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    Day 2 Outlook >
Jul 28, 2015 1300 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Tue Jul 28 12:53:29 UTC 2015 (Print Version | 20150728 1300Z Day 1 shapefile | 20150728 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 281253

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0753 AM CDT TUE JUL 28 2015

   VALID 281300Z - 291200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS UPPER MS RIVER VALLEY
   TO KS/MO/NEB BORDER REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS ELSEWHERE FROM LS AND NRN MN TO
   SWRN KS AREA...

   ...THERE IS A MRGL RISK OF SVR TSTMS MAINLY NRN PARTS OF NEW
   ENGLAND...

   ...SUMMARY...
   ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE FROM NORTHERN MINNESOTA
   AND LAKE SUPERIOR REGION TO SOUTHWESTERN KANSAS AND VICINITY. 
   WITHIN THAT SWATH...THE MOST PROBABLE AREA FOR GREATER
   CONCENTRATIONS OF SEVERE WEATHER APPEARS TO BE FROM EASTERN NEBRASKA
   ACROSS PARTS OF IOWA TO SOUTHWESTERN WISCONSIN.  A MARGINAL RISK FOR
   SEVERE THUNDERSTORMS ALSO EXISTS OVER MAINLY NORTHERN NEW ENGLAND.

   ...SYNOPSIS...
   IN MID/UPPER LEVELS...ANTICYCLONE IS FCST TO REBUILD OVER S-CENTRAL
   CONUS...WITH RIDGING WWD ACROSS CA AND NEWD TO HUDSON BAY.  W OF
   THAT RIDGE...CYCLONE IS EJECTING NEWD FROM NERN MT ACROSS SRN
   SK...WITH TROUGH SWWD OVER NRN CA.  ASSOCIATED 500-MB LOW SHOULD
   CROSS SERN SK BY AROUND 00Z THEN REACH MB/ONT BORDER NEAR END OF
   PERIOD.  GIVEN POSITIVE TILT AND EXPECTED DEAMPLIFICATION OF
   TRAILING TROUGH...BULK OF SUBSTANTIAL HEIGHT FALLS AND DCVA SHOULD
   REMAIN EITHER OVER CANADA OR BEHIND U.S. PORTION OF SFC COLD FRONT
   DESCRIBED BELOW.  FARTHER E...COMPACT CYCLONE -- NOW EVIDENT IN
   MOISTURE-CHANNEL IMAGERY OVER PARTS OF NRN QUE AND ADJOINING EXTREME
   WRN LABRADOR -- IS FCST TO DIG SEWD TOWARD ERN NB BY END OF
   PERIOD...WITH ASSOCIATED HEIGHT FALLS AND STRENGTHENING NWLYS/NLYS
   ALOFT SPREADING OVER PARTS OF MAINE OVERNIGHT.

   AT SFC...CYCLONE NOW OVER SERN SK SHOULD BECOME MORE DEEPLY OCCLUDED
   AND MORE VERTICALLY STACKED WITH LOW ALOFT.  ASSOCIATED SFC COLD
   FRONT WAS ANALYZED AT 11Z OVER ERN DAKOTAS..CENTRAL NEB...WRN
   KS...AND SERN CO.  BY 00Z THIS FRONT SHOULD REACH N-CENTRAL
   MN...SERN NEB...CENTRAL KS AND NERN NM.  BY 12Z COLD FRONT SHOULD
   ADVANCE TO WRN LS...CENTRAL WI...NRN MO...AND NWRN OK...DECELERATING
   AND PERHAPS STALLING OVER TX PANHANDLE AND ADJACENT ERN NM.  SFC
   TROUGH/WIND SHIFT AND WEAK COLD FRONT...ASSOCIATED WITH SERN
   CANADIAN PERTURBATION ALOFT...WILL MOVE SEWD ACROSS MAINE TODAY.

   ...MID-UPPER MS VALLEY REGION TO CENTRAL PLAINS...
   SPECIFICS OF CONVECTIVE GENESIS AND EVOLUTION OVER THIS REGION TODAY
   WILL BE STRONGLY DEPENDENT ON MESOSCALE DETAILS.  HOWEVER...GENERAL
   SCENARIO REMAINS VALID OF TSTMS DEVELOPING THIS AFTN AND OFFERING
   SVR WIND/HAIL RISK SEVERAL HOURS ALONG/AHEAD OF SFC COLD FRONT...AND
   NEAR AND S OF BOUNDARIES RELATED TO MORNING MCS ACTIVITY.

