DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 081620
SWODY1
SPC AC 081617

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1117 AM CDT WED APR 08 2009

VALID 081630Z - 091200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
AN UPR LVL LOW AND ASSOCIATED SURFACE TROUGH/COLD FRONT WILL
PROGRESS EWD ACROSS THE GREAT BASIN AND INTO THE CENTRAL ROCKIES
THROUGH THE DAY AND NIGHT. MEANWHILE...LEE TROUGH DEVELOPMENT OVER
THE HIGH PLAINS WILL EVENTUALLY CONSOLIDATE INTO A SURFACE CYCLONE
OVER THE SRN PLAINS TOWARD THE END OF THE PERIOD...RESULTING IN
STRENGTHENING SOUTHERLY LOW LVL RETURN FLOW OVER TX. FARTHER
EAST...A PERTURBATION ALONG THE WRN SIDE OF A BROAD UPR TROUGH OVER
THE NERN CONUS WILL MOVE TOWARD THE CENTRAL APPALACHIANS THROUGH THE
DAY...AND THEN THE CSTL CAROLINA PLAINS DURING THE NIGHT.

...GREAT BASIN/ROCKIES...
A PLUME OF RELATIVELY HIGHER PWAT VALUES /AOA 0.35 IN PER GPS TPW
GUIDANCE/ WILL CONTINUE TO SPREAD E-NEWD ACROSS THE GREAT
BASIN/ROCKIES DURING THE DAY AS AN UPR TROUGH SHIFTS FROM NV INTO
ID/WY. COLD MID LVL TEMPERATURES /AOB -20 DEG C AT 500 MB BASED ON
12Z RAOB DATA/ WILL ACCOMPANY THE MOISTENING
ENVIRONMENT...CONTRIBUTING TO VERY STEEP LAPSE RATES. THUNDERSTORM
COVERAGE IS EXPECTED TO INCREASE DURING THE AFTERNOON...AND SMALL
HAIL WILL BE POSSIBLE WITH THE STRONGER CORES /PARTICULARLY OVER ERN
ID AND NRN UT INTO WY WHERE DEEP LAYER SHEAR IS EXPECTED TO BE
SLIGHTLY STRONGER/...BUT THESE STORMS ARE CURRENTLY ANTICIPATED TO
REMAIN BELOW SEVERE LEVELS.

...KY/TN/VA...
A LOW AMPLITUDE UPR LVL IMPULSE/VORT MAX WAS OBSERVED IN MID MORNING
WV IMAGERY TRANSLATING SEWD THROUGH IA/IL...AND IS FORECAST TO MOVE
ACROSS ERN KY/TN BY MID TO LATE AFTERNOON. COLD TEMPERATURES ALOFT
/AROUND -10 DEG C AT 700 MB/ COMBINED WITH AFTERNOON HEATING WILL
RESULT IN VERY STEEP LOW LVL LAPSE RATES /AOA 9 C PER KM IN THE 0-3
KM LAYER/. THIS WILL CONTRIBUTE TOWARD THE DEVELOPMENT OF A COUPLE
HUNDRED J/KG OF MUCAPE...WHICH MAY EXTEND INTO THE MIXED PHASE
REGION FAVORING ISOLATED LIGHTNING STRIKES. SMALL HAIL/GRAUPEL MAY
OCCUR WITH AFTERNOON THUNDERSTORMS...BUT SEVERE STORMS ARE NOT
EXPECTED.

..GARNER/EVANS.. 04/08/2009

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