SWODY1
SPC AC 061619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT WED JUN 06 2007
VALID 061630Z - 071200Z
..THERE IS A MDT RISK OF SVR TSTMS OVER A LARGE PORTION OF THE
DAKOTAS...CENTRAL AND NORTHEAST NEBRASKA AND WESTERN MINNESOTA...
..THERE IS A SLGT RISK OF SVR TSTMS INTO THE CENTRAL AND NRN PLAINS
TOWARD THE UPPER MS RIVER VALLEY...
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF FL...
..SYNOPSIS...
POWERFUL LATE SPRING STORM OVER INTERMOUNTAIN REGION DRIVES ENEWD
INTO NRN/CENTRAL PLAINS TONIGHT. DEEPENING SURFACE LOW SCENTRAL WY
WILL CONTINUE TO INTENSIFY AS IT TRACKS INTO WRN SD BY LATE THIS
AFTERNOON. THE ATTENDANT STRONG COLD FRONT CURRENTLY FROM NEAR RKS
SWD ALONG UT/CO BORDER INTO NWRN AZ CONTINUES EWD AND REACHES THE
HIGH PLAINS BY LATE THIS AFTERNOON.
VERY STRONG MID /80KT AT 500MB/ AND UPPER /140KT AT 300MB/ JET SRN
INTERMOUNTAIN REGION CONTINUES ENEWD CROSSING THE SRN ROCKIES THIS
AFTERNOON AND THEN WELL OUT INTO THE CENTRAL PLAINS OVERNIGHT.
A PRONOUNCED N/S HIGH PLAINS DRY LINE WILL SET UP DURING THE
AFTERNOON LOCATED FROM NWRN NEB SWD JUST E OF CO/KS BORDER INTO SWRN
TX. AN ELEVATED MIX LAYER HAS OVERSPREAD THE HIGH PLAINS AND WILL
EFFECTIVELY CAP THE ATMOSPHERE E OF DRY LINE MUCH OF THE AFTERNOON.
SLY 40-50 KT LOW LEVEL JET E OF DRY LINE WILL TRANSPORT GULF
MOISTURE NWD UNDER THE CAP THRU THE DAY WITH STRONG INSTABILITY
DEVELOPING.
..NRN PLAINS...
ALL PARAMETERS WILL BE IN PLACE FOR AN OUTBREAK OF SEVERE
THUNDERSTORM COMMENCING BY MID AFTERNOON AS THE COLD FRONT REACHES
THE LOCATION OF THE HIGH PLAINS DRY LINE. INITIAL DEVELOPMENT OF
SEVERE THUNDERSTORMS EXPECTED JUST TO THE N OF TRACK OF SURFACE LOW
ACROSS NERN WY/SERN MT WHERE NLY COMPONENT OF BOUNDARY LAYER FLOW
WILL MAINTAIN SUFFICIENT LOW LEVEL MOISTURE/INSTABILITY. THIS SHOULD
OCCUR BETWEEN 18-20Z AND THEN STORMS WILL RAPIDLY EXPAND E AND SE AS
THE STRONG COLD FRONT PLOWS INTO THE... BY THEN... MDTLY UNSTABLE
AIR MASS IN PLACE E OF DRY LINE WITH MLCAPES IN EXCESS OF 2000 J/KG.
SUPERCELLS WILL BE MOST LIKELY EARLY IN THE SEVERE EPISODE WITH BOTH
TORNADOES AND LARGE HAIL GIVEN AVAILABLE SHEAR AND CAPE. HOWEVER
ALL THE MODELS GENERATE A VERY STRONG SQUALL LINE SIGNAL BY THIS
EVENING...WHICH SEEMS REASONABLE GIVEN THE INTENSITY OF THE STORM
THAT DEVELOPS INTO THE NRN PLAINS. A DERECHO TYPE EVENT CERTAINLY
SEEMS A REAL POSSIBILITY WHICH WILL INCLUDE WIDESPREAD POSSIBLY
SIGNIFICANT WIND DAMAGE RACING NEWD ACROSS THE DAKOTAS INTO WRN MN
OVERNIGHT.
..CENTRAL PLAINS...
INHIBITION EXPECTED TO HOLD OFF STORM INITIATION CENTRAL HIGH PLAINS
MUCH OF THE AFTERNOON. HOWEVER PRIOR TO 00Z AS THE INTENSE
MID/UPPER JET AND COLD FRONT MOVES EWD INTO THE CENTRAL HIGH
PLAINS...ACCOMPANIED BY STRONG SYNOPTIC SCALE ASCENT AND MID LEVEL
COOLING...THE CAP SHOULD BEGIN TO ERODE. WHILE THE AIRMASS AND
SHEAR WILL BE VERY FAVORABLE ALONG AND E OF THE DRY LINE FOR
SUPERCELLS INCLUDING TORNADOES AND LARGE HAIL...THERE IS
CONSIDERABLE UNCERTAINLY HOW MANY STORMS WILL BE ABLE TO DEVELOP.
THE GREATER THREAT THIS EVENING EXPECTED ACR0SS CENTRAL NEB WITH A
MORE CONDITIONAL THREAT SWD INTO KS.
..SERN U.S...
12Z SOUNDINGS FROM MFL AND TBW INDICATE TODAY SHOULD BE QUITE ACTIVE
WITH THUNDERSTORMS INCREASING IN COVERAGE AND INTENSITY ACROSS MUCH
OF THE FL PENINSULA THIS AFTERNOON. THIS WILL OCCUR AHEAD OF WEAK
SHORTWAVE TROUGH SHEARING APART OVERNIGHT OVER THE GULF OF MEXICO.
MLCAPES ARE ALREADY IN EXCESS OF 2000 J/KG WITH LITTLE OR NO CAPPING
OVER MUCH OF THE CENTRAL/SRN FL PEN. DEEP LAYER SHEAR REMAINS WEAK
OVER SRN FL...BUT 12Z SOUNDINGS AT JAX/TLH INDICATE STRONGER SHEAR
INTO NRN FL. THUS A FEW ORGANIZED CLUSTERS/STORMS...INCLUDING
SUPERCELLS...MAY SUPPORT HIGHER SEVERE PROBABILITIES AND SLGT RISK
OVER THIS REGION.
.HALES/BRIGHT.. 06/06/2007
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