Day 110: Forecast Still on Track

Posted by pmarsh on 20 Apr 2010 | 0 comments

Last night I mentioned a possible high risk, high reward scenario for storm chasers on “the day before the day before”, also known as Wednesday.  Well, it turns out that the Storm Prediction Center is keeping an eye on the potential as well.  Above is this afternoon’s “Convective Outlook” for tomorrow (Wednesday).  Notice the words “See Text” over Oklahoma?  This means that while the threat of severe thunderstorms does not appear to be sufficient for a “Slight Risk” (there are spatial and frequency requirements for severe thunderstorms to justify a Slight Risk), the threat is certainly non-zero and the reader should read the outlook for more information.  The official text is below.

   DAY 2 CONVECTIVE OUTLOOK
   NWS STORM PREDICTION CENTER NORMAN OK
   1213 PM CDT TUE APR 20 2010

   VALID 211200Z - 221200Z

   ...NO SVR TSTM AREAS FORECAST...

   FAIRLY IMPRESSIVE UPPER TROUGH WILL MOVE ONSHORE ALONG THE CA COAST
   BEFORE MOVING INTO THE GREAT BASIN LATE WEDNESDAY.  DOWNSTREAM OF
   THIS FEATURE...UPPER RIDGING WILL GRADUALLY SHIFT EAST INTO THE
   CNTRL/SRN PLAINS AS HEIGHT FALLS SPREAD ACROSS THE SRN ROCKIES.  AT
   THE SURFACE...WEAK CYCLOGENESIS IN THE LEE OF THE SRN ROCKIES SHOULD
   DAMPEN OUT OVER THE TX PANHANDLE EARLY IN THE PERIOD AS LARGE SCALE
   FORCING BEGINS TO FOCUS ACROSS THE SRN ROCKIES IN ADVANCE OF UPPER
   TROUGH.  RESULTANT LEE TROUGH/DRY LINE SHOULD RETREAT INTO EXTREME
   ERN NM BY PEAK HEATING WITH AN E-W SURFACE TROUGH OR WARM FRONT-LIKE
   BOUNDARY EXPECTED TO EXTEND ALONG THE RED RIVER.  THE RED RIVER
   BOUNDARY WILL LIKELY SERVE AS THE DEMARCATION FOR EARLY-MID DAY
   CONVECTION DRIVEN IN LARGE PART BY WARM ADVECTION.  THIS
   ACTIVITY...POSSIBLY AN MCS-LIKE CLUSTER...SHOULD SPREAD ACROSS OK
   BEFORE WEAKENING OVER AR AS VEERED LLJ DECREASES AND BEGINS TO
   RESPOND TO WRN U.S. TROUGH OVER THE SRN HIGH PLAINS.  STRONG HEATING
   WILL LIKELY BE FOCUSED OVER THE PLAINS OF ERN NM/WEST TX SOUTH OF
   THE WARM FRONT AND FORECAST SOUNDINGS SUGGEST SFC-BASED PARCELS
   COULD REACH THEIR CONVECTIVE TEMPERATURES ACROSS UPSLOPE REGIONS OF
   THE HIGH PLAINS BY LATE AFTERNOON.  EVEN SO...DEEP LAYER SHEAR IS
   NOT EXPECTED TO BE PARTICULARLY STRONG...BUT VEERING PROFILES WITH
   HEIGHT DO FAVOR ROTATING UPDRAFTS...ESPECIALLY WHERE LOW LEVEL FLOW
   IS DECIDEDLY ELY ALONG/NORTH OF WARM FRONT.  AT THIS TIME WILL
   MAINTAIN 5% PROBABILITIES FOR PRIMARILY LARGE HAIL WITH ANY SLOW
   MOVING SUPERCELLS.  A SLIGHT RISK MAY NEED TO BE ADDED TO PORTIONS
   OF THE SRN HIGH PLAINS IN LATER OUTLOOKS IF IT APPEARS DIURNAL
   HEATING WILL CONTRIBUTE TO SUBSTANTIAL CONVECTIVE
   DEVELOPMENT...PRIMARILY ACROSS THE TX SOUTH PLAINS.

   ..DARROW.. 04/20/2010

The “See Text” area is outlined by the 5% risk level contoured above.  Notice how it is shaped very similar to the areas I discussed yesterday.

Lastly, the local National Weather Service Forecast Office in Norman, Oklahoma is also watching the same scenario very closely.  The image above was taken from their enhanced weather and graphicast webpage.