FXUS62 KJAX 280738
AFDJAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
235 AM EST SAT NOV 28 2009
...PATCHY FROST LIKELY THIS MORNING...
...ANOTHER STORM SYSTEM TO AFFECT AREA NEXT WEEK...
.SHORT TERM...LATEST MSAS ANALYSIS SHOWS HIGH PRESSURE HAS SETTLED
OVER THE LOWER MISSISSIPPI VALLEY TONIGHT WITH RIDGING EASTWARD
THROUGH THE PANHANDLE. POSITION OF THE HIGH REMAINS SUFFICIENTLY
WEST OF THE AREA TO ALLOW FOR CONTINUED LIGHT FLOW BETWEEN 5 TO 10
MPH WHICH HAS HELPED CURB TEMPERATURE DROP. OVER THE SOUTHEAST GA
PORTION WHERE CIRRUS HAS BEEN MOST PREVALENT...TEMPERATURES ARE
SOME 4 TO 6 DEGREES ABOVE GUIDANCE PROJECTIONS AND WILL NEED TO
ADJUST IN THE INITIALIZED GRID SET. THE WARMER TEMPS WILL ALSO
HAVE AN IMPACT ON FROST COVERAGE TONIGHT AND WILL LIKELY BACK OFF
ON MENTION OF AREAS AND LIMIT TO PATCHES FOR THIS MORNING.
HIGH WILL SHIFT EASTWARD TODAY PROVIDING FOR A FAIR WEATHER PATTERN
CHARACTERIZED BY DRY CONDITIONS AND CONTINUED COOL TEMPS IN THE
LOW TO MID 60S. CIRRUS SHOULD BE A MAINSTAY FOR THE NEXT 24 TO 48
HOURS AS MID LEVEL IMPULSES MOVE THROUGH AREA WHILE EMBEDDED IN
SWIFT WESTERLY FLOW ALOFT.
LATEST MODEL GUIDANCE SHOWS SURFACE HIGH SHIFTING FURTHER EASTWARD
THAN EARLIER PROJECTIONS FOR SUN MORNING WHICH SHOULD ALLOW FOR
MORE OF A RETURN FLOWN TO DEVELOP. ALONG WITH A FEW STRATO-CU
DEVELOPING...INCREASED WIND FLOW SHOULD KEEP TEMPS A DEGREE OR TWO
ABOVE GUIDANCE.
FOR THE REMAINDER OF THE SHORT TERM PERIOD...BENIGN WEATHER WILL
BE THE RULE THROUGH MONDAY WITH SOUTHWEST FLOW BRINGING IN
SLIGHTLY MODERATED TEMPS AND DEWPOINTS. MAJOR STORM SYSTEMS
HOWEVER WILL REMAIN WEST OF THE AREA THROUGH LATE MON AFTERNOON.
NEXT SYSTEM WILL EMANATE FROM THE NORTHERN STREAM AND WILL INVOLVE
A FRONTAL BOUNDARY ENTERING INTO OUR NORTHWEST ZONES BY 00Z TUE.
MOST OF THE HIGH MOISTURE CONTENT AIR WITH THIS SYSTEM WILL BE ON
THE BACKSIDE OF THE FRONT AND THEREFORE CONDITIONS WILL BE QUITE
STABLE WITHIN PRECIP BAND. WILL CARRY CHANCES POPS AS MAIN
DYNAMICS LIFT TO THE NORTH AND RAIN CHANCES WILL BE SOLELY
DEPENDENT ON CONVERGENCE ALONG THE FRONT WHICH LOOKS LIMITED
THROUGH TUESDAY NIGHT.
.LONG TERM...FRONT WILL PUSH THROUGH THE AREA AND STALL THROUGH
12Z TUE. MODELS ARE IN GOOD AGREEMENT IN 4 CORNERS CUTOFF LOW
EJECTING OUT AND INTO THE SOUTHERN PLAINS THROUGH TUE AFTERNOON.
