SPC AC 031939
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0239 PM CDT FRI JUL 03 2009
   
   VALID 032000Z - 041200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL HIGH
   PLAINS...CNTRL PLAINS AND MID-MO VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF CNTRL AND ERN
   MT...
   
   THE GREATEST CHANGE TO THE 20Z OUTLOOK IS TO TAKE THE SLIGHT RISK
   OUT OF FLORIDA. ALTHOUGH MODERATE INSTABILITY IS IN PLACE IN
   FL...STORM COVERAGE IS LESS THAN EXPECTED. IN ADDITION...VERY WEAK
   VERTICAL SHEAR PROFILES SHOULD KEEP ANY SEVERE THREAT MARGINAL THIS
   AFTERNOON. ANOTHER CHANGE TO THE OUTLOOK IS TO ADD PARTS OF WRN AND
   NRN NEB INTO THE SLIGHT RISK AREA WHERE MODERATE INSTABILITY IS
   ALREADY IN PLACE ACCORDING TO THE RUC. MODEL FORECASTS DEVELOP
   SCATTERED THUNDERSTORMS IN THE NEB PANHANDLE WHERE WSR-88D VWPS
   SUGGEST VERTICAL SHEAR PROFILES ARE ADEQUATE FOR SEVERE STORMS WITH
   HAIL THE MOST LIKELY THREAT. ANOTHER CHANGE TO THE OUTLOOK IS TO
   MAKE THE SLIGHT RISK IN ERN MONTANA SMALLER AND CO-LOCATED WITH A
   POCKET OF MODERATE INSTABILITY ANALYZED BY THE RUC.
   LASTLY...ADJUSTED THE 5 PERCENT PROBABILITIES TO BETTER AGREE WITH
   CURRENT CONVECTIVE DEVELOPMENT...MESOSCALE FEATURES AND SHORT-TERM
   MODEL FORECASTS.
   
   ..BROYLES.. 07/03/2009
   
   .PREV DISCUSSION... /ISSUED 1141 AM CDT FRI JUL 03 2009/
   
   ...CENTRAL PLAINS...
   WEAK/ELEVATED TSTMS FROM SRN NEB TO KS/MO BORDER AREA APPEAR THE
   RESULT OF WEAK MID LEVEL DISTURBANCE AND MARGINAL ISENTROPIC LIFT ON
   THE NOSE OF PLAINS LLJ EARLY TODAY. AS THIS LEADING DISTURBANCE
   CRESTS THE UPPER RIDGE...A SERIES OF STRONGER SHORT WAVE IMPULSES
   ARE FORECAST TO DEVELOP EAST AND FLATTEN THE NRN PERIPHERY OF HOT
   SUB-TROPICAL ANTICYCLONE ACROSS THE SRN PLAINS. LEE/THERMAL LOW...
   CURRENTLY NEAR CO/KS BORDER...WILL MAKE SLOW EWD PROGRESS INTO KS
   THIS AFTERNOON. LIFT AND LOW LEVEL CONVERGENCE ARE LIKELY TO BE
   ENHANCED NEAR THIS LOW BY THE APPROACH OF MID LEVEL SHORT WAVES NOW
   OVER WY/CO AND NM PER WV IMAGERY. DESPITE WARM TEMPS ALOFT...INTENSE
   SURFACE HEATING ALONG AND SOUTH OF DIFFERENTIAL HEATING/WARM FRONTAL
   BOUNDARY SETTING UP NEAR KS/NEB BORDER WILL CONTRIBUTE TO SCATTERED
   SURFACE BASED TSTM INITIATION NEAR THE LOW AND WARM FRONT LATER
   TODAY. ADDITIONAL STORMS ARE LIKELY DEVELOP AND INCREASE ACROSS THE
   HIGHER TERRAIN OF NM/CO/WY AND SPREAD EAST WITH THE APPROACHING
   SHORT WAVE DISTURBANCES AND HEATING OF THE DAY.
   
   ACROSS KS/NEB AND POINTS EAST...SLY/SELY LOW LEVEL FLOW WILL VEER
   AND INCREASE WITH HEIGHT RESULTING IN DEEP-LAYER EFFECTIVE SHEAR ON
   THE ORDER OF 40-50KT. THIS SHOULD PROVE SUFFICIENT FOR SUPERCELLS
   NEAR THE LOW AND WARM FRONT FROM LATE AFTERNOON INTO THE EVENING.
   ALONG WITH LARGE HAIL AND DAMAGING WINDS...A TORNADO OR TWO CANNOT
   BE COMPLETELY RULED OUT WITH ANY DISCRETE AND PERSISTENT SUPERCELL
   TRACKING NEAR THESE SURFACE FEATURES.
   
