SWODY1
SPC AC 050550
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT SUN AUG 05 2007
VALID 051200Z - 061200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM IA EWD ACROSS THE MS
VALLEY/SRN GREAT LAKES/MIDWEST...
..SYNOPSIS...
COAST-TO-COAST BELT OF FASTER WLY FLOW WILL ARC NEWD FROM THE BASE
OF A WEST COAST TROUGH...ACROSS THE ROCKIES/NRN PLAINS AND CNTRL
CANADA...THEN GENERALLY EWD FROM THE GREAT LAKES TO THE NORTHEAST. A
STRONG SHORT WAVE TROUGH...EMBEDDED WITHIN THE FASTER WLY FLOW
ACROSS SASKATCHEWAN/MANITOBA...IS FORECAST TO TRACK EAST ACROSS
ONTARIO/QUEBEC WITH ASSOCIATED COLD FRONT SINKING ACROSS THE BORDER
FROM MT/ND EWD TO THE UPPER GREAT LAKES. WEAK HEIGHT FALLS EMANATING
FROM THE LARGER SCALE TROUGH OVER THE WRN U.S. WILL SPREAD INLAND
OVER THE NRN ROCKIES AND ENHANCE ASCENT ACROSS THE FRONT OVER
MT...AND PERHAPS ALONG LEE/THERMAL TROUGH/FRONT INTERSECTION OVER
THE DAKOTAS.
FARTHER SOUTH... BROAD WARM CONVEYOR BELT AND RESIDUAL SYNOPTIC
BOUNDARY WILL EXIST WITHIN WEAKER LARGE SCALE FLOW REGIME ON THE
NRN/ERN PERIPHERY OF SCNTRL U.S. UPPER RIDGE...FROM THE CNTRL HIGH
PLAINS EWD ACROSS THE MIDWEST AND INTO THE MID ATLANTIC. LOW
AMPLITUDE SHORT WAVE DISTURBANCES...SOME CONVECTIVELY-INDUCED AND
SUSTAINED...ARE LIKELY TO MAINTAIN LIFT AND FRONTAL WAVE DEVELOPMENT
MOVING EAST ALONG THIS BOUNDARY TODAY AND TONIGHT.
..UPPER MS VALLEY/GREAT LAKES/MIDWEST TO NORTHEAST LATE...
WEAKLY ORGANIZED MCS IS EXPECTED TO BE ONGOING EARLY TODAY ACROSS
PARTS OF THE UPPER MS VALLEY AND MIDWEST ON THE EDGE OF THE PLAINS
CAPPING INVERSION AND NOSE OF WSWLY LLJ/WARM CONVEYOR BELT. COLD
POOL/DIFFERENTIAL HEATING ASSOCIATED WITH THIS ACTIVITY WILL ACT TO
ENHANCE LOW LEVEL TEMPERATURE CONTRAST ACROSS RESIDUAL SYNOPTIC
FRONTAL ZONE...EMANATING FROM A WEAK FRONTAL WAVE/LOW OVER WI/IA
AREA EWD ACROSS IL/LOWER MI/IND/OH AREAS. DESPITE GENERALLY WARM MID
LEVEL TEMPERATURES AND WEAK LAPSE RATES...VERY MOIST BOUNDARY LAYER
AND DIURNAL HEATING IN THE WARM SECTOR WILL CONTRIBUTE TO THE
DEVELOPMENT OF STRONG INSTABILITY /MLCAPE 1500-2000 J PER KG/.
WITH HEATING AND PERSISTENT LOW LEVEL CONVERGENCE NEAR THE FRONT AND
LOW...CONVECTION SHOULD INCREASE IN COVERAGE AND INTENSITY NEAR
THESE FEATURES...AND ACROSS THE WARM SECTOR...GIVEN RELATIVELY
LIMITED INHIBITION EAST OF THE MS RIVER. ON THE LARGER
SCALE...DEEP-LAYER WLY/UNIDIRECTIONAL FLOW OF MOSTLY UNIFORM SPEED
IS EVIDENT IN FORECAST SOUNDINGS ACROSS THE WARM SECTOR. THIS WOULD
SUGGEST THAT STORMS IN THESE AREAS WOULD TEND TO BE WEAKLY ORGANIZED
AND MULTICELLULAR WITH SOME POTENTIAL FOR WET MICROBURSTS. NEAR THE
LOW AND FRONT...FROM IL ACROSS LOWER MI TO OH...LOW LEVEL SHEAR
PROFILES MAY PROVE MORE SUPPORTIVE OF STRONGER UPDRAFT
ROTATION...ESPECIALLY IN THOSE AREAS WHERE GREATER DESTABILIZATION
/LOW LEVEL UPDRAFT ACCELERATION/ IS REALIZED. SOME SUPERCELL OR
BOWING CHARACTERISTICS MAY EVOLVE FROM STORMS IN THESE AREAS WITH
ATTENDANT TORNADO/DAMAGING WIND AND HAIL THREATS.
