DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 051955
SWODY1
SPC AC 051952

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0252 PM CDT THU SEP 05 2013

VALID 052000Z - 061200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR THE PAC NW AND NRN
ROCKIES...

...PAC NW AND NRN ROCKIES...
THUNDERSTORMS WILL EXPAND IN COVERAGE OVER CNTRL/ERN ORE THIS
AFTERNOON AHEAD OF AN UPPER-LEVEL SHORTWAVE TROUGH CURRENTLY
EJECTING NEWD ACROSS NRN CA. THIS ACTIVITY WILL SPREAD NWD INTO WA
LATER THIS AFTERNOON/EVENING. ADDITIONAL STORMS ARE ALSO FORMING
ALONG THE LEADING EDGE OF A MIDLEVEL DRY SLOT SPREADING NWD OVER NV
INTO SWRN ID. TEMPERATURES WARMING THROUGH THE 70S TO MID 80S
COMBINED WITH DEWPOINTS RANGING FROM THE UPPER 40S IN CNTRL ORE TO
NEAR 60 IN SRN ID WILL SUPPORT MLCAPE VALUES FROM 500-1500 J/KG. IN
ADDITION...DEEP-LAYER SLY FLOW WILL BE PRONOUNCED ACROSS THE
AREA...WITH MIDLEVEL SPEEDS NEAR 50 KT INCREASING TO 90 KT IN THE
UPPER-LEVELS. THUS...FAST MOVING MULTICELL CLUSTERS AND BOWING LINE
SEGMENTS WILL BE POSSIBLE...AND WILL POSE A THREAT FOR DAMAGING
WINDS. STEEP MIDLEVEL LAPSE RATES...COOL MIDLEVEL TEMPERATURES /-10
TO -16 C AT 500 MB/...AND 0-6 KM BULK SHEAR AOA 50 KT WILL ALSO
SUPPORT LARGE HAIL.

...NRN HIGH PLAINS...
HIGH BASED STORMS ARE FORECAST TO EVOLVE EWD OFF OF THE HIGHER
TERRAIN IN ERN WY THIS AFTERNOON AND EVENING. STEEP LAPSE
RATES...WEAK TO MODERATE CAPE...AND DEEP BOUNDARY LAYER MIXING MAY
SUPPORT A THREAT FOR STRONG/SEVERE WIND GUSTS.

..GARNER.. 09/05/2013

.PREV DISCUSSION... /ISSUED 1128 AM CDT THU SEP 05 2013/

...SYNOPSIS...
WHILE BROAD UPPER RIDGING WILL CONTINUE TO PREVAIL ACROSS MUCH OF
THE U.S. THIS PERIOD...SUPPRESSION OF THE RIDGE IS EXPECTED ALONG
ITS NWRN PERIPHERY...AS AN UPPER LOW WHICH HAS LINGERED FOR SEVERAL
DAYS JUST OFF THE PAC NW COAST SHIFTS INTO WA/OREGON WITH TIME.

MEANWHILE IN THE EAST...A SLOW EWD SHIFT IN THE TROUGH AXIS OVER ERN
CANADA AND THE NERN U.S. IS EXPECTED. THOUGH SOME SERN U.S.
CONVECTION WILL ACCOMPANY THE REMNANT SURFACE FRONT ASSOCIATED WITH
THE ERN TROUGH...THE MAIN FOCUS FOR STRONG/SEVERE CONVECTION WILL
REMAIN ACROSS THE NWRN QUARTER OF THE COUNTRY.

...PAC NW VICINITY...
WITH A SLOW ONSHORE SHIFT OF THE UPPER LOW UNDERWAY...CONTINUED
MID-LEVEL COOLING WILL OCCUR ALONG WITH AN INCREASE IN THE FLOW
FIELD ALOFT. RESULTING DIURNAL DESTABILIZATION OF THE AIRMASS
ACROSS A LARGE PORTION OF THE NWRN U.S. COMBINED WITH INCREASINGLY
FAVORABLE SHEAR CONTINUES TO SET THE STAGE FOR RELATIVELY WIDESPREAD
CONVECTIVE DEVELOPMENT AND ASSOCIATED/ISOLATED SEVERE POTENTIAL.
ATTM...IT APPEARS THAT THREAT FOR DAMAGING WINDS AND SOME HAIL WILL
SLOWLY INCREASE THROUGH THE DIURNAL HEATING CYCLE...MAXIMIZING INTO
THE LATE AFTERNOON AND EARLY EVENING HOURS BUT LIKELY CONTINUING IN
AT LEAST A MARGINAL/ISOLATED CAPACITY WELL INTO THE SECOND HALF OF
THE PERIOD AS THE UPPER LOW MOVES FULLY ONSHORE.

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