SWODY1
SPC AC 052000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SUN JUL 05 2009
VALID 052000Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL HIGH
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GULF COAST
STATES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN
KY...TN...NRN AL AND NW GA...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE ERN
CAROLINAS...
FOR THIS 20Z OUTLOOK ISSUANCE...THE MOST SIGNIFICANT CHANGE IS TO
SMALLIFY THE SLIGHT RISK AREA OVER THE GULF COAST STATES. A GAP IN
THE SLIGHT IS INTRODUCED OVER PARTS OF SC WHERE RUC ANALYSIS
SUGGESTS MODERATE INSTABILITY HAS FAILED TO DEVELOP THIS AFTERNOON.
FURTHER NORTHEAST ALONG THE COASTS OF SC AND NC...MODERATE
INSTABILITY IS ALREADY IN PLACE. AS A SFC LOW TRACKS EWD TOWARD THIS
AREA THIS EVENING...THE VERTICAL SHEAR ENVIRONMENT MAY SUPPORT AN
ISOLATED SUPERCELL THREAT SO LEFT THE SLIGHT ALONG THE COASTS. THE
SRN FRINGE OF THE SLIGHT OVER THE GULF COAST STATES HAS BEEN TRIMMED
NEAR THE IMMEDIATE GULF COAST WHERE FORECAST SOUNDINGS AND WSR-88D
VWPS SHOW VERY WEAK FLOW THROUGH A DEEP LAYER. IN ADDITION...REMOVED
THE SLIGHT OVER CNTRL TX WHERE WEAK VERTICAL SHEAR IS ALSO EVIDENT.
A FEW MARGINALLY SEVERE PULSE STORMS MAY STILL OCCUR IN THE 5
PERCENT AREA OVER ECNTRL TX DUE TO THE MODERATE TO STRONG
INSTABILITY ALREADY IN PLACE. THE FOURTH CHANGE IS TO TRIM THE
SLIGHT RISK AREA IN KY AND TN BEHIND THE COLD FRONT ONGOING WITH THE
CURRENT CONVECTION. LASTLY...ADJUSTED THE 5 PERCENT LINES TO BETTER
ACCOUNT FOR REGIONAL VARIATIONS IN INSTABILITY ANALYZED BY THE RUC
AND TO ACCOUNT FOR CURRENT RADAR DEPICTIONS.
..BROYLES.. 07/05/2009
.PREV DISCUSSION... /ISSUED 1202 PM CDT SUN JUL 05 2009/
...AMENDED OUTLOOK TO INCLUDE PARTS OF KY/TN IN SLGT RISK AREA...
...KY/TN...
STORMS DEVELOPING AHEAD OF SURFACE LOW AND WITHIN GRADUALLY
DESTABILIZING AIRMASS MAY INTENSIFY THROUGH THE AFTERNOON. POCKET OF
GREAT SHEAR COINCIDENT WITH THIS RECENT CONVECTIVE DEVELOPMENT WOULD
SUGGEST SOME SUPERCELL POTENTIAL AND ATTENDANT THREATS OF HAIL AND
DAMAGING WINDS AS LINES/CLUSTERS OF STORMS INCREASE AND SPREAD ESEWD
WITH THE WEAK SURFACE LOW/WAVE.
...TX EWD ACROSS GULF STATES TO SOUTHEAST...
NUMEROUS TSTM OUTFLOW BOUNDARIES PRECEED DEEP-LAYER SYNOPTIC COLD
FRONT FROM TX ACROSS THE LOWER MS VALLEY TO GA/AL. A MOIST AND
INCREASINGLY UNSTABLE AIR MASS IN ADVANCE OF THESE WEAKLY
CONVERGENCE SURFACE BOUNDARIES...COUPLED WITH MODEST LARGE SCALE
ASCENT/HEIGHT FALLS ACROSS THIS EXTENSIVE REGION...WILL LEAD TO AN
INCREASE IN TSTM COVERAGE AND INTENSITY THROUGH TODAY. WHILE MID
LEVEL LAPSE RATES WILL REMAIN MARGINAL FOR MORE ROBUST STORM
UPDRAFTS...AREAS OF INTENSE HEATING WILL RESULT IN HIGH DCAPE VALUES
IN EXCESS OF 1000 J PER KG. DAMAGING WET DOWNBURSTS ALONG WITH HEAVY
RAIN WILL BE THE PRIMARY THREATS AS STORMS AND STORM CLUSTERS
DEVELOP THROUGH THE AFTERNOON. MULTICELLULAR DEEP CONVECTION SHOULD
GENERATE A FEW LARGER COLD POOLS INTO LATE AFTERNOON/EARLY EVENING
WITH DEEP-LAYER WLY FLOW 20-30KT PROVING SUFFICIENT FOR SOME BOWING
SEGMENTS AND A PERSISTING/LOCAL WIND DAMAGE THREAT.