   FORECAST STRENGTHENING OF THE LLJ TO AOA 50 KT AFTER DARK SUGGESTS
   ANY CONGEALING TSTM CLUSTERS MAY CONTINUE TO BE SUPPORTED LATE INTO
   THE NIGHT AND PERHAPS GROW UPSCALE INTO LINEAR MCS SPREADING EAST
   ACROSS THE MO RIVER VALLEY AND INTO PARTS OF IA/MO BY EARLY SAT.
   MORE ORGANIZED COLD POOL AND DEEP CONVECTION PREFERENTIALLY ALIGNED
   WITH STRENGTHENING LOW THROUGH MID LEVEL FLOW COULD RESULT IN
   SCATTERED DAMAGING WINDS ACROSS THESE AREAS THROUGH LATE TONIGHT.
   
   ...FL WWD ALONG IMMEDIATE GULF COAST...
   EXPECT TSTMS TO CONTINUES TO DEVELOP AND INCREASE IN AREAL COVERAGE
   INTO THIS AFTERNOON ALONG AND SOUTH OF QUASI-STATIONARY FRONTAL ZONE
   OVER NRN FL. WHILE MID LEVEL FLOW ACROSS THE REGION WILL REMAIN
   MARGINAL FOR GREATER STORM ORGANIZATION...LATEST OBJECTIVE DATA
   INDICATES THAT INTENSE HEATING WAS RESULTING IN STRONG INCREASE IN
   DCAPE VALUES FROM THE ERN PNHDL ACROSS NRN FL ATTM. GIVEN WEAK
   INHIBITION AND ABUNDANT MOISTURE/INSTABILITY...EXPECT MARGINALLY
   ORGANIZED/MULTICELL TSTMS WITH THE CAPABILITY OF DAMAGING WINDS AND
   SOME HAIL TO PERSIST ACROSS MUCH OF FL WELL INTO THE AFTERNOON.
   
   ...MT...
   WEAK MID LEVEL DISTURBANCE AND ASSOCIATED FRONTAL SURGE EAST OF THE
   HIGH TERRAIN COMBINED WITH GREATER LOW LEVEL MOISTURE AND INCREASING
   INSTABILITY SHOULD CONTRIBUTE TO INCREASINGLY STRONG TSTMS ACROSS
   CNTRL/ERN MT TODAY. A FEW STOUT CELLS WERE ALREADY DEVELOPING OFF
   THE HIGHER TERRAIN AND EXPECT THIS TREND TO CONTINUE. DEEP-LAYER
   SHEAR ON THE ORDER OF 30-35KT SUGGESTS A FEW STORMS COULD ATTAIN
   SUPERCELL CHARACTERISTIC WITH ATTENDANT THREATS OF LARGE HAIL AND
   HIGH WINDS.
   
   ...NORTHEAST...
   UNUSUALLY DEEP MEAN TROUGHING ACROSS NEW ENGLAND AND PARTS OF THE
   NORTHEAST WILL BE REINFORCED THIS PERIOD AS ANOTHER STRONG IMPULSE
   DIVES SEWD FROM ONTARIO AND PRODUCES ANOTHER ROUND OF WEAK HEIGHT
   FALLS ACROSS NERN NY AND NRN NEW ENGLAND. LOW STATIC STABILITY AND
   MARGINAL BACKGROUND ASCENT WITHIN THE TROUGH AXIS WILL AGAIN FAVOR A
   DIURNAL INCREASE IN CONVECTION...ESPECIALLY ACROSS THOSE AREAS
   RECEIVING GREATER SURFACE HEATING THROUGH EARLY AFTERNOON. LIMITED
   CAPE AND MARGINAL CLOUD-BEARING SHEAR WITHIN THE SLACK FLOW IN THE
   TROUGH AXIS SUGGEST THAT SEVERE STORM POTENTIAL SHOULD BE LOW.
   HOWEVER...A FEW STORMS WILL BE CAPABLE OF HAIL/BRIEF STRONG/GUSTY
   WIND FROM LATE AFTERNOON TO EARLY EVENING.
   
   ...SOUTHEAST ACROSS INTERMOUNTAIN WEST...
   INTENSE SURFACE HEATING ON THE WRN PERIPHERY OF MONSOON MOISTURE
   PLUME SHOULD SPUR WIDESPREAD TSTM DEVELOPMENT FROM AZ ACROSS UT AS
   WELL AS THE ROCKIES AND INTO THE INTERIOR NW. MUCH OF THIS
   CONVECTION WILL BE WEAKLY ORGANIZED DUE TO LIMITED FLOW/SHEAR AND
   WILL BE TIED TO ELEVATED HEAT SOURCES/TERRAIN. ISOLATED STRONG TO
   SEVERE WIND GUSTS AND PERHAPS A FEW MARGINAL SEVERE HAIL EVENTS
   COULD OCCUR THROUGH THE LATE AFTERNOON.
   
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