Monday, May 28, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281628
SWODY1
SPC AC 281625

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1125 AM CDT MON MAY 28 2007

VALID 281630Z - 291200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NORTHERN
PLAINS...

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MID
ATLANTIC STATES...

..NORTHERN PLAINS...
STRONG UPPER TROUGH IS DEEPENING OVER ID/WRN MT THIS MORNING...AND
IS FORECAST TO MOVE ACROSS MT/WY THROUGH THE FORECAST PERIOD.
MEANWHILE...STRONG SOUTHERLY LOW LEVEL WINDS ARE TRANSPORTING MOIST
AND UNSTABLE AIR MASS NORTHWARD THROUGH THE NORTHERN PLAINS. THIS
WILL SET THE STAGE FOR NUMEROUS THUNDERSTORMS THIS AFTERNOON FROM
NORTHWEST MN AND EASTERN ND INTO EASTERN WY AND WESTERN NEB.
PRESENT INDICATIONS ARE THAT COLD FRONT SURGING EASTWARD ACROSS THE
DAKOTAS WILL BE THE PRIMARY FOCUS FOR CONVECTIVE INITIATION BY MID
AFTERNOON...ALONG AN AXIS FROM NEAR DVL - EAST OF BIS - MBG. STEEP
LOW AND MID LEVEL LAPSE RATES WILL COMBINE WITH DEWPOINTS RISING
INTO THE LOWER 60S...RESULTING IN CAPE VALUES OVER 2000 J/KG. UPPER
TROUGH WILL REMAIN WELL WEST OF THIS AREA THIS AFTERNOON...BUT WEAK
LEAD SHORTWAVE TROUGH NOW OVER SOUTHEAST MT MAY AID INITIATION.
SUPERCELLS CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS...AND
ISOLATED TORNADOES ARE POSSIBLE. ACTIVITY WILL LIKELY DEVELOP
SOUTHWESTWARD ALONG FRONT INTO RAP/CDR AREA...AND SOUTHWARD ALONG
DRYLINE INTO NORTHEAST CO/WESTERN KS WHERE VERTICAL SHEAR WILL BE
WEAKER. STORMS ARE EXPECTED TO PERSIST MUCH OF THE EVENING AND
SPREAD EASTWARD ACROSS EASTERN DAKOTAS AND INTO WESTERN MN.

ANOTHER AREA OF CONVECTIVE DEVELOPMENT IS EXPECTED THIS AFTERNOON
OVER NORTHEAST WY. POSTFRONTAL SURFACE WINDS ARE EXPECTED TO BECOME
NORTHEASTERLY...ENHANCING UPSLOPE FLOW INTO THE BIGHORNS.
INSTABILITY WILL BE MARGINAL...BUT PERHAPS SUFFICIENT FOR ISOLATED
STRONG/SEVERE STORMS CAPABLE OF HAIL AND GUSTY WINDS. THESE STORMS
WILL LIKELY MOVE EASTWARD ACROSS WESTERN SD AFTER DARK.

..MID ATLANTIC...
SOUTHERN FRINGE OF STRONGER WESTERLY FLOW ALOFT LIES ACROSS
PA/MD/NORTHERN VA TODAY. WEAK RESIDUAL SURFACE BOUNDARY EXTENDS
FROM EASTERN WV INTO NJ...AND MAY BE FOCUS FOR ISOLATED
THUNDERSTORMS THIS AFTERNOON. VERTICAL SHEAR IS RATHER WEAK AND
WILL LIMIT CONVECTIVE ORGANIZATION. HOWEVER...STRONG HEATING WILL
LEAD TO STEEP LOW LEVEL LAPSE RATES AND THE POTENTIAL FOR
GUSTY/DAMAGING WINDS IN STRONGEST CELLS.

.HART/CROSBIE.. 05/28/2007

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