DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 240557
SWODY1
SPC AC 240555

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT WED OCT 24 2012

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM WRN UPPER MI AND ADJACENT
WRN LK SUPERIOR SSWWD INTO IA/ERN NEB...

...SYNOPSIS...
THE LARGE SCALE MID- AND UPPER-LEVEL TROUGH OVER THE WRN U.S. IS
FORECAST TO MAKE STEADY EWD PROGRESS THIS PERIOD...AS EMBEDDED
SHORTER-WAVELENGTH TROUGHING SHIFTS QUICKLY EWD FROM THE GREAT
BASIN/INTERIOR W EARLY TO THE PLAINS BY THE END OF THE PERIOD. THE
LARGE-SCALE TROUGH WILL BE ACCOMPANIED BY VERY STRONG FLOW
ALOFT...WHICH WILL SPREAD INTO THE CENTRAL U.S. THROUGH THE PERIOD.

AT THE SURFACE...A LOW INITIALLY INVOF KS/NEB IS FORECAST TO SHIFT
NEWD TOWARD SERN MN THROUGH THE FIRST HALF OF THE PERIOD...WHILE
PRIMARY CYCLOGENESIS INCREASES ACROSS THE SERN CO VICINITY. AS THIS
OCCURS...THE SURFACE FRONT SHOULD MAKE LITTLE EWD PROGRESS ACROSS
THE PLAINS. DURING THE SECOND HALF OF THE PERIOD HOWEVER...THE CO
LOW IS PROGGED TO SHIFT QUICKLY NEWD AND EVENTUALLY MERGE WITH THE
MN LOW. BY THE END OF THE PERIOD...THE LOW SHOULD RESIDE INVOF
WI...WITH THE TRAILING COLD FRONT HAVING SHIFTED EWD TO EXTEND FROM
WI SSWWD ACROSS CENTRAL OK INTO NRN AND WRN TX BY 25/12Z.

...LK SUPERIOR/WRN UPPER MI SSWWD INTO THE MID MO VALLEY AREA...
AS THE AFOREMENTIONED COLD FRONT LINGERS IN PLACE ACROSS THE CENTRAL
U.S. AHEAD OF THE WRN UPPER TROUGH DURING THE FIRST HALF OF THE
PERIOD...A CAPPED BOUNDARY LAYER WILL PREVAIL AS THE UPPER RIDGE AND
ASSOCIATED SUBSIDENCE PERSIST.

WITH DAYTIME HEATING OF THE MOIST WARM SECTOR...MODERATE CAPE IS
FORECAST TO DEVELOP ABOVE THE BOUNDARY-LAYER CAP. EVENTUALLY...AS
HEIGHT FALLS SPREAD ACROSS THE PLAINS...SOME CAP WEAKENING IS
FORECAST -- WHICH MAY BE SUFFICIENT TO ALLOW SOME REALIZATION OF THE
UNSTABLE ENVIRONMENT IN THE FORM OF ISOLATED STORM DEVELOPMENT.
INITIATION APPEARS MOST LIKELY TO OCCUR OVER THE UPPER MS VALLEY IN
THE 22-00Z TIME FRAME...ALONG THE IMMEDIATE FRONTAL ZONE. SHOULD
THIS INDEED OCCUR...LARGE HAIL AND DAMAGING WINDS WILL BE
POSSIBLE...AS STORMS QUICKLY ORGANIZE GIVEN VERY FAVORABLE
BACKGROUND FLOW FIELD. A TORNADO OR TWO WOULD ALSO BE POSSIBLE --
PARTICULARLY INVOF WRN WI -- TO THE NE OF THE ANTICIPATED SURFACE
LOW POSITION WHERE LOW-LEVEL SHEAR WOULD BE MAXIMIZED.

ATTM...WILL MAINTAIN ONLY 15% HAIL/WIND AND 5% TORNADO
PROBABILITY...AS EVOLUTION OF AFTERNOON SURFACE-BASED STORMS ALONG
THE FRONT IS NOT A CERTAINTY. SEVERAL HIGH-RES MODELS -- ALONG WITH
A BROAD VIEW OF THE OVERALL PATTERN -- SUGGEST THAT CAPPING COULD
HINDER SUCH DEVELOPMENT...WITH CONVECTIVE DEVELOPMENT BEING MAINLY
CONFINED TO THE COOL SIDE OF THE BOUNDARY AFTER DARK. STILL...WITH
HAIL LIKELY TO OCCUR EVEN IN THIS SCENARIO...SLIGHT RISK IS WELL
WARRANTED...BUT AN INCREASE IN PROBABILITIES WILL NOT BE INSERTED
THIS FORECAST DUE TO THE UNCERTAINTIES.

WHETHER DIURNAL/SURFACE-BASED STORMS DEVELOP OR NOT...AN EXPANSION
IN CONVECTION ON THE COOL SIDE OF THE BOUNDARY APPEARS FAIRLY LIKELY
DURING THE EVENING AND OVERNIGHT...WITH SHOWERS AND STORMS
DEVELOPING SWD ACROSS KS -- AND POSSIBLY INTO NRN OK/WRN MO --
THROUGH THE END OF THE PERIOD. WHILE SOME HAIL THREAT IS
POSSIBLE...STORMS SHOULD WANE IN INTENSITY THROUGH LATTER STAGES OF
THE PERIOD.

..GOSS/GARNER.. 10/24/2012

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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.