Friday, September 25, 2009

DAY1SVR: Day 1 Convective Outlook Resent 1

ACUS01 KWNS 252059
SWODY1
SPC AC 252056

DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
0356 PM CDT FRI SEP 25 2009

VALID 252000Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE TX
PANHANDLE AND NWRN OK...

...TX PANHANDLE/NWRN OK/SCNTRL KS...

HAVE MADE MINOR ADJUSTMENTS TO EARLIER OUTLOOK ACROSS THE SRN/CNTRL
PLAINS REGION. LATEST DIAGNOSTIC DATA SUGGESTS BUOYANCY WILL PLAY
AN IMPORTANT ROLE IN ROBUST UPDRAFT DEVELOPMENT...AND THIS HAS
SHIFTED/DEVELOPED FARTHER SOUTH THAN EXPECTED AT 1630Z. THICK
LAYERED CLOUDINESS...ALONG WITH PRECIPITATION...HAS IMPEDED SFC
HEATING AHEAD OF COLD FRONT ACROSS MUCH OF KS WITH THE STRONGEST
INSTABILITY LOCATED ACROSS THE TX PANHANDLE INTO NWRN OK. THIS IS
COINCIDENT WITH STEEPER LAPSE RATES BENEATH SRN LOBE OF COOLEST MID
LEVEL TEMPERATURES. VIS SATELLITE IMAGERY SUPPORTS THIS WITH
SCATTERED THUNDERSTORM ACTIVITY LOCATED ACROSS NWRN OK...SWWD INTO
THE NERN TX PANHANDLE. WITH TIME ADDITIONAL STORMS MAY EVOLVE INTO
THE CNTRL TX PANHANDLE...THEN SPREAD INTO NWRN OK IN LINE WITH
EARLIER THINKING. AT THIS TIME IT APPEARS HAIL IS THE GREATEST
CONCERN.

..DARROW.. 09/25/2009

.PREV DISCUSSION... /ISSUED 1107 AM CDT FRI SEP 25 2009/

...NWRN OK AND SRN KS...
RESIDENT UPPER LOW THIS MORNING LOCATED SWRN CORNER NE/CO
BORDER...WILL FINALLY RESPOND TO INCREASINGLY WESTERLIES ACROSS SRN
CANADA AND BEGIN THE EJECTION PROCESS TODAY. VORT LOBE THAT HAS
ROTATED AROUND LOW MOVING SWD THRU ERN CO WILL HEAD EWD ACROSS SRN
KS/NRN OK LATER THIS AFTERNOON/EVENING.

WEAK SURFACE LOW SWRN KS WITH TROUGH EXTENDING INTO TX PANHANDLE
WILL PROVIDE A FOCUS FOR SURFACE BASED CONVECTIVE INITIATION BY
MID/LATE AFTERNOON AS THIS FEATURE SHIFTS EWD ACROSS WRN KS INTO
NWRN OK. WITH STEEP LAPSE RATES ASSOCIATED WITH COLD CORE UPPER
CIRCULATION AND STRONG LOW LEVEL HEATING...COUPLED WITH 35-40KT OF
DEEP LAYER SHEAR...CONDITIONS WILL BE IN PLACE FOR A FEW SEVERE
THUNDERSTORMS. EARLIER FORECASTS KEPT SVR PROBS AT A MINIMUM DUE TO
EXPECTED LIMITED INSTABILITY...MLCAPE AOB 500 J/KG. HOWEVER WITH
OBSERVED LOW 50 DEWPOINTS AND PWAT OF ABOUT .70 IN...SBCAPE TO 1000
J/KG COULD DEVELOP IN AREAS OF FULL HEATING BY MID AFTERNOON FROM
SCENTRAL KS INTO NWRN/NCENTRAL OK. THUS HAVE INCREASED THE THREAT
OF LARGE HAIL AND AS A RESULT ADDED A LOW END SLIGHT RISK FOR THE
AREAS EXPECTED TO DESTABILIZE THE GREATEST AHEAD OF SURFACE TROUGH.
WHILE SHEAR IS SUFFICIENT FOR ROTATING UPDRAFTS...THE MARGINAL
AMOUNT OF INSTABILITY LIMITS ANY TORNADO THREAT TO A POSSIBLE
BRIEF/ISOLATED OCCURRENCE. SUNSET SHOULD LEAD TO A QUICK END OF ANY
SEVERE THREAT.

...PORTIONS OF TN VALLEY...
HAVE TRIMMED THE LOW SEVERE WIND PROBABILITIES TO REGION OF OBSERVED
GREATEST HEATING/INSTABILITY FROM MID TN TO NRN AL. FURTHER W
EXTENSIVE CLOUD COVER PRECLUDES ANY VIGOROUS UPDRAFT POTENTIAL. WITH
THE VERY MOIST AIR MASS...PWAT NEAR 2 INCHES...AND MLCAPES TO 2000
J/KG WHERE SURFACE TEMPS REACH MID 80S...A FEW STRONG DOWNDRAFTS ARE
LIKELY. WEAK SHEAR AND LAPSE RATES PRECLUDES ANY MORE THAN A LOW
SEVERE WIND PROB...I.E. SEE TEXT.

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