SWODY1
SPC AC 271551
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1051 AM CDT SAT JUN 27 2009
VALID 271630Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE DAKOTAS
AND WESTERN MN...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MS VALLEY INTO
THE CENTRAL HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE EASTERN CAROLINAS...
...ND/SD/MN...
MORNING WATER VAPOR LOOPS SHOW A WELL-DEFINED SHORTWAVE TROUGH
MOVING EASTWARD ACROSS EASTERN MT/WESTERN ND. SCATTERED
THUNDERSTORMS ARE EXPECTED TO CONTINUE TO DEVELOP IN VICINITY OF
THIS FEATURE THROUGH MID AFTERNOON OVER CENTRAL ND...SPREADING
EAST-SOUTHEASTWARD INTO PARTS OF SD/MN DURING THE EVENING. COOL
TEMPERATURES ALOFT AND STEEP LAPSE RATES...COUPLED WITH SUFFICIENT
EFFECTIVE VERTICAL SHEAR FOR ORGANIZED MULTICELL OR ISOLATED
SUPERCELL STRUCTURES...WILL POSE A RISK OF LARGE HAIL AND GUSTY
WINDS IN STRONGER CELLS.
...UPPER MS VALLEY...
A SURFACE COLD FRONT IS MOVING EASTWARD ACROSS IA THIS MORNING...AND
WILL BE THE FOCUS FOR SCATTERED THUNDERSTORMS THIS AFTERNOON.
RELATIVELY STRONG HEATING AHEAD OF THE FRONT ALONG WITH DEWPOINTS IN
THE 60S TO NEAR 70F WILL YIELD MLCAPE VALUES OF 1500-2500 J/KG AND A
RELATIVELY WEAK CAP. STORMS ARE EXPECTED TO INITIATE ALONG THE
FRONT OVER CENTRAL IA/SOUTHEAST MN BY LATE AFTERNOON AND SPREAD INTO
WI/IL/MO DURING THE EVENING. LINEAR FORCING AND MARGINAL VERTICAL
SHEAR AHEAD OF THE FRONT SUGGEST THE RISK OF A MULTICELL SQUALL LINE
CAPABLE OF DAMAGING WINDS AND HAIL.
...MO/KS/OK...
ALL MODEL GUIDANCE IS IN GENERAL AGREEMENT THAT A TRAILING COLD
FRONT EXTENDING FROM MO INTO NORTHWEST OK WILL BECOME CONVECTIVELY
ACTIVE BY EARLY EVENING. STORMS ARE LIKELY TO DEVELOP FIRST IN THE
DEEPLY MIXED BOUNDARY LAYER AIRMASS OF THE TX/OK PANHANDLES. STORMS
WILL THEN PROPAGATE/DEVELOP EASTWARD ALONG THE FRONT INTO NORTHWEST
OK AND EVENTUALLY ACROSS KS. STORMS MAY ALSO DEVELOP SOUTHWESTWARD
FROM IA/IL ACTIVITY INTO MO. THUNDERSTORMS ALONG THIS AXIS WILL BE
IN REGION OF HOT SURFACE TEMPERATURES AND SUFFICIENT CAPE FOR STRONG
UPDRAFTS/DOWNDRAFTS AND A RISK OF LOCALLY DAMAGING WINDS. THE
SEVERE THREAT SHOULD SUBSIDE BY LATE EVENING AS DIURNAL COOLING
ENSUES.
...CAROLINAS...
AN UPPER TROUGH REMAINS OVER THE EASTERN STATES TODAY...WITH A
SERIES OF SHORTWAVE TROUGHS ROTATING SOUTHEASTWARD FROM THE OH
VALLEY INTO THE WESTERN ATLANTIC. STRENGTHENING NORTHWESTERLY
DEEP-LAYER FLOW WILL LIKELY LIMIT INLAND PUSH OF CAROLINA SEA BREEZE
TODAY. ALSO...TIMING OF SHORTWAVE TROUGHS SUGGEST WEAK SUBSIDENCE
WILL BE OVER THE REGION UNTIL LATE AFTERNOON OR EARLY EVENING WHICH
MAY LIMIT AREAL COVERAGE OF STORMS UNTIL LATER. AROUND 00Z...MORE
NUMEROUS THUNDERSTORMS MAY DEVELOP BOTH ALONG THE SEABREEZE AND THE
HIGHER TERRAIN OF UPSTATE SC. MODERATE INSTABILITY AND RATHER
STRONG VERTICAL SHEAR WILL SUPPORT A RISK OF ORGANIZED SEVERE STORMS
CAPABLE OF DAMAGING WINDS AND HAIL. OVERALL COVERAGE OF SEVERE
THREAT IS UNCERTAIN...BUT WILL MAINTAIN CATEGORICAL SLIGHT.
...FL EAST COAST...
SCATTERED THUNDERSTORMS ARE OCCURRING THIS MORNING OVER THE CENTRAL
FL PENINSULA. OTHER STORMS ARE LIKELY LATE THIS AFTERNOON ALONG THE
EAST COAST AS WESTERLY LOW LEVEL WINDS ENHANCE CONVERGENCE ALONG
THAT SEA BREEZE. MORNING RAOBS AT TBW/MFL SHOW SUBSTANTIAL CAPE/PW
VALUES AND THE PRESENCE OF SOME DRY AIR AT MID LEVELS. THIS WILL
HELP TO PROMOTE STRONG DOWNDRAFTS AND POTENTIAL WET MICROBURSTS THIS
AFTERNOON ALONG THE SEA BREEZE. SLIGHTLY LOWER WBZ/MELTING LEVELS
MAY ALSO AID IN THE RISK OF HAIL IN THE STRONGEST STORMS.
..HART/HURLBUT.. 06/27/2009
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