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    Day 2 Outlook >
Apr 18, 2015 1300 UTC Day 1 Convective Outlook
Updated: Sat Apr 18 12:58:02 UTC 2015 (Print Version | 20150418 1300Z Day 1 shapefile | 20150418 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 181258

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0758 AM CDT SAT APR 18 2015

   VALID 181300Z - 191200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS TO S
   TX...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING SLGT RISK...AND EWD
   ALONG GULF COASTAL PLAIN TO SWRN GA AND FL PANHANDLE...

   ...SUMMARY...
   ISOLATED TO WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED TODAY FROM
   THE CENTRAL PLAINS TO SOUTH TEXAS...SOME OF WHICH MAY PRODUCE SEVERE
   GUSTS AND HAIL.  A FEW TORNADOES CANNOT BE RULED OUT.

   ...SYNOPSIS...
   IN MID-UPPER LEVELS...SPLIT-FLOW PATTERN IS FCST TO PREVAIL OVER
   CONUS THROUGH PERIOD...WITH SPLIT OCCURRING AROUND LARGE CYCLONE
   CURRENTLY CENTERED OVER SRN CO.  ASSOCIATED CYCLONIC FLOW EXTENDS
   WELL SWD TO W-CENTRAL MEX...WITH PRONOUNCED RIDGING TO ITS E FROM
   DAKOTAS SEWD ACROSS MID MS VALLEY AND TN VALLEY.  ACCOMPANYING
   500-MB LOW IS FCST TO WEAKEN GRADUALLY AS IT MOVES ERRATICALLY EWD
   ACROSS CENTRAL HIGH PLAINS...REACHING WRN KS AND DEVOLVING INTO
   OPEN-WAVE TROUGH NEAR END OF PERIOD.  MOISTURE-CHANNEL IMAGERY
   INDICATES SRN-STREAM PERTURBATION OVER W-CENTRAL MEX...WHICH IS
   EXPECTED TO EJECT NEWD ACROSS NERN MEX...REACHING MID/UPPER TX
   OFFSHORE WATERS AND SE TX/SWRN LA AREA AROUND 00Z...THEN PIVOTING
   NEWD TOWARD WRN TN OVERNIGHT.

   IN MID/UPPER-LEVEL NRN STREAM...COMPACT BUT STG SHORTWAVE TROUGH
   CURRENTLY NEAR ONT/QUE BORDER IS EXPECTED TO DIG SEWD ACROSS NRN NY
   TO VT/NH BY 00Z...THEN MOVE WELL OFFSHORE OVER ATLC OVERNIGHT.  THIS
   PERTURBATION WILL BE PRECEDED BY SFC CYCLONE AND ASSOCIATED COLD
   FRONT...MOVING SEWD OVER THESE AREAS DURING DAYLIGHT HOURS.

   FARTHER SW AT SFC...11Z ANALYSIS SHOWED WEAK SFC LOWS OVER S-CENTRAL
   NEB AND SWRN KS...CONNECTED BY TROUGH...WITH COLD FRONT SWD ACROSS
   TX PANHANDLE THEN SWWD OVER SERN NM.  DRYLINE WAS EVIDENT JUST E OF
   FRONT IN PANHANDLE...THEN SSWWD ACROSS PERMIAN BASIN INTO BIG BEND
   REGION.  SRN PORTION OF FRONT SHOULD WEAKEN TODAY...WHILE NRN
   PORTION BLENDS WITH DRYLINE OVER PANHANDLES AND WITH TROUGH OVER KS.
    DRYLINE SHOULD SHIFT EWD TO EXTREME ERN PANHANDLES OR EXTREME WRN
   OK...W-CENTRAL TX AND NRN COAHUILA THIS AFTN.

   ...CENTRAL PLAINS TO S TX AND GULF COAST...
   WIDELY SCATTERED TO LOCALLY SCATTERED TSTMS SHOULD DEVELOP ACROSS
   BROAD SWATH OF CENTRAL CONUS AND GULF COAST REGION TODAY...OFFERING
   AT LEAST MRGL POTENTIAL FOR DAMAGING GUSTS AND HAIL.

