FXUS61 KLWX 252307 AAA
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
607 PM EST FRI DEC 25 2009
.SYNOPSIS...
LOW PRESSURE WILL BRING RAIN TO THE REGION TONIGHT. LOW PRESSURE
WILL MOVE NORTH AND EAST OF THE AREA SATURDAY. HIGH PRESSURE WILL
BRIEFLY BUILD OVERHEAD SUNDAY. AN UPPER LEVEL LOW PRESSURE AND
SURFACE COLD FRONT WILL MOVE ACROSS SUNDAY NIGHT AND MONDAY...WITH
HIGH PRESSURE BUILDING IN FOR THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
UPDATE...
CANCELLED THE WIND ADVISORY...EXTENDED THE WINTER WEATHER ADVISORY
FOR THE UPPER REACHES OF THE POTOMAC HIGHLANDS...CANCELLING IT FOR
THE SRN COUNTIES. SHELTERED VALLEYS OF THE WV PANHANDLE STILL
RECEIVING ICE ACCRETION ON BACK-ROADS AND MOST UNTREATED SURFACES.
MANY MESO-OBS AND OTHER TEMP SENSORS HANGING ONTO A 30-32 DEGREE
RANGE OVER THE LAST SEVERAL HRS...EXPECTING MORE OF THE SAME FOR
THE NEXT SEVERAL HRS...AS RAINFALL GRADUALLY COMES TO AN END
ACROSS THE AREAS.
PREV DISC...
ISSUED DENSE FOG ADVISORY FOR BASICALLY THE NRN HALF OF THE CWA
INCLUDING THE METRO AREAS. MANY OBS ACROSS THIS AREA DROPPING TO
1/2SM OR BELOW...AND W/ CONDITIONS STAYING MOIST AND THE INCOMING
RAIN STILL A FEW HRS FROM IMPACTING THEM ENOUGH TO MIX-OUT SOME OF
THE LOWER VSBYS. WILL MONITOR THRU THE EVENING TO SEE HOW MUCH THE
INCOMING RAIN BANDS ACT UPON THE CONDITIONS OVER THE ADVISORY
AREA. AFTER SOME OF THE MORE INTENSE RAINFALL MOVES TO THE
NE...EXPECTING A RETURN TO AREAS OF DENSE FOG...SO EITHER AN
EXPANSION IN AREA AND/OR TIME MAY BE NEEDED BY THE LATE EVENING
UPDATE.
LOW PRESSURE WILL BRING RAIN TO THE REGION TONIGHT. FLOOD WATCH
CONTINUES. DISCUSSION IN HYDRO SECTION BELOW.
DEWPOINTS WILL CONTINUE TO RISE DUE TO AN EASTERLY FLOW OFF THE
ATLANTIC. THE HIGHER DEWPOINTS WILL INTERACT WITH THE SNOW PACK
BRINGING AREAS OF FOG. HAVE NOT ISSUED A DENSE FOG ADVISORY WITH
THIS PACKAGE THINKING THAT RAINFALL MAY KEEP VSBYS UP JUST A BIT.
A DENSE FOG ADVISORY WILL HAVE TO BE STRONGLY CONSIDERED BY THE
NEXT SHIFT.
THE WIND ADVISORY REMAINS IN EFFECT THROUGH MIDNIGHT. A STRONG
LOW-LEVEL JET WILL BRING WIND GUSTS AROUND 45 MPH ALONG THE RIDGE
TOPS. ACROSS THE VALLEYS...WINDS WILL BE MUCH LIGHTER DUE TO THE
INVERSION.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
LOW PRESSURE WILL SLOWLY MOVE NORTHEAST SATURDAY EVENTUALLY
REACHING SOUTHERN NEW JERSEY BY SATURDAY EVENING. RAIN WILL END
FROM SOUTHWEST TO NORTHEAST DURING THE DAY. CLOUDS WILL BREAK FOR
SOME SUNSHINE ACROSS THE SOUTHWESTERN CWA...FURTHER NORTH AND EAST
CLOUDS MAY HANG ON FOR MUCH OF THE DAY.
MAX TEMPS WILL BE IN THE 40S AND LOWER 50S ACROSS MOST LOCATIONS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
DP VERT STACKED SFC-H5 LOPRES STILL SPIRALS INVOF GRTLKS SAT
NGT-SUN. LCLLY AREA WL BE W/IN SUBSIDENCE FM RDGG BTWN LOW AND CDFNT
TO THE E. THAT WL LEAD TO MAINLY DRY CONDS...W/ PERHAPS A FEW
SPRNKLS/FLURRIES SLIDING INTO THE MTNS /CLSR TO PVA/ LT SUN. WUD
ALSO XPCT AT LEAST PRTL CLRG SAT NGT BEFORE MSTR/CLDS ADVECT BACK ON
SUN. CPLD W/ CU DVLPMNT DUE TO THE STEEPER LAPSE RATES...SUN SHUD BE
A MOCLDY DAY.
SPEAKING OF TEMPS...CAA YET TO COMMENCE IN EARNEST BY THIS PT. RADL
COOLING WL BE DECENT AT NGT...BUT MAXT WL BE CLS TO NRML.
