SWOD48
SPC AC 170851
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CDT SUN MAY 17 2009
VALID 201200Z - 251200Z
...DISCUSSION...
AN AMPLIFIED LARGE SCALE PATTERN WILL LIKELY CONTINUE FROM THE
MIDDLE INTO LATTER PART OF THE WEEK. THIS REGIME WILL GENERALLY BE
CHARACTERIZED BY A BROAD UPPER RIDGE OVER THE SOUTHWEST/SOUTH
CENTRAL CONUS...WITH THE STRONGER WESTERLIES LARGELY CONFINED TO
CANADA AND THE NORTHERN TIER OF THE LOWER 48. WHILE PERIODIC SEVERE
TSTMS WILL BE POSSIBLE...LIMITED MOISTURE RETURN WILL LIKELY
PRECLUDE ANY WIDESPREAD SEVERE EPISODES FOR AT LEAST THE FIRST PART
OF THE DAY 4-8 PERIOD...AND NO 30% DAY-1 EQUIVALENT SEVERE
PROBABILITIES ARE WARRANTED AT THIS TIME.
WITH RELATIVELY GOOD GEFS/ECMWF CONSENSUS...SOME SEVERE TSTMS WILL
BE POSSIBLE ACROSS THE UPPER MIDWEST/NORTH CENTRAL PLAINS ON
WEDNESDAY/DAY 4...IN ASSOCIATION WITH A PROGRESSIVE SHORTWAVE TROUGH
AND EASTWARD ADVANCING COLD FRONT. IN SPITE OF EXPECTATIONS FOR
RELATIVELY STRONG KINEMATICS/AMPLE LAPSE RATES...MEAGER BOUNDARY
LAYER MOISTURE SHOULD PRECLUDE A MORE APPRECIABLE THREAT. FOR
THURSDAY-SATURDAY DAYS 5-7...CURRENT THINKING IS THAT THE MAIN
PROSPECTS FOR ANY SEVERE TSTMS WILL BE PRIMARILY CONFINED TO THE
NORTH CENTRAL HIGH PLAINS/FRONT RANGE VIA A POST-FRONTAL UPSLOPE
REGIME...ALTHOUGH WESTERLIES WILL TEND TO REMAIN MODEST.
OTHERWISE...SEVERE TSTMS MAY BE POSSIBLE ACROSS THE NORTHEAST
STATES/NEW ENGLAND AROUND DAY 6/FRIDAY ALONG/AHEAD OF A COLD FRONT
AND PARENT UPPER TROUGH...BUT PREDICTABILITY IS INHERENTLY LOW ALONG
WITH UNKNOWNS REGARDING MOISTURE.
..GUYER.. 05/17/2009
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