Tuesday, April 27, 2010

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 270730
SWODY3
SPC AC 270729

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT TUE APR 27 2010

VALID 291200Z - 301200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY REGION
SSWWD INTO PARTS OF OK/N TX...

...SYNOPSIS...
LARGE UPPER LOW/TROUGH INITIALLY CENTERED OVER THE INTERMOUNTAIN
WEST WILL MAKE SLOW EWD PROGRESS THIS PERIOD...INCREASINGLY
AFFECTING THE CENTRAL CONUS.

AT THE SURFACE...AN OCCLUDED SYSTEM WILL PROGRESS ACROSS THE NRN AND
CENTRAL PLAINS. BY THE END OF THE PERIOD...THE OCCLUDED FRONT IS
EXPECTED TO ARC SEWD FROM A LOW OVER THE ND/NRN MN VICINITY ACROSS
THE UPPER MS VALLEY...AND THEN ON SWWD AS A COLD FRONT ACROSS
IA...ERN KS/WRN MO...ERN OK...AND INTO CENTRAL TX.

...MID MO VALLEY REGION SSWWD INTO PARTS OF OK/N TX...
BOUNDARY-LAYER MOISTURE WILL CONTINUE SPREADING NWD INTO THE CENTRAL
U.S. AS STRONG SLY FLOW CONTINUES...WITH DEWPOINTS AROUND 60 F
SPREADING INTO OK/KS AND INTO THE MID MO VALLEY REGION. DAYTIME
HEATING OF THE MOISTENING -- BUT CAPPED -- BOUNDARY LAYER WILL
CONTRIBUTE TO AFTERNOON DESTABILIZATION...WITH 1000 TO 1500 J/KG
MIXED-LAYER CAPE EXPECTED TO EVOLVE.

WHILE SURFACE EVOLUTION ACROSS THE CENTRAL PLAINS DIFFERS WITHIN THE
NAM AND GFS SOLUTIONS...ATTM EXPECT CAP EROSION ALONG SOME
COMBINATION OF A FRONT AND/OR DRYLINE FROM THE MID MO VALLEY INTO
CENTRAL KS/WRN OK TO EVENTUALLY RESULT IN ISOLATED STORM
DEVELOPMENT.

WHILE THE CAP SHOULD LIMIT STORM COVERAGE DURING THE
AFTERNOON...VERY STRONG/VEERING FLOW WITH HEIGHT SPREADING ACROSS
THE CENTRAL U.S. WILL YIELD SHEAR VERY FAVORABLE FOR
STRONGLY-ROTATING SUPERCELL STORMS. THUS...ANY STORM WHICH DEVELOPS
SHOULD QUICKLY BECOME SEVERE...WITH VERY LARGE HAIL EXPECTED ALONG
WITH THE POTENTIAL FOR LOCALLY-DAMAGING WINDS. WHILE DEGREE OF
LOW-LEVEL SHEAR WILL BE VERY SUPPORTIVE OF TORNADO
POTENTIAL...SOMEWHAT LIMITED LOW-LEVEL MOISTURE - AND THE FAIRLY
DEEP BOUNDARY LAYER WHICH SHOULD RESULT -- SHOULD LIMIT THE OVERALL
TORNADO THREAT.

OVERNIGHT...STORMS SHOULD BECOME MORE LINEARLY-ORGANIZED ALONG THE
ADVANCING COLD FRONT. WHILE DECREASING INSTABILITY AND CHANGE IN
STORM MODE SHOULD YIELD A SLOW DECREASE IN HAIL/TORNADO
POTENTIAL...MARGINAL HAIL/DAMAGING WIND POTENTIAL WILL LIKELY
PERSIST WELL INTO THE OVERNIGHT HOURS.

..GOSS.. 04/27/2010

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