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    Day 2 Outlook >
Jun 29, 2015 1300 UTC Day 1 Convective Outlook
Updated: Mon Jun 29 12:56:18 UTC 2015 (Print Version | 20150629 1300Z Day 1 shapefile | 20150629 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 291256

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0756 AM CDT MON JUN 29 2015

   VALID 291300Z - 301200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS MAINLY OVER PORTIONS
   CENTRAL/ERN KY AND SWRN OH...

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MN/WI...

   ...THERE IS A MRGL RISK OF SVR TSTMS ELSEWHERE FROM ERN TN TO SERN
   INDIANA AND WRN OH...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING SLGT RISK OVER
   UPPER MS VALLEY REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS PORTIONS CENTRAL
   HIGH/PLAINS...CENTRAL/SRN ROCKIES TO AZ...

   ...THERE IS A MRGL RISK OF SVR TSTMS NRN ROCKIES AND PORTIONS ERN
   WA/NERN ORE...

   ...SUMMARY...
   ORGANIZED SEVERE THUNDERSTORMS WILL BE POSSIBLE TODAY ACROSS PARTS
   OF THE MIDDLE OHIO VALLEY REGION AND THE UPPER MISSISSIPPI VALLEY. 
   ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE FROM THE CENTRAL AND
   SOUTHERN HIGH PLAINS TO ARIZONA...AND OVER THE NORTHERN ROCKIES.

   ...SYNOPSIS...
   IN MID/UPPER LEVELS...CONUS PORTION OF LARGE-SCALE PATTERN WILL
   CONTINUE TO FEATURE TROUGHING OVER ERN STATES AND STG ANTICYCLONE
   OVER GREAT BASIN...WITH RIDGE FROM NWRN MEX TO NRN ROCKIES. 
   SHORTWAVE TROUGH -- CURRENTLY EXTENDING FROM SRN LM SWD ACROSS WRN
   INDIANA -- IS FCST TO PIVOT EWD TO OH THROUGH 00Z WHILE SLOWLY
   WEAKENING.  THIS WILL OCCUR AS HEIGHT FALLS DEVELOP IN ADVANCE OF
   ANOTHER PERTURBATION NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER
   SRN/CENTRAL MB...AND FCST TO MOVE SEWD TO NEAR LM BY END OF PERIOD. 
   SFC CYCLONE ASSOCIATED WITH LEADING PERTURBATION -- ANALYZED
   INITIALLY OVER ERN IL -- SHOULD MOVE ACROSS CENTRAL INDIANA TO
   OH...WHILE TRAILING WEAK FRONT/WIND SHIFT LINE FURTHER LOSES
   DEFINITION WITH TIME. 

   MEANWHILE...MID/UPPER-LEVEL SHORTWAVE TROUGH INITIALLY LOCATED NEAR
   COASTAL ORE/CA BORDER IS EXPECTED TO MOVE OBLIQUELY INLAND THROUGH
   MIDDAY THEN NEWD ACROSS WA/SRN BC...PENETRATING MEAN POSITION OF
   RIDGE OVER SRN AB/NWRN MT BY 12Z. 

   ...OH VALLEY OUTLOOK AREA...
   DESPITE DIFFUSE/FRONTOLYTIC NATURE OF ASSOCIATED CYCLONE AND SFC
   BOUNDARY...WIDELY SCATTERED TO SCATTERED TSTMS IN BOTH DISCRETE AND
   CLUSTERED MODES SHOULD FORM THIS AFTN AND LAST INTO AT LEAST EARLY
   EVENING.  OUTFLOW/DIFFERENTIAL-HEATING ZONES SHOULD ASSIST WITH
   FOCUSING CONVECTIVE DEVELOPMENT AND SVR POTENTIAL ON MESOBETA TO
   LOCAL SCALE.  DAMAGING GUSTS AND LARGE HAIL EACH ARE EXPECTED...AND
   A COUPLE OF TORNADOES ALSO ARE POSSIBLE.  ACTIVITY WILL BE ENABLED
   BY COMBINATION OF WEAK CONVERGENCE INVOF LOW/BOUNDARIES...FAVORABLE
   DIURNAL HEATING/MOISTURE BEHIND MORNING CLOUD/PRECIP PLUME...AND
   WEAK CINH...WITH SFC DEW POINTS COMMONLY 60S F.  

   THOUGH LAPSE RATES ALOFT WILL BE MODEST...800-1500 J/KG MLCAPE
   APPEARS MOST PROBABLE...AMIDST EFFECTIVE-SHEAR MAGNITUDES GENERALLY
   25-35 KT.  AS SUCH...MAIN STORM CHARACTER WILL BE
   MULTICELLULAR...AND ANY SUPERCELL POTENTIAL WILL NEED LOCALIZED
   HELP.  TIME SERIES OF FCST SOUNDINGS FROM SEVERAL PROGS SUGGEST
   DECREASING LOW-LEVEL SHEAR AND FAVORABLY CURVED BUT SHRINKING
   HODOGRAPH SIZE WITH TIME.  THIS APPEARS REASONABLE FOR MOST OF AREA
   GIVEN WEAKENING OF MIDLEVEL PERTURBATION AND DECREASE/VEERING OF
   NEAR-SFC WINDS.  HOWEVER...AT LEAST TRANSIENT SUPERCELL THREAT STILL
   MAY EXIST ESPECIALLY NEAR FAVORABLY ORIENTED SFC BOUNDARIES THAT CAN
   SUPPORT LOCALLY BACKED FLOW AND BOUNDARY-LAYER VORTICITY
   ENHANCEMENT.  SVR THREAT SHOULD DIMINISH GRADUALLY AFTER DARK AS
   DIABATIC COOLING STRENGTHENS/DEEPENS STATICALLY STABLE SFC LAYER. 

