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    Day 2 Outlook >
Dec 22, 2014 2000 UTC Day 1 Convective Outlook
Updated: Mon Dec 22 19:59:59 UTC 2014 (Print Version | 20141222 2000Z Day 1 shapefile | 20141222 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 221959

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0159 PM CST MON DEC 22 2014

   VALID 222000Z - 231200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF THE LOWER MS
   VALLEY AND CENTRAL GULF COAST REGION...

   ...SUMMARY...
   ISOLATED SEVERE STORMS MAY OCCUR THIS AFTERNOON THROUGH EARLY
   TUESDAY OVER PARTS OF THE LOWER MISSISSIPPI VALLEY AND CENTRAL GULF
   COAST REGION.

   ...20Z UPDATE...
   FORECAST SCENARIO REMAINS ESSENTIALLY UNCHANGED /SEE PRIOR
   DISCUSSION BELOW/...INCLUDING ASSOCIATED CAVEATS/LIMITATIONS
   ASSOCIATED WITH WHAT IS STILL EXPECTED TO BE A SPORADIC/ISOLATED
   SEVERE RISK AT MOST. BASED ON LATEST OBSERVATIONS/ GUIDANCE...THE
   MARGINAL RISK WAS SPATIALLY ADJUSTED ACROSS A SMALL PART OF LA/MS
   WHERE STORM COVERAGE SHOULD REMAIN LIMITED WITHIN THE MARGINALLY
   MOIST WARM SECTOR GIVEN RESIDUAL MID-LEVEL CAPPING /REFERENCE 12Z
   SOUNDINGS FROM LAKE CHARLES AND JACKSON MS/ AMID THE ABSENCE OF
   GREATER FORCING FOR ASCENT.

   ..GUYER.. 12/22/2014

   .PREV DISCUSSION... /ISSUED 1029 AM CST MON DEC 22 2014/

   ...SYNOPTIC SETUP...
   PATTERN WILL FURTHER AMPLIFY OVER THE LWR 48 THROUGH TUE AS RIDGE
   REMAINS STNRY OFF THE CA CST WHILE BROAD TROUGH STRENGTHENS OVER THE
   CNTRL U.S. INTENSIFICATION OF THE TROUGH WILL BE ACCOMPLISHED BY THE
   CONTINUED SSE ADVANCE OF 175 KT JET STREAK NOW CROSSING THE NRN
   RCKYS...AND BY A SERIES OF WEAKER IMPULSES OVER THE NRN AND CNTRL
   PLNS EXPECTED TO CONSOLIDATE INTO A CLOSED LOW OVER THE LWR MO VLY.
   THIS SETUP WILL STRENGTHEN AND SLIGHTLY BACK EXISTING SWLY FLOW OVER
   THE LWR MS VLY/GULF CST.

   AT LWR LVLS...WRN PART OF WEAK FRONT THAT HAS BEEN STALLED OVER THE
   NRN GULF OF MEXICO AND THE WRN ATLANTIC IN RECENT DAYS SHOULD BEGIN
   DRIFTING N LATER TODAY AND TNGT AS SFC PRESSURES FALL OVER THE LWR
   MS AND TN VLYS. NWD MOVEMENT OF THE FRONT WILL ALLOW FAIRLY
   SUBSTANTIAL MOISTURE /PW AROUND 1.50 INCHES/ NOW OVER THE CNTRL AND
   ERN GULF TO SPREAD INLAND ACROSS THE CNTRL/ERN GULF CST
   REGION...WITH SFC DEWPOINTS IN THE UPR 50S F EXPECTED AS FAR N AS
   THE AL-MS-TN BORDER AREA BY 12Z TUE. SFC CYCLOGENESIS
   WILL...HOWEVER...LIKELY REMAIN WELL REMOVED FROM THE RETURNING
   MOISTURE...WITH THE MAIN SFC LOW EXPECTED TO FORM OVER SRN IA/NRN
   MO...BENEATH INTENSIFYING UPR VORT.  

   ...LWR MS VLY/CNTRL GULF CST LATER TODAY THROUGH EARLY TUE...
   COMBINATION OF GRADUALLY STRENGTHENING SWLY FLOW AND INCREASING
   MOISTURE WILL YIELD AN ENVIRONMENT THAT WILL BECOME AT LEAST
   CONDITIONALLY FAVORABLE FOR STRONG TO SVR TSTMS...MAINLY LATER TODAY
   THROUGH EARLY TUE OVER THE CNTRL GULF CST REGION. MODEST LARGE-SCALE
   FORCING FOR ASCENT AND ABSENCE OF STRONG LOW-LVL SOURCES OF ASCENT
   SUGGEST...HOWEVER...THAT THE SVR THREAT SHOULD REMAIN SPORADIC...AND
   COVERAGE ISOLD.

   STRENGTHENING SWLY DEEP SHEAR WILL RESULT IN SIZABLE...LOOPED
   LOW-LVL HODOGRAPHS BY THIS EVE AND THROUGH EARLY TUE IN ZONE OF WEAK
   TO MODEST SFC-BASED INSTABILITY /SBCAPE 250-1000 J PER KG/ NEAR
   NWD-MOVING FRONT OVER SRN PARTS OF LA-MS-AL AND THE WRN FL
   PANHANDLE. SATELLITE/MODEL DATA SUGGEST...HOWEVER...THAT LARGE-SCALE
   FORCING FOR ASCENT WILL BE LIMITED UNTIL PERHAPS LATE IN THE PERIOD
   WHEN A JET-ENTRANCE REGION CIRCULATION EVOLVES OVER THE CNTRL GULF
   CST. MEANWHILE...MID-LVL LAPSE RATES WILL BE WEAK.

   NEVERTHELESS...WITH SFC DEWPOINTS INCREASING TO THE MID-UPR 60S F
   ALONG THE CNTRL GULF CST...WEAKLY CONFLUENT LOW-LVL FLOW MAY BE
   SUFFICIENT TO SUPPORT A COUPLE SHORT LINES/SMALL CLUSTERS OF SFC OR
   NEAR-SFC-BASED STORMS LATE TNGT AND EARLY TUE FROM SRN LA-SRN MS EWD
   INTO THE WRN FL PANHANDLE. THIS ACTIVITY...AND ANY MORE WDLY
   SCTD...SMALL STORMS THAT MAY FORM S OF THE FRONT...COULD CONTAIN A
   SPORADIC TORNADO/ISOLD DMGG WIND THREAT...ESPECIALLY GIVEN ENHANCED
   LOW-LVL VEERING PROFILES NEAR THE BOUNDARY. 

   FARTHER N...STRENGTHENING 925-850 MB WAA/MOISTURE TRANSPORT SHOULD
   FOSTER INCREASING COVERAGE OF ELEVATED CONVECTION/STORMS NNEWD INTO
   THE LWR OH VLY BY MORNING.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z

        
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