   PARAMETRIC SUPPORT APPEARS GREATEST FROM CENTRAL PLAINS TO S TX
   WHERE STRONGEST SFC HEATING AND SOMEWHAT FAVORABLE DEEP SHEAR ARE
   EXPECTED.  MULTIPLE CONVECTIVE COMPLEXES AND COLD POOLS HAVE CROSSED
   THIS REGION DURING LAST 2 DAYS...RENDERING LOW LEVELS VERY
   FRAGMENTED IN TERMS OF MOISTURE AND INSTABILITY.  SFC DEW POINTS
   HAVE FALLEN INTO 50S WITHIN AT LEAST 100 NM E OF DRYLINE FROM I-10
   NWD...WITH MOSTLY LOW-MID 60S FARTHER E.  MORNING RAOBS INDICATE
   MOIST LAYER IS SHALLOW ACROSS MUCH OF THIS AREA...YET STILL
   SUFFICIENT TO SUPPORT TSTMS THAT MAY BECOME STG-SVR IN POCKETS OF
   AFTN DESTABILIZATION.  SPECIFIC FOCI FOR TSTM INITIATION APPEAR
   NEBULOUS E OF DRYLINE ATTM BECAUSE OF MULTIPLE OVERLAID COLD POOLS
   OF VARYING SCALES AND AGES...AND WEAKNESS OF SFC WINDS THAT WILL
   PERSIST ACROSS ALL BUT CENTRAL HIGH PLAINS PART OF THIS CORRIDOR
   THROUGH MOST OF TODAY.  AS SUCH...WHILE A FEW SUPERCELLS AND SEVERAL
   ORGANIZED MULTICELL CLUSTERS AND ADDITIONAL WIND-PRODUCING COLD
   POOLS ARE POSSIBLE...MESOSCALE AND SMALLER FACTORS PRECLUDE
   ASSIGNING MORE THAN BROAD-BRUSHED SVR AREA ATTM.

   RICH...RELATIVELY UNDISTURBED MARITIME-TROPICAL AIR MASS IS CONFINED
   TO GULF SE OF ONGOING MCS LOCATED S OF LA...AND ASSOCIATED OUTFLOW
   BOUNDARY THAT EXTENDS SWWD ACROSS GULF TO NERN MEX.  SFC DEW POINTS
   REMAIN IN 70S BEHIND THIS BOUNDARY OVER DEEP S TX...WITH UPPER 60S
   AS FAR N AS HOU AREA IN SE TX.  12Z RAOBS SHOW SHALLOW MOIST LAYER
   COMPARED TO PREVIOUS DAYS AS WELL.  POCKETS OF 1000-1500 J/KG
   MLCAPE...LOCALLY HIGHER...ARE EXPECTED FROM CENTRAL PLAINS TO RED
   RIVER REGION...WITH 1500-2500 J/KG VALUES PSBL OVER CENTRAL/S TX. 
   ALTHOUGH HEIGHT FALLS ARE FCST ACROSS MUCH OF THIS SWATH AS
   MID-UPPER-LEVEL PERTURBATION PROGRESSES EWD...WEAKER DEEP SHEAR IS
   EXPECTED OVER MOST OF REGION COMPARED TO PREVIOUS 2 DAYS.  THIS WILL
   BE RELATED LARGELY TO WEAKENING OF THAT LOW/TROUGH FEATURE AND
   ASSOCIATED MIDLEVEL GRADIENT FLOW.  WHILE STILL FAVORABLE FOR
   SVR...CAPE/SHEAR PARAMETER SPACE WILL BE SOMEWHAT REDUCED OVERALL
   AND VERY FRAGMENTED AS WELL.

   MEANWHILE...SVR RISK APPEARS TO HAVE DIMINISHED ALONG CENTRAL GULF
   COASTAL PLAIN AND LOWER MS DELTA...THANKS TO LARGE MCS OVER NRN GULF
   AND RELATED AREA OF CLOUDS/PRECIP THAT WILL KEEP INLAND REGIONS FROM
   DESTABILIZING SUBSTANTIALLY WELL INTO AFTN.

   ...NERN NY AND NEW ENGLAND...
   SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP
   MIDDAY THROUGH AFTN IN ZONE OF INCREASING LARGE-SCALE
   ASCENT...JUXTAPOSED WITH IMPINGEMENT OF SFC LOW AND COLD FRONT ON
   AREAS OF FAVORABLE DIABATIC SFC HEATING.  THOUGH MOISTURE WILL
   REMAIN MRGL WITH SFC DEW POINTS 30S AND 40S OVER THIS
   REGION...STEEPENING LAPSE RATES AND SFC HEATING SHOULD SUPPORT
   ESSENTIALLY CINH-FREE/SFC-BASED EFFECTIVE-INFLOW PARCELS PRIOR TO
   FROPA.  MLCAPE 100-400 J/KG IS EVIDENT IN FCST SOUNDINGS...ATOP
   WELL-MIXED/INVERTED-V THERMODYNAMIC PROFILES IN SUBCLOUD LAYER. 
   THIS ALONG WITH MOMENTUM TRANSFER IN DOWNDRAFTS...SHOULD SUPPORT STG
   GUSTS WITH SOME CONVECTION OVER REGION.  ATTM POTENTIAL FOR
   SVR/50-KT CONVECTIVE WIND AT SFC APPEARS VERY ISOLATED AND
   UNCERTAIN...TOO MUCH SO FOR AOA 5%/MRGL UNCONDITIONAL PROBABILITIES.

   ..EDWARDS/PICCA.. 04/18/2015

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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