ACUS01 KWNS 252000
SWODY1
SPC AC 251959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT FRI JUN 25 2010
VALID 252000Z - 261200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF SRN MN...NRN
IA...AND WEST CENTRAL/SWRN WI...
...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM THE NRN PLAINS
SEWD INTO THE UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN EXTENT OF THE
CENTRAL GULF COAST STATES TO THE SERN STATES...
...PART OF MID MO AND UPPER MS VALLEYS/WRN GREAT LAKES...
A SMALL SWD EXPANSION OF THE SLIGHT/MODERATE RISK AREAS HAS BEEN
MADE WITH THIS OUTLOOK ISSUANCE FROM FAR NERN NEB ACROSS NRN AND
CENTRAL IA....WHILE PORTIONS OF EAST CENTRAL MN /MILLE LACS REGION/
EWD INTO NRN/ERN WI HAVE BEEN REMOVED FROM THE SLIGHT RISK.
THE SRN MODIFICATION IS DUE TO ONGOING STRONG DESTABILIZATION ACROSS
THE MID MO VALLEY WHICH IS EXPECTED TO AID IN EVENTUAL BACKBUILDING
OF AN MCS THAT IS PROGGED TO DEVELOP BY EVENING OVER ERN SD/SRN MN.
ALTHOUGH WLY FLOW ALOFT SHOULD SUPPORT AN ESEWD PROPAGATION OF THE
MCS INTO PARTS OF WRN/SWRN WI AND NWRN IL TONIGHT...THE RESERVOIR OF
VERY STRONG INSTABILITY AND STRENGTHENING SWLY LLJ INTO IA WILL
FAVOR BACKBUILDING ALONG SWRN/SRN FLANK OF THE MCS. THESE TRENDS
ARE SUPPORTED BY THE 12Z NAM/15Z HRRR. FARTHER N FROM MILLE LACS
AREA OF MN INTO NRN/ERN WI...WEAKER INSTABILITY SHOULD LIMIT THE
SEVERE WEATHER THREAT ACROSS THESE AREAS.
FOR ADDITIONAL MESOSCALE DETAILS...REFER TO SPC MESOSCALE
DISCUSSIONS 1121 /FOR WEST CENTRAL/SRN ND AND NRN SD/...1123 /FOR
ERN SD...SRN MN...AND EXTREME NWRN IA/...AND SUBSEQUENT WATCHES/
DISCUSSIONS.
...SERN STATES WWD TO SERN OK AND CENTRAL/ERN TX...
SLIGHT RISK AREA HAS BEEN EXTENDED SWD INTO SRN GA/FAR NRN FL AND
WWD INTO MORE OF NRN MS...GIVEN RECENT REGIONAL RADAR TRENDS OF
ONGOING TSTM COVERAGE WITHIN A VERY UNSTABLE AIR MASS /MLCAPE
3000-4000 J PER KG/. DAMAGING WIND AND HAIL WILL REMAIN THE PRIMARY
THREATS THROUGH EARLY EVENING. 5 PERCENT HAIL/WIND PROBABILITIES
HAVE BEEN ADJUSTED FARTHER WEST ACROSS PARTS OF NRN/ERN TX DUE TO
TRENDS IN REGIONAL RADAR IMAGERY WITH ONGOING ACTIVITY WITHIN AN
UNSTABLE/WEAKLY SHEARED ENVIRONMENT.
..PETERS.. 06/25/2010
.PREV DISCUSSION... /ISSUED 1130 AM CDT FRI JUN 25 2010/
...ERN DAKOTAS ACROSS MN TO NRN IA AND WI...
LEADING SHORTWAVE TROUGH...EMBEDDED WITHIN A BAND OF FASTER WLY MID
LEVEL FLOW...WAS MOVING EWD THROUGH MN/ERN SD THIS MORNING...WHILE
ANOTHER SHORT WAVE TROUGH WAS LOCATED IN MT. CONSIDERABLE CLOUDS AND
SCATTERED CONVECTION/PCPN STRETCHED FROM THE MN ARROWHEAD/NWRN WI
SWWD BACK TO NEAR THE ERN SD/ND BORDER. IN THE WAKE OF THIS LEAD
SHORTWAVE TROUGH...CONVECTION IS EXPECTED TO REMAIN WEAK OR ELEVATED
DUE TO WEAK SHORTWAVE RIDGING/ STRENGTHENING CAPPING INVERSION.
HOWEVER...DEEP LAYER SHEAR IN CLOUD BEARING LAYER AND MUCAPES AROUND
1500 J/KG MAY SUPPORT A FEW ELEVATED STORMS WITH MARGINALLY SEVERE
HAIL INTO THE AFTERNOON HOURS.