THE UPR LOW FINALLY FILLS AND EJECTS EWD SUN NGT-MON. LOOKING FOR
SCT SHSN ACRS ENTIRE CWFA SUN NGT /WRN SLOPES OF APPLCHNS SHUD
RECEIVE A DECENT SNWFL OUT OF THIS/ THEN REVERT BACK TO A MAINLY MTN
PTTN DURING MON. SINCE MD N OF DC WL BE VERY NEAR THE TRACK OF THE
UPR LOW...WL BE KEEPING SCHC THERE AS WELL...AS FEEL THERE SHUD BE A
FEW FLURRIES ARND. THIS WL BE WHEN THE CAA RESUMES...AND TEMPS ONCE
AGN BLO SEASONALL MEANS.
HIPRES BLDS ACRS CWFA TUE-WED. TEMPS RMN BLO NRML THRU THE PD. ATTN
THEN DRAWN TWD THE GLFMEX CST...WHERE WK LOPRES DVLPS WED NGT-ELY
THU...AND EJECTS OFF THE CAROLINA/DELMARVA COAST AOB 12Z FRI. IF
THAT PANS OUT /AND THERE/S A LOT OF ROOM FOR THINGS TO CHG/ THERE
CUD BE ANTHR SNW STORM FOR CWFA NEW YRS EVE/DAY. ATTM...THREAT WL
BE REPRESENTED BY CHC SN THU NGT...SPCLY FOR ERN SXNS.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
RAIN WILL AFFECT THE TERMINALS TONIGHT INTO SATURDAY MORNING. CIGS
AND VSBYS WILL REMAIN IFR/SUBIFR DURING THIS TIME. VSBYS WILL
IMPROVE LATER SATURDAY MORNING AND AFTERNOON ONCE THE RAIN
STOPS...BUT IFR CIGS ARE POSSIBLE THROUGHOUT MUCH OF THE
DAY...ESPECIALLY ACROSS THE NORTHERN AND EASTERN TERMINALS.
VFR THRU SUN...THEN MVFR PSBL SUN NGT AS UPR IMPULSE PASSES...
SUPPORTING SCT SHSN. CHCS BEST AT MRB. A FEW FLURRIES MAY LINGER
INTO MON. WL BE A VFR/OCNL MVFR MIX.
VFR REST OF PD.
&&
.MARINE...
WINDS WILL CONTINUE TO INCREASE FROM THE EAST AHEAD OF LOW PRESSURE
TONIGHT. WINDS WILL SLOWLY DIMINISH SATURDAY BEHIND THE LOW. WIND
GUSTS TONIGHT AROUND 30 KNOTS ARE EXPECTED ACROSS THE LOWER TIDAL
POTOMAC AND CHESAPEAKE BAY. WILL NOT ISSUE A GALE WARNING WITH THIS
PACKAGE DUE TO THE RELATIVELY COOLER WATERS. HOWEVER...WINDS AROUND
35 KNOTS WILL BE JUST A FEW HUNDRED FEET FROM THE SURFACE.
WATERS WL BE BTWN CDFNT TO THE E AND LOPRES OVR GRTLKS. NO FLAGS
XPCTD SAT NGT-SUN AS NW WNDS BACK TO THE S. UPR IMPULSE WL PASS
MON...WHICH WL SWING WNDS BACK TO THE NW AND INCR SPDS. SCA PSBL.
&&
.HYDROLOGY...
LOW PRESSURE WILL TRACK THROUGH THE REGION TONIGHT. AN EASTERLY
FLOW AHEAD OF THIS SYSTEM WILL CONTINUE TO DRAW IN WARMER AIR FROM
THE ATLANTIC...CAUSING THE PTYPE TO BE RAIN. PRECIPITABLE WATERS
WILL CONTINUE TO INCREASE DUE TO AN INCREASING EAST-SOUTHEAST
LOW-LEVEL JET. THE MOISTURE COMBINED WITH THE LIFT WILL BRING
MODERATE TO OCCASIONALLY HEAVY RAIN. RAINFALL AMOUNTS AROUND 1 TO
1.5 INCHES ARE EXPECTED. OVER ONE INCH OF LIQUID REMAINS IN THE SNOW
PACK ACROSS MANY LOCATIONS. MELTING SNOW WILL COMBINE WITH THE RAIN
TO BRING THE THREAT FOR FLOODING...ESPECIALLY ACROSS URBAN
AREAS...SMALL STREAMS...AND AREAS WITH POOR DRAINAGE.
THE COMBINED RAFL/RUNOFF WL LEAD TO RIVER RISES SAT...TO NEAR 3/4
BANKFULL. HIEST RISES ON THE RAPPAHANNOCK AND LWR PORTION OF THE
PTMC. THE TRIBS TO THE PTMC MAY APPCH FLOOD STAGE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLOOD WATCH THROUGH LATE TONIGHT FOR DCZ001.
DENSE FOG ADVISORY UNTIL 1 AM EST SATURDAY FOR DCZ001.
MD...FLOOD WATCH THROUGH LATE TONIGHT FOR MDZ004>007-009>011-013-
014-016>018.
DENSE FOG ADVISORY UNTIL 1 AM EST SATURDAY FOR MDZ003>007-
009>011-013-014-501-502.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
MDZ003-501-502.
VA...FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ025>027-029>031-
036>042-050>057.
DENSE FOG ADVISORY UNTIL 1 AM EST SATURDAY FOR VAZ027>031-
040>042-052>054.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
VAZ028.
WV...DENSE FOG ADVISORY UNTIL 1 AM EST SATURDAY FOR WVZ050>053-055-
501>504.
WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR
WVZ050>052-055-501>504.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST SATURDAY FOR ANZ530>534-
537>543.
SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ535-536.
&&
$$
UPDATE...GMS
PREV DISCUSSION...BJL/HTS
