Spring bipolarism

3/12/2014 5:45 Update:
The SPC has issued a severe thunderstorm watch for the moderate possibility of damaging winds from convection associated with a cold front.There is also a low chance of weak tornadoes embedded within the line of storms. This means that severe thunderstorms are possible.

 THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85
   STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES SOUTH
   SOUTHWEST OF RALEIGH NORTH CAROLINA TO 5 MILES NORTHWEST OF
   WILMINGTON DELAWARE.  FOR A COMPLETE DEPICTION OF THE WATCH SEE
   THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
   FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
   DO PRODUCE TORNADOES.

   &&

   DISCUSSION...A BAND OF SHOWERS AND THUNDERSTORMS IS INTENSIFYING
   OVER CENTRAL VA AND NORTHWEST NC.  THESE STORMS ARE EXPECTED TO
   SPREAD ACROSS THE WATCH AREA THIS EVENING.  DESPITE VERY LIMITED
   INSTABILITY...STRONGER STORMS WILL POSE A RISK OF LOCALLY DAMAGING
   WIND GUSTS.

   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM
   MOTION VECTOR 25040.

ORIGINAL TEXT:
March is the month of bipolar weather. Warm air clashes with the retreating cold air and we are stuck in between the war. As a result, we get wild swings in weather. Tomorrow is one of those examples. Tomorrow will be cloudy, with showers and possibly a thunderstorm in the afternoon as a cold front comes through. Temps will be near 70, unless the sun shows, then we may hit the low 70s. Temps will plummet wednesday evening after the frontal passage. Raw model outputs put us near 20 by thursday morning. However, the models tend to overdo the cold air coming over the mountains so out lows will likely be in the mid 20s. Even then, any remaining moisture on the roads may freeze, not to mention the possibility of a few snowflakes on the back end. Nothing spectacular, just conversational flakes. Thursday will be in full winter mode, with highs in the upper 30s but feeling warmer due to the higher sun angle. This cold blast will be short lived, with temps back into the 50s to near 60 by the weekend before cooling down for next week.

NAM Forecast temps Thursday morning. 20 degrees in DC

Something else of note is that this system will also bring lots of wind. After the frontal passage, strom NW winds will come across the region, with gusts approaching or exceeding 50 mph. 

Wind gust map in knots. Multiply by 1.15 to get mph

Strong winds may also be present in the thunderstorms during the frontal passage late afternoon and into the evening. 

The SPC's take on the severe potential:

probability of severe weather occurring within 20 miles of a point

ITH THE EXIT REGION OF A 70-90-KT H5 JET CORE OVERSPREADING THE
   WARM SECTOR BUOYANCY ABOVE A SWLY LLJ INCREASING TO 50-60 KT...WIND
   PROFILES WILL BE FAVORABLE FOR LOW-TOPPED...ORGANIZED CONVECTION.
   THUNDERSTORMS ARE EXPECTED TO BECOME ORGANIZED INTO FAST MOVING
   QUASI-LINEAR SEGMENTS WITH EMBEDDED LEWP STRUCTURES INVOF THE COLD
   FRONT. STRONG CONVECTIVE MOMENTUM TRANSPORT WILL SUPPORT THE
   POTENTIAL FOR DAMAGING WIND GUSTS...WITH THIS POTENTIAL BOLSTERED BY
   THE STRONG CROSS-FRONTAL...SYNOPTIC PRESSURE RISE-FALL COUPLET.
   STRONG LOW-LEVEL SHEAR -- E.G. AROUND 30-40 KT OF 0-1-KM BULK 
   SHEAR -- WILL SUPPORT SOME POTENTIAL FOR LINE-EMBEDDED MESOVORTICES
   TO PRODUCE TORNADOES.

   THE GREATEST SVR POTENTIAL WILL EXTEND ACROSS THE ERN PANHANDLE OF
   WV INTO NRN VA...CNTRL/WRN MD...THE DISTRICT OF COLUMBIA...AND
   S-CNTRL PA...WHICH MAY HAVE THE GREATEST OPPORTUNITY TO EXPERIENCE
   PRE-FRONTAL INSOLATION. THERE WILL BE SOME POTENTIAL FOR A MORE
   WIDESPREAD SVR-WIND EVENT TO TAKE PLACE IN THESE AREAS...POTENTIALLY
   WARRANTING HIGHER SVR PROBABILITIES IN SUBSEQUENT OUTLOOKS.
   HOWEVER...SUCH POTENTIAL WILL BE PREDICATED ON THE DEGREE OF
   INSOLATION-ENHANCED STEEPENING OF LOW-LEVEL LAPSE RATES...FOR WHICH
   SOME UNCERTAINTY EXISTS. STORMS ARE EXPECTED TO MOVE OFF THE COAST
   AS THE FRONT MOVES OFFSHORE.

It basically says that we will be in an marginally unstable environment tomorrow and an fast moving squall line of shallow convective activity may cross the area, bringing strong mid level winds to the surface.

Next week is Saint Patricks day...mid march... spring time...but we also know that winter does not want to leave. Problem maybe?

Thanks for reading!

-Alex