AS UPPER WAVE AND LARGE SCALE ASCENT APPROACHES FROM THE WEST THIS
AFTERNOON...MODELS ARE FAIRLY CONSISTENT ON STORMS DEVELOPING NEAR
REMNANT OUTFLOW BOUNDARY...WHICH IS EXPECTED TO REMAIN
QUASI-STATIONARY FROM NRN SD EWD INTO CENTRAL MN. ALSO...A WEAK
SURFACE LOW WAS LOCATED IN WRN SD AND SHOULD DRIFT EWD ALONG THE
BOUNDARY INTO ERN SD. THE ENHANCED CONVERGENCE ALONG BOUNDARY
...ESPECIALLY AHEAD OF SURFACE LOW...AND DIURNAL DESTABILIZATION OF
MOIST BOUNDARY LAYER FAVORS SURFACE BASED STORMS FORMING BY MID/LATE
AFTERNOON. GIVEN THE COMBINATION OF STRONG INSTABILITY AND 50 KT
BULK SHEAR...SUPERCELLS WITH VERY LARGE HAIL AND HIGH WINDS ARE
LIKELY SHORTLY AFTER INITIATION. ALSO...THE MOISTENING BOUNDARY
LAYER AND STRONGER LOW LEVEL SHEAR ALONG BOUNDARY MAY YIELD A
TORNADO OR TWO...GENERALLY IN THE WRN PORTION OF THE MDT RISK AREA.
A FEW HOURS AFTER STORMS DEVELOP...STRONG OUTFLOWS FROM STORMS ARE
EXPECTED TO EVOLVE INTO AN MCS. ALTHOUGH THE MEAN FLOW WOULD SUPPORT
A MORE EWD MOTION OF MCS...COMBINATION OF STRENGTHENING LOW LEVEL
JET FROM SRN NEB NEWD INTO SERN MN/WRN WI AND VERY STRONG
INSTABILITY AXIS OVER ERN SD/NEB WOULD SUPPORT THE SYSTEM MOVING
MORE SEWD THAN EWD. THEREFORE THE MODERATE RISK AND THREAT FOR
DAMAGING WINDS...WITH SOME CONVECTIVE GUSTS POSSIBLY A0A 80
MPH...HAS BEEN SHIFTED SEWD ON THE ERN END.
...CAROLINAS WWD ACROSS THE TN VALLEY TO THE SRN PLAINS...
WEAK FRONTAL BOUNDARY STRETCHED FROM THE ERN CAROLINAS WWD INTO NRN
AL/MS. STRONG HEATING...TEMPERATURES WARMING INTO THE MID 90S ACROSS
MOST OF THE AREA...OF THE VERY MOIST BOUNDARY LAYER... DEWPOINTS IN
THE MID 70S...SHOULD CONTRIBUTE TO NUMEROUS STORMS THIS AFTERNOON. A
BAND OF WNWLY 15-20KT FLOW ALOFT...COUPLED WITH VARIOUS SUBTLE
BOUNDARIES...MAY CONTRIBUTE TO SOME STORM ORGANIZATION. BRIEF AND
SPORADIC WIND DAMAGE SHOULD BE THE MAIN THREAT.
ELSEWHERE...WEAK VERTICAL SHEAR BUT STRONG INSTABILITY WILL SUPPORT
ISOLD/RANDOM WET MICROBURSTS DURING THE AFTERNOON.
...INTERIOR NORTHWEST/NRN ROCKIES...
ALL MODELS ARE CONSISTENT IN FORECASTING THUNDERSTORMS INCREASING IN
A SW-NE ORIENTED SWATH FROM NRN CA NEWD INTO WRN MT. WHILE
INSTABILITY IS NOT FORECAST TO BE PARTICULARLY STRONG...MLCAPES AOB
1000 J/KG AND A WEAK FRONTAL ZONE MAY SUPPORT A FEW PERSISTENT
STORMS WITH MARGINAL HAIL AND WIND POTENTIAL.
...FOUR CORNERS REGION...
DIURNAL HEATING COUPLED WITH MID LEVEL VORTICITY CENTER LOCATED ON
WRN FLANK OF SUBTROPICAL RIDGE OVER ERN AZ...WILL LIKELY AID IN HIGH
BASED AFTERNOON TSTMS. GIVEN 20-30 KT MID LEVEL SLY WINDS WITHIN
DEEPLY MIXED/DRY BOUNDARY LAYER...A POTENTIAL EXISTS FOR
STRONG/GUSTY SURFACE WINDS.
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