SWODY1
SPC AC 180100
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0800 PM CDT FRI AUG 17 2007
VALID 180100Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS TONIGHT ACROSS PARTS OF THE
NORTHERN PLAINS....
..NORTHERN PLAINS...
A CLUSTER OF STORMS CONTINUES TO DEVELOP/INTENSIFY NEAR A SURFACE
LOW ACROSS WESTERN SOUTH DAKOTA. THIS IS BEING SUPPORTED BY FORCING
ASSOCIATED WITH A SHORT WAVE IMPULSE PROGRESSING THROUGH THE CREST
OF A BROADER SCALE UPPER RIDGE ACROSS THE NORTHERN ROCKIES/PLAINS.
AS THE UPPER IMPULSE CONTINUES EASTWARD THIS EVENING...AND A
SOUTHERLY LOW-LEVEL JET STRENGTHENS TO 40-50 KTS INTO THE VICINITY
OF A FRONTAL ZONE EXTENDING EAST SOUTHEAST OF THE LOW...THE
EVOLUTION OF A SIZABLE MESOSCALE CONVECTIVE SYSTEM APPEARS POSSIBLE.
ALTHOUGH FLOW FIELDS ARE ONLY WEAK TO MODERATE IN
STRENGTH...VEERING FROM AN EASTERLY COMPONENT NEAR THE SURFACE TO
WESTERLY AT MID-LEVELS IS CREATING STRONG DEEP LAYER SHEAR WHICH
WILL AID ORGANIZATION IN A WEAK TO MODERATELY UNSTABLE ENVIRONMENT.
AND...THERMODYNAMIC PROFILES APPEAR UNSATURATED ENOUGH TO PROMOTE A
GROWING SURFACE COLD POOL IN RESPONSE TO EVAPORATIVE COOLING.
THE RISK FOR DAMAGING WINDS IS EXPECTED ACROSS MUCH OF
WESTERN/CENTRAL SOUTH DAKOTA BEFORE SYSTEM FINALLY BEGINS TO WEAKEN
AS IT SPREADS TOWARD THE MID MISSOURI VALLEY AFTER 06Z.
HOWEVER...THREAT FOR LARGE HAIL MAY CONTINUE INTO THE OVERNIGHT
HOURS...AS ADDITIONAL STORMS DEVELOP DOWNSTREAM OF CONVECTIVE
SYSTEM...IN LOW-LEVEL WARM ADVECTION REGIME ALONG RETREATING FRONTAL
ZONE ACROSS THE MID MISSOURI VALLEY.
..NORTHEAST...
VIGOROUS CONVECTIVE DEVELOPMENT IS ONGOING AHEAD OF A SURFACE FRONT
ADVANCING ACROSS NORTHERN MID ATLANTIC COASTAL AREAS THIS EVENING.
THIS IS BEING AIDED BY FORCING ASSOCIATED WITH A 70-90 KT
NORTHWESTERLY 500 MB JET STREAK DIGGING SOUTHEAST OF THE LOWER GREAT
LAKES REGION. BULK OF ACTIVITY IS ALREADY SPREADING OFFSHORE...BUT
AN ISOLATED STRONG/SEVERE STORM IS STILL POSSIBLE ACROSS PARTS OF
CENTRAL/SOUTHERN NEW JERSEY THROUGH THE 02-03Z TIME FRAME.
..SOUTHEAST...
A LARGE BUT DISORGANIZED CLUSTER OF STORMS DEVELOPING SOUTHWARD
ACROSS SOUTHERN GEORGIA/SOUTHEAST ALABAMA IS EXPECTED TO RAPIDLY
WEAKEN BY 02-03Z. THIS WILL OCCUR MOSTLY IN RESPONSE TO
STABILIZATION ASSOCIATED WITH LOSS OF DAYTIME HEATING...BUT THE AIR
MASS ACROSS NORTHERN FLORIDA INTO PARTS OF SOUTHERN ALABAMA/GEORGIA
HAS ALSO BEEN COOLED/STABILIZED BY SEA BREEZE.
**FOR MORE SPECIFIC INFORMATION CONCERNING ONGOING STORMS...PLEASE
REFER TO THE LASTEST SPC MESOSCALE DISCUSSIONS.
.KERR.. 08/18/2007
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