SPC AC 270619
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 AM CST THU DEC 27 2007
VALID 281200Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY INTO
THE SRN APPALACHIANS...
...SYNOPSIS...
MODELS INDICATE STRONG SHORT WAVE TROUGH CURRENTLY OVER THE GREAT
BASIN WILL MOVE FROM THE CENTRAL PLAINS AT THE START OF THE DAY 2
PERIOD ENEWD ACROSS THE GREAT LAKES REGION AS A 100 KT MIDDLE LEVEL
JET STREAK PROGRESSES ACROSS THE OH VALLEY.
AT THE SURFACE...A LOW OVER THE LOWER MS VALLEY WILL MOVE NEWD
DURING THE DAY ACROSS THE OH VALLEY...EVENTUALLY MERGING WITH A
BROADER REGION OF LOW PRESSURE MOVING EWD FROM THE MIDDLE MS VALLEY.
THIS PRIMARY LOW WILL LIFT NEWD DURING THE NIGHT INTO SERN ONTARIO
AS SECONDARY CYCLOGENESIS OCCURS OFF THE NJ COAST. A COLD FRONT
TRAILING SWWD FROM THE MS/OH VALLEY LOW WILL MOVE EWD REACHING
EXTREME ERN KY/NERN AL/SERN LA BY 29/00Z...CONTINUING TO A LINE FROM
THE NJ COAST ACROSS CENTRAL NC AND CENTRAL GA INTO THE NORTH CENTRAL
GULF OF MEXICO LINE BY THE END OF THE PERIOD. A WARM FRONT ACROSS
THE SERN STATES WILL LIFT NWD THROUGH THE PERIOD...ALTHOUGH REMNANTS
OF COLD AIR DAMMING MAY INHIBIT ITS NWD PROGRESS OVER THE
APPALACHIANS. THE WARM FRONT IS FORECAST TO MOVE ACROSS THE
CAROLINAS AND ERN PARTS OF KY AND TN DURING THE DAY AND ACROSS THE
DELMARVA FRIDAY NIGHT.
...LOWER MS VALLEY INTO TN VALLEY...
PRIMARILY ELEVATED THUNDERSTORMS WILL BE ONGOING AT THE START OF THE
PERIOD OVER PARTS OF LA AND MS IN ASSOCIATION WITH STRONG WARM
ADVECTION AS A 50-60 KT SSWLY LOW LEVEL JET MOVES ACROSS THE LOWER
MS VALLEY. MOISTURE IS EXPECTED TO CONTINUE INCREASING NWD DURING
THE MORNING WITHIN THE EXPANDING WARM SECTOR...CONTRIBUTING TO AIR
MASS DESTABILIZATION WITH MUCAPE OF 500-1000 J/KG FORECAST BY
15-18Z. FORECAST SOUNDINGS SUGGEST SURFACE-BASED CONVECTION WILL
BECOME MORE LIKELY BY MID MORNING WITH AN INCREASING THREAT FOR A
FEW SEVERE STORMS TO DEVELOP. VERY STRONG DEEP LAYER SHEAR /50 KT
OR GREATER IN THE LOWEST 6 KM/ WILL ENHANCE STORM ORGANIZATION AND
INTENSITY AND PROVIDE A FAVORABLE KINEMATIC ENVIRONMENT SUPPORTIVE
OF SUPERCELLS. IN ADDITION...VERY STRONG LOW LEVEL SHEAR AND SRH
SUGGEST A POSSIBILITY FOR ISOLATED TORNADOES...MAINLY OVER PARTS OF
SERN LA...SRN/ERN MS...NRN/WRN AL...AND NWRN GA THROUGH THE
AFTERNOON HOURS.
STORMS ARE LIKELY TO SPREAD NWD/NEWD INTO PARTS OF ERN TN AND
POSSIBLY SWRN NC BY LATE MORNING/EARLY AFTERNOON WITHIN REGION OF
STRONG NWD MOISTURE FLUX AS THE LOW LEVEL JET LIFTS NEWD ACROSS THE
TN VALLEY. VERY STRONG VERTICAL SHEAR PROFILES SUGGEST POTENTIAL
FOR ISOLATED SEVERE STORMS ACROSS THIS REGION ALTHOUGH MORE LIMITED
INSTABILITY MAY IMPACT SEVERE COVERAGE.
ALL ACTIVITY IS EXPECTED TO SPREAD SLOWLY EWD THROUGH THE EVENING
HOURS...WITH SEVERE THREAT GRADUALLY DIMINISHING AFTER 00Z AS THE
STRONGEST DYNAMIC FORCING LIFTS NEWD INTO THE MID ATLANTIC STATES.
...PARTS OF ERN KY/WV/SWRN VA...
A NARROW AXIS OF MARGINAL LOW LEVEL MOISTURE /SURFACE DEW POINTS IN
THE LOW-MID 50S/ MAY SPREAD NWD TOWARD THE UPPER OH VALLEY AS THE
SURFACE LOW CONSOLIDATES TO THE WEST AND THE LOW LEVEL JET LIFTS
NEWD ACROSS THIS AREA. ALTHOUGH INSTABILITY WILL BE QUITE LIMITED
WITH MUCAPE AOB 250 J/KG...VERY STRONG VERTICAL SHEAR SUGGESTS
POTENTIAL FOR LOW-TOPPED STRONG/SEVERE THUNDERSTORMS DURING THE
AFTERNOON AND EVENING. FORECAST SOUNDINGS SHOW 65 KT WINDS BELOW
850 MB INDICATING POSSIBILITY OF VERTICAL TRANSFER OF HORIZONTAL
MOMENTUM TO THE GROUND WITHIN CONVECTIVE DOWNDRAFTS WITH PRIMARY
THREAT FOR LOCALIZED WIND DAMAGE.
..WEISS.. 12/27/2007
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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