DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 171730
SWODY2
SPC AC 171728

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT SAT AUG 17 2013

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF CENTRAL/ERN ND
INTO NWRN MN...

...NRN PLAINS TO NWRN MN...
A WEAK MIDLEVEL TROUGH MOVING THROUGH THE PACIFIC NORTHWEST TO NRN
ROCKIES DURING DAY 1 WILL REMAIN PROGRESSIVE...YET STILL WEAK...ON
DAY 2 WITH THIS FEATURE LIKELY REACHING CENTRAL/ERN ND LATE SUNDAY
AFTERNOON/EARLY EVENING. A WEAK SURFACE TROUGH ANALYZED THIS
MORNING OVER ERN MT WILL ADVANCE EWD FROM CENTRAL ND ON SUNDAY...AND
SHOULD EXTEND FROM NWRN MN THROUGH SOUTH CENTRAL ND TO WRN SD AND
SERN WY BY 19/00Z. SLY LOW LEVEL WINDS OVER THE CENTRAL/NRN PLAINS
TODAY INTO DAY 2 WILL SUPPORT MOISTURE RETURN WITH SURFACE DEWPOINTS
INTO THE MID 60S REACHING LOCATIONS E OF THE SURFACE TROUGH SUNDAY
AFTERNOON. THIS...COMBINED WITH A PLUME OF STEEP MIDLEVEL LAPSE
RATES /7.5-8.5 C PER KM/ SPREADING EWD ACROSS THE DAKOTAS TO NRN
MN...AND SURFACE HEATING WILL RESULT IN MODERATE INSTABILITY /MLCAPE
TO AROUND 2000 J PER KG/. FORECAST SOUNDINGS SHOW MUCH OF THIS
REGION WILL BE CAPPED THROUGH THE AFTERNOON. HOWEVER...BY LATE
AFTERNOON OR TOWARD 19/00Z...FORCING FOR ASCENT ALONG THE SURFACE
WIND SHIFT AND WITH DPVA SPREADING EWD WITH THE MIDLEVEL TROUGH
SHOULD PROVE SUFFICIENT IN WEAKENING THE INHIBITION FOR SURFACE
BASED STORMS. 40 KT WLY MIDLEVEL WINDS ATOP 20-25 KT SWLY FLOW WILL
RESULT IN 25-35 KT OF EFFECTIVE BULK SHEAR SUNDAY AFTERNOON/EVENING
FOR BOTH MULTICELL AND SUPERCELL STORM MODES...WITH HAIL AND
DAMAGING WINDS THE PRIMARY THREATS. ACTIVITY WILL MOVE EWD INTO
NWRN MN DURING THE EVENING.

...WRN-NWRN GULF COAST...
LATE DAY 1 TO THE FIRST SEVERAL HOURS OF DAY 2 /SUNDAY MORNING/ HAS
THE POTENTIAL FOR A LOW SEVERE WIND/TORNADO THREAT ALONG THE CENTRAL
GULF COAST...WITHIN A CORRIDOR OF CONVECTION ALONG A FRONTAL ZONE
EXTENDING NEWD THROUGH FAR SERN LA/SERN MS/SWRN AL AND THE WRN FL
PANHANDLE. A LOW SEVERE PROBABILITY HAS BEEN INTRODUCED FOR MAINLY
THE 12-18Z PERIOD OF THE DAY 2.

MODELS CONTINUE TO DIFFER WITH THE TRACK OF AN AREA OF LOW PRESSURE
ON SUNDAY FROM ITS CURRENT LOCATION OVER THE SWRN GULF OF MEXICO. AN
INCREASE IN LOW LEVEL WINDS AND SHEAR SHOULD OCCUR ALONG THE ERN-NRN
PERIPHERIES OF THIS LOW WHICH WOULD ENHANCE THE POTENTIAL FOR LOW
SEVERE WIND AND/OR A TORNADO THREAT. ONCE THE TRACK OF THIS SYSTEM
BECOMES MORE CERTAIN...THEN PARTS OF THE LA AND/OR TX COASTS MAY
NEED TO HAVE SEVERE PROBABILITIES INTRODUCED FOR LATE SUNDAY
NIGHT/EARLY MONDAY MORNING.

..PETERS.. 08/17/2013

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