FXUS62 KTAE 050832
AFDTAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
300 AM EST SAT DEC 5 2009
...FREEZING TEMPERATURES EXPECTED TONIGHT ACROSS MUCH OF THE AREA...
.SYNOPSIS...
AT 3 AM EST...RADAR SHOWED TWO BANDS OF SW-NW MOVING SHOWERS ACROSS
LOCAL AREA. THE LATTER BAND SHOULD BE EAST OF LOCAL REGION BY
MID-MORNING.
AT UPPER LEVELS...
THE LARGE SCALE SYNOPTIC PATTERN IS HIGHLIGHTED BY A HIGH BUILDING
OVER GULF OF ALASKA...A CLOSED LOW EVOLVING OVER PAC NE/NRN
INTERMOUNTAIN REGION...AND A SHARPENING LONG WAVE TROUGH
WITH SEVERAL LOBES OF ENERGY EMBEDDED WITHIN THAT DOMINATES MOST OF
U.S. AXIS NOW EAST OF MISS VALLEY WITH STRONG UPPER JET FROM BASE
OF THE TROUGH ACROSS FL PANHANDLE TO MID ATLANTIC REGION. TROUGH
BECOMING MODESTLY NEGATIVELY TILTED AS POTENT SHORT WAVE ENERGY
ROUNDING ITS BASE WILL TRANSLATE EAST ALONG THE NORTHERN GULF COAST
REST OF OVERNIGHT HOURS. WV IMAGERY SHOWS ABUNDANT MOISTURE
STREAMING NORTHEAST AHEAD OF THIS FEATURE ACROSS THE SOUTHEASTERN
STATES.
AS INTERMOUNTAIN LOW SHIFTS EWD THRU WEEKEND...TROUGH WILL BE
SHUNTED EWD. BY THIS AFTERNOON...H2 TROUGH WILL DEAMPLIFY AS SECOND
SHORTWAVE NOW MOVING INTO LWR MS VALLEY ACCELERATES NEWD TO REACH
CAROLINAS THIS EVE AND ATLC COAST TONIGHT. NAM IS SLIGHTLY DEEPER
AND/OR SLOWER THAN THE GFS AND NEARLY ALL OTHER GUIDANCE WHICH SHOWS
THE MID LVL TROF CROSSING THE EAST COAST EARLY THIS EVE. WILL TREND
TOWARDS GFS IN TIMING. AS SHORT WAVE IMPULSES DROP DOWN INTO SRN
ROCKIES REST OF WEEKEND...INTER MOUNTAIN LOW WILL DEEPEN INTO TROUGH
ACCOMPANIED BY STRENGTHENING SLY LOW LEVEL FLOW. THIS WILL SERVE AS
FOCUS FOR WHAT HAS BECOME A REPETITIVE EL NINO PATTERN OF
SHORTWAVES/TROUGHS SPAWNING SURFACE LOWS MOVING EWD ACROSS GULF AND
THIS WILL REPRESENT OUR NEXT WEATHER SYSTEM DURING THE UPCOMING MID
WEEK PERIOD.
AT LOWER LEVELS...
A COMPLEX PATTERN CONTINUES TO EVOLVE ACROSS THE GULF OF MEXICO. ONE
WEAK AREA OF LOW PRESSURE OVER THE SOUTHEASTERN GULF MERGED WITH
ANOTHER DEVELOPING LOW IN THE W/CNTRL GULF BAROCLINIC ZONE LAST
NIGHT UNDERNEATH THE ABOVE ADVANCING UPPER LEVEL SHORT WAVE. DURING
THE PREDAWN HOURS...THIS LOW WILL MOVE ACROSS THE EASTERN GULF OF
MEXICO/FL PENINSULA ALONG LIFTING WARM FRONT...AND SOUTH OF THE
COASTAL WATERS REACHING ATLC COAST THIS MORNING. AHEAD OF IT...AREA
OF LIFT N OF FRONTAL BOUNDARY AND AIDED BY SWLY FLOW ALOFT...
GENERATING SUBSTANTIAL ISENTROPIC UPGLIDE TO THE EAST AND NORTHEAST
OF THE LOW TRACK WILL CONTINUE THE LIGHT TO MODERATE RAIN
OVERSPREADING CWA. HOWEVER...MOST Q-G FORCING WILL REMAIN IN THE
COOL SECTOR INHIBITING CYCLOGENESIS AND LIMITING HEAVY RAIN AND ANY
CHANCES OF TSTMS. THE WARM FRONT WILL STALL WELL SHORT OF MARINE
AREA AND THEN BEGIN TO RETREAT SEWD BY LATE THIS MORNING AS PRIMARY
LOW BECOMES ESTABLISHED OFF THE ATLANTIC SEABOARD.
