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    Day 2 Outlook >
Jul 26, 2016 1630 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Tue Jul 26 16:30:33 UTC 2016 (Print Version | 20160726 1630Z Day 1 shapefile | 20160726 1630Z Day 1 KML)
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 Forecast Discussion
   SPC AC 261630

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CDT TUE JUL 26 2016

   VALID 261630Z - 271200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS MAINLY WRN/CENTRAL PARTS OF
   NEB/SD...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING SLGT RISK AND
   EXTENDING ACROSS CENTRAL MN TO UPPER MI...

   ...THERE IS A MRGL RISK OF SVR TSTMS TIDEWATER VA/NC TO LOWER OH
   VALLEY...

   ...SUMMARY...
   THUNDERSTORMS SHOULD PRODUCE SEVERE GUSTS AND LARGE HAIL THIS
   AFTERNOON AND EVENING OVER PARTS OF WESTERN AND CENTRAL NEBRASKA AND
   SOUTH DAKOTA.  DAMAGING GUSTS...A FEW NEAR SEVERE LIMITS...ARE
   POSSIBLE TODAY FROM PARTS OF THE VIRGINIA/NORTH CAROLINA TIDEWATER
   AREA TO PARTS OF THE OHIO VALLEY.

   ...SYNOPSIS...
   BASIC CONUS UPPER-AIR PATTERN THROUGH REMAINDER OF PERIOD WILL BE
   CHARACTERIZED BY...
   1.  STG ANTICYCLONE CENTERED OVER SRN GREAT BASIN REGION...MOVING
   LITTLE.
   2.  WRN EXTENSION OF BERMUDA HIGH OVER COASTAL CAROLINAS...FCST TO
   ERODE/SHIFT EWD OVER ATLC.
   3.  TROUGHING AND ASSOCIATED VORTICITY MAXIMA AND WEAK 500-MB LOWS
   IN SUBTROPICAL ELYS...INITIALLY EXTENDING FROM LOWER MS VALLEY SWWD
   ACROSS NWRN GULF AND LOWER TX COAST REGION.  SRN PART IS EXPECTED TO
   PROCEED WWD OVER S TX...LOWER RIO GRANDE VALLEY AND NERN MEX...WHILE
   NRN LOBE SHIFTS NNWWD FROM MS TO SRN AR.  THIS WILL CONTRIBUTE TO
   REGIONAL GEN-TSTM POTENTIAL THROUGHOUT PERIOD.
   4.  BELT OF NEARLY ZONAL FLOW OVER NRN CONUS AND SRN CANADA...WITH
   SEVERAL EMBEDDED/LOW-AMPLITUDE SHORTWAVES.  OF THOSE...TWO MAIN
   PERTURBATIONS RELEVANT TO THIS OUTLOOK ARE EVIDENT IN
   MOISTURE-CHANNEL IMAGERY AND UPPER-AIR ANALYSES...
   ...A.  OVER IA/IL/MO...AND FCST TO MOVE EWD TO OH BY 12Z...WITH
   GRADUAL WEAKENING.
   ...B.  OVER ERN MT AND NRN WY...FCST TO MOVE EWD WITH SOME SWD
   EXPANSION POSSIBLE THIS EVENING AND TONIGHT BY MEANS OF CONVECTIVE
   SUPPLEMENTATION OF VORTICITY.

   AT SFC...15Z ANALYSIS SHOWED COLD FRONT OFFSHORE SRN NEW ENGLAND
   COAST AND WSWWD ACROSS SRN DELMARVA..BECOMING WAVY/QUASISTATIONARY
   WWD THROUGH WEAK LOWS OVER SRN INDIANA AND NERN OK...THEN DIFFUSE
   SWWD THROUGH OUTFLOW FROM CENTRAL OK CONVECTION OF LAST NIGHT. 
   FRONTAL ZONE SHOULD REMAIN QUASISTATIONARY OVERLAND FROM MO EWD
   TODAY...MODULATED ON MESOBETA TO LOCAL SCALES BY CONVECTIVELY
   GENERATED BAROCLINICITY. WRN PORTION WILL BECOME DIFFUSE ACROSS SRN
   PLAINS AS LOW DEVELOPS ALONG OUTFLOW BOUNDARY AND QUASISTATIONARY
   FRONTAL ZONE OVER NWRN NEB/SWRN SD AREA.  THAT FRONT WILL EXTEND
   NEWD ACROSS SD THEN ENEWD OVER CENTRAL MN..BECOMING COLD FRONT
   FARTHER E OVER NWRN ONT...MOVING OVER LS TO UPPER MI TONIGHT.

   ...N-CENTRAL PLAINS TO UPPER MI...
   EPISODIC CLUSTERS OF TSTMS SHOULD DEVELOP THROUGH THIS EVENING NEAR
   AND SE OF FRONTAL ZONE...OUTFLOW BOUNDARY AND LEE TROUGH...AS WELL
   AS OVER BLACK HILLS.  THIS WILL BE IN ADDITION TO ANY ONGOING...
   ISOLATED/MRGL HAIL POTENTIAL FROM TSTMS OVER NERN SD.  DAMAGING
   GUSTS AND LARGE HAIL WILL BE PRIMARY CONCERNS.  AXIS OF WIND THREAT
   IS SOMEWHAT DISPLACED E AND SE OF THAT FOR HAIL...GIVEN LIKELIHOOD
   OF EVOLUTION FROM MORE HAIL-SUPPORTING EARLY/DISCRETE MODES TO
   WIND-CONDUCIVE AGGREGATED CLUSTERS WITH TIME.

