Monday, March 03, 2008

SPC, GFS, NAM



   DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1157 PM CST SUN MAR 02 2008

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS SERN AR...MUCH OF LA AND
MS...AND INTO EXTREME WRN FRINGES OF AL...

...THERE IS A SLGT RISK OF SVR TSTMS FROM E TX ACROSS THE LOWER AND
MID MS VALLEY INTO THE TN VALLEY/CENTRAL GULF COAST REGION...

...SYNOPSIS...
SIGNIFICANT SEVERE WEATHER EVENT CENTERED INVOF THE LOWER MS VALLEY
IS FORECAST THIS PERIOD -- INCLUDING THE POTENTIAL FOR
WIDESPREAD/DAMAGING WINDS AND SEVERAL/POTENTIALLY-SIGNIFICANT
TORNADOES.

LARGE MID-LEVEL TROUGH -- INITIALLY CONSISTING OF A PHASED NRN AND
SRN STREAM SYSTEM -- SHOULD EXTEND FROM MN SWWD ACROSS THE CENTRAL
PLAINS INTO NM AT THE START OF THE PERIOD. THIS TROUGH IS FORECAST
TO SHIFT EWD ACROSS THE PLAINS/UPPER MS VALLEY WITH TIME THROUGH THE
FIRST HALF OF THE PERIOD. DURING THE SECOND HALF OF THE
PERIOD...THE NRN STREAM FEATURE IS FORECAST TO ACCELERATE EWD ACROSS
THE GREAT LAKES AND EVENTUALLY INTO QUEBEC...WHILE THE SRN STREAM
FEATURE EVOLVES INTO A CLOSED LOW -- FORECAST TO MOVE INTO AR BY
04/12Z. THE SRN STREAM FEATURE WILL BE ACCOMPANIED BY A VERY
STRONG/INTENSIFYING DEEP-LAYER WIND FIELD...INCLUDING A 100-PLUS KT
SSWLY H5 JET STREAK.

AT THE SURFACE...COLD FRONT WILL SWEEP ACROSS THE MIDWEST AND INTO
THE NORTHEAST...WHILE A SURFACE LOW DEVELOPS ON THE TRAILING PORTION
OF THIS FRONT AS THE SRN STREAM FEATURE ALOFT STRENGTHENS. THIS LOW
-- FORECAST INVOF SRN AR/NRN LA/W CENTRAL MS AT 04/00Z -- IS
EXPECTED TO MOVE NEWD INTO MIDDLE TN BY THE END OF THE PERIOD AS
COLD FRONT SWEEPS ACROSS THE LOWER MS VALLEY AND INTO THE CENTRAL
GULF COAST REGION.

...E TX EWD ACROSS THE LOWER AND MID MS VALLEY INTO SRN KY/TN/NWRN
GA/AL/WRN AND CENTRAL FL PANHANDLE...
STORMS SHOULD BE ONGOING ALONG/AHEAD OF THE ADVANCING COLD FRONT AT
THE START OF THE PERIOD -- FROM SERN MO/AR SWWD ACROSS NERN AND INTO
CENTRAL TX. AS SRN STREAM UPPER FEATURE STRENGTHENS...SURFACE LOW
SHOULD DEVELOP/MOVE NEWD ALONG THE FRONT ACROSS E TX...ALLOWING THE
FRONT TO MOVE QUICKLY SEWD ACROSS TX. BY EARLY AFTERNOON...SLY FLOW
WITHIN THE WARM SECTOR FLOW ADVECTING LOW-LEVEL MOISTURE NWD...ALONG
WITH SOME HEATING...WILL RESULT IN MODEST DESTABILIZATION /AOB 1000
J/KG/...LIMITED BY WEAK LAPSE RATES ALOFT.

DESPITE THIS...VERY STRONG DEEP-LAYER WIND FIELD -- EXPECTED TO VEER
SUBSTANTIALLY AND INCREASE RAPIDLY WITH HEIGHT -- WILL RESULT IN
DEEP-LAYER SHEAR VERY FAVORABLE FOR SEVERE STORMS...AND LOW-LEVEL
SHEAR HIGHLY-SUPPORTIVE OF TORNADOES. THUS...EXPECT SEVERE THREAT
TO INCREASE THROUGH THE LATE MORNING INTO THE AFTERNOON. BY MID
AFTERNOON...A WELL-DEFINED LINE OF STORMS SHOULD BE MOVING TOWARD
THE LOWER MS RIVER...WITH AT LEAST SOME POTENTIAL FOR ISOLATED
STORMS DEVELOPING AHEAD OF THE MAIN CONVECTIVE LINE. WHILE LIMITED
DEGREE OF INSTABILITY RAISES SOME QUESTION AS TO THE EXTENT OF
ISOLATED/PRE-FRONTAL CELLULAR DEVELOPMENT...ATTM IT APPEARS THAT THE
POTENTIAL IS GREAT ENOUGH TO SUGGEST THE POSSIBILITY OF
MULTIPLE/POTENTIALLY-DAMAGING TORNADOES. TORNADOES WILL ALSO BE
POSSIBLE WITHIN THE MAIN CONVECTIVE LINE...THOUGH THE PRIMARY THREAT
WITH THIS LINE WILL LIKELY BE WIDESPREAD/POSSIBLY SIGNIFICANT WIND
DAMAGE.

AFTER DARK...A SLOW DECREASE IN INSTABILITY IS EXPECTED...BUT VERY
STRONG/VEERING WIND FIELD WILL LIKELY CONTINUE TO SUPPORT A THREAT
FOR DAMAGING WINDS AND TORNADOES. CONVECTION SHOULD SHIFT ACROSS MS
AND WRN PORTIONS OF TN AND KY DURING THE EVENING...AND THEN SPREAD
ACROSS THE REMAINDER OF KY...TN...AL...AND INTO THE FL PANHANDLE
THROUGH THE END OF THE PERIOD. WHILE THE SEVERE THREAT SHOULD
SLOWLY DECREASE INTO THE EARLY MORNING...SOME SEVERE POTENTIAL IS
EXPECTED TO PERSIST THROUGH THE END OF THE PERIOD.


Latest GFS output for Midnight tomorrow.


Latest NAM output for Midnight tomorrow.

Great summary from Tim Coleman at Alabamawx.com

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