SOME UPSCALE DEVELOPMENT OF THIS CONVECTION IS LIKELY THROUGH THE
NIGHTTIME HOURS FROM THE ERN GREAT LAKES EWD TO THE NORTHEAST AS
WAVE/LOW...AND ASSOCIATED LONG-LIVED MCV/SHORT WAVE TROUGH...BEGIN
TO PHASE WITH THE STRONGER SYSTEM ACROSS ERN CANADA. WHILE THE
CHANCE FOR TSTMS SHOULD INCREASE INTO THE NORTHEAST ON THE NOSE OF
INTENSIFYING LOW LEVEL JET...SEVERE POTENTIAL WITH THIS ACTIVITY
SHOULD DECREASE WITH EWD EXTENT AS CONVECTION BECOMES INCREASINGLY
REMOVED FROM STRONGER INSTABILITY RESIDING OVER THE MIDWEST AND
PLAINS.
..PLAINS WWD ACROSS ERN CO...
QUASI-STATIONARY WIND SHIFT BOUNDARY WILL EXTEND FROM THE LOW OVER
IA SWWD ACROSS NEB/KS AND THEN BACK INTO THE FRONT RANGE IN CO. WEAK
CONVERGENCE ALONG THE BOUNDARY...AND UPSLOPE FLOW IN CO...WILL
LIKELY AID CONVECTIVE DEVELOPMENT WITHIN INCREASINGLY UNSTABLE AIR
MASS. GENERALLY WEAK FLOW AND WARM TEMPERATURES ALOFT SHOULD LIMIT
STORM PERSISTENCE AND SEVERE THREAT. HOWEVER...A FEW STORMS NEAR THE
BOUNDARY...OR WITHIN WEAKLY VEERED FLOW ACROSS ERN CO...COULD
BRIEFLY ACHIEVE ROTATION WITH ISOLATED HAIL/HIGH WIND OR BRIEF
TORNADO EVENTS POSSIBLE.
..MID ATLANTIC...
SCATTERED TSTMS ARE FORECAST TO DEVELOP ACROSS THE APPALACHIANS AND
EWD TOWARD THE TIDEWATER/DELMARVA THIS AFTERNOON ALONG RESIDUAL
FRONTAL SEGMENT ACROSS THESE AREAS. AIR MASS CHARACTERISTICS WILL BE
SIMILAR TO POINTS WEST WITH WEAK LAPSE RATES BUT HIGH MOISTURE
CONTENT AND HEATING YIELDING STRONG DESTABILIZATION. WITH LOW-MID
LEVEL FLOW GENERALLY AOB 15 KT...EXPECT MESOSCALE BOUNDARY
INTERACTIONS TO POSSIBLY ENHANCE MULTICELL STORM ORGANIZATION WITH
ISOLATED CELLS PRODUCING LOCALLY STRONG TO DAMAGING WIND GUSTS.
LIMITED COVERAGE OF THIS THREAT DOES NOT APPEAR TO SUPPORT HIGHER
SEVERE PROBABILITIES AT THIS TIME.
..NRN PLAINS/MT...
STRONG INSTABILITY IS FORECAST NEAR FRONT/LEE TROUGH INTERSECTION
ACROSS THE WRN DAKOTAS DURING THE AFTERNOON. DEEP-LAYER ASCENT
ACROSS THIS REGION MAY BE FURTHER SUPPORTED BENEATH RIGHT ENTRANCE
REGION OF JET STREAK CROSSING SRN CANADA. HOWEVER..REGION DOES
REMAIN WITHIN RIDGING ALOFT WITH LIMITED LARGE SCALE HEIGHT FALLS.
NAM-WRF INDICATES THE POTENTIAL FOR ROBUST BUT CONCENTRATED STORM
DEVELOPMENT ACROSS THE WRN DAKOTAS THROUGH LATE IN THE PERIOD WHILE
ENSEMBLE GUIDANCE INDICATES LOWER PROBABILITY FOR DEVELOPMENT. IF
STORMS CAN FORM...SHEAR AND INSTABILITY WILL LIKELY BE SUFFICIENT
FOR SUPERCELLS. GIVEN SOME UNCERTAINTY AND TIMING ISSUES...ONLY LOW
PROBABILITY SEVERE WILL BE ISSUED FOR THIS CONDITIONAL THREAT.
HOWEVER...A SLGT RISK MAY BE NEEDED IN LATER OUTLOOKS.
FARTHER WEST...HIGH-BASED FAST MOVING CONVECTION MAY AGAIN ARISE
ACROSS THE HIGHER TERRAIN FROM ERN ID ACROSS WRN MT AND WY. WEAK
CONVECTIVE INSTABILITY ACROSS THESE AREAS SHOULD LIMIT OVERALL
SEVERE THREAT BUT A COUPLE STRONG TO SEVERE WIND GUSTS MAY OCCUR.
.CARBIN/JEWELL.. 08/05/2007
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