   NARROW/S-N CORRIDOR OF FAVORABLE LOW-LEVEL MOISTURE WAS EVIDENT IN
   925- AND 850-MB ANALYSES THIS MORNING...ATOP SFC DEW POINTS
   GENERALLY 60S F.  THIS WILL SUPPORT 1500-3000 J/KG MLCAPE THIS AFTN
   BENEATH STEEP MIDLEVEL LAPSE RATES OF 8-9 DEG C/KM.  25-40 KT
   EFFECTIVE-SHEAR MAGNITUDES WILL SUPPORT MAINLY ORGANIZED
   MULTICELLS...THOUGH TRANSIENT SUPERCELL STRUCTURES ALSO ARE
   POSSIBLE.  MOIST PLUME WILL SHIFT EWD SOMEWHAT FROM LATE AFTN
   THROUGH EVENING...BUT NOT AS FAST AS CONVECTIVE MOTION.  SEVERAL
   HOURS OF TIME WINDOW FOR UPSCALE GROWTH OF AFTN CONVECTION INTO MCS
   WILL BE AVAILABLE ACROSS PORTIONS SD/NEB.  THROUGH LATE-EVENING AND
   OVERNIGHT HOURS...TSTM COVERAGE AND OVERALL SVR THREAT ARE EXPECTED
   TO DIMINISH WITH TIME.  ACTIVITY SHOULD ENCOUNTER PROGRESSIVELY
   LOWER-THETAE AIR WITH EWD EXTENT...RELATED TO COMBINATION OF
   DIABATIC SFC STABILIZATION AND RELATIVELY DRY TRAJECTORIES EMANATING
   FROM LOW-LEVEL ANTICYCLONE THAT FOLLOWED PASSAGE OF SRN FRONTAL
   ZONE.

   ADDITIONAL TSTMS SHOULD DEVELOP ALONG PREFRONTAL SFC CONFLUENCE
   ZONES AND LAKE-BREEZE BOUNDARIES OVER PORTIONS MN/NRN WI/UPPER
   MI...PRIMARILY DURING AFTN AND INTO EARLY EVENING WHEN CAPE IS
   MAXIMIZED AND MLCINH IS MINIMIZED.  ISOLATED DAMAGING GUSTS AND
   LARGE HAIL WILL BE POSSIBLE.

   ...TIDEWATER TO LOWER OH VALLEY...
   IN ADDITION TO ONGOING CONVECTION OVER SRN INDIANA...WIDELY
   SCATTERED TO SCATTERED TSTMS ARE EXPECTED TO DEVELOP NEAR AND S OF
   FRONTAL ZONE THROUGH AFTN ACROSS MUCH OF THIS CORRIDOR.  MAIN
   CONCERN WILL BE SPORADIC DAMAGING WINDS AND ISOLATED SVR GUSTS. 
   THIS REGION WILL RESIDE ALONG SRN RIM OF WLYS ALOFT...AND JUST N OF
   WEAK RIDGING EXTENDING WWD FROM BERMUDA HIGH.  SUBTLE FORCING FOR
   ASCENT PRECEDING WEAKENING MIDLEVEL SHORTWAVE TROUGH ALSO MAY
   SUPPORT CONVECTIVE POTENTIAL ACROSS WRN/NWRN PORTIONS OF OUTLOOK
   AREA.

   MORNING RAOBS AND SFC ANALYSIS SHOW RICH LOW-LEVEL MOISTURE
   SURMOUNTED BY MODEST MIDLEVEL LAPSE RATES...WITH PW GENERALLY 1.5-2
   INCHES AND SFC DEW POINTS 70S F...EXCEPT 60S AT HIGHER ELEVATIONS IN
   APPALACHIANS.  VIS IMAGERY SHOWS LITTLE SUBSTANTIAL CLOUD COVER AWAY
   FROM ONGOING CONVECTION.  THIS WILL FOSTER SUSTAINED...STG SFC
   HEATING THAT WILL ERODE MLCINH AND SUPPORT TSTM DEVELOPMENT TODAY...
   OFFSETTING THOSE MODEST LAPSE RATES ALOFT ENOUGH TO YIELD MLCAPE
   1000-2500 J/KG.  LIGHT LOW-LEVEL WINDS WITH PREDOMINANT WLY
   COMPONENT WILL LIMIT VERTICAL SHEAR...WITH PULSE AND MULTICELLULAR
   MODES LIKELY.  OUTFLOWS AND SEA BREEZES WILL BECOME INCREASINGLY
   IMPORTANT WITH TIME THIS AFTN INTO EARLY EVENING AS FOCI FOR
   SUBSEQUENT STAGES OF TSTM DEVELOPMENT...UNTIL COMBINATION OF EVENING
   NOCTURNAL COOLING AND INCREASING COVERAGE OF OUTFLOW AIR REDUCES
   TSTM INTENSITY/COVERAGE.

   ..EDWARDS/CONIGLIO.. 07/26/2016

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z

        
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Page last modified: July 26, 2016
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