...UPSLOPE AREAS OF CENTRAL ROCKIES...
MOIST UPSLOPE FLOW AND DIFFERENTIAL HEATING WILL AGAIN CONTRIBUTE TO
WIDESPREAD TSTM DEVELOPMENT ACROSS THE ROCKIES TODAY. VEERING
PROFILES IN LOWER PART OF STORM UPDRAFTS AND BELT OF SLIGHTLY STRONG
MID-LEVEL FLOW FORECAST ACROSS FRONT RANGE FROM WY TO NRN NM COULD
SUPPORT A FEW SUPERCELLS WITH POTENTIAL FOR LARGE HAIL AND DAMAGING
DOWNBURST WINDS. FORECAST PROFILES INDICATE A SSELY STORM MOTION AND
WEAK LOW LEVEL HODOGRAPHS SUGGESTING LIMITED EWD
DEVELOPMENT/MOVEMENT AND LOW TORNADO POTENTIAL.
...PACIFIC NW TO NRN ROCKIES...
STRONG PACIFIC TROUGH EVIDENT ON WV IMAGERY WILL BE ACCOMPANIED BY
STRENGTHENING MID LEVEL WINDS ACROSS WA/OR AND INTO ID LATE IN THE
PERIOD. THIS INCREASE IN DEEP LAYER SHEAR WILL COINCIDE ACROSS
INTERIOR WA/OR WITH POCKETS OF STRONGER DIURNAL DESTABILIZATION AND
TSTM DEVELOPMENT. A FEW STRONGER STORMS MAY PERSIST GIVEN
INCREASINGLY FAVORABLE FORCING AND SHEAR AND RESULT IN LOCALLY
STRONG DOWNBURSTS AND HAIL. FARTHER EAST...MORE ISOLATED DEVELOPMENT
INITIATING OVER MOUNTAINOUS TERRAIN THIS AFTERNOON MAY SPREAD TO THE
LOWER ELEVATIONS ACROSS MT/ID. HOWEVER...MUCH OF THE REGION EAST OF
ID WILL REMAIN UNDER THE INFLUENCE OF NEUTRAL TO SLIGHT HEIGHT RISES
THROUGH THE PERIOD OF MAX HEATING TODAY.
...LOWER MI...
POTENT SHORT WAVE TROUGH SPREADING SEWD ACROSS THE UPPER GREAT LAKES
REGION SHOULD AID TSTM DEVELOPMENT WITHIN WEAK TO MODESTLY UNSTABLE
AIRMASS ACROSS LOWER MI THIS AFTERNOON. LATEST GUIDANCE INDICATES
THAT SHEAR AND INSTABILITY WILL SUPPORT LINES/CLUSTERS OF RELATIVELY
LOW-TOPPED THUNDERSTORMS AND PERHAPS A COUPLE OF SUPERCELLS. PRIMARY
THREAT WILL BE MARGINALLY SEVERE HAIL AND BRIEF DAMAGING WINDS WITH
THE MORE PERSISTENT/STRONGER STORM UPDRAFTS. LIMITED AREAL COVERAGE
OF SEVERE THREAT...AND POTENTIAL FOR STORMS TO WEAKEN RAPIDLY WITH
LOSS OF HEATING WARRANTS GENERALLY LOWER PROBABILITIES. HOWEVER...
THE NEED FOR HIGHER SEVERE HAIL/WIND PROBABILITIES WILL BE
REASSESSED IN NEXT OUTLOOK.
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