12/31 - 5:30pm - New Year's Eve... Here Comes the COLD!

It's New Year's Eve and people are already gathered around Times Square in New York City. It's the end of a decade and time to start a new weather pattern as well. Judging by computer models, I think Mother Nature may have some interesting plans in store for the start of 2010.

COLD. Whether you live in Louisville, Kansas City, Denver, or even Jackson, Mississippi, you're going to hear and say that word a lot over the next few weeks. Arctic air, and I do mean ARCTIC, will finally push into the eastern half of the US this evening and tomorrow. The Arctic Oscillation is very negative right now, meaning high pressure over the Arctic is pushing the cold air south. We're overdue for this cold blast because the AO has been negative for all of this month, but now it's going off the charts negative. Louisville will have highs in the 20's this week and next, with lows plunging into the single digits at times. Mississippi may have trouble pushing 40 for highs next week and lows will certainly dip into the teens.

SNOW. That's a word many in the Ohio, Mississippi, and Tennessee Valleys have been saying for weeks now, but nothing has really come of it. Now that the cold air will finally be in place, snow looks like a fair bet for these areas. The GFS model has been bringing a couple of nice storms through these areas sometime between the 7th and 12th and it's not backing off. Right now the storms are pretty suppressed to the south on the GFS because of the intense cold air in place over the Central US, but if history repeats itself, one or both of these storms may drift northward on the computer models over the next few days. Louisville would certainly be impacted if this happens.

Here's what the NWS in Louisville says about the first storm for Wednesday and Thursday:

THIRD...AND PERHAPS OF MOST CONCERN...IS A STORM SYSTEM WHICH THE LATEST 12Z GFS AND ECMWF(AND TO SOME DEGREE THE GEFS ENSEMBLES) ARE TRYING TO SHOW FOR WEDNESDAY NIGHT AND/OR THURSDAY. BOTH MODELS DIG A SIGNIFICANT SHORTWAVE SEWD OUT OF CANADA AND CARVE OUT A NICE UPPER SYSTEM OVER THE NATIONS MIDSECTION. IN TURN...AN AREA OF SNOW DEVELOPS IN THE MODELS AND HEADS ACROSS OUR AREA. MODELS HINTED AT SOME FORM OF A SYSTEM IN PREVIOUS RUNS AS WELL. AT THIS TIME RANGE HOWEVER...MODELS CAN BE EXPECTED TO CHANGE FROM RUN TO RUN ON THEIR FORECASTED EVOLUTION AND POSITION OF THE SYSTEM. THUS...WILL ONLY MAKE MINOR CHANGES TO CURRENT FCST...THAT BEING TO ADD A CHANCE OF SNOW ON THURSDAY...TO THAT ALREADY IN THE FCST FOR WEDNESDAY NIGHT. MODEL QPF AT THIS TIME IS NOT MUCH...BUT IN A COLD AIR MASS...SNOW-LIQUID RATIOS WOULD BE QUITE HIGH. SOMETHING TO KEEP AN EYE ON...BUT CERTAINLY SUBJECT TO MUCH CHANGE BETWEEN NOW AND THEN.

Mississippi may see some snow action from this system, and the NWS in Jackson is right on top of this:

THINGS LOOK TO CHANGE ON WEDNESDAY HOWEVER AS BOTH THE GFS/ECMWF SHOW A POTENT UPPER TROUGH DIGGING INTO THE PLAINS WHICH SHIFTS THE SURFACE HIGH THAT WILL BE IN PLACE TO THE EAST...ALLOWING WEAK WARM/MOIST RETURN FLOW TO DEVELOP. STILL PRETTY FAR OUT TO BE CERTAIN ON ANY DETAILS BUT MODELS ARE HINTING AT THIS TROUGH DEVELOPING A WEST GULF LOW ON WEDNESDAY THAT WILL BRING A RETURN OF PRECIP CHANCES TO THE ARKLAMISS WEDNESDAY MORNING INTO THURSDAY. LOOKING AT FORECAST SOUNDINGS...THIS SYSTEM WILL BE CAPABLE OF BRINGING A RAIN/SNOW MIX TO AREAS NORTH OF I-20 WITH PRIMARILY RAIN SOUTH OF I-20 ALTHOUGH THE 06Z GFS BUFR SOUNDINGS SHOW A PRETTY GOOD INDICATION OF SNOW AS FAR SOUTH AS HBG. ADDITIONALLY...IT APPEARS LOOKING AT THE TEMP PROFILES THAT 850-700MB TEMPS WILL REMAIN BELOW FREEZING ALTHOUGH IF STRONGER WARM AIR ADVECTION OCCURS AND THESE LEVELS NUDGE ABOVE FREEZING WE COULD SEE SOME ICE EARLY WEDNESDAY BEFORE STRONGER COLD AIR ADVECTION TRANSITIONS EVERYTHING TO SNOW IN THE AFTERNOON. CONFIDENCE IS NOT HIGH ENOUGH TO WARRANT ANY OUTLOOKS THIS FAR OUT...BUT THE POSSIBILITY OF A SIGNIFICANT WINTER STORM...EITHER COMPOSED OF ICE AND SNOW...OR JUST SIGNIFICANT SNOW ACCUMULATIONS MAY VERY WELL BE ON THE HORIZON FOR THIS TIME PERIOD.

We'll see how this and the second system between the 9th and 12th develops. Maybe it's finally our turn in KY, IN, TN, TN, MS, and AL to get some snow!