SPC AC 191730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT THU AUG 19 2010
VALID 201200Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MIDWEST/UPPER GREAT
LAKES/LOWER MO VALLEY...
...SYNOPSIS...
ALTHOUGH SOME LARGE SCALE AMPLIFICATION WILL OCCUR MAINLY OVER THE
WESTERN STATES BY FRIDAY NIGHT...A PROGRESSIVE/LOW AMPLITUDE BELT OF
WESTERLIES WILL PERSIST OVER THE NORTHERN HALF OF THE CONUS. THE
COMPLEX UPPER TROUGH CURRENTLY OVER THE CENTRAL-NORTHERN ROCKIES
TODAY WILL CONTINUE TO ADVANCE STEADILY EASTWARD ON
FRIDAY...CROSSING THE LOWER/MIDDLE MO VALLEY AND UPPER MIDWEST/UPPER
GREAT LAKES THROUGH FRIDAY NIGHT.
...LOWER/MIDDLE MO VALLEY AND MIDWEST TO UPPER GREAT LAKES...
IT IS PROBABLE THAT SEVERAL CLUSTERS OF THUNDERSTORMS WILL BE
ONGOING EARLY FRIDAY MORNING ACROSS THE UPPER MIDWEST INCLUDING
PORTIONS OF MN/WI...SOUTHWESTWARD TO EAST-CENTRAL PORTIONS OF
NEB/KS. SPECIFIC DETAILS ARE UNCLEAR ON THE DEGREE OF SUBSEQUENT
DESTABILIZATION/AFTERNOON TSTM DEVELOPMENT ALONG/AHEAD OF AN
EASTWARD ADVANCING WEAK COLD FRONT/SURFACE TROUGH. HOWEVER...WITH
THE BRUNT OF THE PREVIOUSLY MENTIONED UPPER TROUGH SHIFTING
EAST-NORTHEASTWARD TOWARD THE UPPER MS RIVER VALLEY DURING THE
DAY...IT SEEMS PROBABLE THAT REINVIGORATED TSTM COVERAGE/INTENSITY
SHOULD OCCUR DURING THE AFTERNOON COINCIDENT WITH THE WEAK COLD
FRONT/SURFACE TROUGH AND/OR PRE-FRONTAL BOUNDARIES/CORRIDORS OF
PRE-FRONTAL CONVERGENCE AMID STRONGER AFTERNOON
HEATING/DESTABILIZATION.
ALTHOUGH MUCH DEPENDS ON EARLY DAY CLOUD COVER AND PRECIPITATION AS
MENTIONED...CURRENT THINKING IS THAT THE STRONGEST
HEATING/DESTABILIZATION WILL OCCUR ACROSS PORTIONS OF IA/PERHAPS WI
AS WELL AS MO/EASTERN KS DURING THE AFTERNOON. CORRIDORS OF MLCAPE
TO 2000-3500 J/KG ARE PLAUSIBLE...BENEATH WEST-SOUTHWESTERLY MID
LEVEL FLOW OF 35-40 KT ATTENDANT TO THE ADVANCING UPPER TROUGH.
WHILE SOME SUPERCELLS WILL BE POSSIBLE...MULTICELL STORMS SHOULD BE
DOMINANT. OVERALL...DAMAGING WINDS AND SEVERE HAIL WILL BE THE
PRIMARY CONCERNS ON FRIDAY. WITH THAT SAID...A TORNADO THREAT MAY
ALSO EXIST...APPEARING MOST PROBABLE ACROSS NORTHERN/EASTERN
PORTIONS OF WI INTO THE UP OF MI...AHEAD OF THE SURFACE LOW AND NEAR
A RETREATING WARM FRONT. HERE...FORECAST SOUNDINGS IMPLY STRONG DEEP
TROPOSPHERIC FLOW/AMPLE LOW LEVEL HODOGRAPH CURVATURE FOR SUPERCELLS
WITH A TORNADO RISK PROVIDED SUFFICIENT DAYTIME DESTABILIZATION AND
A CONDUCIVE CONVECTIVE MODE.
OTHERWISE...ONE OR MORE NOCTURNAL TSTM CLUSTERS WILL LIKELY
EVOLVE/SPREAD EASTWARD THROUGH THE OVERNIGHT ACROSS THE MO
OZARKS/MIDDLE MS VALLEY AND UPPER GREAT LAKES...BUT THE OVERALL
SEVERE THREAT SHOULD GRADUALLY DIMINISH AS NEAR-SURFACE BUOYANCY
BECOMES EXHAUSTED.
...EASTERN ND/FAR NORTHWEST MN...
ALTHOUGH THE PRIMARY PORTION OF THE MO VALLEY/UPPER MIDWEST UPPER
TROUGH WILL MOVE ESSENTIALLY EAST OF THIS REGION EARLY IN THE
DAY...AN ASSORTMENT OF NUMERICAL GUIDANCE IS INDICATIVE OF AFTERNOON
TSTM DEVELOPMENT ALONG A COLD FRONT ACROSS SOUTHERN MANITOBA BY
FRIDAY LATE AFTERNOON. WITH LIMITED FORCING ON THE LARGE
SCALE...MODEL FORECAST SOUNDINGS EXHIBIT A DEGREE OF SUBSIDENCE-TYPE
WARMING ALOFT. NONETHELESS...RESIDUAL MOISTURE/BUOYANCY IN TANDEM
WITH THE SOUTH-SOUTHEASTWARD MOVING COLD FRONT...ALONG WITH STRONGLY
VEERED WIND PROFILES...COULD YIELD STORMS CAPABLE OF GUSTY
WINDS/HAIL INTO PORTIONS OF EASTERN ND/NORTHWEST MN.
..GUYER.. 08/19/2010
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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