Friday, December 7, 2007

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 070831
SWODY3
SPC AC 070829

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CST FRI DEC 07 2007

VALID 091200Z - 101200Z

..NO SVR TSTM AREAS FORECAST...

..TX THROUGH THE LOWER MS VALLEY...

SHORTWAVE TROUGH FORECAST TO EJECT INTO THE CNTRL HIGH PLAINS EARLY
SUNDAY WILL CONTINUE NEWD INTO THE UPPER MS VALLEY AND DEAMPLIFY AS
IT CRESTS UPPER RIDGE. MEANWHILE...UPPER TROUGH WILL CONTINUE TO
AMPLIFY SWD INTO NRN MEXICO WITH WEAK SHORTWAVE RIDGING DOWNSTREAM
OVER ERN PARTS OF THE SRN PLAINS INTO THE LOWER MS VALLEY. AT THE
SURFACE A NOSE OF COLD...SHALLOW HIGH PRESSURE WILL CONTINUE TO
SPREAD SWD THROUGH THE SRN PLAINS. BY SUNDAY EVENING THIS BOUNDARY
IS FORECAST TO EXTEND FROM THE OH VALLEY SWWD THROUGH AR...AND INTO
SWRN TX.

BOUNDARY LAYER DEWPOINTS IN THE MID TO UPPER 60S WILL LIKELY EXIST
IN PRE-FRONTAL WARM SECTOR FROM PARTS OF CNTRL AND ERN TX INTO THE
LOWER MS VALLEY. HOWEVER...WEAK LAPSE RATES AND POTENTIAL AREAS OF
CLOUDS WILL LIMIT INSTABILITY IN WARM SECTOR. A STRONG SWLY LOW
LEVEL JET INITIALLY FROM ERN TX THROUGH THE LOWER MS VALLEY EARLY
SUNDAY WILL SHIFT NEWD THROUGH THE OH VALLEY BY EVENING IN RESPONSE
TO SHORTWAVE TROUGH CRESTING UPPER RIDGE. LOW LEVEL SHEAR WILL BE
ENHANCED ALONG THE LOW LEVEL JET AXIS FROM NERN TX INTO AR SUNDAY
MORNING...BUT SHOULD GRADUALLY WEAKEN DURING THE DAY. STORMS WILL
LIKELY CONTINUE DEVELOPING PRIMARILY WITHIN ZONE OF ASCENT ALONG AND
JUST N OF COLD FRONT. HOWEVER...SOME CONVECTION MAY ALSO BE POSSIBLE
WITHIN THE WEAKLY CAPPED WARM SECTOR. WEAK SHORTWAVE RIDGING WILL
LIKELY LIMIT MAGNITUDE OF DEEP SHEAR WITH SRN EXTENT INTO THE LOWER
MS VALLEY AND TX DURING THE DAY. HOWEVER...VERTICAL SHEAR MAY BE
SUFFICIENT FOR SOME ORGANIZED STORM STRUCTURES IN VICINITY OF THE
FRONT...ESPECIALLY FROM PARTS OF NERN TX INTO AR. BEST CHANCE FOR
ISOLATED SEVERE STORMS DURING THE DAY WILL BE WITH ANY ACTIVITY THAT
CAN DEVELOP AHEAD OF THE FRONT FROM ERN TX INTO THE LOWER MS VALLEY.
OTHERWISE...STORMS DEVELOPING ALONG FRONT WILL LIKELY BECOME
ELEVATED AS THEY ARE UNDERCUT. THE EXPECTED MARGINAL THERMODYNAMIC
ENVIRONMENT...WEAK UPPER RIDGING AND TENDENCY FOR THE LOW LEVEL JET
TO WEAKEN WITH TIME SHOULD LIMIT OVERALL SEVERE THREAT. AT THIS TIME
WILL INTRODUCE LOW SEVERE PROBABILITIES.

OVERNIGHT...THE LOW LEVEL JET IS FORECAST TO STRENGTHEN FARTHER WEST
ACROSS TX IN RESPONSE TO UPSTREAM HEIGHT FALLS. THIS WILL LIKELY
ENHANCE LIFT AND CONTRIBUTE TO SOME BACKBUILDING OF STORMS ALONG AND
N OF THE FRONT INTO W CNTRL AND SWRN TX WHERE SLIGHTLY STEEPER LAPSE
RATES MAY EXIST. THIS ACTIVITY MAY POSE A THREAT FOR MARGINALLY
SEVERE HAIL.

.DIAL.. 12/07/2007

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