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    Day 2 Outlook >
Aug 1, 2015 0600 UTC Day 1 Convective Outlook
Updated: Sat Aug 1 05:58:04 UTC 2015 (Print Version | 20150801 1200Z Day 1 shapefile | 20150801 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 010558

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1258 AM CDT SAT AUG 01 2015

   VALID 011200Z - 021200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MO VALLEY INTO
   PARTS OF THE UPPER MS VALLEY REGION...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK FROM
   CENTRAL NEB/SD TO WI...NORTHERN MO...AND WESTERN AND NORTHERN IL...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS NORTHERN NEW ENGLAND...

   ...SUMMARY...
   ISOLATED TO SCATTERED SEVERE STORMS CAPABLE OF HAIL...DAMAGING
   WINDS...AND A TORNADO THREAT SHOULD DEVELOP LATE THIS AFTERNOON IN
   SOUTHEAST SOUTH DAKOTA.  ADDITIONAL STRONG TO SEVERE STORMS ARE
   EXPECTED TO INCREASE IN COVERAGE ACROSS IOWA AND INTO THE UPPER
   MISSISSIPPI VALLEY THIS EVENING WITH A CONTINUED POTENTIAL FOR ALL
   SEVERE HAZARDS...THOUGH DAMAGING WINDS MAY BECOME THE MORE PROMINENT
   THREAT. A FEW SEVERE STORMS WITH HAIL AND STRONG WIND GUSTS MAY ALSO
   OCCUR OVER NORTHERN NEW ENGLAND THIS AFTERNOON.

   ...SYNOPSIS...
   AN AMPLIFIED UPPER PATTERN WILL PREVAIL THROUGH TODAY AND TONIGHT...
   WITH A RIDGE IN THE WEST AND A BROAD LONGWAVE TROUGH IN THE EASTERN
   U.S. WHICH IS ANCHORED BY A DEEP CLOSED LOW LOCATED OVER HUDSON BAY.
   THIS CLOSED LOW SHOULD BEGIN TO SHIFT SOUTHWARD LATE IN THE FORECAST
   PERIOD.  A STRONG CYCLONIC FLOW REGIME WILL EXTEND FROM CENTRAL
   CANADA AND THE NORTH-CENTRAL U.S. THROUGH THE GREAT LAKES AND OH
   VALLEY TO THE NORTHEAST STATES.  A LEAD SHORTWAVE TROUGH WILL TRACK
   EASTWARD ACROSS NORTHERN NEW ENGLAND DURING PEAK HEATING THIS
   AFTERNOON.  MEANWHILE...FARTHER UPSTREAM A WEAK MIDLEVEL SHORTWAVE
   TROUGH...CURRENTLY LOCATED ACROSS THE NORTHERN U.S. ROCKIES PER
   MOISTURE-CHANNEL IMAGERY...IS FORECAST TO REACH CENTRAL AND EASTERN
   SD WITHIN THE NWLY FLOW ALOFT BY LATE THIS AFTERNOON AND THEN
   PROCEED THROUGH THE UPPER MS VALLEY THIS EVENING AND SATURDAY NIGHT.
   STRONGEST HEIGHT FALLS ARE EXPECTED ACROSS THE UPPER MIDWEST AFTER
   02/00Z AS A SEPARATE SHORTWAVE TROUGH MOVES INTO THIS REGION FROM
   WESTERN CANADA...AND THE HUDSON BAY LOW BEGINS TO SHIFT SOUTHWARD.

   AT THE SURFACE...A BOUNDARY...CURRENTLY EXTENDING FROM CENTRAL MO
   NWWD THROUGH SOUTHEAST TO NORTHWEST NEB...WILL MOVE TO THE NORTHEAST
   AS A WARM FRONT TODAY...ADVANCING THROUGH THE MID MO TO UPPER MS
   VALLEYS.  MEANWHILE...A PRE-FRONTAL TROUGH/DRY LINE WILL MOVE EAST
   ACROSS THE NORTHERN PLAINS WITH A COLD FRONT ADVANCING ACROSS THE
   DAKOTAS SATURDAY NIGHT.