24-HR RAINFALL TOTALS WILL AVERAGE BETWEEN A 1/4 AND 1/2 INCH...WITH
UP TO AN INCH OVER THE EASTERN FL BIG BEND. DESPITE WINTRY PRECIP
LIKELY JUST TO OUR N/W...OBS REINFORCED BY PARTIAL THICKNESSES THAT
HOLD ABOVE TYPICAL VALUES UNTIL AFTER THE PRECIP HAS EXITED TO THE
EAST BODE AGAINST ANY PRECIP MIX TO MAKE IT HERE.
&&
.SHORT TERM (TODAY THROUGH MONDAY)...
TODAY...
EXPECT AREAS OF FOG EARLY. OTHERWISE...SURFACE LOW MOVES OFF THE
SOUTHEAST COAST EARLY THIS MORNING WITH THE SHORTWAVE AXIS/UPPER
TROUGH CROSSING EWD SHORTLY THEREAFTER. DRIER AIR WILL QUICKLY
FILTER IN BEHIND THE LOW AND SHOULD END ANY LINGERING SHOWERS ACROSS
THE EASTERN HALF OF THE AREA BY MID MORNING. 0-50 PCT W-E MORNING
POP. IMPROVING CONDITIONS ARE ANTICIPATED FOR THE LATE MORNING AND
AFTERNOON WITH PARTIAL CLEARING WORKING WEST TO EAST. RATHER CHILLY
LOW LEVEL AIRMASS WILL CONTINUE WITH 850MB TEMPS BETWEEN 0-4C. HIGH
TEMPS LOOK TO REACH AROUND 50 NORTH AND WEST OF DOTHAN TO THE MIDDLE
AND UPPER 50S ACROSS THE FLORIDA BIG BEND.
TONIGHT...
CONFIDENCE INCREASING FOR OUR FIRST POTENTIAL SIGNIFICANT FREEZE
EVENT TONIGHT/EARLY SUNDAY MORNING. SURFACE HIGH PRESSURE WILL SLIDE
TO OUR NORTH WITH AN EXTENSION OF THE RIDGE DOWN INTO THE NE GULF.
THIS RIDGE EXTENSION SHOULD ALLOW OUR WINDS TO GO LIGHT AFTER
SUNSET. ANY LINGERING CLOUDS WILL EXIT TO OUR EAST DURING THE
EVENING WITH MOSTLY CLEAR SKIES THROUGH THE NIGHT. THE LIGHT
WINDS/DRY LOW LEVEL AIR...AND ALREADY CHILLY AIRMASS WILL SET UP
DECENT RADIATIONAL COOLING CONDITIONS. GUIDANCE CONSENSUS BRING MUCH
OF THE AREA DOWN INTO THE UPPER 20S WEST OF APALACHICOLA RIVER TO
NEAR 30 EAST OF RIVER FOR 2-4 HRS TOWARD SUNRISE SUNDAY MORNING.
THIS YIELDS 5-7B HOURS AOB 32 DEGREES COLDEST SITES SE ALA/SW GA TO
2-3 HRS SE BIG BEND. ERN BIG BEND AND S/CNTRL GA BORDERLINE FREEZE A
CLOSE CALL BUT WILL ISSUE FREEZE WATCH FOR ENTIRE CWA AND LET NEXT
SHIFT UPGRADE/REFINE AS NECESSARY.
SUNDAY...
NO POPS. FAIR AND QUIET WEATHER AFTER THE COLD START. SURFACE
HIGH PRESSURE WILL BE IN CONTROL WITH AFTERNOON HIGH TEMPS UP 4-7
DEGREES FROM SATURDAY. TEMPS FROM MID 50S SE ALA TO MID 60S SE BIG
BEND. DO EXPECT AN INCREASE IN HIGH LEVEL CIRRUS... ESPECIALLY THE
SECOND HALF OF THE DAY AS OUR NEXT POTENTIAL WEATHER SYSTEM
ORGANIZES TO OUR WEST.
MONDAY...
NO POPS. AS HIGH MOVES OFFSHORE AND NEXT LOW APPROACHES WRN
CWA...WINDS VEER AND MAX TEMPS RISE TO MID 60S SE ALA TO LOW 70S SE
BIG BEND. 40-20 PCT W-E AFTN POP.
.LONG TERM...(MONDAY NIGHT-FRI).
THE ACTIVE SRN STREAM WILL KEEP THE RAIN CHANCES UP THROUGH PORTIONS
OF THE EXTENDED PERIOD AS SEVERAL UPPER-LEVEL PULSES OF ENERGY
PROGRESS NORTHEAST OVER THE SRN REGION IN THE SOUTHWEST FLOW ALOFT.