   ...UPPER MS VALLEY STATES...
   ISOLATED...MRGLLY SVR HAIL IS POSSIBLE FROM ELEVATED TSTMS THIS
   MORNING OVER NRN MN...HOWEVER MAIN SVR THREAT SHOULD TAKE PLACE
   LATER.  ONE OR TWO BKN BANDS OF TSTMS SHOULD DEVELOP THIS AFTN AS
   BOUNDARY LAYER DESTABILIZES...GROWING UPSCALE INTO LOOSELY ORGANIZED
   CLUSTERS AS SOME DISCRETE CELLS PERSIST.  SPORADIC HAIL AND DAMAGING
   GUSTS ARE EXPECTED AS ACTIVITY MOVES OVER WELL-MIXED SUBCLOUD
   LAYERS...WITH ENOUGH NEAR-SFC MOISTURE TO SUPPORT 500-1000 J/KG
   MLCAPE.  ALTHOUGH SHORTWAVE RIDGING EXISTS OVER THIS AREA
   NOW...HEIGHT FALLS AND LARGE-SCALE DCVA/DESTABILIZATION ALOFT ARE
   EXPECTED.  WEAK NEAR-SFC WINDS AND UNIDIRECTIONAL FLOW SHOULD LIMIT
   HODOGRAPH SIZE...WITH 25-35 KT EFFECTIVE-SHEAR MAGNITUDES
   COMMON...INDICATING PREDOMINANT MULTICELL MODE.  SFC
   WIND-SHIFT/CONFLUENCE LINE IS EXPECTED TO MOVE SEWD ACROSS THIS
   REGION AHEAD OF PERTURBATION ALOFT...PROVIDING LIFT IN ADDITION TO
   THAT FROM SFC DIABATIC HEATING.  THREAT SHOULD DIMINISH FAIRLY
   QUICKLY AFTER DARK. 

   ...CENTRAL HIGH/PLAINS...CENTRAL/SRN ROCKIES TO AZ...
   WIDELY SCATTERED TSTMS ARE EXPECTED TO FORM THIS AFTN ACROSS MTNS
   AND FOOTHILLS AS WELL AS EWD-EXTENDING DIVIDES...AND PERHAPS
   RESIDUAL OUTFLOW/DIFFERENTIAL-HEATING ZONE ASSOCIATED WITH ONGOING
   PRECIP OVER ERN CO.  LARGE HAIL AND DAMAGING GUSTS MAY FALL FROM A
   FEW MORE LONG-LIVED/INTENSE CELLS.  LOW-LEVEL FLOW WILL HAVE UPSLOPE
   COMPONENT OVER MUCH OF CORRIDOR FROM ERN CO TO ERN NM...NEAR AND
   BEHIND WEAK FRONT/WIND SHIFT TRAILING FROM OH VALLEY LOW.  AS THIS
   AIR MASS...WITH SFC DEW POINTS GENERALLY UPPER 40S AND 50S F...IS
   HEATED THIS AFTN...WEAK MIDLEVEL LAPSE RATES WILL BE OFFSET ENOUGH
   TO YIELD 500-1000 J/KG MLCAPE...AMIDST STG DIRECTIONAL SHEAR. 
   HOWEVER...LOW-LEVEL WINDS WILL BE WEAK...LIMITING HODOGRAPH SIZE AND
   LOW-LEVEL SHEAR...DESPITE 40-50 KT EFFECTIVE-SHEAR MAGNITUDES. 
   ADDITIONAL WIDELY SCATTERED/ISOLATED TSTMS WILL OFFER RISK OF A FEW
   GUSTS NEAR SVR LIMITS FARTHER SW ACROSS WRN NM INTO AZ. 

   ...NWRN CONUS...
   WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS AFTN IN AND NEAR
   MRGL-SVR OUTLOOK AREA...INITIALLY OVER HIGHER TERRAIN...MOVING
   GENERALLY NEWD WHILE OFFERING STG TO LOCALLY DAMAGING GUSTS AND
   ISOLATED HAIL NEAR SVR LIMITS.  WEAK LARGE-SCALE FORCING FOR ASCENT
   AHEAD OF PAC SHORTWAVE TROUGH SHOULD SPREAD OVER AREAS EXPERIENCING
   POCKETS OF FAVORABLE SFC DIABATIC HEATING BEHIND AREAS OF CLOUDS
   CURRENTLY EVIDENT IN IR IMAGERY THAT ARE ASSOCIATED WITH LIGHT
   PRECIP PER PATCHES OF REFLECTIVITY LOOPS.  ENOUGH LOW-LEVEL MOISTURE
   WILL REMAIN AMIDST BOUNDARY-LAYER MIXING TO SUPPORT HIGH-BASED
   TSTMS...WITH MLCAPE IN 700-1200 J/KG RANGE AND LOCALLY HIGHER. 
   DESPITE WLY COMPONENT TO NEAR-SFC FLOW...EFFECTIVE-SHEAR MAGNITUDES
   IN 40-45 KT RANGE ARE FCST...SUGGESTING SOME ORGANIZATION AND
   PERSISTENCE TO STRONGER CELLS AND SHORT CONVECTIVE LINES.

   ..EDWARDS/ROGERS.. 06/29/2015

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

        
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