FXUS62 KMLB 240050
AFDMLB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
750 PM EST WED DEC 23 2009
.DISCUSSION...
CURRENT WEATHER...HIGH PRESSURE STRETCHING FROM THE NORTHEAST GULF
AND FLORIDA TO THE MID ATLANTIC STATES SHOULD MOVE LITTLE THE
REMAINDER OF THE NIGHT RESULTING IN LIGHT EAST TO SOUTHEAST WINDS.
STABLE MARINE AIR MASS PRECLUDES PUTTING SIGNIFICANT POP INTO THE
FORECAST AND THE LESS THAN 15 PERCENT LOOKS GOOD FOR THE REST OF THE
NIGHT. ONSHORE FLOW WILL HOLD TEMPERATURES ALONG THE COAST SEVERAL
DEGREES ABOVE THEIR CLIMO VALUES WHILE OVER THE INTERIOR WED MORNING
LOWS WILL GENERALLY IN THE LOW AND MID 50S...EXCEPT FOR THE USUAL
COOLER SPOTS SCATTERED AROUND THE FORECAST AREA.
MADE CHANGES TO TEMP...WIND GRIDS AND THEIR RELATIVE DERIVATIVE
GRIDS FOR THE OVERNIGHT. HOWEVER...NO SWEEPING LARGE SCALE CHANGES
DONE.
AVIATION...VFR. SCATTERED-BROKEN ABOVE FL120.
MARINE...BUOYS RECORDING EASTERLY WINDS 10 TO 15 KNOTS AND 3 TO 4
FOOT SEAS COMPOSED OF WIND WAVE AND A 2 FOOT 11 SECOND NORTHEAST
SWELL.
CHANGES TO WIND GRIDS TO SHOW STRONGER INCREASING WINDS LATE
OVERNIGHT WITH EXERCISE CAUTION MAINLY BEYOND 40 MILES OF SHORE
WHICH SHOULD BLEND IN WELL WITH THE FORECAST SMALL CRAFT ADVISORY
STARTING THURSDAY AFTERNOON.
PREVIOUS DISCUSSION...
TONIGHT/THURSDAY...LOW PRESSURE OVER TEXAS WILL PUSH INTO THE LOWER
MISSISSIPPI VALLEY TONIGHT AND INTENSIFY INTO A MAJOR WINTER STORM
AS IT LIFTS NORTHWARD INTO THE MIDWEST THURSDAY. THIS SYSTEM WILL
DRAG A COLD FRONT EASTWARD TOWARD THE FL PANHANDLE LATE IN THE DAY
TOMORROW. AHEAD OF THIS SYSTEM AND OVER ECFL WINDS WILL REMAIN OUT
OF THE EAST TONIGHT AND EVENTUALLY INCREASE TOMORROW WITH BREEZY
WINDS EXPECTED ALONG MUCH OF THE COAST. HIGH LEVEL CLOUD DECK OVER
THE AREA WILL PUSH EAST WITH SOME BRIEF CLEARING POSSIBLE LATE
TONIGHT BEFORE ANOTHER CIRRUS DECK MOVES IN WELL AHEAD OF THE
FRONTAL BOUNDARY EARLY TOMORROW. CLOUDS AND ONSHORE FLOW WILL KEEP
TEMPS MORE MILD TONIGHT WITH LOWS IN THE MID/UPPER 50S FROM I-4
CORRIDOR AND TOWARDS THE NORTH AND WEST. WHILE FARTHER SOUTH WILL
SEE MIN TEMPS IN THE LOW-MID 60S...EXCEPT UPPER 60S DIRECTLY ALONG
THE TREASURE COAST WHERE ONSHORE WINDS WILL BE SLIGHTLY STRONGER.
MOISTURE WILL BEGIN TO RETURN NORTHWARD TOMORROW WITH A SLIGHT
CHANCE FOR SHOWERS MAINLY OVER THE INTERIOR AND OVER SOUTH CENTRAL
FLORIDA THURS AFT. HIGHS WILL CONTINUE THEIR PROGRESSIVE DAILY
WARMING TREND WITH MAX TEMPS IN THE MID/UPPER 70S.
CHRISTMAS EVE THROUGH CHRISTMAS DAY...LOW LEVEL WINDS WILL VEER FROM
SELY TO SSWLY OVERNIGHT INTO CHRISTMAS MORNING AS LOW PRES LIFTS
FROM SRN PLAINS UP MISS VALLEY REGION. DECENT MOISTURE AND
INCREASING LOW LEVEL CONVERGENCE WILL BE AIDED BY INCREASING ASCENT
AND SOME VORT ENERGY. SHEAR/HELICITY VALUES HIGHEST ACROSS THE
NORTH. INSTABILITY WILL BE LIMITED AND HIGHEST ACROSS THE SOUTH.
