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    Day 2 Outlook >
Jul 15, 2013 1300 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Mon Jul 15 12:55:37 UTC 2013 (Print Version | Day 1 shapefile | Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Tornado Wind Hail
 Population  Cities/Towns  CWAs  Interstates  Counties  ARTCC  FEMA Regions

Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 23,740 78,727 Williston, ND...Glendive, MT...Plentywood, MT...Portal, ND...
 Forecast Discussion
   SPC AC 151251

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0751 AM CDT MON JUL 15 2013

   VALID 151300Z - 161200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NERN MT AND NWRN ND...

   ...SYNOPSIS...
   MID-UPPER LEVEL PATTERN WILL BE DOMINATED BY STRONG ANTICYCLONE OVER
   NERN CONUS...WELL-DEFINED CYCLONE MOVING WSWWD OVER SRN PLAINS...AND
   JET OF CYCLONIC FLOW PRIMARILY FOCUSED OVER CANADIAN PRAIRIE
   PROVINCES.  CYCLONE WAS CENTERED OVER SRN OK AT 12Z AND FCST TO
   PROCEED WWD ACROSS TX PANHANDLE THROUGH REMAINDER PERIOD.  RELATED
   CONVECTIVELY-AIDED SFC COLD FRONT -- ANALYZED FROM COASTAL SE TX
   WNWWD ACROSS S-CENTRAL TX TO TRANS-PECOS REGION OF W TX -- SHOULD
   CONTINUE SWWD ACROSS BIG-BEND REGION AND SRN NM INTO
   CHIHUAHUA...WHILE DRIFTING SWD ACROSS S TX.

   MEANWHILE...NRN-STREAM SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE
   CHANNEL IMAGERY OVER SRN BC AND WRN WA -- WILL EJECT NEWD ACROSS AB
   TODAY THEN WEAKEN AND ACCELERATE TO NRN MB OVERNIGHT...IN RESPONSE
   TO UPSTREAM SHORTWAVE AMPLIFICATION OVER NW TERRITORIES AND NRN SK. 
   PRECEDING SFC COLD FRONT IS EXPECTED TO MOVE SEWD ACROSS MT
   TODAY...REACHING NERN THROUGH S-CENTRAL MT AROUND 00Z AND SRN MB TO
   NERN WY BY 12Z.

   ...NRN HIGH PLAINS...
   WIDELY SCATTERED TO SCATTERED TSTMS ARE FCST TO DEVELOP THIS AFTN
   AND EVENING ALONG OR JUST AHEAD OF COLD FRONT OVER MT...SOME OF
   WHICH MAY BECOME SUPERCELLULAR WHILE STILL RELATIVELY
   DISCRETE...THEN EVOLVING INTO ONE OR MORE BOWING SEGMENTS.  ACTIVITY
   THEN SHOULD SHIFT EWD TO NEWD OVER PORTIONS NERN MT AND NWRN ND
   BEFORE MOVING INTO CANADA AND/OR DISSIPATING OVERNIGHT.  DAMAGING
   GUSTS AND LARGE HAIL ARE POSSIBLE -- INCLUDING POTENTIAL FOR
   ISOLATED SIGNIFICANT/DAMAGING HAIL.  ALSO...AS SRN EXTENSION OF
   THREAT OVER SK...SOME TORNADO RISK MAY DEVELOP WITH ANY DISCRETE
   STORM THAT MOVES INTO HIGH-THETAE AIR OVER NERN MT AND EXTREME NWRN
   ND.

   LARGE-SCALE DCVA/ASCENT ASSOCIATED WITH SHORTWAVE TROUGH WILL 
   REMAIN LARGELY OVER CANADA...YIELDING LITTLE NET CHANGE IN 500-MB
   HEIGHTS OVER NRN HIGH PLAINS.  HOWEVER...GRADUAL WWD SHIFT OF NERN
   CONUS HIGH COMBINED WITH PASSAGE OF THAT SHORTWAVE ACROSS PRAIRIE
   PROVINCES WILL TIGHTEN GRADIENT FLOW ALOFT...THEREBY ENHANCING DEEP
   SHEAR.  MEANWHILE...INCREASING SELY BOUNDARY-LAYER FLOW WILL ADVECT
   RICHER MOISTURE INTO REGION FROM DAKOTAS...JUXTAPOSING WITH STEEP
   MIDLEVEL LAPSE RATES SEEN IN 12Z GGW RAOB.  NET RESULT SHOULD BE
   BELT OF 2000-2500 J/KG MLCAPE IN PRECONVECTIVE ENVIRONMENT
   SUPERIMPOSED WITH 45-50 KT EFFECTIVE SHEAR MAGNITUDES...PRIMARILY
   OVER 15% WIND/HAIL AREA.

   MAIN UNCERTAINTY INVOLVES HOW FAR SWD CONVECTION WILL BUILD
   ALONG/AHEAD OF FRONT...WITH CURRENT SLGT RISK APPROXIMATING MEDIAN
   SOLUTION OF SUSTAINED CONVECTIVE PRECIP AMONG OPERATIONAL PROGS AND
   SREF MEMBERS.  FARTHER S...CONVECTIVE AND SVR POTENTIAL BECOMES MORE
   MRGL/CONDITIONAL DUE TO CONCERNS OVER WEAKER LOW-LEVEL
   CONVERGENCE...DRIER INFLOW LAYERS YIELDING LESS CAPE...PRESENCE OF
   WEAKER DEEP SHEAR WITH SWD EXTENT...AND GREATER DISTANCE FROM
   DEEP-LAYER LIFT PRECEDING CANADIAN SHORTWAVE TROUGH.  HOWEVER...ANY
   TSTMS MOVING OVER THOSE DEEPLY WELL-MIXED SUBCLOUD LAYERS WILL OFFER
   POTENTIAL FOR SVR GUSTS AND HAIL.

   ..EDWARDS/SMITH.. 07/15/2013

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: July 15, 2013
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