SWODY1
SPC AC 160554
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT TUE OCT 16 2007
VALID 161200Z - 171200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
A DYNAMIC LARGE-SCALE PATTERN WILL EXIST OVER THE CONUS THIS PERIOD
AS INTENSE UPPER LEVEL JET STREAK ORIGINATING OVER THE ERN PACIFIC
DIGS SEWD THROUGH THE SWRN STATES...EFFECTIVELY ENHANCING HEIGHT
FALLS/TROUGHING FROM THE WRN INTERMOUNTAIN REGION EWD INTO THE CNTRL
AND SRN PLAINS. AS THIS OCCURS...DOWNSTREAM SHORT WAVE TROUGH IS
EXPECTED TO WEAKEN WHILE LIFTING NEWD THROUGH THE UPPER MS VALLEY
AND GREAT LAKES.
IN THE LOW LEVELS...BAROCLINIC ZONE ARCING FROM OCCLUDED SURFACE LOW
OVER SWRN MN EWD THROUGH THE UPPER MIDWEST AND THEN INTO THE OH
VALLEY WILL WEAKEN THROUGH THE DAY IN CONCERT WITH DE-AMPLIFYING
UPPER SYSTEM. FARTHER TO THE W...LEE CYCLOGENESIS IS FORECAST TO
OCCUR OVER ERN CO WITH LEE TROUGH STRENGTHENING OVER THE SRN HIGH
PLAINS. A WARM FRONT WILL RAPIDLY LIFT NWD THROUGH THE SRN
PLAINS...NAMELY DURING THE LATTER HALF OF THE FORECAST PERIOD.
..LOWER MI INTO IND/OH...
COLLOCATION OF MID-LEVEL THERMAL TROUGH AND LOW-LEVEL MOISTURE AXIS
/DEWPOINTS OF 55-60 F/ WILL CONTRIBUTE TO THE DEVELOPMENT OF WEAK
CONVECTIVE INSTABILITY AHEAD OF SURFACE FRONT THIS AFTERNOON WITH
MLCAPES OF 400-700 J/KG. TSTMS ARE EXPECTED TO INCREASE IN COVERAGE
AND INTENSITY BY AFTERNOON AS FORCING FOR ASCENT ASSOCIATED WITH
WEAKENING SHORT WAVE TROUGH ACTS ON DESTABILIZING AIR MASS.
FORECAST SOUNDINGS SUGGEST THAT 30-40 KT OF DEEP LAYER SHEAR WILL
EXIST ACROSS INSTABILITY AXIS...WITH SOME POTENTIAL FOR A FEW
ORGANIZED STORMS CAPABLE OF MARGINALLY SEVERE HAIL AND LOCALLY
STRONG WIND GUSTS THROUGH THE AFTERNOON AND EVENING HOURS.
..WRN TX INTO WRN OK...
40-50 KT LLJ WILL BECOME ESTABLISHED OVER THE CNTRL/SRN PLAINS
TONIGHT IN RESPONSE TO INCREASING HEIGHT/PRESSURE FALLS TO THE W.
THIS WILL RESULT IN THE RAPID FLUX OF LOW-LEVEL MOISTURE NWD THROUGH
THE REGION...AND BENEATH A PLUME OF STEEPER MID-LEVEL LAPSE RATES
BEING ADVECTED EWD FROM THE ROCKIES. THESE DIFFERENTIAL ADVECTIONS
WILL CONTRIBUTE TO CONSIDERABLE AIR MASS DESTABILIZATION OVERNIGHT
COINCIDENT WITH INCREASING VERTICAL WIND SHEAR.
TSTM DEVELOPMENT WILL BECOME INCREASINGLY LIKELY LATE THIS EVENING
ALONG WRN EDGE OF LLJ AXIS OVER WRN TX WITH ACTIVITY
MOVING/DEVELOPING NEWD INTO WRN OK BY WEDNESDAY MORNING. FORECAST
SOUNDINGS SUGGEST THAT THE MAJORITY OF STORMS WILL BE SLIGHTLY
ELEVATED WITHIN A THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY MUCAPES
OF 500-1000 J/KG WITH SOME THREAT OF SEVERE HAIL. THERE IS SOME
INDICATION THAT A STORM OR TWO MAY BE SURFACE-BASED OR NEAR
SURFACE-BASED WITH A BRIEF TORNADO POSSIBLE GIVEN EFFECTIVE SRH
VALUES OF 250-350 M2/S2.
SHOULD IT BECOME APPARENT THAT STRONGER INSTABILITY WILL DEVELOP
THAN IS CURRENTLY FORECAST...PORTIONS OF AREA MAY NEEDED TO BE
UPGRADED TO A SLIGHT RISK IN LATER OUTLOOKS.
.MEAD/GUYER.. 10/16/2007
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