SPC AC 091718
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1218 PM CDT THU JUL 09 2009
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE MIDWEST AND
WESTERN GREAT LAKES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL HIGH
PLAINS...
...SYNOPSIS...
AS AN EXPANSIVE UPPER RIDGE REMAINS CENTERED OVER THE SOUTHERN
PLAINS...THE BRUNT OF AN UPPER TROUGH OVER THE CENTRAL CANADIAN
PROVINCES WILL SHIFT EASTWARD OVER MANITOBA/ONTARIO ON FRIDAY WITH
AN ASSOCIATED MID/UPPER JET STREAK CROSSING THE UPPER MIDWEST AND
GREAT LAKES REGION. PRIMARY SURFACE FRONT WILL DEVELOP EASTWARD
ACROSS THE UPPER MISSISSIPPI VALLEY...WHILE THE TRAILING/SLOWER
MOVING PORTION OF THE FRONT EXTENDS SOUTHWESTWARD ACROSS THE LOWER
MO VALLEY INTO KS/SOUTHEAST CO.
...MIDWEST/WESTERN GREAT LAKES...
ON THE NOSE OF A RELATIVELY STRONG SOUTHWESTERLY/VEERING LOW LEVEL
JET ACROSS THE CENTRAL PLAINS AND ADJACENT MO VALLEY...IT SEEMS
PROBABLE THAT SCATTERED TSTMS AND POTENTIALLY ONE OR MORE MCS/S WILL
BE ONGOING ACROSS PORTIONS OF THE UPPER MS VALLEY AND/OR
LOWER/MIDDLE MO VALLEY AT THE BEGINNING OF THE PERIOD FRIDAY
MORNING. MUCH OF THE SUBSEQUENT DETAILS ARE STILL UNCERTAIN ON
FRIDAY LARGELY OWING TO THIS EARLY DAY TSTM POTENTIAL...BUT A
DIURNAL UPSWING IN COVERAGE/INTENSITY SEEMS LIKELY DURING THE
AFTERNOON ACROSS THE REGION WHERE DESTABILIZATION CAN OCCUR IN
EARNEST. THIS COULD OCCUR ON THE SOUTHERN PERIPHERY OF THE
AFOREMENTIONED EARLY DAY STORMS/ALONG REMNANT CONVECTIVE
OUTFLOW...WITH OTHER DEVELOPMENT POSSIBLE FARTHER NORTH ALONG THE
SOUTHWEST-NORTHEAST ORIENTED SURFACE FRONT. WITH A MOIST AIRMASS AND
EXPECTATIONS FOR MIDDLE 60S TO LOWER 70S F SURFACE
DEWPOINTS...MODERATE TO STRONG POTENTIAL INSTABILITY AND
STRENGTHENING MID/HIGH LEVEL FLOW WOULD SUPPORT WELL-ORGANIZED
SEVERE TSTMS INCLUDING SUPERCELLS. LARGE HAIL AND PERHAPS A FEW
TORNADOES WILL BE POSSIBLE...AND STORM CONSOLIDATION/POTENTIAL
UPSCALE MCS GROWTH AND/OR A NOCTURNALLY STRENGTHENING LOW LEVEL JET
MAY YIELD AN INCREASING DAMAGING WIND THREAT BY EARLY EVENING.
...CENTRAL HIGH PLAINS...
OWING TO THE NORTHWARD-EXPANDING UPPER RIDGE AND BUILDING HEIGHTS
ALOFT...IT SEEMS PROBABLE THAT MUCH OF THE CENTRAL PLAINS MAY REMAIN
CAPPED ON FRIDAY...ESPECIALLY AWAY FROM THE HIGHER TERRAIN/FRONT
RANGE. REGARDLESS...DEEP MIXING AND INCREASINGLY MOIST LOW LEVEL
UPSLOPE TRAJECTORIES SHOULD FOSTER TSTM DEVELOPMENT BY LATE
AFTERNOON/EARLY EVENING ACROSS THE CENTRAL HIGH PLAINS...INCLUDING
PORTIONS OF EASTERN WY/SOUTHWEST SD/NEB PANHANDLE/EASTERN CO
SOUTHWARD TO PERHAPS NORTHEAST NM AND PORTIONS OF THE OK/TX
PANHANDLES. POTENTIALLY AIDED BY A LATE DAY MID LEVEL IMPULSE ON THE
PERIPHERY OF THE UPPER RIDGE...MODERATELY STRONG VERTICAL
SHEAR/VEERING WIND PROFILES MAY SUPPORT SOME SUPERCELLS AND A
SOMEWHAT MORE ORGANIZED SEVERE POTENTIAL ACROSS NORTHEAST CO/EASTERN
WY AND ADJACENT PORTIONS OF WESTERN NEB/NORTHWEST KS FRIDAY
AFTERNOON/EARLY EVENING. DAMAGING WINDS AND SEVERE HAIL WILL BE THE
PRIMARY HAZARDS ACROSS THE REGION.
...FL PENINSULA...
SOUTHEAST STATES UPPER LOW WILL CONTINUE TO SETTLE SOUTHWARD OVER
THE FL PENINSULA INTO FRIDAY...ACCOMPANIED BY RELATIVELY COOL MID
LEVEL TEMPERATURES OF -8C TO -10C AT 500 MB. CLOUD COVER MAY TEND TO
LIMIT THE DEGREE OF DIURNAL DESTABILIZATION ESPECIALLY IN PROXIMITY
TO THE SOUTHWARD-SAGGING FRONTAL ZONE ACROSS THE CENTRAL FL
PENINSULA...BUT SUFFICIENTLY STEEP LAPSE RATES/BUOYANCY MAY EXIST
WITHIN A WEAKLY SHEARED REGIME FOR A FEW STRONG WIND GUSTS/PERHAPS
HAIL THROUGH FRIDAY AFTERNOON.
..GUYER.. 07/09/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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