000
FXUS61 KLWX 211051
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
551 AM EST SAT NOV 21 2009

.SYNOPSIS...
HIGH PRESSURE WILL CROSS THE REGION AND SETTLE OVER NEW ENGLAND
THROUGH THE WEEKEND. A LOW PRESSURE AREA WILL MOVE UP COASTAL
CAROLINA SUNDAY NIGHT INTO TUESDAY...BRINGING RAIN. HIGH PRESSURE
WILL RETURN LATE TUESDAY...THOUGH A COLD FRONTAL PASSAGE IS
EXPECTED IN THE MIDDLE TO LATE PORTIONS OF NEXT WEEK.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A QUICK UPDATE FOR SKY COVER EARLY THIS MORNING. STRATUS DECK
AROUND 4 KFT HAS MADE IT EAST OF THE BLUE RIDGE MOUNTAINS. WILL GO
AHEAD AND BUMP UP THE SKY COVER BETWEEN THE WASHINGTON METRO AREA
AND THE MASON DIXON LINE. OTHERWISE...NO CHANGES.

PREVIOUS DISCUSSION BELOW.

HIGH PRESSURE WILL REMAIN ACROSS THE EASTERN OHIO VALLEY TODAY.
LIGHT NORTHERLY SURFACE FLOW WILL CONTINUE...WITH HIGHS RANGING FROM
THE MIDDLE 40S IN THE HIGHER TERRAIN TO UPPER 50S ACROSS THE
PIEDMONT. NO PRECIP IS ANTICIPATED.

WATER VAPOR LOOP AND 500MB ANALYSIS SHOWS A TROUGH ACROSS THE
CENTRAL GREAT LAKES...WITH STRONG SHORTWAVE ENERGY ROTATING THROUGH
THE BASE. THE TROUGH WILL CONTINUE TO MOVE EASTWARD TODAY...AND SET
UP ALONG THE MASON DIXON LINE THROUGH TONIGHT. THE GFS AND NAM ARE
SLIGHTLY DIFFERENT WITH THEIR SOLUTIONS FOR THE TROUGH
EVOLUTION...AND BOTH INITIALIZED RATHER WELL. THE NAM DEVELOPS A CUT
OFF LOW ACROSS THE NORTHERN CWFA OVERNIGHT...WHILE THE GFS MAINTAINS
A SHEAR AXIS. NEITHER MODEL IS PRODUCING PRECIP...JUST INCREASED
CLOUDINESS.

250MB JET STREAK CONTINUES TO HELP SPREAD CIRRUS ACROSS THE CWFA
EARLY THIS MORNING. EXPECT THE CIRRUS TO HANG AROUND MOST OF
TODAY...AT TIMES BECOMING OPAQUE. HAVE OPTED TO GO PARTLY SUNNY FOR
TODAY...RATHER THAN MOSTLY SUNNY FOR MOST OF THE CWFA. THE NW CWFA
SHOULD REMAIN CLOUDY/MOSTLY CLOUDY IN THE BKN/OVC STRATUS DECK.
THICKER CIRRUS COULD LEND TO TEMPS BEING A DEGREE OR SO COOLER THAN
GUIDANCE. SINCE THE MAV MOS HAS BEEN PERFORMING RATHER WELL...HAVE
USED THOSE NUMBERS AND BUMPED TEMPS DOWN A DEGREE OR TWO.

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
CIRRUS AND LOWER STRATUS DECK IN THE NW ARE EXPECTED TO THIN OUT A
BIT BY THE EVENING...HOWEVER MOISTURE FROM THE GULF STATES SYSTEM IS
EXPECTED TO STREAM NORTHWARD OVERNIGHT. PARTLY CLOUDY/MOSTLY CLOUDY
SKIES ARE EXPECTED MAINLY AFTER MIDNIGHT. MAV NUMBERS CONTINUE TO
VERIFY SLIGHTLY BETTER THAN THE OTHER GUIDANCE...AND HAVE USED FOR
THE OVERNIGHT MINS.

.LONG TERM /SUNDAY THROUGH FRIDAY/...
SUNDAY...FLOW BECOMES NELY WITH HIGH PRESSURE OVER NEW ENGLAND AND
AN APPROACHING COASTAL LOW OFF THE CAROLINAS. CLOUDS IN THE REGION
DUE TO COASTAL SYSTEM...SO EXPECT MOSTLY SUNNY SKIES UNTIL CLOUD
BANK ROLLS N-WARD IN ADVANCE OF THE LOW. WITH MORE SUN NRN
ZONES...MAX TEMPS SUNDAY COULD BE THE INVERSE OF NORMAL WITH WARMEST
/AROUND 60F/ LOCALES IN HARFORD/BALTIMORE AND COOLER /MID 50S/
NELSON/ALBEMARLE.

