DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 180722
SWODY3
SPC AC 180720

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0220 AM CDT TUE SEP 18 2012

VALID 201200Z - 211200Z

...SYNOPSIS...
IN MID-UPPER LEVELS...MEAN TROUGH WILL PERSIST OVER GREAT LAKES...MS
VALLEY AND NRN/WRN GULF THROUGH PERIOD. SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY NEAR BORDER OF BC AND NW
TERRITORIES -- WILL MOVE SEWD ACROSS WI...UPPER MI...AND LS DAY-2.
THIS FEATURE WILL EJECT NEWD TO JAMES BAY REGION AND WEAKEN
DAY-3...WHILE AT LEAST TWO OTHER CLOSELY-SPACED/NW-FLOW
PERTURBATIONS DIG INTO LARGE-SCALE TROUGH POSITION OVER LS AND UPPER
MIDWEST. BY END OF PERIOD...BROAD BELT OF CYCLONIC FLOW WILL COVER
NRN PLAINS...GREAT LAKES AND SERN CANADA...WITH MID-UPPER JET CORE
OVER SK...DAKOTAS...SRN MN...LOWER MI...ERN ONT...AND SRN QUE.

AT SFC...CENTRAL CONUS COLD FRONT DESCRIBED IN DAY-2 OUTLOOK SHOULD
REACH SRN ONT...WRN OH...AND SRN IL BY 21/00Z. TRAILING SEGMENT OF
THIS BOUNDARY SHOULD BECOME QUASISTATIONARY WITH WEAK FRONTAL-WAVE
LOWS POSSIBLE...FROM MO TO NW OK TO NERN NM. MOST PROBABLE AREA FOR
FRONTAL-WAVE LOW FORMATION DURING AFTERNOON/EVENING APPEARS TO BE TX
PANHANDLE OR SWRN KS. DRYLINE AT 21/00Z SHOULD EXTEND FROM THAT LOW
SSWWD OVER EXTREME SERN NM/LOWER PECOS VALLEY REGION.

...S-CENTRAL PLAINS TO OZARKS REGION...
LOW-LEVEL FRONTAL ZONE AND SFC WAVE MAY PROVIDE FOCI FOR HIGH-BASED
TSTM POTENTIAL DURING LATE AFTERNOON. STG VEERING OF FLOW WITH
HEIGHT IS FCST BENEATH DIFLUENT NW WINDS ALOFT. HOWEVER...WEAK
LOW-LEVEL SPEEDS WILL LIMIT HODOGRAPH SIZE. STG GUSTS OR ISOLATED
HAIL ARE POSSIBLE...BUT ANY SVR POTENTIAL APPEARS VERY
ISOLATED...UNCERTAINLY FOCUSED AND CONDITIONAL ATTM.

ADDITIONAL TSTMS MAY DEVELOP OVERNIGHT ACROSS PORTIONS SRN/SERN KS
INTO SRN MO...AS MOISTURE INCREASES WITHIN SWLY LOW-LEVEL WAA REGIME
AND PARCELS RISE ISENTROPICALLY TO LFC. GIVEN ITS CLOSER PROXIMITY
TO SRN RIM OF STRONGER MID-UPPER LEVEL FLOW THAN AFTN
CONVECTION...DEEP SHEAR MAY BE SUFFICIENT TO SUPPORT A FEW ORGANIZED
TSTMS WITH HAIL POSSIBLE. ATTM...UNCERTAINTIES IN LOCATION/TIMING
OF ANY SUCH ELEVATED CONVECTION PRECLUDE UNCONDITIONAL SVR
PROBABILITIES.

..EDWARDS.. 09/18/2012

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