind shear and maybe some drying of the air at that level to increase instability.

When you put the expected helicity (caused by wind shear) and the instability together for today, you get the Energy Helicity Index (EHI). According to the 14z RAP model, the EHI may try to ramp up a little bit in Northeast Colorado and it even breaks out a little bit of precipitation just west of there too. Surface heating is going to be massive since temperatures will be in the 90's and 100's in some places, so we're hoping this also helps overcome some of the warm temperatures aloft (the cap) so that isolated storms can develop. We're grasping for small features today since there isn't any one thing jumping out to get our attention, but so far it looks like a storm or two could fire on the elevation near Cheyenne. We'll also be watching an area closer to Rapid City, SD to see how things develop up that way.

Follow my continuous chase updates on my Twitter and Facebook accounts today!

6/23 - 11:30pm MDT - Who's Ready to Go North?

Our tour guests have been through orientation and now we're ready to set off for our northward journey tomorrow from Denver to the region where Wyoming, Nebraska, and South Dakota meet. This area will be on the northwestern side of the large ridge in the middle of the country and on the eastern side of the trough coming onshore from the Pacific. This means there will be southwesterly winds aloft, at 500 mb or 18,000 feet, to hopefully bring in some drier air so that instability will increase when it contrasts with the warm, moist air at the surface that will be rising into it. While weak in speed, the winds up there will also increase wind shear because they will be at odds with the easterly and southeasterly winds at the surface. This will increase helicity a little bit, which is a corkscrew-like rotation in the atmosphere that is good for fueling rotating thunderstorms.

Moisture shouldn't be too big of a deal since dewpoints will be in the 60's, but we'll be eying the potential for issues with the the cap, which is a warm layer of air above the surface that inhibits thunderstorm development. All the warm air in place over the central part of the country breeds strong capping since the warm air is in place at the mid levels, but the models are suggesting that this cap may be overcome tomorrow afternoon and lead to some isolated storms. At this point there is nothing that suggests any storm that forms will be anything past marginally severe, but the helicity that the NAM model is picking up on above is certainly worth keeping an eye on.

The Storm Prediction Center has a general thunderstorm risk out for our target area tomorrow with no chance for severe weather. Since storms will be pretty isolated and in a fairly unpopulated area, it may not be worth it for them to issue any sort of severe risk with a setup this marginal. We'll see how things have developed overnight when we set out in the morning though. A secondary low may try to form in western South Dakota tomorrow according to the NAM and that may influence our decision on where to go if it forms since the best winds will be just to the north of the low center. Hopefully we'll see some storms!

Follow me on Twitter and Facebook for the latest tomorrow!

5/30 - 12am CDT - Upslope Storms Part Deux Fell Flat

Our second attempt in chasing upslope storms within a week fell flat today. Like last time, the cap stayed on too tight and a layer of clouds and fog overspread our target area just as we thought storms would initiate. While we waited this afternoon just east of Cheyenne, WY, we ran into Mike Bettes and the Weather Channel's Great Tornado Hunt crew.

The very fog that moved into our target area only grew thicker as we moved into Nebraska to try and limit our driving time needed for tomorrow. At it's thickest point, the fog dropped visibility to around 300 feet as we headed east on I-80. We literally could not see the signs on the side of the road until they were just to the right of the edge of our hood.

Tomorrow could be a pretty big day in the Dakotas and Northern Nebraska. The Storm Prediction Center has issued a Moderate Risk (45%) for portions of the area and expects a few significant tornadoes tomorrow afternoon before the storms merge into a linear line. I'll have an update tomorrow morning when we get on the road, which will be early so that we can get to our target on time.

5/28 - 11:45pm MDT - An End to a Great Week!

Not one thunderstorm developed in Wyoming today while we were out there. The cap (warm layer of air above the surface that inhibits storm development) was on too tight today and all the cumulus cloud development we saw was suppressed. Storms didn't even develop in North Dakota as forecast due to capping issues and surface winds becoming westerly earlier than forecast. At least we had a nice tour of Southeast Wyoming!

Storm Chasing Adventure Tours is saying goodbye to the guests on tour 4 tomorrow morning here in Denver and welcoming our new guests for tour 5 tomorrow night. Tour 5 is going to be very big, with 24 people in four SUVs. I won't be the only Kentuckian out here for much longer either. WAVE 3 TV meteorologist and good friend Kevin Harned from Louisville will arrive here tomorrow to begin chasing with us as a driver and forecaster.

It looks like we'll start out chasing on Sunday in either Kansas, Oklahoma, or the Texas Panhandle. A pair of disturbances pushing through the Plains next week should make most of the week pretty active, but there may be a couple down days.

5/28 - 10am MDT - Wyoming and Colorado

The best risk for severe weather today is in North Dakota, but we won't be able to make it there on time today. It's an eleven hour drive from Denver and we have to be back tonight for everyone's flights out tomorrow. Instead of North Dakota, we're going to shoot for the Wyoming/Colorado border area. Southwest flow aloft coupled with southeast surface winds and a batch of dry air coming into the area in the upper atmosphere should put the right ingredients in place for severe weather. A lack of a good source of lift and a strong cap in place may be a problem today, but we're hoping upslope flow overcomes some of these issues. The SPC has issued a 2% risk of tornadoes for the area, so maybe we'll be able to find some good storms today!

If severe weather develops today we'll be streaming LIVE video at http://stormchasertv.com. I'll also have the latest updates on Twitter and Facebook.