DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 131728
SWODY2
SPC AC 131726

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT SAT OCT 13 2007

VALID 141200Z - 151200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL AND
SRN PLAINS...

..SYNOPSIS...
UPPER TROUGH OVER THE CENTRAL ROCKIES INTO THE SWRN STATES AT 12Z
SUNDAY WILL MOVE EWD INTO THE PLAINS AS NEXT UPSTREAM PACIFIC TROUGH
DEEPENS AS IT APPROACHES THE WEST COAST. THIS WILL ALLOW BAND OF
SWLY MID LEVEL FLOW EXTENDING FROM THE SRN PLAINS TO LOWER MO/MID MS
VALLEYS TO STRENGTHEN TO 50-60 KT. IN THE LOW LEVELS...ATTENDANT
SURFACE LOW IS FORECAST TO TRACK FROM WRN KS ENEWD...BUT WEAKENING
WITH TIME...AS IT SHOULD REACH SWRN IA BY 12Z MONDAY. TRAILING COLD
FRONT WILL SPREAD EWD AND IS EXPECTED TO MERGE WITH AND OVERTAKE THE
DRY LINE ACROSS CENTRAL KS TO NWRN OK DURING THE MID-LATE
AFTERNOON...WITH A SIMILAR TREND OCCURRING SWD INTO NW TX THROUGH
SUNDAY EVENING/OVERNIGHT.

..PARTS OF THE CENTRAL AND SRN PLAINS...
AS THE UPPER SYSTEM AND ATTENDANT SURFACE LOW/TRAILING COLD FRONT
SPREAD EWD INTO THE CENTRAL/SRN PLAINS...SLY LOW LEVEL WINDS ARE
EXPECTED TO BECOME ESTABLISHED FROM THE WRN GULF INTO THE SRN
PLAINS. GULF MOISTURE WILL RETURN NWD WITH SURFACE DEWPOINTS IN THE
LOWER 60S EXPECTED TO REACH FROM WRN/CENTRAL OK TO CENTRAL KS SUNDAY
AFTERNOON. STEEP MID LEVEL LAPSE RATES WITHIN ELEVATED MIXED LAYER
ATOP LOW LEVEL MOISTURE RETURN WILL RESULT IN A NARROW AXIS OF
MODERATE INSTABILITY SUNDAY AFTERNOON ALONG AND E OF THE DRY LINE
WHERE SURFACE HEATING SHOULD BE THE STRONGEST.

AT 12Z SUNDAY...AN AREA OF SHOWERS WITH EMBEDDED TSTMS MAY BE
ONGOING FROM CENTRAL OK INTO ERN KS ALONG WARM CONVEYOR BELT... WITH
GREATER TSTM COVERAGE FROM DAY 1 LIKELY FARTHER N WITHIN WAA/
ISENTROPIC ASCENT TO THE N OF THE WARM FRONT ACROSS NEB INTO IA.
THE NRN ACTIVITY SHOULD PERSIST THROUGH THE DAY WITHIN WAA
REGIME...WITH STRONGER STORMS ALONG THE SRN PERIPHERY INTO SRN NEB
POSING A SEVERE WEATHER THREAT GIVEN PROXIMITY TO GREATER
INSTABILITY.

GIVEN THE POSITIVE TILT OF THE UPPER SYSTEM AND SOMEWHAT WEAK HEIGHT
FALLS...FORECAST SOUNDINGS SUGGEST TSTM DEVELOPMENT SHOULD OCCUR AS
THE COLD FRONT MERGES WITH THE DRY LINE IN CENTRAL KS TO WRN OK
SUNDAY AFTERNOON WEAKENING THE CAP. STRENGTHENING MID LEVEL WINDS
WILL SUPPORT STRONG DEEP LAYER SHEAR. MODELS INDICATE POTENTIAL FOR
AN INITIAL BROKEN LINE OF TSTMS WITH EMBEDDED SUPERCELLS WITH A
THREAT FOR LARGE HAIL AND DAMAGING WINDS. AN ISOLATED TORNADO
THREAT IS ALSO POSSIBLE...GIVEN SUFFICIENT LOW LEVEL VEERING/SHEAR
AND LOW LCLS. A SQUALL LINE IS EXPECTED TO FORM BY SUNDAY EVENING
AS LLJ VEERS...BECOMING PARALLEL TO FLOW ALOFT.

DESPITE THE LOSS OF DAY TIME HEATING SUNDAY EVENING...THE CONTINUED
INFLUX OF LOW LEVEL MOISTURE INTO OK/KS MAINTAINING LOW LCLS
COMBINED WITH STRENGTHENING SLY LLJ SUGGEST AN ISOLATED TORNADO
THREAT COULD PERSIST ACROSS THIS REGION AS THE SQUALL LINE ADVANCES
EWD. EVENTUAL DECREASE IN SEVERE WEATHER THREAT IS EXPECTED LATER
SUNDAY EVENING AS THE CONVECTIVE INSTABILITY DIMINISHES.

.PETERS.. 10/13/2007

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