Saturday, April 14, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 141247
SWODY1
SPC AC 141245

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0745 AM CDT SAT APR 14 2007

VALID 141300Z - 151200Z

..THERE IS A MDT RISK OF SVR TSTMS TODAY INTO THIS EVENING FOR SE
MS...CENTRAL AND SRN AL...WRN GA...AND THE WRN FL PANHANDLE...

..THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
THE LOWER MS VALLEY TO THE CAROLINAS BY TONIGHT...

..SYNOPSIS...
A SRN STREAM SHORTWAVE TROUGH IS SHEARING NEWD FROM OK INTO
MO/IL...WHILE AN UPSTREAM WAVE OVER W TX ROTATES EWD TOWARD THE
LOWER MS VALLEY. THIS SRN STREAM SYSTEM WILL GRADUALLY PHASE WITH A
SEPARATE NRN STREAM WAVE OVER THE UPPER MS VALLEY/GREAT LAKES BY
LATE IN THE PERIOD. AN INITIAL FRONTAL WAVE IN EXTREME NW MS WILL
PROGRESS GENERALLY EWD NEAR THE MS/AL/TN BORDERS DURING THE
DAY...AND THE PHASING OF THE TWO FLOW STREAMS WILL CONTRIBUTE TO
DEEPENING OF THE SURFACE CYCLONE TONIGHT FROM THE PIEDMONT INTO THE
TIDEWATER AREA.

..SRN MS INTO AL/SW GA AREA TODAY...
THE PHASING FLOW STREAMS AND SURFACE CYCLOGENESIS WILL HELP MAINTAIN
STRONG DEEPER LAYER FLOW THROUGH THE WARM SECTOR FROM THE GULF
STATES TODAY INTO THE CAROLINAS OVERNIGHT...AND STRONG DEEP LAYER
SHEAR WITH LONG HODOGRAPHS. THE LOW-LEVEL THERMODYNAMIC ENVIRONMENT
IS RATHER POOR INITIALLY ACROSS MUCH OF AL/WRN GA...BUT SHOULD
IMPROVE RAPIDLY DURING THE DAY AS A RESULT OF HORIZONTAL MOISTURE
ADVECTION AND MIXING OF MOISTURE DOWNWARD. BY ROUGHLY 18Z IN
CENTRAL/SRN AL...MODEST MID LEVEL LAPSE RATES...BOUNDARY LAYER
DEWPOINTS OF 66-70 F...AND SURFACE TEMPERATURES OF 75-80 F WILL
RESULT IN MLCAPE VALUES OF 1000-1500 J/KG. THE COMBINATION OF
MODERATE INSTABILITY AND STRONG DEEP LAYER SHEAR SHOULD SUPPORT
EMBEDDED SUPERCELL AND/OR BOWING STRUCTURES WITHIN THE BROKEN
SQUALL LINE MOVING FROM MS TOWARD AL WHICH SHOULD INTENSIFY DURING
THE DAY...AS WELL AS THE POSSIBILITY OF ISOLATED SUPERCELLS IN
ADVANCE OF THE LINE AS THE LOW-LEVELS DESTABILIZE AND CONVECTIVE
INHIBITION WEAKENS. A FEW TORNADOES...DAMAGING WINDS...AND ISOLATED
LARGE HAIL CAN BE EXPECTED WITH THE STRONGER STORMS...ESPECIALLY
FROM MIDDAY THROUGH THIS EVENING.

..CAROLINAS TONIGHT...
SOMEWHAT WEAKER INSTABILITY AND LESSER BOUNDARY LAYER MOISTURE /MID
60S BOUNDARY LAYER DEWPOINTS/ ARE EXPECTED OVERNIGHT INTO THE
CAROLINAS. HOWEVER...VERY STRONG LOW-LEVEL SHEAR /0-1 KM SRH OF
300-500 M2/S2/ WILL ACCOMPANY A 50-60 KT LLJ IN THE WARM SECTOR. AN
OCCASIONAL TORNADO AND DAMAGING WINDS WILL CONTINUE TO BE POSSIBLE
OVERNIGHT WITH SUPERCELLS AND/OR BOWING SEGMENTS ALONG THE PATH OF
THE SURFACE CYCLONE...DESPITE THE WEAK SURFACE-BASED INSTABILITY.

.THOMPSON/TAYLOR.. 04/14/2007

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