DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 150554
SWODY2
SPC AC 150552

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1252 AM CDT SAT SEP 15 2012

VALID 161200Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
PATTERN TRANSITION WILL TAKE PLACE ALOFT THIS PERIOD...AS RELATIVELY
LOW-AMPLITUDE NRN-STREAM CURRENTLY IN PLACE OVER NRN CONUS YIELDS TO
STRENGTHENING MEAN TROUGH OVER UPPER GREAT LAKES AND MS VALLEY. TWO
MAIN SHORTWAVE FEATURES WILL CONTRIBUTE TO THIS...

1. SERIES OF SMALL/WEAK VORTICITY MAXIMA AND SPEED MAX NOW OVER NWRN
CANADA IS FCST TO PHASE AND STRENGTHEN DAY-1 WHILE MOVING SEWD AWAY
FROM BUILDING MEAN RIDGE. BY START OF PERIOD...THIS SHOULD RESULT
IN POSITIVELY TILTED SHORTWAVE TROUGH FROM WRN MB WSWWD ACROSS SK TO
ERN AB. DURING DAY-2...NRN PORTION OF ITS VORTICITY FIELD WILL
CALVE OFF AND EJECT ENEWD OVER SRN HUDSON BAY...WHILE SRN PORTION
PROCEEDS SEWD AND AMPLIFIES FURTHER. BY 17/12Z...STG HEIGHT FALLS
ARE FCST OVER UPPER GREAT LAKES AND UPPER MS VALLEY AS SHORTWAVE
TROUGH REACHES NWRN MN...CENTRAL SD AND WRN NEB. AT
SFC...STRENGTHENING COLD FRONT SHOULD MOVE FROM 16/12Z POSITION NEAR
THUNDER BAY AND ABR-RAP-BIL LINE TO 17/00Z POSITION FROM ISLE ROYALE
AREA SWWD TO WEAK WAVE LOW BETWEEN YKN-VTN...AND EXTREME SERN WY.
AT THAT TIME...DRYLINE SHOULD EXTEND FROM ERN SANDHILLS OF NEB SWD
ACROSS CENTRAL KS TO WRN OK AND SW TX...AND WILL BE OVERTAKEN BY
COLD FRONT FROM N-S THROUGH REMAINDER PERIOD. BY END OF
PERIOD...FRONT SHOULD EXTEND FROM LS SWWD ACROSS IA TO CENTRAL/SWRN
KS AND NERN NM.

2. SW-NE ELONGATED MID-UPPER CYCLONE -- NOW CENTERED OVER SRN NM --
IS EXPECTED TO MOVE ESEWD ACROSS WRN/CENTRAL/ERN TX MOSTLY IN
OPEN-WAVE CONFIGURATION. THIS FEATURE WILL MAINTAIN SLGT POSITIVE
TILT THROUGH PERIOD. WHILE PROGS ARE MUCH MORE CONSISTENT WITH
TIMING AND PHASE SPEED OF THIS FEATURE THAN THEY WERE 24 HOURS
AGO...THERE STILL IS CONSIDERABLE SPREAD AMONG SREF MEMBERS AND
OPERATIONAL SPECTRAL/NAM REGARDING AMPLITUDE. THIS...IN
TURN...RESULTS IN SUBSTANTIAL DIFFERENCES IN LOW-LEVEL MASS
RESPONSE...WITH WEAK SPECTRAL SFC TROUGH AND PRONOUNCED NAM SFC LOW
OVER N-CENTRAL GULF APPROXIMATING SREF EXTREMES ON EITHER END.

...NERN NEB TO WI...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP INVOF FRONT
IMPINGING ON PROGRESSIVELY DESTABILIZING BOUNDARY-LAYER AIR
MASS...DURING MID-LATE AFTERNOON. ISOLATED DAMAGING GUSTS AND/OR
LARGE HAIL MAY OCCUR FROM MOST INTENSE CELLS. COVERAGE IS MORE
QUESTIONABLE WITH SWWD EXTENT FROM SIOUX-LAND AREA INTO NRN NEB DUE
TO DRIER BOUNDARY-LAYER AIR STRONGER EML-RELATED MLCINH...THOUGH
CONVECTION THAT DOES DEVELOP IS MORE LIKELY TO BE RELATIVELY
DISCRETE. BY AFTERNOON...MOIST ADVECTION/TRANSPORT SHOULD LEAD TO
CORRIDOR OF 50S TO LOW 60S F SFC DEW POINTS AHEAD OF FRONT.
MODIFIED FCST SOUNDINGS SUGGEST 1000-1500 J/KG MLCAPE IN SERN SD/SRN
MN/WRN WI CORRIDOR...AND SOME VEERING/CURVATURE TO LOW-LEVEL
HODOGRAPHS...BUT WITH ONLY 25-35 KT EFFECTIVE SHEAR MAGNITUDES.
BUOYANCY SHOULD DIMINISH FROM WRN WI NEWD ACROSS LOWER MI.
ATTM...SVR POTENTIAL APPEARS TOO MRGL AND TRANSIENT FOR CATEGORICAL
OUTLOOK.

..EDWARDS.. 09/15/2012

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.