DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 170602
SWODY1
SPC AC 170600

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT MON SEP 17 2012

VALID 171200Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SOUTHEAST
U.S....

...SYNOPSIS...
A STRENGTHENING MID-LEVEL TROUGH WILL CONTINUE DIGGING SEWD FROM THE
N CENTRAL U.S. TOWARD THE MIDWEST REGION THIS PERIOD. MEANWHILE...A
SECOND WEAKER TROUGH/LOW CROSSING THE SRN PLAINS/WRN GULF
COAST/LOWER MS VALLEY REGIONS IS PROGGED TO EVENTUALLY BECOME
ABSORBED INTO THE INCREASING ERN U.S. CYCLONIC FLOW...RESULTING IN A
SHARP/EXPANSIVE TROUGH IN THE MIDDLE AND UPPER TROPOSPHERE EXTENDING
FROM HUDSON BAY SWD TO THE CENTRAL GULF OF MEXICO BY THE END OF THE
PERIOD.

AT THE SURFACE...A COLD FRONT INITIALLY STRETCHED FROM THE UPPER
GREAT LAKES REGION SWWD TO SWRN KS WILL CONTINUE PROGRESSING
EWD/SEWD WITH TIME...AND SHOULD EXTEND FROM THE LK ERIE VICINITY
SWWD ACROSS THE MID OH VALLEY TO THE MID MS VALLEY BY THE END OF THE
PERIOD. MEANWHILE....A WEAK SURFACE LOW SHIFTING NEWD ACROSS THE
WRN GULF AND EVENTUALLY THE CENTRAL GULF COAST REGION SHOULD
GRADUALLY WEAKEN...EVENTUALLY BECOMING ABSORBED INTO THE
LARGER-SCALE PRESSURE TROUGH ASSOCIATED WITH THE ADVANCING COLD
FRONT.

...THE SOUTHEAST...
NUMEROUS BANDS OF SHOWERS AND STORMS ARE PROGGED TO SHIFT NEWD
ACROSS THE GULF COAST REGION THROUGH THE DAY TODAY...WITHIN A ZONE
OF WARM ADVECTION AHEAD OF THE S CENTRAL U.S. UPPER SYSTEM AND
ASSOCIATED/WEAK SURFACE LOW. WITH TIME...THE CONVECTION WILL SHIFT
GRADUALLY EWD...EVENTUALLY SPREADING ACROSS THE SRN APPALACHIANS
REGION AND INTO THE CAROLINAS.

AS THE UPPER SYSTEM ADVANCES...ENHANCED FLOW ALOFT ATOP LOW-LEVEL
SELY WINDS WILL RESULT IN SHEAR SUPPORTIVE OF ORGANIZED/WEAKLY
ROTATING CONVECTION. IN PARTICULAR...IT APPEARS THAT A WEAK WARM
FRONT WILL LIFT NEWD ACROSS THE CENTRAL GULF COAST REGION AND INTO
THE SRN APPALACHIANS DURING THE LATE AFTERNOON/EARLY EVENING HOURS
-- PROVIDING A ZONE OF BACKED LOW-LEVEL FLOW ENHANCING THE LOW-LEVEL
SHEAR. GIVEN A WEAKLY UNSTABLE BUT VERY MOIST LOW-LEVEL
ENVIRONMENT...THIS ZONE OF ENHANCED SHEAR MAY BE SUFFICIENT TO
SUPPORT ISOLATED TORNADO POTENTIAL -- WARRANTING AN UPGRADE TO
SLIGHT RISK ACROSS THIS AREA. A LARGER/LOW-PROBABILITY THREAT AREA
FOR WIND AND PERHAPS A TORNADO IS BEING INTRODUCED FROM SRN LA ENEWD
INTO THE CAROLINAS...WITHIN THE BROADER WARM ADVECTION ZONE. WHILE
SHIFTING W-E WITH TIME...SOME SEVERE POTENTIAL WILL LIKELY CONTINUE
THROUGH THE END OF THE PERIOD ACROSS ROUGHLY THE ERN HALF OF THE
OUTLOOK AREA.

...PORTIONS OF LOWER MI SWWD INTO E CENTRAL/NERN MO...
SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST TO DEVELOP DURING
THE AFTERNOON HOURS NEAR AND TO THE COOL SIDE OF THE COLD FRONT
ADVANCING SEWD ACROSS THIS REGION...AS MARGINAL INSTABILITY /AROUND
500 J/KG MIXED-LAYER CAPE/ DEVELOPS. ALONG WITH THE MODEST
INSTABILITY...STRONGER FLOW ALOFT SHOULD LAG THE SURFACE FRONT --
PARTICULARLY FROM SRN LK MI SWWD WHERE SLIGHTLY GREATER
DESTABILIZATION POTENTIAL EXISTS. STILL...THE OVERALL ENVIRONMENT
FROM NRN LOWER MI SWWD TO ACROSS W CENTRAL IL INTO ADJACENT NERN AND
E CENTRAL MO MAY SUPPORT A LOW-END/ISOLATED THREAT FOR HAIL AND/OR
GUSTY WINDS -- AND THUS WILL MAINTAIN LOW SEVERE PROBABILITIES
ACROSS THIS REGION.

..GOSS/SMITH.. 09/17/2012

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