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    Day 2 Outlook >
Oct 25, 2014 1300 UTC Day 1 Convective Outlook
Updated: Sat Oct 25 12:48:34 UTC 2014 (Print Version | 20141025 1300Z Day 1 shapefile | 20141025 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 251248

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0748 AM CDT SAT OCT 25 2014

   VALID 251300Z - 261200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS NWRN CA...SWRN ORE...

   ...SUMMARY...
   SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS
   NORTHWESTERN CALIFORNIA AND SOUTHWESTERN OREGON FROM MIDDAY THROUGH
   THIS AFTERNOON.  A FEW OF THESE MAY BRING THE RISK OF A WEAK/BRIEF
   TORNADO.  THUNDERSTORMS WILL ALSO DEVELOP ACROSS NORTHERN PARTS OF
   NEW YORK AND NEW ENGLAND...OFFERING SPORADIC SMALL HAIL.

   ...SYNOPSIS...
   PROGRESSIVE UPPER-AIR PATTERN IS FCST ACROSS CONUS TODAY...LEADING
   TO SOME DEAMPLIFICATION OF STG 500-MB RIDGE NOW OVER ROCKY MOUNTAIN
   STATES.  BY 12Z...THIS RIDGE SHOULD BE LOCATED NEAR AN SAT-MKC-GFK
   LINE THEN NNWWD OVER WRN MB.  TO ITS W...STG HEIGHT FALLS ARE FCST
   AS MID/UPPER-LEVEL CYCLONE -- NOW EVIDENT IN MOISTURE-CHANNEL
   IMAGERY OFFSHORE ORE -- BECOMES OPEN-WAVE IN NATURE AND EJECTS NEWD
   ACROSS PAC NW.  THOUGH VORTICITY FIELD ASSOCIATED WITH THIS CYCLONE
   WILL WEAKEN CONSIDERABLY...
   1. TRAILING VORTICITY BANNER WILL SWEEP NEWD OVER ORE AND NRN CA
   BEHIND LOW-LEVEL FRONTAL ZONE...AND 
   2. SEVERAL SEPARATE LOBES NOW DIGGING SEWD BEHIND MAIN TROUGH WILL
   PIVOT THROUGH THAT TROUGH. 
   RESULT SHOULD BE NET INLAND PENETRATION OF MID/UPPER TROUGHING TO
   CENTRAL PORTIONS WA/ORE AND NERN CA BY END OF PERIOD. 

   ...NWRN CA...SWRN ORE...
   LOW-LEVEL FRONTAL ZONE CONTINUES TO SHIFT INLAND IN ASSOCIATION WITH
   ARC OF PRECIP FROM NRN ORE COAST SSEWD ACROSS NWRN CA.  BEHIND
   THIS...WIDELY SCATTERED CONVECTION OVER THIS REGION SHOULD PEAK IN
   INTENSITY FROM MIDDAY THROUGH AFTN AND MAY OFFER BRIEF/SMALL TORNADO
   POTENTIAL...WHETHER WITH INLAND STORM-SCALE/MINI-SUPERCELL PROCESSES
   OR WATERSPOUT MOVING ASHORE. APCHG SHORTWAVE TROUGH WILL RESULT IN
   COOLING ALOFT...STEEPENING LOW/MIDDLE-LEVEL LAPSE RATES...SFC-BASED
   EFFECTIVE-INFLOW PARCELS...AND WEAK BUOYANCY WITH MLCAPE GENERALLY
   BELOW 250 J/KG. WINDOW OF OPPORTUNITY SHOULD TRANSLATE EWD ACROSS
   MRGL OUTLOOK AREA THIS AFTN WHERE THOSE THERMODYNAMIC CONDITIONS
   JUXTAPOSE WITH WRN PORTION OF RELATIVELY BACKED NEAR-SFC
   FLOW...ASSOCIATED HODOGRAPH ENLARGEMENT...AND FAVORABLE EFFECTIVE
   SHEAR TO SUPPORT STORM-SCALE ROTATION.  MAIN LIMITING FACTOR WILL BE
   LACK OF MORE ROBUST INSTABILITY...THEREFORE UNCONDITIONAL
   PROBABILITIES ARE KEPT QUITE SMALL ATTM. 

   ...NERN CONUS...
   MID/UPPER-LEVEL CYCLONE OVER CANADIAN MARITIMES...AND ADJACENT ATLC
   WATERS...IS FCST TO EJECT AWAY FROM THAT REGION AND WEAKEN. 
   HOWEVER...HEIGHTS ARE FCST TO FALL OVER MUCH OF LOWER GREAT
   LAKES...MID-ATLC AND NEW ENGLAND REGIONS DURING DAY-1.  THIS WILL
   OCCUR AS STG SHORTWAVE TROUGH NOW OVER NRN ONT...AND TRAILING MAXIMA
   IN WINDS/VORTICITY ALOFT OVER SRN MB AND NRN MN...MOVE ESEWD AND
   STRENGTHEN.  DURING 00-06Z TIME FRAME...CLOSED 500-MB CYCLONE SHOULD
   FORM OVER SWRN QUE AND MOVE EWD TO ST. LAWRENCE RIVER BY 12Z. 
   ASSOCIATED SFC COLD FRONT WILL PRECEDE THESE FEATURES BY SWEEPING
   EWD ACROSS MID ATLC AND NEW ENGLAND TODAY.  SCATTERED
   CONVECTION...INCLUDING SOME EMBEDDED TSTMS...SHOULD DEVELOP INVOF
   THAT FRONT.  DESPITE COOL SFC TEMPS AND SFC DEW POINTS MAINLY IN 40S
   F...STRENGTH OF COOLING ALOFT AND RESULTANT ENHANCEMENT OF
   LOW/MIDDLE-LEVEL LAPSE RATES WILL BE SUFFICIENT TO YIELD SFC-BASED
   INFLOW PARCELS...WITH MLCAPE GENERALLY REMAINING BELOW 200 J/KG. 
   FCST SOUNDINGS SUGGEST SOME BUOYANCY MAY REACH LEVELS SUITABLE FOR
   LTG PRODUCTION...AND SMALL HAIL AND GUSTY WINDS ALSO ARE POSSIBLE. 
   HOWEVER...SVR POTENTIAL APPEARS TOO CONDITIONAL EVEN FOR MRGL
   PROBABILITIES ATTM.

   ..EDWARDS/JIRAK.. 10/25/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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