Friday, August 30, 2013

Aug 30, 2013 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT FRI AUG 30 2013

VALID 301200Z - 311200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF WRN AND CNTRL
ND...

...SYNOPSIS...

A TYPICAL LATE SUMMER PATTERN WILL PERSIST INTO FRIDAY WITH AN UPPER
RIDGE CENTERED FROM THE SRN/CNTRL PLAINS INTO THE CNTRL
ROCKIES...KEEPING THE BELT OF STRONGER WLYS ACROSS THE NRN TIER
STATES. UPPER TROUGH EMBEDDED WITHIN THIS BELT OF STRONGER FLOW NOW
MOVING INTO THE PACIFIC NW WILL ADVANCE THROUGH THE SWRN CANADIAN
PROVINCES. FARTHER EAST...THE SHORTWAVE TROUGH NEAR THE ARROWHEAD OF
MN WILL CONTINUE ESEWD THROUGH THE GREAT LAKES REGION DURING THE DAY
AND INTO THE NERN STATES FRIDAY NIGHT. THIS FEATURE WILL FORCE A
COLD FRONT SWD THROUGH THE GREAT LAKES AREA WITH TRAILING PORTIONS
LIKELY TO STALL OVER THE CNTRL PLAINS. FARTHER WEST...A LEE TROUGH
WILL SETUP ACROSS THE NRN HIGH PLAINS WITH A COLD FRONT ADVANCING
SEWD THROUGH MT IN ASSOCIATION WITH THE UPPER TROUGH MOVING THROUGH
THE SWRN CANADIAN PROVINCES.

...NRN HIGH PLAINS...

LOW-LEVEL WINDS WILL SHIFT TO SELY IN POST FRONTAL REGIME WEST OF
SFC RIDGE MOVING THROUGH ERN CANADA. THIS WILL MAINTAIN UPPER 50S TO
60F DEWPOINTS OVER THE NRN HIGH PLAINS EAST OF LEE TROUGH BENEATH
STEEP MID-LEVEL LAPSE RATES. SFC HEATING WILL DESTABILIZE THE
BOUNDARY LAYER AND CONTRIBUTE TO AXIS OF MODERATE INSTABILITY
/1500-2000 J/KG MLCAPE/ ACROSS THE WRN DAKOTAS. UPPER RIDGE AXIS
SHOULD DEAMPLIFY OVER THE NRN PLAINS AS SHORTWAVE TROUGH OVER THE
PACIFIC NW MOVES THROUGH SWRN CANADA. SYNOPTIC FORCING FOR ASCENT
WILL REMAIN WEAK OVER THE HIGH PLAINS...AND THERE IS SOME CONCERN
THAT STORM COVERAGE COULD REMAIN LIMITED. HOWEVER...DEEP MIXING AND
CONVERGENCE ALONG PRE-FRONTAL/LEE TROUGH MAY BE SUFFICIENT FOR A FEW
STORMS TO DEVELOP DURING THE AFTERNOON. OTHER STORMS MAY INITIATE
OVER THE HIGHER TERRAIN OF NRN WY INTO MT AND MOVE INTO THE HIGH
PLAINS. WIND PROFILES WILL STRENGTHEN ALONG NRN PERIPHERY OF
DEAMPLIFYING UPPER RIDGE WITH 35-40 KT EFFECTIVE SHEAR SUPPORTIVE OF
SUPERCELLS. ISOLATED LARGE HAIL WILL BE THE MAIN THREATS THROUGH MID
EVENING.

...GREAT LAKES AND OH VALLEY AREA...

SHORTWAVE TROUGH NOW OVER THE UPPER MS VALLEY WILL SHIFT SEWD
THROUGH THE GREAT LAKES REGION DURING THE DAY ATTENDED BY A SWD
ADVANCING COLD FRONT. THE MOIST WARM SECTOR WILL DESTABILIZE SOUTH
OF THIS BOUNDARY WITH MLCAPE FROM 2000-2500 J/KG POSSIBLE.
HOWEVER...THE DEEPER FORCING AND BELT OF STRONGER FLOW ALOFT
ATTENDING THE SHORTWAVE TROUGH WILL TEND TO REMAIN NORTH AND SHIFT
EAST OF WHERE STRONGER DESTABILIZATION IS OCCURRING.
NEVERTHELESS...A FEW STORMS WILL LIKELY REDEVELOP ALONG THE SWD
ADVANCING COLD FRONT DURING THE AFTERNOON. WIND PROFILES WITH
VERTICAL SHEAR FROM 25-35 KT SHOULD GENERALLY PROMOTE
MULTICELLS...BUT THE THERMODYNAMIC ENVIRONMENT MAY SUPPORT SOME
THREAT FOR ISOLATED STRONG TO DAMAGING WIND GUSTS AND HAIL. WILL
MAINTAIN 5% SEVERE PROBABILITIES THIS OUTLOOK...BUT A CATEGORICAL
RISK MAY BE NEEDED IN LATER UPDATES.
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