First things first…let’s get this weekend out of the way. Despite a nearly perfect storm track for Tennessee snow, it’s going to be too warm due to a lack of a “cold-air” source. Here’s NWS Nashville’s take on the situation:
“AN ACTIVE WX PATTERN IS EXPECTED ACROSS MUCH OF THE U.S IN THE EXTENDED FORECAST. FOR MID TN…SATURDAY WILL BEGIN WITH RAINY CONDITIONS AS A SHORTWAVE TROUGH LIFTS NORTHEAST ACROSS THE MID STATE AND A SURFACE LOW MOVES FROM THE GULF COAST TO THE EAST COAST. IT IS NOT OUT OF THE QUESTION THAT SOME WET SNOWFLAKES WILL MIX WITH THE RAIN AT TIMES…BUT MODEL SOUNDINGS HAVE COME INTO PRETTY GOOD AGREEMENT WITH A COLD RAIN SCENARIO FOR MID TN. THE RAIN WILL DIMINISH WEST TO EAST SATURDAY AFTERNOON THROUGH SATURDAY NIGHT. ”
Here’s a map valid for 6am tomorrow morning, courtesy of the 12z GFS:
And a companion map of the 16z HRRR:
Here’s the 12z NAM skew-T for 6-7am tomorrow morning:
The air appears to be just cold enough for some frozen precip to fall. Since the temps ARE borderline, the winter episode will be brief, but will bring all modes of winter precip – some sleet, some snow, some freezing rain, and of course, plain ole rain. From NWS Nashville:
“THIS CONTINUES TO LOOK LIKE A RATHER HIGH POP EVENT AS COMPARED TO ACTUAL QFP VALUES…I.E. LITTLE IN THE WAY OF ACCUMULATIONS…EVENTHOUGHS OF THE FREEZING OR FROZEN VARIETY…ACROSS THE MID STATE. MODEL POP VALUES ARE ON AVERAGE MUCH LOWER THAN MULTIPLE GUIDANCE SOLUTIONS GAVE AT THIS TIME YESTERDAY. MULTIPLE GUIDANCE AND MODEL CONSENSUS PRODUCTS LOOKED AT…INCLUDING BUFKIT SOUNDINGS…AND ONE COULD ARGUE THE SPECTRUM OF POSSIBILITIES HERE ACROSS THE MID STATE…ESPECIALLY NW AND PLATEAU COUNTIES LATE TONIGHT INTO THE MID MORNING HRS ON THRU. SOME MODEL SOLUTIONS/SOUNDINGS…ALONG WITH NATIONAL GUIDANCE…ADVERSITIES AN ALL COLD RAIN EVENT…WITH SOME OTHERS SHOWING A WINTRY MIX…WITH THE GAMET OF FREEZING TO FROZEN POSSIBILITIES ESPECIALLY ACROSS NW AND PLATEAU COUNTIES BECAUSE OF TEMPS CLOSER TO FREEZING ACROSS THESE LOCATIONS. ALL IN ALL…THE MOST LIKELY PCPN TO OCCUR WOULD BE A RAIN/SLEET MIX ACROSS THE NRN HALF OF THE MID STATE…BUT CAN ALSO NOT RULE OUT SOME FREEZING RAIN MIXED IN…AND EVEN SOME BRIEF LIGHT SNOWFALL ACROSS THESE COLDER LOCATIONS APPROACHING DAYBREAK. THUS…REALLY NEED ADDITIONAL MODEL RUN(S) AND DAY CREW FORECASTER DISCRETION FOR ADDITIONAL CLARIFICATION HERE ON SPECIFIC PCPN TYPES FOR SPECIFIC LOCATIONS…AND AT THIS TIME…WILL JUST GO WITH A CHANCE OF A RAIN/SLEET/FREEZING RAIN EVENT ACROSS MOST OF THE MID STATE EARLY THRU THE MID MORNING HRS ON THU. AGAIN…ACCUMULATIONS ARE EXPECTED TO BE MINIMAL AT BEST…WITH LOCATIONS ACROSS THE NRN HIGHLAND RIM…APPROACHING THE TN/KY BORDER REGION MOST LIKELY. WILL MENTION THIS SCENARIO IN THE MORNING HAZARDOUS WX OUTLOOK PRODUCT ALSO AND AM LEANING TOWARD ISSUING AFTER PRESS TIME A SPECIAL WEATHER STATEMENT FOR ADDITIONAL CLARIFICATION FOR THIS ENTIRE EVENT.EXPECTING LOWS TONIGHT ACROSS THE MID STATE MAINLY IN THE LOWER 30S.”
So, not a huge deal, but one we need to keep our eyes on the system arrives at/near morning drive time. Who wants to talk about the possibilities of a white Christmas?
(Too much? Perhaps…)
Our all-inclusive #tspotter disclaimer: use models as guidance, not gospel. The European model gives us this scenario for the Tuesday/Wednesday timeframe of next week:
There’s a lot going on here, but mainly focus on the top right diagram of each picture. There’s a low pressure area north of New Orleans and it moves directly over Tennessee and is near the Great Lakes by Christmas Eve. The low, as it slides northeast, looks to undergo some measure of bombogenesis, or explosive deepening. What that does, it enhances the winds on the backside of the low and that helps to usher in some really cold air. The system itself has pushed off to the north, but often times, the northwest flow behind a departing storm is sometimes unstable and will set off some convective-type snow showers, which look to last well into Christmas Eve night.
I know there’s a lot to digest here, but there’s a lot of stuff going on – and will continue past Christmas if extended model data holds. Keep it pegged here for updates.