Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 301252
SWODY1
SPC AC 301250

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT TUE SEP 30 2014

VALID 301300Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF NEB AND SD...

...SUMMARY...
SCATTERED THUNDERSTORMS WITH A CONDITIONAL RISK FOR HAIL AND A
TORNADO OR TWO WILL OCCUR OVER PARTS OF SOUTH DAKOTA AND NEBRASKA
TODAY. A FEW STRONG TO LOCALLY SEVERE STORMS ARE EXPECTED LATE THIS
AFTERNOON INTO TONIGHT FROM EASTERN NEBRASKA AND WESTERN IOWA
SOUTHWESTWARD INTO NORTHWEST TEXAS. A FEW STORMS WITH HAIL MAY OCCUR
THIS AFTERNOON OVER PENNSYLVANIA AND ADJACENT STATES.

...SYNOPTIC SETUP...
POTENT WRN SD SHORTWAVE TROUGH EXPECTED TO CONTINUE NNE TO NEAR LK
WINNIPEG THIS PERIOD AS UPSTREAM IMPULSE AMPLIFIES SE INTO THE GRT
BASIN WITH LARGER-SCALE TROUGH ENCOMPASSING THE WRN HALF OF THE
CONUS. FARTHER E...SHORTWAVE TROUGH NOW OVER LWR MI SHOULD MOVE SE
INTO ERN OH LATER TODAY...BEFORE CONTINUING E INTO NJ EARLY WED.

SFC LOW ASSOCIATED WITH SD SYSTEM SHOULD TRACK NNE TO NEAR THE SD-ND
BORDER THIS EVE AND INTO SRN MB BY 12Z WED AS TRAILING COLD FRONT
WEAKENS AND CONTINUES SE ACROSS THE CNTRL PLNS. ASSOCIATED WARM
SECTOR WILL BECOME INCREASINGLY NARROW TODAY AS COLD FRONT OVERTAKES
WAVY WARM/STNRY FRONT EXTENDING E/SE INTO THE OH VLY.

...SD/NEB SSW INTO NW TX TODAY/TNGT...
A BAND OF SCTD...LOW-TOPPED TSTMS WITH A CONDITIONAL RISK FOR
MARGINALLY SVR HAIL AND/OR A COUPLE TORNADOES WILL EXIST TODAY
ALONG/AHEAD OF COLD FRONT CROSSING PARTS OF NEB AND SD. COOL SFC AIR
EMANATING FROM UPR GRT LKS SFC RIDGE WILL KEEP CORRIDOR OF SFC-BASED
BUOYANCY RATHER NARROW...AND STRONGEST LARGE-SCALE FORCING FOR
ASCENT WILL LIFT INTO NRN SD AND ND BY LATE IN THE DAY. BUT
COMBINATION OF MODEST SFC HEATING AND MID-LVL COOLING/ASCENT WITH
MAIN UPR VORT COULD FOSTER SUFFICIENTLY STRONG UPDRAFTS TO POSE A
SVR RISK GIVEN SUBSTANTIAL LOW-LVL DIRECTIONAL SHEAR ACROSS THE
REGION...ESPECIALLY THIS AFTN FROM N CNTRL SD SEWD INTO NE NEB.

LATER TODAY INTO TNGT...ADDITIONAL TSTMS MAY FORM FROM ERN NEB AND
WRN IA SSWWD INTO NW TX AS SECONDARY/TRAILING VORT LOBE ASSOCIATED
WITH THE EJECTING SD TROUGH OVERSPREADS DECELERATING COLD FRONT.
COMBINATION OF MODERATE /30 KT/ SW TO WSWLY DEEP SHEAR WITH MLCAPE
ON THE ORDER OF 1000-1500 J/KG MAY PROMOTE A FEW
LONGER-LIVED/SUSTAINED STORMS CAPABLE OF LOCALLY SVR HAIL AND/OR
WIND INTO TNGT.

...PA/SRN NY/NRN WV/SE OH THIS AFTN...
SATELLITE SUGGESTS THAT MI UPR LOW WILL SOMEWHAT AMPLIFY AS IT MOVES
SE INTO OH TODAY. ASSOCIATED MID-LVL COOLING/ASCENT...WITH 500 MB
TEMPS AOB MINUS 15 C...COUPLED WITH SFC HEATING AND CONVERGENCE
ALONG/AHEAD OF COLD FRONT NOW IN CNTRL-ERN OH...COULD YIELD SCTD
STRONG STORMS...ESPECIALLY OVER WRN...NRN...AND CNTRL PA LATER
TODAY. MODEST DEEP SHEAR AND LIMITED BOUNDARY LAYER MOISTURE SHOULD
LIMIT PREDOMINANT RISK TO MARGINALLY SVR HAIL.

..CORFIDI/COHEN.. 09/30/2014



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