SPC AC 151239
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0739 AM CDT MON JUN 15 2009
VALID 151300Z - 161200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
ACROSS MUCH OF KS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL
PLAINS...ACROSS THE MID MS VALLEY...INTO THE CAROLINAS...
A BROAD UPPER TROUGH IS IN PLACE TODAY OVER THE SOUTHWEST U.S. WHILE
A BAND OF MODERATELY STRONG WEST-SOUTHWESTERLY FLOW EXTENDS ACROSS
THE CENTRAL PLAINS INTO THE MID MS VALLEY. SEVERAL WEAK SHORTWAVE
TROUGHS ARE EMBEDDED IN THIS FLOW PATTERN...AND WILL AID IN THE
DEVELOPMENT OF MULTIPLE ROUNDS OF STRONG/SEVERE STORMS TODAY FROM
THE HIGH PLAINS INTO THE TN VALLEY. OTHER MORE ISOLATED SEVERE
STORMS ARE POSSIBLE AS FAR EAST AS THE CAROLINAS...AND OVER PARTS OF
PA/NY/NEW ENGLAND.
...MO/AR/IL/KY/TN...
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE OCCURRING THIS MORNING
ACROSS MUCH OF NORTHERN AND EASTERN MO. THESE STORMS ARE IN A
REGION OF STRONG LOW LEVEL WARM/MOIST ADVECTION. A SMALLER SCALE
BOW ECHO IS CURRENTLY TRACKING EAST-SOUTHEASTWARD ACROSS EASTERN KS
AND WILL LIKELY PROPAGATE DOWN THE WEST EDGE OF THE AFOREMENTIONED
PRECIPITATION SHIELD THROUGH MUCH OF THE DAY. AT ITS PRESENT
SPEED...THESE STORMS WILL BE OVER CENTRAL MO AROUND MIDDAY...AND
EVENTUALLY INTO WESTERN KY/TN BY EVENING. MODEL GUIDANCE IS
INCONSISTENT IN THE EVOLUTION OF THIS MCS...BUT MODERATE INSTABILITY
ALONG AND SOUTH OF THE PROJECTED PATH COUPLED WITH FAVORABLE
WESTERLY FLOW ALOFT WILL POSE A RISK OF INTENSIFICATION AND THE
THREAT OF DAMAGING WINDS AND HAIL.
...CENTRAL PLAINS...
A SURFACE LOW IS FORECAST TO DEEPEN THIS AFTERNOON OVER SOUTHWEST
KS...WITH EASTERLY LOW LEVEL WINDS BEING MAINTAINED NORTH OF LOW
ACROSS MUCH OF WESTERN KS. MEANWHILE...STRONG HEATING WILL OCCUR
WEST OF THE DRYLINE NEAR THE KS/CO BORDER YIELDING AFTERNOON MLCAPE
VALUES OF 2000-3000 J/KG. THE CAPPING INVERSION IS EXPECTED TO BE
ELIMINATED BY MID/LATE AFTERNOON ALONG THE DRYLINE...WITH ISOLATED
THUNDERSTORM DEVELOPMENT LIKELY. STORMS WILL MOVE INTO A VERY MOIST
LOW LEVEL AIRMASS WITH SUFFICIENT DEEP LAYER EFFECTIVE SHEAR TO
PROMOTE SUPERCELL STORM STRUCTURES. BACKED LOW LEVEL WINDS AND
SUFFICIENT LOW LEVEL SHEAR WILL ALSO POSE A RISK OF A FEW TORNADOES
DURING THE EARLY EVENING. HOWEVER...THE MAIN THREATS APPEAR TO BE
VERY LARGE HAIL AND DAMAGING WINDS AS STORMS ORGANIZE AND TRACK
EASTWARD ACROSS MUCH OF KS. AGREEMENT BETWEEN OPERATIONAL AND
MESOSCALE MODEL GUIDANCE...ALONG WITH LATEST OBSERVATIONAL
DATA...APPEAR SUFFICIENT TO PROVIDE CONFIDENCE IN UPGRADE TO A
CATEGORICAL MODERATE RISK FOR MUCH OF KS.
...WESTERN SD/NEB...
SIMILAR TO YESTERDAY...IT APPEARS LIKELY THAT SCATTERED
THUNDERSTORMS WILL DEVELOP AGAIN THIS AFTERNOON AND EVENING FROM THE
BLACK HILLS SOUTHWARD INTO WESTERN NEB. STEEP LOW/MID LEVEL LAPSE
RATES AND 25-40 KNOTS OF EFFECTIVE SHEAR WILL PROMOTE SUPERCELLS
CAPABLE OF LARGE HAIL AND PERHAPS ISOLATED TORNADOES.
...CAROLINAS...
A BROAD AREA OF 30-35 KNOT WESTERLY MID LEVEL WINDS WILL BE PRESENT
TODAY OVER THE CAROLINAS. DESPITE WEAK LOW LEVEL WINDS...THIS WILL
PROVIDE SUFFICIENT DEEP LAYER SHEAR TO SUPPORT ORGANIZED MULTICELL
STORMS CAPABLE OF LOCALLY DAMAGING WINDS AND HAIL THIS AFTERNOON.
STORMS SHOULD WEAKEN RAPIDLY AROUND SUNSET WITH THE LOSS OF DAYTIME
HEATING.
...NY/PA/VT/MA/CT...
COOL MID LEVEL TEMPERATURES ASSOCIATED WITH AN UPPER TROUGH OVER THE
NORTHEAST UNITED STATES WILL PROVIDE RELATIVELY STEEP MID LEVEL
LAPSE RATES THIS AFTERNOON OVER PARTS OF NY/PA AND WESTERN NEW
ENGLAND. A FEW CELLS COULD BECOME STRONG/SEVERE WITH A RISK OF HAIL
AND GUSTY/DAMAGING WINDS. ACTIVITY IS EXPECTED TO REMAIN RATHER
ISOLATED AND DISORGANIZED AT THIS TIME.
..HART/JEWELL.. 06/15/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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