DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 300439
SWODY1
SPC AC 300437

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 PM CDT SAT SEP 29 2012

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS LOWER MS VALLEY/CNTRL GULF...

...SYNOPSIS...
AN ERN GREAT LAKES UPPER LOW WILL DRIFT NEWD TO MAINE THROUGH THE
FORECAST PERIOD...WITH COLD TEMPERATURES ALOFT LEADING TO EFFICIENT
LIGHTNING PRODUCTION OVER PORTIONS OF THE NORTHEAST COINCIDENT WITH
DIURNAL HEATING.

MEANWHILE...A SHORT WAVE UPPER TROUGH WILL PROGRESS INTO THE N CNTRL
STATES...WITH AN ATTENDANT SURFACE COLD FRONT PROGRESSING THROUGH
THE NRN PLAINS AND UPPER MS VALLEY...AND A LEE SURFACE TROUGH
DEVELOPING OVER THE CNTRL PLAINS.

FARTHER S...A SRN PLAINS UPPER LOW WILL PROGRESS SLOWLY TOWARDS THE
LOWER MS VALLEY...WITH A DEEPENING SURFACE LOW SHIFTING ENEWD ACROSS
E TX...LA AND MS.

ELSEWHERE...AN UPPER RIDGE AND STRENGTHENING SURFACE HIGH PRESSURE
WILL BUILD ACROSS THE WEST.

...LOWER MS VALLEY/CNTRL GULF...
PERSISTENT UPPER-LEVEL DIVERGENCE ATTENDANT TO AN UPPER LOW WILL
LIKELY MAINTAIN SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD...WITH
HEAVY RAINFALL CONTINUING AMIDST A TROPICAL AIR MASS CHARACTERIZED
BY PWAT VALUES NEAR 2-2.25 INCH. INSTABILITY WILL BE LIMITED BY
ASSOCIATED WEAK/MOIST LAPSE RATES AND CLOUD COVER THAT WILL HINDER
STRONGER SURFACE HEATING...LEADING TO QUESTIONABLE COVERAGE OF
SEVERE THUNDERSTORMS AND TORNADOES. HOWEVER...MODEST LOW-LEVEL
SHEAR/VEERING PROFILES WILL BE CONDUCIVE TO AT LEAST TRANSIENT
LOW-LEVEL CIRCULATIONS THROUGH THE MORNING AND AFTERNOON.

BY EVENING AND ESPECIALLY INTO THE OVERNIGHT PERIOD...A RELATIVE JET
MAX ALOFT IS FORECAST TO EJECT NEWD ACROSS THE WRN GULF...WITH A
SUBSEQUENT STRENGTHENING OF A SLY LOW-LEVEL JET OVER THE CNTRL GULF
STATES...AND THE DEEPENING OF A SURFACE LOW OVER MS. AS
SUCH...TORNADIC POTENTIAL INCLUDING THE POSSIBILITY OF A SLOWLY EWD
PROGRESSING BROKEN SQUALL LINE MAY INCREASE OVERNIGHT ACROSS
PORTIONS OF MS...AL...REACHING THE WRN FL PANHANDLE BY 12Z/MON.
HOWEVER...MARGINALLY SUPPORTIVE THERMODYNAMIC PROFILES CONTINUE TO
CAST UNCERTAINTY ON THE MAGNITUDE OF THE POTENTIAL SEVERE WEATHER
EVENT.

...NERN CO/NWRN KS/CNTRL NEB...
MARGINAL LOW-LEVEL MOISTURE RETURN WILL OCCUR ON THE PERIPHERY OF A
TROPICAL AIR MASS AMIDST WEAK SLY/SELYS. THOUGH INSTABILITY AND
MOISTURE WILL BE LIMITED AND LIKELY HINDER A GREATER COVERAGE OF
STORMS...AT LEAST ISOLD DIURNALLY-DRIVEN HIGH-BASED STORMS ARE
POSSIBLE ALONG A LEE SURFACE TROUGH. COOL TEMPERATURES ALOFT /-14 AT
500 MB/ MAY SUPPORT A FEW SUSTAINED UPDRAFTS...WITH HAIL PRODUCTION
POSSIBLE. DMGG WINDS MAY OCCUR AS STORMS QUICKLY COLLAPSE.

..HURLBUT/KERR.. 09/30/2012

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