   SVR PROBABILITIES HAVE BEEN REDUCED OVER MOST AREAS BEHIND EXISTING
   MCS...WHERE ENOUGH DESTABILIZATION TO RENDER OUTFLOW POOL SUPPORTIVE
   OF ORGANIZED SVR THREAT NOW APPEARS UNLIKELY BETWEEN DENSE MCS
   CLOUD/PRECIP PLUME AND SFC COLD FRONT.  THAT SAME THICK CLOUD/PRECIP
   PLUME ALSO SHOULD PERSIST FOR MANY HOURS AND RESTRICT DIURNAL
   DESTABILIZATION SUBSTANTIALLY ACROSS MOST OF NRN MN AND NWRN WI. 
   WHILE ADDITIONAL CONVECTIVE DEVELOPMENT CANNOT BE RULED OUT N OR NW
   OF MCS...ESPECIALLY INVOF CANADIAN BORDER...UNCONDITIONAL SVR
   POTENTIAL APPEARS TO HAVE BEEN STUNTED ENOUGH TO DOWNGRADE FROM
   15%/SLGT LEVEL.

   FARTHER S...REMAINDER OF REGION ALONG AND SE OF MCS PRECIP PLUME AND
   ASSOCIATED OUTFLOW/DIFFERENTIAL HEATING BOUNDARIES WILL REMAIN
   CHARACTERIZED BY RICH...EVAPOTRANSPIRATIVELY BOOSTED BOUNDARY-LAYER
   MOISTURE...WITH SFC DEW POINTS UPPER 60S TO MID 70S F BY MID AFTN.
   MLCAPE WILL INCREASE SWD AWAY FROM THICKER CLOUD COVER...WITH VALUES
   GENERALLY RANGING FROM 2000-3500 J/KG.  HOWEVER...DECREASE WITH SWD
   EXTENT IS EXPECTED FOR DEEP SHEAR...DCVA AND HEIGHT FALLS...GIVEN
   FCST PATH OF MID/UPPER-LEVEL CYCLONE.  AS SUCH...MOSTLY
   MULTICELLULAR MODES ARE LIKELY...THOUGH ISOLATED SUPERCELLS...LIKELY
   OF HEAVY-PRECIP CHARACTER...ALSO ARE POSSIBLE GIVEN MRGL/35-40 KT
   EFFECTIVE-SHEAR MAGNITUDES.

   WITH SWWD EXTENT FROM MO RIVER VALLEY...AIR MASS ALONG/AHEAD OF COLD
   FRONT WILL BE CHARACTERIZED BY NARROWER ZONE OF RELATIVELY HIGH DEW
   POINTS...STRONGER SFC HEATING...WEAKER LOW-LEVEL WINDS...AND SMALLER
   DEEP-SHEAR VALUES.  THAT HEATING...ALONG WITH LIFT INVOF
   FRONT...SHOULD SUPPORT WIDELY SCATTERED TSTMS THIS AFTN WITH
   WELL-MIXED SUBCLOUD LAYER SUPPORTING STG/ISOLATED SVR GUSTS...AND
   MAINTENANCE OF ISOLATED SVR HAIL TO SFC.  THREAT SHOULD BE STRONGLY
   TIED TO DIURNAL PROCESSES AND SHOULD DIMINISH MARKEDLY AFTER DARK.

   ...NEW ENGLAND...
   ISOLATED TO WIDELY SCATTERED TSTMS SHOULD FORM TODAY INVOF WIND
   SHIFT/FRONT AND MOVE SEWD ACROSS THIS REGION...OFFERING SPORADIC
   HAIL NEAR SVR LIMITS AND STG GUSTS.  UNCERTAINTY REMAINS REGARDING
   EXTENT AND MAGNITUDE OF DESTABILIZATION THAT CAN OCCUR BEHIND BAND
   OF ELEVATED TSTMS THAT HAS MOVED OFFSHORE MAINE COAST...REINFORCING
   ALREADY COOL/STABLE BOUNDARY LAYER.  DNVA AND WEAK HEIGHT RISES ALSO
   ARE FCST FOR SEVERAL MORE HOURS AS ASSOCIATED VORTICITY LOBE PASSES
   OFFSHORE.  STILL...IR AND EARLY VIS IMAGERY INDICATE ENOUGH CLEARING
   THAT SUSTAINED INSOLATION MAY RENDER SFC-BASED EFFECTIVE-INFLOW
   PARCELS IN PREFRONTAL SECTOR THROUGH THIS AFTN...THOUGH BULK OF
   HEIGHT FALLS AND LARGE-SCALE ASCENT ALOFT SHOULD REMAIN BEHIND
   BOUNDARY.

   ..EDWARDS/COOK.. 07/28/2015

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

        
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