SWODY1
SPC AC 031947
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT FRI JUN 03 2011
VALID 032000Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MS
VALLEY AND GREAT LAKES REGION...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL GULF
COAST STATES...
SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR 20Z. THE FIRST
CHANGE IS TO CONSOLIDATE THE 30 PERCENT HAIL PROBABILITY WITH THE
SIGNIFICANT HAIL HATCHED AREA AND 5 PERCENT TORNADO PROBABILITY
WHERE THE MODELS ARE IN AGREEMENT CONCERNING CONVECTIVE DEVELOPMENT.
THIS AREA IS ALSO COINCIDENT WITH THE STRONGEST COMBINATION OF
INSTABILITY AND DEEP LAYER SHEAR. HAVE ORIENTED THE 30 PERCENT WIND
DAMAGE PROBABILITY SLIGHTLY DOWNSTREAM OF THE GREATEST HAIL
PROBABILITIES WHERE LINEAR MCD DEVELOPMENT WILL BE MOST LIKELY EARLY
THIS EVENING. ANOTHER CHANGE TO THE OUTLOOK IS TO REMOVE NE
AL...MUCH OF GA AND WRN SC FROM THE SLIGHT RISK AREA WHERE
CONVECTION HAS YET TO INITIATE. HAVE CONCENTRATED THE SLIGHT RISK
AREA ACROSS SRN AND CNTRL AL AND SW GA WHERE MESOANALYSIS SHOWS
STRONG INSTABILITY AND SOME MODEL FORECAST INITIATE SCATTERED STORMS
THIS AFTERNOON. HAVE LEFT A 5 PERCENT PROBABILITY OF WIND DAMAGE AND
HAIL ACROSS THE AREA OF THE SLIGHT RISK AREA THAT WAS REMOVED. OTHER
THAN THESE CHANGES...HAVE REMOVED THUNDER FROM MUCH OF THE LOWER TO
MS VALLEY AND ACROSS PARTS OF THE TN VALLEY WHERE CONVECTION IS NOT
FORECAST BY MOST OF THE MODEL FORECASTS.
..BROYLES.. 06/03/2011
.PREV DISCUSSION... /ISSUED 1112 AM CDT FRI JUN 03 2011/
...SYNOPSIS...
E OF THE DEEPENING COLD LOW OFF CA COAST TO LOW OVER
SASKATCHEWAN/MANITOBA THERE IS A BROAD SWLY FLOW. DOWNSTREAM FULL
LATITUDE RIDGE MOVES ONLY SLOWLY EWD ACROSS WRN GREAT LAKES WITH
UPPER HIGH REMAINING OVER AR.
N/S COLD FRONT MOVING INTO WRN MN FROM WHERE IT EXTENDS SWWD ACROSS
NEB INTO SERN CO. A WEAK WAVE ALONG THE COLD FRONT IN W CENTRAL MN
WITH A WARM FRONT TRAILING SEWD ACROSS SWRN WI AND WILL BE LIFTING
NWD THU THE AFTERNOON ALLOWING A MOIST AND INCREASINGLY UNSTABLE AIR
MASS TO SPREAD ACROSS ERN MN INTO WI.
...UPR MS VLY/WRN GRT LKS THIS AFTN THROUGH TNGT...
CONSIDERABLE CLOUD COVER REMAINING FROM OVERNIGHT CONVECTION WILL
CONTINUE TO THIN ACROSS ERN MN/NRN WI INTO THE AFTERNOON ALLOWING
STRONG HEATING/DESTABILIZATION TO OCCUR AHEAD OF THE COLD FRONT
ACROSS THE EXPANDING WARM SECTOR.
THE COMBINATION OF STEEP MID LEVEL LAPSE RATES AND DEWPOINTS RISING
TO AROUND 70F WILL LEAD TO MDT/STG INSTABILITY BY MID AFTERNOON WITH
MLCAPES TO AOA 3000 J/KG. WITH THE PRONOUNCED EML ACROSS THE
AREA...TIMING OF SURFACE INITIATION OF SEVERE THUNDERSTORMS IS A
CONCERN AND APPEARS SHOULD BE DELAYED TO MID OR LATE AFTERNOON.
LACK OF ANY SUBSTANTIAL UPPER FORCING WITH THE SWLY FLOW WILL LIKELY
REQUIRE FULL HEATING TO OVERCOME THE CAPPING NOW IN PLACE.
ONCE STORMS FORM...40-50 KT DEEP WSWLY SHEAR AND STEEP MID LVL LAPSE
RATES SHOULD SUPPORT SUPERCELLS/SUSTAINED STORMS WITH LARGE
HAIL...DMGG WIND...AND POSSIBLY TORNADOES. THE LATTER THREAT SHOULD
BE GREATEST IN NRN WI...WHERE LOW LVL SRH SHOULD BE MAXIMIZED IN
ZONE OF LOW LCLS NEAR THE WARM FRONT.
BY EARLY TONIGHT...EXPECT STORMS TO MERGE INTO ONE OR MCS/S. WIND
PROFILES AND THERMODYNAMIC ENVIRONMENT APPEAR FAVORABLE FOR BOWING
SEGMENTS WITH AN INCREASING THREAT DMGG WIND IN WI AND POSSIBLY NRN
MI.
...ERN GULF CST STATES/GA/SC THIS AFTN/EVE...
MODERATE TO STRONG INSTABILITY WILL ONCE AGAIN DEVELOP WITHIN A
HOT/MOIST AIR MASS OVER MUCH OF THE SOUTHEAST THIS AFTERNOON. SFC
HEATING AND TERRAIN CIRCULATIONS SHOULD INITIATE SCTD AREAS OF
STORMS BY MID-AFTERNOON IN WEAKLY CAPPED ENVIRONMENT. GIVEN STEEP
LOW/MID-LVL LAPSE RATES AND 20+ KT MID LVL FLOW...A FEW MULTICELL
CLUSTERS WITH SVR HAIL/LOCALLY DMGG WIND INTO THIS EVE.
..CNTRL PLNS LT THIS AFTN THROUGH TNGT...
MODERATE INSTABILITY SHOULD DEVELOP TODAY AHEAD OF CNTRL PLNS PART
OF COLD FRONT. WARM MID LVL TEMPS WILL DELAY STORM DEVELOPMENT
UNTIL LATE IN THE DAY. ISOLD STORMS LATE THIS AFTN/EVE COULD YIELD
DMGG WIND FROM ERN CO INTO WRN KS/SW NEB GIVEN DEEPLY MIXED BOUNDARY
LAYER. STORM COVERAGE SHOULD INCREASE AFTER SUNSET AS FORCING FOR
ASCENT IS AUGMENTED BY DEVELOPING JET ENTRANCE REGION ALOFT...AND BY
NOCTURNAL STRENGTHENING OF SSWLY LLJ. AS STORMS SPREAD N/NE ALONG
AND N OF FRONT...THEY MAY EVOLVE INTO AN MCS WITH AN ATTENDANT
THREAT FOR HAIL AND PERHAPS LOCALLY DMGG WIND. HOWEVER...RELATIVELY
WARM MID LVL TEMPS /AROUND MINUS 10C AT 500 MB/ AND CONGEALING OF
STORMS SHOULD LIMIT OVERALL INTENSITY AND DURATION OF SVR THREAT.
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