Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 131243
SWODY1
SPC AC 131241

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0641 AM CST SAT FEB 13 2016

VALID 131300Z - 141200Z

...NO SVR TSTM AREAS FORECAST...

...SUMMARY...
ISOLATED THUNDERSTORMS WITH LOCALLY GUSTY WINDS ARE POSSIBLE THIS
AFTERNOON AND EVENING FROM PARTS OF SOUTHERN MONTANA AND NORTHERN
WYOMING TO THE BLACK HILLS AND PINE RIDGE REGIONS.

--- TECHNICAL DISCUSSION ---

...SYNOPSIS...
IN MID/UPPER LEVELS...SYNOPTIC-SCALE TROUGHING OVER ERN CONUS IS
EXPECTED TO WEAKEN AND SHIFT EWD.  ASSOCIATED UPPER CYCLONE SE OF
JAMES BAY IS FCST TO PIVOT SEWD ACROSS NEW ENGLAND THROUGH ABOUT
09Z...THEN DEVOLVE TO OPEN WAVE AS IT MOVES OFFSHORE.  TRAILING/
BROAD REGIME OF WNWLY 500-250-MB LAYER FLOW WILL COVER MUCH OF
CENTRAL AND WRN CONUS.  WITHIN THAT...STG SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER ERN PORTIONS WA/ORE -- IS
FCST TO CROSS ID THIS MORNING.  BY 00Z...TROUGH SHOULD REACH ERN MT
AND CENTRAL WY.  BY 12Z...TROUGH SHOULD EXTEND FROM SWRN MN SWD TO
MKC AREA.

AT SFC...COLD/CONTINENTAL MASS OF HIGH PRESSURE COVERED MOST OF
CENTRAL/ERN CONUS ON 11Z CHART...ANCHORED BY 1041-MB HIGH OVER MN.
LEE TROUGHING WAS DRAWN FROM NRN MT TO ERN NM.  LEE TROUGH WILL
SHIFT EWD TO ERN MT...BLACK HILLS REGION...ERN CO AND NM/TX
PANHANDLE BORDER REGION BY 00Z...WITH A FEW WEAK LOWS PERHAPS
ATTACHED...AS SFC HIGH MOVES SEWD TO INDIANA.  BY 12Z...SFC TROUGH
SHOULD EXTEND FROM CENTRAL ND TO ERN KS TO WEAK LOW OVER RED RIVER
VALLEY REGION OF N TX AND SRN OK.  POCKETS OF RELATIVELY ENHANCED
BAROCLINICITY OR WEAK COLD FRONT MAY ACCOMPANY THAT TROUGH OVER
PARTS OF CENTRAL/NRN PLAINS.

...NORTHERN HIGH PLAINS...
ISOLATED TO WIDELY SCATTERED TSTMS ARE POSSIBLE FROM MIDDAY THROUGH
MUCH OF AFTN...WITHIN PLUME OF PRECIP AND EMBEDDED CONVECTION MOVING
EWD TO SEWD ACROSS OUTLOOK AREA.  LOW-LEVEL CONVERGENCE INVOF LEE
TROUGH WILL IMPINGE UPON DESTABILIZING BOUNDARY LAYER AHEAD OF
TROUGH/FRONT...AMIDST WEAK LOW-LEVEL MOISTURE.  CONSIDERABLE
MIDLEVEL COOLING IS EXPECTED AS DCVA PLUME IMMEDIATELY PRECEDING
SHORTWAVE TROUGH SHIFTS OVER THIS REGIME...RESULTING IN SUFFICIENTLY
STEEP LOW/MIDDLE-LEVEL LAPSE RATES TO SUPPORT MUCAPE APCHG 500 J/KG
AND MLCAPE 50-200 J/KG.  BUOYANT PROFILES...WHERE THEY EXIST IN FCST
SOUNDINGS...GENERALLY EXTEND INTO SUITABLE ICING LAYERS TO SUPPORT
LTG PRODUCTION.  DESPITE AREAS OF HIGH CLOUDS...SUFFICIENT SFC
HEATING AND BOUNDARY-LAYER MIXING MAY OCCUR TO SUPPORT ISOLATED STG
GUSTS...ESPECIALLY WHERE ENHANCED BY MOMENTUM TRANSFER FROM STRONGER
GRADIENT FLOW ALOFT.  UNCERTAINTIES ON DEGREE OF MIXING/HEATING AND
LACK OF MORE ROBUST MOISTURE PRECLUDE SVR PROBABILITIES.

..EDWARDS/COHEN.. 02/13/2016

$$


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