GIVEN THE SHEAR AND POSITIVE CAPE VALUES THINK IT WILL BE REASONABLE
TO EXPAND LOW THUNDER MENTION IN WITH SCT POPS ALL AREAS. ON
CHRISTMAS DAY...PREFRONTAL CAPE VALUES INCREASING TO AROUND 1500
J/KG MUCH OF THE AREA SO WILL KEEP A LOW THUNDER IN WITH THE SCT
N/LKLY S POPS. OVERNIGHT LOWS INTO CHRISTMAS MORNING IN THE
LOWER/MID 60S MUCH OF THE AREA...NR 70 TREASURE COAST. DAYTIME HIGHS
ON CHRISTMAS RANGING FROM MID/UPPER 70S N/C SECTIONS AND NR 80 IN
THE SOUTH AND WITH DEW POINTS IN THE MID/UPPER 60S IT WILL FEEL
RATHER HUMID. COOLING OFF A LITTLE INTO LOW 50S N/UPPER 50S-LOW 60S
SOUTH CHRISTMAS NIGHT BEHIND THE FRONT.
PREVIOUS EXTENDED FORECAST...SAT...LATEST GFS RUN TRIES TO OVERRUN
SOME MOISTURE ALONG WITH SOME MID-LEVEL IMPULSES AND UPPER LEVEL JET
SUPPORT ACROSS THE OLD 850 MB FRONT ON SAT AND PUSH OUT 30%-60% POPS
ALIGNED NORTH-SOUTH ACROSS OUR COVERAGE WARNING AREA. AT PRESENT
WILL CONTINUE TO KEEP AN EYE ON THIS SCENARIO BUT WILL LEAVE ONLY A
20% MENTION FOR SHOWERS AREAWIDE. THE ECMWF MOVES THE AFOREMENTIONED
SYSTEM THROUGH THE AREA ON FRI LEAVING US DRY ON SAT. SO WILL NOT
MAKE ANY FURTHER CHANGES TO THIS PERIOD WITHOUT FURTHER MEDIUM RANGE
MODEL CONSISTENCY.
SUN-TUE...WITH HIGHER PRESSURES GRADUALLY BUILDING INTO THE REGION
DURING THIS TIME AND WITH A LIGHT NORTHERLY COMPONENT OF WIND AT THE
SURFACE EXPECT A MAINLY DRY EXTENDED. HOWEVER...THERE WILL BE A
STRONGER UPPER JET OVERHEAD THROUGH THIS TIME AND ANY RESIDUAL
MOISTURE ALONG WITH A PASSING SHORTWAVE IMPULSE OVERHEAD COULD TOUCH
OFF AN ISOLATED SHOWER. WITH MID-HIGH LEVEL MOISTURE DURING THIS
TIME THERE WILL LIKELY BE PERIODS OF PREVAILING HIGH OVERCAST. HIGHS
MAINLY IN THE LOW-UPPER 60S FROM KISM-KTTS NORTHWARD WITH A SURGE OF
COOLER AIR AGAIN BY TUE. UPPER 60S TO LOWER 70S FOR HIGHS FURTHER
SOUTH TOWARD MARTIN COUNTY AND NEAR LAKE OKEECHOBEE. LOWS IN GENERAL
WILL AVERAGE A FEW TO SEVERAL DEGREES BELOW CLIMO.
&&
.AVIATION...VFR.
&&
.MARINE...WINDS WILL REMAIN OUT OF THE EAST TONIGHT AND CONTINUE TO
INCREASE INTO TOMORROW BECOMING MORE SOUTHEAST WELL AHEAD OF AN
APPROACHING FRONTAL BOUNDARY MOVING EASTWARD TOWARD THE FL
PANHANDLE. OVER THE SOUTHERN AND OFFSHORE WATERS WINDS WILL INCREASE
TO AROUND 15-20 KTS TONIGHT AND EVENTUALLY BECOME AROUND 20 KTS
OFFSHORE BY MID AFT THURSDAY. WILL PUT SCEC HEADLINES IN THE CWF FOR
TONIGHT AND WILL ISSUE A SCA FOR THE OFFSHORE WATERS STARTING AT 1PM
THURS AFT. SEAS WILL ALSO BUILD UNDER THESE INCREASING WINDS UP TO 5
FT OVER THE SOUTHERN WATERS TONIGHT TO 6 FT OFFSHORE TOMORROW. WILL
CONTINUE SCA INTO EARLY MORNING HOURS OF SATURDAY...BUT WILL BE
TRANSITIONING TO MORE OF A HAZARDOUS SEAS CONCERN BY LATER IN THE
SCA PERIOD. NEARSHORE WATERS EXPECTED TO NEED CAUTION HEADLINES AND
MAY EVEN NEED TO EXPAND SOUTHERN NEAR SHORE LEG INTO SCA SINCE
CONDITIONS LOOK BORDERLINE THERE. ONLY A MODEST IMPROVEMENT OVER THE
WEEKEND WITH CAUTION STATEMENTS LIKELY NEEDED OFFSHORE WATERS.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...SMALL CRAFT ADVISORY FROM 1 PM THURSDAY TO 4 AM EST SATURDAY FOR
WATERS FROM FLAGLER BEACH TO VOLUSIA BREVARD COUNTY LINE 20
TO 60 NM OFFSHORE-WATERS FROM SEBASTIAN INLET TO JUPITER
INLET 20 TO 60 NM OFFSHORE-WATERS FROM VOLUSIA BREVARD
COUNTY LINE TO SEBASTIAN INLET 20 TO 60 NM OFFSHORE.
&&
$$
WIMMER/CRISTALDI
