Post by SKYSUMMIT on Jan 9, 2008 8:48:22 GMT -6
...SRN OH VALLEY SWD TO CNTRL/ERN GULF COAST...
CURRENT SURFACE OBSERVATIONS AND MODEL GUIDANCE INDICATE THAT COLD
FRONT NOW MOVING THROUGH THE WRN AND CNTRL GULF COAST SHOULD WEAKEN
AND EVENTUALLY DISSIPATE OVER THE SHELF WATERS AS LEE CYCLOGENESIS
OCCURS OVER THE CNTRL/SRN HIGH PLAINS. BUOY OBSERVATIONS AND GOES
SOUNDER IPW IMAGERY SHOW A MOIST AIR MASS IMMEDIATELY TO THE S OF
THIS BOUNDARY /DEWPOINTS OF AROUND 70F/...WHICH WILL BE POISED TO
RETURN NWD BEGINNING DURING THE DAY ONE FORECAST PERIOD.
INDEED...STRENGTHENING SWLY LLJ WILL SUPPORT THE RAPID NWD/NEWD
ADVECTION OF AN INCREASINGLY MOIST BOUNDARY LAYER FROM THE CNTRL
GULF COAST THROUGH THE TN INTO SRN OH VALLEYS WITH DEWPOINTS
INCREASING TO AROUND 50F ALONG THE OH RIVER...TO MID/UPPER 60S ALONG
THE GULF COAST. THIS MOISTURE COUPLED WITH STEEPENING MIDLEVEL
LAPSE RATES ARE FORECAST TO CONTRIBUTE TO MODERATE INSTABILITY BY
AFTERNOON OVER SRN LA THROUGH SERN MS INTO CNTRL AL WITH ENVIRONMENT
ONLY BECOMING WEAKLY UNSTABLE ACROSS NRN PORTIONS OF SLIGHT RISK
AREA.
SURFACE-BASED TSTMS ARE EXPECTED TO INCREASE RAPIDLY IN BOTH
COVERAGE AND INTENSITY BY MID/LATE MORNING AHEAD OF COLD FRONT FROM
THE TN VALLEY TO THE CNTRL GULF COAST AS HEIGHT FALLS AHEAD OF UPPER
TROUGH BEGIN TO OVERSPREAD DESTABILIZING WARM SECTOR. TROPOSPHERIC
WIND FIELDS ARE FORECAST TO STRENGTHEN CONSIDERABLY THROUGH THE DAY
WITH BOTH DEEP LAYER AND LOW LEVEL SHEAR BECOMING MORE THAN
SUFFICIENT FOR SUPERCELLS AND BOWING STRUCTURES CAPABLE OF TORNADOES
AND DAMAGING WINDS.
THIS SEVERE THREAT MAY DEVELOP AS FAR N AS THE UPPER OH VALLEY INTO
AN ENVIRONMENT CHARACTERIZED BY SMALL INSTABILITY...BUT BOTH STRONG
ISALLOBARIC FORCING AND VERTICAL SHEAR. FARTHER S...SEVERE STORMS
WILL LIKELY CONTINUE AHEAD OF COLD FRONT ACROSS PORTIONS OF
GA...CNTRL/SRN AL AND THE FL PNHDL THURSDAY NIGHT WITH A THREAT OF
DAMAGING WINDS AND PERHAPS A FEW TORNADOES.
From the NWS N.O.'s Disco:
SHORT TERM...
CONVECTION ASSOCIATED WITH THE FRONTAL PASSAGE PRETTY MUCH FIZZLED
UPON REACHING THE ALABAMA STATE LINE AT THE GULF COAST. ONLY
LINGERING RAIN SHOWERS DEPICTING THIS WEAKENING BOUNDARY AND SOME
OVERRUNNING STRATIFORM ALREADY DEVELOPING WEST OF THE FRONT INTO
ACADIANA REGION. WINDS ARE STILL STRONG NORTHERLY AT BROWNSVILLE
TEXAS INDICATING THE FRONT HAS NOT STALLED JUST YET BUT WINDS HAVE
GONE SOUTHERLY ALREADY IN NORTH TEXAS AND THE CENTRAL PLAINS
MEANING THE FRONTS PROGRESS WILL BEGIN TO SLOW SOON. INDICATED A
40 PERCENT CHANCE OF RAIN FOR THE AFTERNOON WITH 20 PERCENT THIS
MORNING FOR LIGHT STRATIFORM PATCHES. ALSO WENT WARMER THAN GFS
AND CLOSER TO NAM TEMPERATURES FOR TODAY AND TONIGHT. IT APPEARS
THE ISENTROPIC LIFT SOFTENS TONIGHT BUT CAN NOT RULE OUT SOME
PASSING MARINE LAYER TYPE SHOWERS OVERNIGHT. WILL MAINTAIN 30
PERCENT. THURSDAY SHOULD BE SIMILAR TO THIS PAST MONDAY AND
TUESDAY REGARDING WARM TEMPERATURES IN DEVELOPING WARM SECTOR.
BETTER ORGANIZATION WITH THUNDERSTORMS AND SPC HAS THE ENTIRE
FORECAST AREA UNDER A SLIGHT RISK FOR SEVERE THUNDERSTORMS. WHILE
THE MODEL SOUNDINGS DO NOT INDICATE AS STEEP A LAPSE RATE ALOFT AS
ON TUESDAY...THERE IS LITTLE NEGATIVE INHIBITION TO OVERCOME.
LOCAL CHAP PROGRAM DOES NOT REALLY HIT THE CONVECTION TOO
HARD...MAINLY MODERATELY STRONG STORMS ON THURSDAY. WILL NOT
MENTION SEVERE WORDING IN ZONES JUST YET BUT WILL MAINTAIN WORDING
IN HWO.