DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 252000
SWODY1
SPC AC 251958

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT WED SEP 25 2013

VALID 252000Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL THROUGH NERN
WY...SERN MT...NWRN SD INTO WRN ND...

...NRN ROCKIES AREA THROUGH NRN HIGH PLAINS...

NO MAJOR CHANGES TO CURRENT FORECAST.

COLD FRONT EXTENDS FROM WRN ND SWWD THROUGH CNTRL AND SWRN WY. DEEP
FORCING FOR ASCENT IS INCREASING IN POST FRONTAL ZONE FROM CNTRL AND
WRN WY THROUGH ERN MT WITHIN EXIT REGION OF JET STREAK ROTATING
THROUGH UPPER TROUGH BASE AND IN ASSOCIATION WITH OROGRAPHIC
PROCESSES. LOW-LEVEL MOISTURE IS LIMITED...BUT COOLING TEMPERATURES
ALOFT AND STEEPENING LAPSE RATES WILL SUPPORT AT LEAST MARGINAL
250-500 J/KG MUCAPE IN VICINITY OF BAROCLINIC ZONE LATER TODAY.
STORMS ARE EXPECTED TO DEVELOP MOSTLY IN POST FRONTAL REGION AND
OVER THE HIGHER TERRAIN AND SPREAD NEWD THROUGH THE HIGH PLAINS THIS
EVENING. WHILE WEAK INSTABILITY COULD ULTIMATELY SERVE AS A LIMITING
FACTOR FOR A MORE ROBUST SEVERE THREAT...RELATIVELY DRY BOUNDARY
LAYERS...STEEP LAPSE RATES AND STRONG DEEP LAYER FLOW SUGGEST A FEW
STORMS COULD PRODUCE ISOLATED STRONG TO DAMAGING WIND GUSTS.

REF SWOMCD 1914 FOR MORE INFORMATION.

..DIAL.. 09/25/2013

.PREV DISCUSSION... /ISSUED 1129 AM CDT WED SEP 25 2013/

...SYNOPSIS...
BROAD WRN U.S. TROUGH WILL FURTHER AMPLIFY THIS PERIOD AS JET STREAK
NOW OFF THE ORE CST CONTINUES SEWD INTO CA AND POTENT DOWNSTREAM
DISTURBANCE NOW OVER NV EJECTS NE ACROSS NW WY/MT. AT THE SFC...LEE
CYCLONE SHOULD DEEPEN OVER ERN WY TODAY AND MOVE NE INTO THE NEB
PANHANDLE/WRN SD TNGT/EARLY THU AS COLD FRONT ASSOCIATED WITH NV
IMPULSE CONTINUES E/SE ACROSS UT AND WY AND OVERTAKES THE LOW. SCTD
TSTMS...SOME OF WHICH COULD YIELD STRONG TO PSBLY SVR SFC
GUSTS...WILL PRECEDE THE IMPULSE OVER PARTS OF THE NRN PLNS.

ELSEWHERE...WEAKER UPR SYSTEM OVER THE OH/TN VLYS SHOULD CONTINUE
E/SE WITH LITTLE CHANGE IN INTENSITY. WEAK FRONTOGENESIS AND
DEVELOPING NW FLOW ON THE SRN FRINGE OF THE SYSTEM SHOULD ALLOW A
WEAK COLD FRONT TO REACH N FL BY THE END OF THE PERIOD.

...NRN HIGH PLNS/NRN PLNS LATE THIS THROUGH TNGT...
LARGE-SCALE FORCING FOR ASCENT/DCVA WILL INCREASE OVER NRN/WRN
WY...SE MT...AND THE WRN DAKOTAS LATER TODAY INTO TNGT AS NV IMPULSE
ACCELERATES NE TOWARD REGION. WHILE STEEPENING LOW TO MID-LVL LAPSE
RATES WILL LEAD TO CONSIDERABLE STATIC INSTABILITY...SPARSE MOISTURE
/SFC DEWPOINTS IN THE 40S F WITH PW AROUND .75 INCH/ WILL LIMIT
CAPE...AND EML CAP LIKELY WILL PRECLUDE DEEP CONVECTIVE DEVELOPMENT
THROUGH MUCH OF THE DAY.

BY LATE AFTN/EVE...HOWEVER...COMBINATION OF STRENGTHENING ASCENT AND
SFC HEATING SHOULD SUFFICIENTLY ERODE CAP TO SUPPORT SCTD STORMS
ALONG AND IMMEDIATELY BEHIND COLD FRONT OVER NRN/CNTRL WY AND SE MT.
A STORM OR TWO ALSO COULD FROM ON LEE TROUGH IN NE WY. THIS ACTIVITY
SHOULD MOVE/DEVELOP RAPIDLY NNE INTO THE WRN DAKOTAS A BIT LATER IN
THE EVE.

WHILE CAPE WILL REMAIN MODEST...50+ KT SSWLY DEEP SHEAR /WITH
FAST...DEEPLY UNIDIRECTIONAL FLOW/...LARGELY LINEAR FORCING FOR
ASCENT...AND STEEP LOW TO MID-LVL LAPSE RATES SUGGEST POTENTIAL FOR
STORMS TO MERGE/ORGANIZE INTO FAST-MOVING...BROKEN LINE SEGMENTS
CAPABLE OF DMGG WIND. THE STORMS COULD PERSIST THROUGH LATE
TNGT/EARLY THU OVER WRN ND...WITH A GRADUALLY DECREASING SVR THREAT
AS THE BOUNDARY LAYER COOLS.

...SE U.S. THIS AFTN...
SOME DIURNAL INCREASE IN STORM STRENGTH/COVERAGE SHOULD OCCUR IN
MODIFIED TROPICAL AIR OVER THE FL PENINSULA THIS AFTN...ESPECIALLY
OVER CNTRL AND SRN SECTIONS WHERE AXIS OF HIGH PW /ABOVE 2 INCHES/
WILL PERSIST. BUT WEAK SHEAR AND ABSENCE OF SIGNIFICANT FORCING FOR
ASCENT IS EXPECTED TO KEEP ANY ASSOCIATED SVR WIND THREAT VERY
ISOLD. FARTHER N OVER INTERIOR PARTS OF THE SOUTHEAST...COMBINATION
OF RELATIVELY STABLE BOUNDARY LAYER AND WEAK FORCING SHOULD PRECLUDE
STRONG STORMS ON SRN SIDE OF OH/TN VLY UPR SYSTEM.

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