SWODY1
SPC AC 271634
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1134 AM CDT THU MAY 27 2010
VALID 271630Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR NY
TO VA...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR THE
NRN HIGH PLAINS...
...NY TO VA THIS AFTERNOON/EVENING...
VISIBLE IMAGERY AND SURFACE OBSERVATIONS SHOW CONVECTION BEGINNING
TO DEVELOP ALONG THE N-S BAROCLINIC ZONE ACROSS ERN NY...IN ADVANCE
OF A WEAK MID LEVEL VORTICITY /POSSIBLE MCV/ CENTER MOVING SSEWD
FROM ONTARIO INTO NY. STRONG SURFACE HEATING W OF THE FRONT AND
BOUNDARY LAYER DEWPOINTS IN THE 60S WILL SUPPORT A CORRIDOR OF
MODERATE INSTABILITY THIS AFTERNOON TO MAINTAIN THE DEVELOPING
CONVECTION. MULTICELL CLUSTERS SHOULD BE THE PRIMARY CONVECTIVE
MODE...WITH SOME POTENTIAL FOR MARGINAL SUPERCELL STRUCTURES ALONG
THE FRONT WHERE LOW-LEVEL SHEAR WILL BE ENHANCED COMPARED TO THE
OPEN WARM SECTOR TO THE W. GIVEN THE DEGREE OF BUOYANCY...STEEP
LOW-LEVEL LAPSE RATES...AND 30-40 KT NWLY MIDLEVEL FLOW...THE
ENVIRONMENT WILL FAVOR THE PRODUCTION OF DAMAGING WINDS AND HAIL
THROUGH THE AFTERNOON ACROSS FROM SRN NY INTO ERN PA...AND FROM LATE
AFTERNOON THROUGH THIS EVENING INTO AT LEAST NRN VA.
...NRN HIGH PLAINS THIS AFTERNOON INTO TONIGHT...
A DEEP MIDLEVEL LOW NEAR THE NRN CA/ORE COASTS WILL DRIFT INLAND/EWD
THROUGH THE PERIOD. A BELT OF STRONG MID-UPPER SSWLY FLOW WILL BE
MAINTAINED FROM THE SRN GREAT BASIN TO THE NRN ROCKIES TO THE E OF
THE LOW. THE EXIT REGION OF THE JET WILL BE FOCUSED OVER MT...AND A
SURFACE LEE CYCLONE WILL PERSIST INVOF SE MT...ALONG A STALLED FRONT
THAT EXTENDS NEWD FROM SE MT INTO WRN ND. MEANWHILE...BOUNDARY
LAYER DEWPOINTS IN THE LOW 60S ARE SPREADING NNWWD FROM NEB ACROSS
WRN SD TO SE MT/WRN ND. THIS MOISTURE WILL COMBINE WITH DAYTIME
HEATING IN CLOUD BREAKS TO SUPPORT AFTERNOON MLCAPE VALUES NEAR 2500
J/KG.
THE PRIMARY FOCUS FOR THUNDERSTORM DEVELOPMENT WILL BE THE
BAROCLINIC ZONE TO THE NE OF THE LEE CYCLONE THIS LATE THIS
AFTERNOON/EVENING. CONVECTIVE INITIATION IS MUCH MORE IN QUESTION
FARTHER S ALONG THE LEE TROUGH WHERE SOME CONVECTIVE INHIBITION
SHOULD LINGER THROUGH THE AFTERNOON. DEEP-LAYER AND LOW-LEVEL
VERTICAL SHEAR WILL BE FAVORABLE FOR RIGHT-MOVING SUPERCELLS ALONG
THE FRONT ACROSS SRN/ERN MT INTO WRN ND...WITH THE POTENTIAL FOR A
FEW TORNADOES AND VERY LARGE HAIL.
...CENTRAL/SRN HIGH PLAINS THIS AFTERNOON/EVENING...
THE SYNOPTIC SCALE TROUGH AND STRONGER MID-UPPER FLOW WILL REMAIN
WELL W OF THE CENTRAL/SRN HIGH PLAINS THROUGH THIS PERIOD.
STILL...BOUNDARY LAYER DEWPOINTS IN THE 50S TO NEAR 60 F AND STRONG
AFTERNOON SURFACE HEATING WILL AGAIN CONTRIBUTE TO A CORRIDOR OF
MODERATE INSTABILITY ALONG AND E OF THE WEAK LEE TROUGH. ISOLATED
THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE THIS AFTERNOON FROM THE
FRONT RANGE IN NM NWD INTO ERN CO...BUT SPARSE COVERAGE AND/OR WEAK
VERTICAL SHEAR WILL TEND TO LIMIT THE OVERALL SEVERE STORM THREAT.
THUS...WILL MAINTAIN LOW /5%/ HAIL AND WIND PROBABILITIES FROM
PREVIOUS OUTLOOK.
..THOMPSON/HURLBUT.. 05/27/2010
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