OUTSIDE OF SOME MINOR TIMING ISSUES...THE MODELS APPEAR TO BE IN
DECENT AGREEMENT THROUGH MUCH OF THIS PERIOD. TEMPERATURES WILL
REMAIN CLOSE TO AVERAGE WITH LOWS IN THE LOWER 40S AND HIGHS IN THE
UPPER 60S. TUESDAY AND WEDNESDAY WILL BE THE TWO DAYS WITH
TEMPERATURES FORECAST TO REMAIN ABOVE AVERAGE AS DEEP MOIST
SOUTHERLY FLOW STREAMS OVER THE AREA AHEAD OF AN APPROACHING COLD
FRONT. THESE WARM TEMPERATURES WILL BE ACCOMPANIED BY INCREASING
RAIN CHANCES THROUGH THIS MID-WEEK PERIOD. CONDITIONS WILL
TEMPORARILY DRY IMPROVE OR DRY OUT WEDNESDAY NIGHT THROUGH THURSDAY
NIGHT BEFORE ANOTHER DEVELOPING WARM FRONT OVER THE NRN GULF LIFTS
NORTHEAST ACROSS THE GULF COAST STATES LEADING TO INCREASING RAIN
CHANCES ONCE AGAIN COME FRIDAY NIGHT.
&&
.MARINE...OVERNIGHT OBSERVATIONS S OF PANHANDLE WATERS INDICATED N
WINDS AROUND 20 KTS WELL OFFSHORE WITH 3-5 FOOT SEAS. SUSTAINED
AROUND 15 KT WITH GUSTS TO 20 KT AT THE BUOYS. NEAR SHORE...SPEEDS
WERE 10-15 KT. WAVE HEIGHTS WERE 2-4 FT. LOW PRESSURE WILL MOVE
OFF THE SOUTHEAST COAST THIS MORNING. THE GRADIENT WILL FURTHER
TIGHTEN...WITH N THEN NW WINDS REACHING SMALL CRAFT ADVISORY LEVELS
ACROSS THE WESTERN LEGS BY SUNRISE...AND SOON AFTER MIDNIGHT FOR THE
REMAINDER OF THE FORECAST WATERS. THESE WINDS REMAIN AT SCA LEVELS
THROUGH MUCH OF THE DAY BEFORE DROPPING TO EXERCISE LEVELS TONIGHT.
&&
.AVIATION...IFR CONDITIONS ALONG WITH LIGHT TO MODERATE RAIN WILL
CONTINUE THROUGH DAYBREAK AS LOW PRESSURE SHIFTS EAST SOUTH OF THE
AREA...MAINLY OVER THE TLH/VLD TERMINALS. RAIN CHANCES WILL DECREASE
THROUGH THE DAY TODAY AS HIGH PRESSURE BUILDS EAST OVER THE REGION.
LIGHT NORTHERLY WINDS WILL CONTINUE. VFR CONDITIONS WILL RETURN BY
THE END OF THE PERIOD AS THE SKIES BEGIN TO CLEAR FROM WEST TO EAST.
&&
.FIRE WEATHER...ALTHOUGH A DRIER AIRMASS IS FORECAST TO MOVE OVER
THE REGION BY SUNDAY IN THE WAKE OF THE SURFACE LOW OVER THE
GULF...COOL AFTERNOON TEMPERATURES WILL NOT SUPPORT CRITICAL
RELATIVE HUMIDITY LEVELS...THUS NO FIRE WEATHER CONCERNS ARE
ANTICIPATED THROUGH THE EARLY PART OF NEXT WEEK.
&&
.HYDROLOGY...MINOR FLOODING IS OCCURRING AND WILL CONTINUE FOR THE
NEXT SEVERAL DAYS AT CARYVILLE AND BLOUNTSTOWN FL.
&&
.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE 56 30 58 42 70/ 20 0 0 10 30
PANAMA CITY 55 34 58 48 69/ 0 0 0 20 30
DOTHAN 50 27 55 40 65/ 0 0 10 10 40
ALBANY 52 28 57 39 66/ 20 0 0 10 20
VALDOSTA 54 31 58 42 69/ 40 0 0 10 20
CROSS CITY 55 31 64 44 72/ 50 0 0 20 30
APALACHICOLA 55 33 61 46 70/ 20 0 0 20 30
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
AL...FREEZE WATCH IN EFFECT FOR TONIGHT.
GA...FREEZE WATCH IN EFFECT FOR TONIGHT.
FL...FREEZE WATCH IN EFFECT FOR TONIGHT.
GM...SMALL CRAFT ADVISORY UNTIL 7 PM EST SATURDAY
&&
$$
AVIATION/FIRE WEATHER/LONG TERM...GIBBS
SYNOPSIS/PUBLIC/MARINE...BLOCK
