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    Day 2 Outlook >
Sep 18, 2014 1300 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Thu Sep 18 12:24:05 UTC 2014 (Print Version | 20140918 1300Z Day 1 shapefile | 20140918 1300Z Day 1 KML)
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 Forecast Discussion
   SPC AC 181224

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0724 AM CDT THU SEP 18 2014

   VALID 181300Z - 191200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   A FEW SEVERE STORMS ARE EXPECTED TO DEVELOP LATER TODAY FROM
   PORTIONS OF THE OZARK PLATEAU TO RED RIVER VALLEY...AS WELL OVER
   PARTS OF THE GREAT BASIN INTO NORTHERN ROCKIES. ELSEWHERE...ISOLATED
   STRONG TO MARGINALLY SEVERE STORMS ARE POSSIBLE ALONG THE SOUTHEAST
   ATLANTIC COAST. GUSTY WINDS AND HAIL ARE THE PRIMARY THREATS.

   ...SYNOPSIS...

   THE LARGE-SCALE PATTERN WILL UNDERGO DE-AMPLIFICATION THIS
   PERIOD...LARGELY DUE TO THE FLATTENING OF THE CNTRL U.S. RIDGE BY A
   STRENGTHENING ZONAL FLOW REGIME BECOMING ESTABLISHED FROM THE NERN
   PACIFIC TO S-CNTRL CANADA. TROUGHS WILL CONTINUE TO BRACKET THE
   DAMPENING RIDGE...ONE OVER THE WRN STATES AND OTHER SITUATED
   GENERALLY E OF THE MS VALLEY.

   AT THE SURFACE...A WEAK COLD FRONT WILL DRIFT SLOWLY SWD THROUGH THE
   SERN U.S. WHILE THE NWRN EXTENSION OF THIS BOUNDARY PIVOTS EWD
   THROUGH THE NRN AND CNTRL PLAINS IN TANDEM WITH A MIGRATORY SURFACE
   LOW TRACKING ACROSS S-CNTRL CANADA. TRAILING SWWD FROM THIS LOW
   PRESSURE...A COLD FRONT WILL MOVE THROUGH THE NRN HIGH PLAINS.

   ...INTERMOUNTAIN WEST THIS AFTERNOON/EVENING...

   DESPITE BECOMING INCREASINGLY CUT OFF FROM THE PRIMARY BELT OF POLAR
   WESTERLIES DEVELOPING ACROSS WRN CANADA...A BELT OF 35-50 KT
   MID-LEVEL FLOW AND WEAK HEIGHT FALLS WILL ATTEND THE WRN U.S. TROUGH
   AS IT SLOWLY EDGES SEWD. THIS HIGHER-MOMENTUM FLOW WILL ALIGN WITH A
   CORRIDOR OF STEEP LOW TO MID-LEVEL LAPSE RATES AND RESULTANT SBCAPE
   OF 500-1000 J/KG RESIDING AHEAD OF A WEAK SURFACE FRONT/TROUGH.
   CONVERGENCE ALONG THIS BOUNDARY COUPLED WITH DEEPENING OROGRAPHIC
   CIRCULATIONS ARE EXPECTED TO FOSTER WIDELY SCATTERED TSTMS BY
   AFTERNOON...A FEW OF WHICH COULD BE STRONG TO MARGINALLY SEVERE AND
   CAPABLE OF LOCALLY STRONG WIND GUSTS AND/OR HAIL.

   ...SERN KS INTO THE RED RIVER VALLEY/ARKLATEX THIS
   AFTERNOON/EVENING...

   A SWWD-PROPAGATING MCS IS ONGOING AS OF 12Z ACROSS PORTIONS OF SERN
   KS AND NERN OK...AIDED BY WEAK WAA/ISENTROPIC ASCENT ALONG A WSWLY
   LLJ AND DCVA ASSOCIATED WITH A WEAK MID-LEVEL PERTURBATION
   PROGRESSING SEWD THROUGH THE LOWER MO VALLEY. THOUGH A TEMPORARY
   DECREASE IN STORM COVERAGE MAY OCCUR THROUGH MID MORNING OWING TO
   THE DIURNAL WEAKENING OF THE LLJ...AN UPTICK IN STORM COVERAGE AND
   INTENSITY IS ANTICIPATED BY AFTERNOON ALONG THE RELATED COLD POOL AS
   IT INTERACTS WITH A MOIST AND MODERATELY UNSTABLE AIR MASS WHERE
   MLCAPE COULD APPROACH 1500-2500 J/KG. 

   EFFECTIVE BULK SHEAR MAGNITUDES ARE FORECAST TO REMAIN GENERALLY
   BELOW 30 KT WHICH SHOULD LIMIT THE POTENTIAL FOR HIGHER-ORDER STORM
   MODES AND A RISK FOR AN ORGANIZED SEVERE WEATHER EPISODE.
   NONETHELESS...THE DEGREE OF INSTABILITY WILL BE SUPPORTIVE OF STRONG
   STORM CLUSTERS OR WEAKLY BOWING LINE SEGMENTS WITH A THREAT FOR
   ISOLATED DAMAGING WIND GUSTS AND HAIL SPREADING SWD THROUGH THE RED
   RIVER VALLEY LATER TODAY.

   ...SERN ATLANTIC COAST THIS AFTERNOON...

   LOW-LEVEL CONVERGENCE/UPLIFT ALONG THE SYNOPTIC COLD FRONT AND
   DEVELOPING SEA BREEZE BOUNDARIES WILL PROMOTE THE DEVELOPMENT OF
   WIDELY SCATTERED AFTERNOON TSTMS AMIDST A MOIST AND AT LEAST
   MODESTLY UNSTABLE AIR MASS. STEEP LOW-LEVEL LAPSE RATES AND 25-30 KT
   OF DEEP-LAYER SHEAR MAY SUPPORT A FEW VIGOROUS STORMS WITH AN
   ATTENDANT RISK FOR MAINLY GUSTY WINDS.

   ..MEAD/BOTHWELL.. 09/18/2014

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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