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    Day 2 Outlook >
Sep 22, 2014 1300 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Mon Sep 22 12:54:54 UTC 2014 (Print Version | 20140922 1300Z Day 1 shapefile | 20140922 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 221254

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0754 AM CDT MON SEP 22 2014

   VALID 221300Z - 231200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   THUNDERSTORMS MAY APPROACH OR BRIEFLY REACH SEVERE LEVELS TODAY OVER
   PARTS OF THE CENTRAL ROCKIES AND ADJACENT HIGH PLAINS...AS WELL AS
   THE GEORGIA AND SOUTH CAROLINA COASTAL PLAIN.

   ...SYNOPSIS...
   SEASONALLY HIGH-AMPLITUDE SYNOPTIC PATTERN CHARACTERIZES
   MIDDLE-UPPER LEVELS TODAY.  EMBEDDED WITHIN LARGER-SCALE CYCLONIC
   FLOW THAT COVERS MUCH OF ERN NORTH AMERICA...THREE PRIMARY 
   SHORTWAVE TROUGHS WILL BE EVIDENT TODAY...
   1. PERTURBATION OVER SRN QUE AND NORTHERN NEW ENGLAND WILL EJECT
   NEWD ACROSS LABRADOR OVERNIGHT AS...
   2. UPSTREAM FEATURE NOW OVER FAR NRN ONT AMPLIFIES AND PIVOTS
   SEWD/EWD ACROSS NEW ENGLAND.
   3. TRAILING VORTICITY/SPEED MAX NOW OVER MID SOUTH MOVES SEWD THEN
   DECELERATES OVER GA...BECOMING CLOSED 500-MB LOW BY 12Z.

   FARTHER W...MEAN RIDGING OVER HIGH PLAINS AND NWWD ACROSS WRN CANADA
   WILL BE PENETRATED BY PERTURBATION NOW DEVOLVING FROM CLOSED CYCLONE
   TO OPEN-WAVE TROUGH OVER UT/SRN ID.  TROUGH SHOULD CROSS WY TODAY
   AND REACH WRN PARTS OF SD/NEB OVERNIGHT.

   AT SFC...11Z ANALYSIS SHOWED COLD FRONT FROM OFFSHORE MID-ATLC
   REGION TO ERN NC...NRN GA...CENTRAL LA...AND W-CENTRAL TX.  FRONT IS
   FCST TO MOVE SEWD ACROSS SERN STATES THROUGH PERIOD...HANGING UP
   SOMEWHAT INVOF WEAK FRONTAL-WAVE LOW THAT WILL DEVELOP TODAY OVER
   SERN GA IN ADVANCE OF APCHG MID-UPPER-LEVEL SHORTWAVE TROUGH.  LEE
   TROUGHING WILL DEEPEN OVER HIGH PLAINS. 

   ...SRN ATLC COASTAL PLAIN...
   WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP THIS AFTN IN
   MULTICELLULAR CLUSTERS ALONG AND AHEAD OF SFC COLD FRONT...LIKELY TO
   BE MOST CONCENTRATED BETWEEN FRONTAL-WAVE LOW-PRESSURE AREA AND
   SC/GA SEA-BREEZE BOUNDARIES.  LATEST SFC ANALYSIS SHOWS POCKET OF
   RELATIVELY MINIMIZED SFC DEW POINTS OVER SRN GA AND COASTAL SC THAT
   MAY LINGER THROUGH MUCH OF TODAY GIVEN
   1. LACK OF STG SFC WINDS TO ADVECT GREATER MOISTURE FROM ELSEWHERE
   AND
   2. DIABATICALLY DRIVEN VERTICAL MIXING OF BOUNDARY LAYER.

   THIS FACTOR WILL LIMIT MLCAPE TO AROUND 1000 J/KG -- LOCALLY HIGHER.
   STILL...BUOYANCY/HEATING AND LIFT NEAR AFOREMENTIONED BOUNDARIES
   SHOULD BE SUFFICIENT TO SUPPORT TSTM DEVELOPMENT...AMIDST
   STRENGTHENING LARGE-SCALE ASCENT THAT PRECEDES APCHG TROUGH. 
   MEANWHILE...WELL-MIXED SUBCLOUD LAYER SHOULD SUPPORT MAINTENANCE OF
   ANY HAIL AND STG GUSTS TO SFC.  LACK OF MORE SUBSTANTIAL LOW-LEVEL
   FLOW AND SHEAR SHOULD PRECLUDE WELL-ORGANIZED SVR RISK...ALTHOUGH
   STRONG UPPER WINDS WILL AID IN VENTILATING DEEP/PERSISTENT
   CONVECTION.

   ...FRONT RANGE AND ADJACENT HIGH PLAINS...
   WIDELY SCATTERED TSTM DEVELOPMENT IS EXPECTED MID-LATE AFTN OVER
   FRONT RANGE AND ADJACENT HIGHER PLAINS TERRAIN NEAR LEE TROUGH. 
   CONVECTION WILL MOVE EWD TO SEWD...OFFERING GUSTS AND HAIL NEAR SVR
   LIMITS AND CONDITIONAL/MRGL TORNADO RISK.  THREAT SHOULD WANE SOON
   AFTER SUNSET WITH LOSS OF SFC-BASED INSTABILITY.

   PATCHY CLOUD COVER WILL SLOW PACE OF DIURNAL/DIABATIC
   DESTABILIZATION TODAY.  NONETHELESS...ENOUGH HEATING IS EXPECTED TO
   REMOVE MLCINH AND OVERCOME MODEST LAPSE RATES ALOFT...FOR
   ESSENTIALLY UNINHIBITED MLCAPE IN 500-1000 J/KG RANGE.  LOW-LEVEL
   SHEAR SHOULD INCREASE DURING LATE AFTN INTO 00-02Z TIME
   FRAME...ALONG WITH 35-40 KT EFFECTIVE-SHEAR MAGNITUDES...BEFORE
   STRENGTHENING/DEEPENING LAYER OF NEAR-SFC STATIC STABILITY TAKES
   OVER.  THIS MAY SUPPORT A SUPERCELL OR TWO FOR A SHORT PERIOD.  MAIN
   LIMITING FACTORS APPEAR TO BE SPARSE COVERAGE AND LACK OF MORE
   ROBUST BUOYANCY.

   ..EDWARDS/MARSH.. 09/22/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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