SUNDAY NIGHT THROUGH MONDAY NIGHT...HIGH PUSHES OFF NEW ENGLAND AND
LOW PUSHES EAST OF HATTERAS...BRINGING ELY FLOW/CAD TO THE AREA.
HAVING ALREADY MOISTENED...EXPECT LIGHT RAIN SPREADING EAST ACROSS
THE AREA WITH EAST FACING SLOPES HAVING THE GREATEST PRECIP
POTENTIAL DUE TO TOPOGRAPHY. SHOULD BE QUITE CLOUDY WITH SOME
RAIN...EXPECT LOW DIURNAL RANGE...MINS MID 40S...MAXES MID 50S.

TUESDAY AND WEDNESDAY...A CLOSED LOW OVER THE CENTRAL PLAINS/MID
WEST TO BREAK CAD WITH SWLY FLOW BY TUESDAY AFTERNOON /DID INCREASE
POPS FOR TUESDAY MORNING ACROSS EASTERN HALF OF CWA DUE TO EXTENDED
CAD/. WARMING TREND TUE /UPPER 50S/ TO WED /AROUND 60F/ AHEAD OF
FROPA.

WEDNESDAY NIGHT/THANKSGIVING...S/W LOBE/S/ FROM THE LOW TO BRING ONE
OR MORE COLD FRONTS PASSAGES IN MID TO LATE WEEK TIMEFRAME BRINGING
PRECIP CHANCES ACROSS THE CWA. HOWEVER...MOISTURE AVAILABILITY FOR
THE MID ATLANTIC IS UNCERTAIN. COLD AIR DOES LOOK TO FOLLOW THE
FRONT...BRINGING A COOL DOWN AND MOUNTAIN WINTRY PRECIP.

THURSDAY NIGHT/FRIDAY...MODELS UNCERTAIN OF LOW INTENSITY AND
TRACK...BUT THE POTENTIAL IS THERE FOR AN EARLY UPSLOPE SNOW EVENT
IN NWLY FLOW AROUND THE BACKSIDE OF THE LOW FEEDING GREAT LAKE
MOISTURE TO THE ALLEGHENY FRONT AND POSSIBLY RIDGES FURTHER EAST.
WILL HAVE TO MONITOR FUTURE MODELS FOR CONSISTENCY/GREATER
DISCERNMENT. IF ANYTHING...COOLING TREND LATE NEXT WEEK.

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS CONTINUE ACROSS THE CWFA AS HIGH PRESSURE REMAINS
ACROSS THE EASTERN OHIO VALLEY. UPPER JET STREAK CONTINUES TO HELP
SPREAD CIRRUS ACROSS THE AREA TONIGHT...WITH CIGS WELL ABOVE 3 KFT.
SOME LOWER STRATUS HAS SETTLED ACROSS KMRB...IN THE NORTHERLY
SURFACE FLOW...BUT CIGS ARE AROUND 4 KFT. EXPECT THE CIRRUS CIGS TO
CONTINUE THROUGH THE AFTERNOON...AT TIMES BKN. THE LOWER STRATUS
SHOULD CONTINUE TO SLOWLY SPREAD ALONG THE MASON DIXON LINE...BUT
CIGS BLO 3 KFT ARE NOT EXPECTED.

ONSHORE NELY FLOW SETS UP SUNDAY...WITH MOISTENING/PRECIP BEGINNING
BY LATE SUNDAY NIGHT AS ELY FLOW SETS UP ACROSS THE TERMINALS. LOW
CIGS AND REDUCED VSBYS IN RAIN/DRIZZLE INTO TUESDAY MORNING. SWLY
FLOW AHEAD OF THE NEXT COLD FRONT LATER TUESDAY/WEDNESDAY WITH
IMPROVED AVIATION CONDITIONS. QUANTITY OF PRECIP ASSOCD WITH FRONT
LOOKS TO BE LOW AT THIS TIME THOUGH WITH TIMING LATER
WEDNESDAY/EARLY THURSDAY CERTAINLY PAY ATTENTION TO SUBSEQUENT
FORECASTS.

.MARINE...
NORTHERLY FLOW IS EXPECTED TO CONTINUE ACROSS THE MARINE AREA
THOUGHT TONIGHT...WITH WIND SPEEDS 15 KT OR LESS.

HIGH PRESSURE BUILDING OVER NEW ENGLAND AND A COASTAL LOW MOVING UP
THE CAROLINAS SUNDAY/NIGHT BRINGS ABOUT NELY FLOW. SMALL CRAFT
ADVISORY WINDS POSSIBLE SUNDAY NIGHT THROUGH MONDAY NIGHT. SWLY FLOW
AHEAD OF THE NEXT FRONT LATER TUESDAY AND WEDNESDAY. ONE OR MORE
FROPAS LATER WEDNESDAY THROUGH FRIDAY TO BRING SOME PRECIP AND
COLDER AIR.

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

UPDATE...LISTEMAA