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    Day 2 Outlook >
Sep 27, 2016 1300 UTC Day 1 Convective Outlook
Updated: Tue Sep 27 12:55:21 UTC 2016 (Print Version | 20160927 1300Z Day 1 shapefile | 20160927 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 271255

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0755 AM CDT TUE SEP 27 2016

   VALID 271300Z - 281200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   THE RISK FOR ORGANIZED SEVERE THUNDERSTORMS APPEARS MINIMAL TODAY
   AND TONIGHT.  A FEW STRONG CELLS MAY DEVELOP OVER PARTS OF THE
   WESTERN CAROLINAS OR SOUTHERN ARIZONA.

   ...SYNOPSIS...
   CONUS UPPER-AIR PATTERN FEATURES THREE CONVECTIVELY PERTINENT
   CYCLONIC-FLOW REGIMES...IN ORDER OF STRENGTH...

   1.  INTENSE/LONG-LIVED CYCLONE CURRENTLY CENTERED OVER NRN LS. 
   ASSOCIATED 500-MB LOW IS FCST TO UNDERGO NET SWD MOTION THROUGH
   PERIOD...REACHING SRN LM BY 12Z.  OCCLUDED LOW-LEVEL CYCLONE SHOULD
   REMAIN ESSENTIALLY VERTICALLY STACKED WITH MID/UPPER-LEVEL VERSION. 

   2.  BROAD/WEAK CYCLONE -- CENTER OF WHICH NOW IS EVIDENT IN
   MOISTURE-CHANNEL IMAGERY OVER N-CENTRAL BAJA.  THIS FEATURE IS FCST
   TO DRIFT NWD TOWARD SRN CA/MEX BORDER THROUGH 12Z...WHILE SLOWLY
   FILLING.

   3.  MERIDIONALLY ELONGATED AREA OF CYCLONIC SHEAR/FLOW...PRESENTLY
   LOCATED OVER PENINSULAR FL.  THIS PERTURBATION WILL EJECT NEWD AND
   WEAKEN THROUGH PERIOD AS GREAT LAKES LOW DIGS SWD. 

   ACCOMPANYING DESTABILIZATION AND LARGE-SCALE LIFT/COOLING ALOFT...
   JUXTAPOSED WITH AT LEAST MARGINALLY FAVORABLE LOW-LEVEL MOISTURE/
   INSTABILITY...ARE EXPECTED TO CONTRIBUTE TO TSTM POTENTIAL OVER
   PORTIONS SWRN CONUS..UPPER GREAT LAKES AND LEEWARD...AND FL/GA
   REGION RESPECTIVELY THROUGH PERIOD. 

   AT SFC...11Z ANALYSIS SHOWED OCCLUDED FRONT ARCHING WELL NEWD OUT OF
   LS CYCLONE...THEN SWD ACROSS NEW ENGLAND BEFORE INTERSECTING WARM/
   COLD FRONTS INVOF RI.  COLD FRONT WAS DRAWN SWWD TO WEAK LOW OVER
   GA/AL BORDER THEN SWWD ACROSS NERN GULF.  FRONTAL ZONE SHOULD BECOME
   QUASISTATIONARY THIS PERIOD FROM GULF NEWD ACROSS CAROLINAS/VA.  SFC
   LOW SHOULD MOVE NEWD FROM FL OVER ATLC WATERS JUST OFFSHORE GA/NC/SC
   ...WITH CONFLUENCE ZONE TRAILING SWD/SSWWD ACROSS ERN/SRN FL. 

   ...WRN CAROLINAS...
   WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP THIS AFTN AND
   EVENING OVER HIGHER TERRAIN OF WRN CAROLINAS AND VICINITY...AND MOVE
   EWD TO SEWD TOWARD PIEDMONT.  COMBINATION OF OROGRAPHIC LIFT...
   DIABATIC SFC HEATING...RESIDUAL FRONTAL LIFT...AND FAVORABLE
   MOISTURE ALONG RIM OF WARM SECTOR...WILL CONTRIBUTE TO THIS REGIME. 
   FCST SOUNDINGS SUGGEST MLCAPE 1500-2000 J/KG MAY DEVELOP AMIDST SFC
   DEW POINTS MID-UPPER 60S F AND PW NEAR 1.5 INCHES...INDICATING
   POTENTIAL FOR SOME STG/WATER-LOADED DOWNDRAFTS.  WHILE STG/DAMAGING
   GUSTS CANNOT BE RULED OUT COMPLETELY WITH MOST INTENSE CELLS...AS IS
   TRUE FOR VIRTUALLY ANY SFC-BASED TSTM AMIDST SUCH BUOYANCY...
   ORGANIZED SVR POTENTIAL APPEARS TOO LOW FOR CATEGORICAL/
   UNCONDITIONAL SVR PROBABILITIES ATTM. 

   ...SRN AZ...
   WIDELY SCATTERED TSTMS MAY AFFECT THIS AREA THROUGH EARLY EVENING...
   A FEW OF WHICH MAY PRODUCE STG GUSTS.  BELT OF ENHANCED AND DIFLUENT
   MID/UPPER-LEVEL WINDS WRAPPING AROUND NERN QUADRANT OF CYCLONE ALOFT
   WILL CONTRIBUTE TO FAVORABLE DEEP/CLOUD-LAYER SHEAR...ESPECIALLY
   OVER SERN AZ BEFORE FLOW BECOMES WEAKER AND MORE DIVERGENT WITH NWD
   EXTENT.  HOWEVER...ONGOING CLOUD/PRECIP ACROSS THIS REGION CASTS
   CONSIDERABLE UNCERTAINTY ON EXTENT OF DESTABILIZATION TODAY...BASED
   ON MODIFIED TUS RAOB. 

   ...ERN/SRN FL..
   WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP THIS AFTN INVOF
   CONFLUENCE ZONE AND SEA BREEZE CIRCULATIONS...AS WELL AS OUTFLOW
   BOUNDARIES AND BOUNDARY INTERSECTIONS RESULTING FROM EARLIEST STAGES
   OF CONVECTIVE CYCLE.  ACTIVITY IS EXPECTED AMIDST RICH LOW-LEVEL
   MOISTURE MANIFEST AS SFC DEW POINTS 70S F AND ROUGHLY 2-INCH PW...
   COMBINING WITH DIABATIC SFC HEATING TO SUPPORT MLCAPE 2000-3000 J/KG
   BASED ON MODIFIED MFL RAOB.  A FEW WATER-LOADED DOWNDRAFTS MAY
   PRODUCE STG GUSTS.  WEAK DEEP-LAYER WINDS AND LACK OF SUBSTANTIAL
   VERTICAL SHEAR WILL MINIMIZE ORGANIZED SVR POTENTIAL.

   ..EDWARDS/PICCA.. 09/27/2016

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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