Thursday, May 21, 2009

DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 210733
SWODY3
SPC AC 210730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU MAY 21 2009

VALID 231200Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...GULF COAST STATES TO ARKLATEX/EASTERN OK AND LOWER MO VALLEY...
IT SEEMS LIKELY THE LOW CURRENTLY ACROSS THE GULF OF MEXICO WILL
MOVE INLAND ACROSS THE CENTRAL GULF COAST REGION ON SATURDAY. AN
INCREASINGLY MOIST BOUNDARY LAYER AND MODERATE LOW LEVEL WIND FIELDS
MAY ACCOMPANY THIS LOW INLAND...BUT WEAK LAPSE RATES/MARGINAL
BUOYANCY AND WEAK MID TROPOSPHERIC FLOW WOULD LIKELY LIMIT
SEVERE/SUPERCELL POTENTIAL IN CONCERT WITH THE LOW.

ON THE NORTH-NORTHWEST PERIPHERY OF THE LOW...WITHIN AN INCREASINGLY
MOIST BOUNDARY LAYER...POCKETS OF STRONGER DIURNAL HEATING MAY
CONTRIBUTE TO A POTENTIALLY UNSTABLE AIRMASS SATURDAY
AFTERNOON/EARLY EVENING. LIMITED CONVERGENCE AND WEAK LOW/MID
TROPOSPHERIC WINDS SHOULD KEEP ANY SEVERE THREAT RATHER
EPISODIC/SCATTERED IN NATURE...ALTHOUGH IT SEEMS PROBABLE THAT AT
LEAST SOME DOWNBURST/PERHAPS PULSE HAIL POTENTIAL WILL EXIST ACROSS
THE LOWER MISSISSIPPI VALLEY/ARKLATEX INTO EASTERN OK/LOWER MISSOURI
VALLEY.

GIVEN INHERENT UNCERTAINTIES AND THE EXPECTED MARGINAL/SPORADIC
NATURE OF THE RISK...WILL NOT INTRODUCE SEVERE PROBABILITIES AT THIS
TIME...AS SUBSEQUENT OUTLOOKS WILL BE ABLE TO BETTER DELINEATE A
PREFERRED CORRIDOR FOR ANY MODEST SEVERE RISK.

...NORTHERN HIGH PLAINS...
THERE IS SOME POTENTIAL THAT A SEMI-ORGANIZED/BUT ISOLATED SEVERE
THREAT MAY DEVELOP ACROSS MT SATURDAY AFTERNOON/EVENING...WITH LOW
LEVEL UPSLOPE VIA AN EASTWARD-EXITING SURFACE HIGH AND POTENTIAL FOR
LATER DAY LARGE SCALE HEIGHT FALLS AHEAD OF A DEVELOPING TROUGH INTO
THE PACIFIC NORTHWEST. LIMITED PREDICTABILITY AND A SEEMINGLY
MARGINAL/ISOLATED SEVERE HAIL/WIND POTENTIAL PRECLUDES SEVERE
PROBABILITIES AT THIS TIME.

..GUYER.. 05/21/2009

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