888
FXUS62 KJAX 210257
AFDJAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSONVILLE FL
957 PM EST FRI NOV 20 2009
..INCREASING RAIN CHANCES THIS WEEKEND
..A FEW STRONG TO SEVERE THUNDERSTORMS POSSIBLE
PUBLIC UPDATE
SPRAWLING HIGH PRESSURE SYSTEM IS CURRENTLY
POSITIONED TO OUR NORTHWEST AND NORTH. THE PLACEMENT OF THIS FEATURE
HAS ENABLED ONSHORE /EASTERLY/ FLOW TO ESTABLISH TODAY ACROSS OUR
EASTERN ZONES...WHILE A MORE NORTHERLY COMPONENT HAS MAINTAINED
DRIER AIR ACROSS OUR WESTERN ZONES. NUMERICAL MODELS INDICATE
MOISTURE TO INCREASE AOA 700 MB OVERNIGHT...WITH HIGH CLOUDS
INITIALLY TRAVERSING THE AREA TRAILING BY SOME MID LEVEL CLOUDS LATE
TONIGHT. FOG TOOLS INDICATE FOG WILL LIKELY ESTABLISH OVERNIGHT...
ESPECIALLY ALONG AND EAST OF THE U.S. HIGHWAY 301 CORRIDOR...WITH
THE POTENTIAL FOR LOCALIZED DENSE FOG REDUCING VISIBILITY TO BELOW A
HALF-MILE. THIS IS CURRENTLY HANDLED IN THE ZFP. CURRENT FORECAST
PACKAGE LOOKS ON TRACK.
AVIATION
CHALLENGING FORECAST AGAIN TONIGHT WITH RESPECT TO FOG
DEVELOPMENT. THE LATEST NAM12 HAS COME IN A LITTLE MORE ROBUST
WITH FOG ALONG THE COAST TONIGHT AND THIS IS IN LINE WITH PATCHY
FOG ALREADY BEING REPORTED AT VQQ..JAX..AND SSI. GIVEN THESE
TRENDS...AMENDMENTS WERE ISSUED TO INCLUDE PREVAILING GROUPS OF
IFR FOG LATER TONIGHT AT ALL TERMINALS. LIFR CONDITIONS WILL BE
POSSIBLE AT TIMES IN PATCHY DENSE FOG.
MARINE
SMALL CRAFT WILL NEED TO EXERCISE CAUTION OVER THE OFFSHORE LEGS
TONIGHT DUE TO LINGERING 4 TO 6 FT SWELLS. WINDS WILL REMAIN OUT
OF THE NORTHEAST GENERALLY LESS THAN 15 KNOTS. THE PREVIOUS
FORECAST IS IN GOOD SHAPE AND NO CHANGES WILL BE NECESSARY.
JAX WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GA...NONE.
AM...NONE.
PREVIOUS PUBLIC
LATEST MSAS ANALYSIS SHOWS HIGH PRESSURE CONTINUES TO
BE THE DOMINANT FEATURE OVER OUR AREA WITH MOISTURE AXIS RESPONSIBLE
FOR FOG THE PAST FEW NIGHTS SHIFTING OFFSHORE THIS MORNING. WITH THE
RETURN OF AN ONSHORE FLOW THIS AFTERNOON...THIS MOISTURE AXIS HAS
ONCE AGAIN TAKEN A POSITION ALONG OUR IMMEDIATE COAST AND HAS
RESULTED IN SCT CU DEVELOPMENT. TO THE WEST...SATELLITE IMAGERY
SHOWS DEEP CONVECTION OVER THE NORTHERN GULF OF MEXICO IN
ASSOCIATION WITH DEVELOPING STORM SYSTEM WHICH LOOKS TO BE A MAJOR
PLAYER FOR NE FL AND SE GA THIS WEEKEND.
FOR TONIGHT...ALTHOUGH MOISTURE REMAINS ALONG THE EASTERN
TIER...FOG TOOLS HAVE NOT BEEN AS AGGRESSIVE FOR THIS CYCLE.
STILL...SOME INDICATIONS OF PATCHY DENSE CONDITIONS FROM THE
CONDENSATION PRESSURE DEFICIT PLOTS AND LATEST NUMERIC GUIDANCE.
THIS MATCHES WELL WITH CURRENT GRID SET AND ONLY LIMITED CHANGES
ARE PLANNED.
SAT STILL LOOKS TO BE A TRANSITION DAY AS WARM FRONTAL BOUNDARY
DEVELOPS OVER THE NORTHEAST GULF AND BEGINS TO LIFT NORTHWARD.
THERE STILL REMAINS SOME SIGNIFICANT TIMING ISSUES WITH THE GFS
OPERATIONAL THE FASTEST...THE SREF THE SLOWEST...AND THE GS
ENSEMBLE SOMEWHERE IN THE MIDDLE. FOR CONTINUITY PURPOSES...WILL
CONTINUE TO THE LEAN TOWARD THE ENSEMBLE SOLUTION WHICH BRINGS
JUST LOW END SCT CHANCES OF LIGHT RAIN TO THE WESTERN SECTIONS
THROUGH 00Z SUN. THEREAFTER...THE MAIN MOISTURE CORE WILL PUSH
INTO THE GA PORTION AND EXTEND SOUTHWARD INTO THE SUWANNEE VALLEY
WITH HIGH END LIKELY POPS. BY 12Z SUN...WARM FRONT WILL LIFT JUST
NORTH OF THE AREA WITH INCREASINGLY SOUTHERLY FLOW AND INSTABILITY
FOR THE AREA AND THE INTRODUCTION OF SCT TSRA TO THE GRIDS.
AS FAR AS SEVERE POTENTIAL...WITH LOW NOW PROGGED TO REMAIN CLOSER
TO THE REGION AND A POTENT SHORTWAVE TO PUSH THROUGH SUN...DYNAMICS
ARE IN PLACE FOR ISOLATED SEVERE STORMS...ESPECIALLY OVER THE
SUWANNEE VALLEY AND THE GA PORTION WHERE 06 KM SHEAR WILL BE THE
HIGHEST. 0-1KM HODOGRAPHS ALSO SHOW POTENTIAL FOR ROTATING
UPDRAFTS OVER THE AREA ALTHOUGH GREATEST POTENTIAL WILL BE NORTH
OF THE AREA. LIMITING FACTOR AS USUAL WILL BE INSTABILITY WITH
MODELS SHOWING A MAX 500 J/KG OF CAPE AND 0 TO -2 LIS. GOOD
DIFFLUENT SIGNATURE ALOFT COULD HELP OVERCOME THESE DEFICIENCIES
AND ALLOW FOR ISOLATED SEVERE AND WILL INCLUDE THIS IN LATEST HWO.
LONG TERM
ACTIVITY WILL PUSH OUT OF THE AREA SUN NIGHT INTO
MONDAY...BUT SOUTHWEST FLOW ALOFT WILL CONTINUE WITH LITTLE TO NO
COOL DOWN IN STORE. MODELS ARE INCONSISTENT WITH HOW FAR MOISTURE
WILL SURGE AHEAD OF NEXT STORM SYSTEM AND WILL LEAVE GRIDS WITH
NIL POPS BASED ON LATEST GFS RUN. DEEPER US EAST COAST TROUGH AND
STRONGER SURFACE HIGH TO THE WEST SHOULD ALLOW FOR BRIEF BELOW
NORMAL TEMPS FOR THE END OF NEXT WEEK.
ZAPPE/SHULER
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