THIS WILL ALLOW FOR QUICK DEVELOPMENT OF LOW PRESSURE OVER THE
NORTHERN GULF WITH A WARM FRONT DEVELOPING THROUGH THE EASTERN
GULF AND INTO THE SUWANNEE VALLEY OF FLORIDA. WHAT IS LIKELY WITH
THIS SYSTEM AT THIS POINT IS THERE WILL BE A CORE OF VERY HEAVY
RAINFALL TO THE EAST OF THE LOW NEAR THE WARM FRONT BY 06Z WED.
WHAT IS UNCLEAR IS WHETHER THIS WILL BE WELL WEST OF THE AREA AS
THE ECMWF AND DGEX SUGGEST OR RIGHT OVER THE SUWANNEE VALLEY AS
THE GFS SHOWS. REGARDLESS...MODELS SHOW HIGH POPS FOR THE AREA FROM
LATE TUE NIGHT THROUGH WED AFTERNOON AND WILL CONTINUE THE GRADUAL
UPWARD TREND IN THE GRIDS TO INCLUDE LIKELY POPS NOW.
AS FAR AS THE SEVERE THREAT...WITH LOW JUST TO THE NORTH OF THE
AREA HELICITIES WILL BE VERY HIGH FOR THE PERIOD. QUESTION AS
ALWAYS WILL BE CAN WE GET THE INSTABILITY TO SUPPORT THE UPDRAFT
NEEDED FOR SUCH HIGH HELICITY VALUES. BEST INSTABILITY LOOKS TO BE
ON WED IN THE WARM SECTOR BEFORE SHEAR VALUES BEGIN TO DECLINE.
50 TO 60 KNOT LOW LEVEL WIND CORE OVER THE AREA WILL ALLOW FOR
MARGINAL SEVERE THREAT AND ISOLATED TORNADO RISK WILL EXIST JUST TO
THE SOUTH OF WARM FRONT.
&&
.AVIATION...VFR CONDITIONS WILL CONTINUE.
&&
.MARINE...WINDS FORECAST TO DROP BELOW SMALL CRAFT THRESHOLDS FOR
THE OFFSHORE WATERS IN A FEW HOURS. BUOY 41012 STILL HAS SUSTAINED
WINDS AROUND 20 KTS...SO WILL MONITOR CLOSELY UNTIL CWF PRODUCT
ISSUANCE. BENIGN CONDITIONS EXPECTED FROM LATER TODAY THRU EARLY
MON. WINDS WILL BEGIN TO INCREASE THEREAFTER IN RESPONSE TO
APPROACHING COLD FRONT...THEN LOW PRESSURE DEVELOPING OVER THE GULF
COAST REGION.
&&
.FIRE WEATHER...STILL NOT A SLAM DUNK RH FORECAST BY ANY MEANS. DO
EXPECT MORE MIXING TODAY WITH DRY AIR BROUGHT TO THE SFC. AS A
RESULT...WILL GET MARGINAL DURATIONS OF 35 PERCENT RH OVER PORTIONS
OF INTERIOR NE FL AND HAVE UPGRADED THE EXISTING FIRE WX WATCH TO A
RED FLAG WARNING. HAVE REMOVED CLAY AND PUTNAM COUNTIES FROM THE
WARNING WITH RH VALUES ONLY EXPECTED TO REACH 35 PERCENT BRIEFLY IN
THESE AREAS.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 63 38 70 43 / 0 0 0 0
SSI 62 46 68 51 / 0 0 0 0
JAX 63 41 73 47 / 0 0 0 0
SGJ 63 48 71 52 / 0 0 0 0
GNV 64 39 73 46 / 0 0 0 0
OCF 65 40 74 48 / 0 0 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...RED FLAG WARNING FROM 11 AM THIS MORNING THRU 5 PM THIS
AFTERNOON FOR ALACHUA-BAKER-BRADFORD-COLUMBIA-GILCHRIST-
HAMILTON-MARION-SUWANNEE-UNION.
FIRE WX WATCH FROM 11 AM SUN MORNING THRU 5 PM SUN AFTERNOON
FOR COLUMBIA-HAMILTON-SUWANNEE.
GA...NONE.
AM...SMALL CRAFT ADVISORY UNTIL 5 AM THIS MORNING FOR ALTAMAHA
SOUND GA TO FLAGLER BEACH FL 20 NM TO 60 NM OFFSHORE.
&&
$$
DEESE/CARROLL