   ...MID MO VALLEY TO UPPER MS VALLEY...
   A FEW SHOWERS AND TSTMS MAY BE ONGOING NEAR THE WARM FRONT IN
   SOUTHERN SD AND NEB AT THE START OF DAY 1...WITH SOME OF THIS
   ACTIVITY POTENTIALLY LINGERING THROUGH THE MORNING TO EARLY
   AFTERNOON GIVEN WEAK LOW-LEVEL WAA.  POLEWARD MOISTURE RETURN IS
   EXPECTED ACROSS THE WARM SECTOR TODAY AS THE WARM FRONT MOVES INTO
   THE MID MO VALLEY THIS AFTERNOON.  THIS COMBINED WITH STRONG
   DIABATIC HEATING BENEATH AN EWD-EXTENDING PLUME OF STEEP MIDLEVEL
   LAPSE RATES WILL RESULT IN VERY STRONG INSTABILITY /MUCAPE 2000-3000
   J PER KG/ BY AFTERNOON.  MODELS SUGGEST NEW STORM INITIATION SHOULD
   OCCUR ACROSS SOUTHEAST SD...NEAR THE INTERSECTION OF THE WARM FRONT
   AND PRE-FRONTAL TROUGH/DRY LINE...AS FORCING FOR ASCENT ATTENDANT TO
   THE NORTHERN ROCKIES TROUGH REACHES THIS REGION LATE THIS AFTERNOON.
   A STRENGTHENING SWLY LLJ ACROSS NERN NEB INTO SWRN MN AND WINDS
   VEERING AND STRENGTHENING WITH HEIGHT WILL BE MORE THAN SUFFICIENT
   FOR ORGANIZED STORMS INCLUDING SUPERCELLS.  EARLY STORM EVOLUTION
   SHOULD SUPPORT ALL SEVERE HAZARDS.  THERE IS SOME INDICATION FOR
   VERY LARGE HAIL TO OCCUR ACROSS THE WESTERN HALF OF THE SLIGHT RISK
   AREA...AND IF CONFIDENCE IS GREATER FOR THIS THREAT IN LATER
   OUTLOOKS...THEN THIS SEVERE PROBABILITY WOULD NEED TO BE INTRODUCED
   AT THAT TIME.

   GIVEN STRONGER HEIGHT FALLS EXPECTED THIS EVENING THROUGH TONIGHT...
   FURTHER STRENGTHENING OF THE SWLY LLJ IS EXPECTED THROUGH TONIGHT
   WITH THIS JET VEERING WITH TIME ACROSS THE UPPER MS VALLEY.  UPSCALE
   GROWTH INTO ONE OR MORE MCS/S IS POSSIBLE WITH ONE MCS DEVELOPING
   S/SEWD THROUGH IA...WHILE ADDITIONAL STORMS AND EVENTUAL MCS
   DEVELOPMENT OCCURS ACROSS SRN AND CENTRAL MN INTO WI.  ALTHOUGH
   DAMAGING WINDS AND HAIL WOULD BE THE PRIMARY THREATS AFTER
   DARK...VERTICALLY VEERING WINDS AND ENHANCED LOW-LEVEL SHEAR IN
   VICINITY OF THE LLJ SUGGEST A TORNADO THREAT COULD PERSIST INTO THE
   EARLY EVENING ACROSS NORTHERN IA AND THE SOUTHERN HALF OF MN.

   ...NORTHERN NEW ENGLAND...
   A COLD FRONT IS EXPECTED TO MOVE ACROSS THIS REGION FROM LATE
   MORNING THROUGH THE AFTERNOON...WITH THE PRE-FRONTAL ENVIRONMENT
   EXPECTED TO HAVE DESTABILIZED GIVEN SOME POLEWARD MOISTURE RETURN
   /PW VALUES OF 1-1.25 INCHES/ COMBINED WITH SURFACE HEATING AND
   MODEST MIDLEVEL LAPSE RATES AROUND 6.5 C/KM.  DEEP-LAYER
   UNIDIRECTIONAL W/SWLY WINDS INCREASING WITH HEIGHT WILL RESULT IN
   LONG...STRAIGHT HODOGRAPHS...WITH EFFECTIVE BULK SHEAR OF 30-40 KT. 
   THIS SUGGESTS MULITICELLS AND SPLITTING SUPERCELLS WILL BE POSSIBLE.
   OVERALL SEVERE-WEATHER COVERAGE SHOULD BE RELATIVELY LOW GIVEN A
   MARGINALLY UNSTABLE WARM SECTOR...WITH ISOLATED HAIL AND STRONG WIND
   GUSTS BEING THE MAIN SEVERE RISK.

   ..PETERS/MARSH.. 08/01/2015

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

        
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