000
FXUS61 KLWX 160812
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
412 AM EDT TUE MAR 16 2010

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE REGION THROUGH THE REMAINDER
OF THE WEEK...BRINGING DRY CONDITIONS AND MODERATING TEMPERATURES.
A STRONG UPPER DISTURBANCE AND ITS ASSOCIATED COLD FRONT ARE
EXPECTED TO IMPACT THE REGION LATE IN THE WEEKEND.

.NEAR TERM /THROUGH WEDNESDAY/...
THE UPPER LOW THAT HAS BEEN OVER THE REGION SINCE LATE LAST WEEK
FINALLY PUSHES OUT OF THE RANGE OF INFLUENCE TODAY. LINGERING
SPRINKLES OVER THE CWA WILL ERODE FROM N TO S AS DRIER AIR SPILLS
DOWN FROM PA TODAY. CLOUDS BREAK WITH THE ARRIVAL OF THIS DRIER
AIR THROUGH THE MORNING HOURS...WITH MOSTLY SUNNY CONDITIONS
EXPECTED ACROSS THE AREA BY THE AFTERNOON /CLOUDS WILL HOLD ON
LONGEST INVOF KCHO/. A COOL START IN THE MID 40S THIS MORNING...
BUT A RAPID WARMUP IS EXPECTED ONCE THE SUNSHINE BREAKS THROUGH.
MAX TEMPS ARE FCST IN THE UPPER 50S WITH SOME LOCALES REACHING
60F...THOUGH A COOL NLY BREEZE 10 TO 15 MPH WILL KEEP APPARENT
TEMPERATURES IN THE LOWER 50S.

JUST SOME HIGH CLOUDS TONIGHT /MOSTLY CLEAR/ UNDER HIGH PRESSURE.
FOG DEVELOPMENT DEPENDS ON HOW MUCH DRYING OCCURS THIS
AFTERNOON...SO WENT WITH PATCHY FOR NOW. MIN TEMPS LOW TO MID
30S...AROUND 40F NEAR SHORE /BAY WATER TEMP IS LOW 40S/.

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
PRIMARY WX WILL BE FOUND ACRS SERN CONUS THRU MUCH OF THE WEEK AS
SERIES OF WAVES CLOSE OFF IN SRN STREAM. MID-ATLC RGN WILL BE
DOMINATED BY SOMEWHAT NEBULOUS MID-LVL FLOW AND SFC HIPRES...WITH
NO PCPN. WDSPRD MAXIMA IN 60S ARE FCST...WITH SOME LOCALES NEAR 70
THU AND FRI.

.LONG TERM /SATURDAY THROUGH MONDAY/...
CHGS XPCD THIS WKEND AS STRONG UPR TROF AMPLIFIES OVER SRN PLNS
FRI NGT AND SAT. HIPRES WILL MOVE SEWD INTO ATLC AND WILL PROMOTE
DVLPMT OF RETURN FLOW FOR THE MID-ATLC RGN. DEEP SWLY FLOW ATOP
THIS MODESTLY MOIST FLOW WILL CONTRIBUTE INCRG CLDS AND SUSTAINED
WARMTH THRU SAT. MAXIMA SAT ONLY SLGTLY COOLER THAN FRI OWING TO
INCRD CLD CVR AND SLGTLY INCRD MSTR.

BY SAT NGT...SRN PLNS TROF WILL CLOSE OFF. KICKER WAVE SHUD AID IN
ITS RAPID EJECTING NEWD TWD OHVLY BY SUN MRNG. LOW-LVL JET LATE
SAT NGT WILL ADVCT CLDS NWD AND MAY GENERATE A FEW SHRA LATE.

AS LOW NEARS...CLD CVR SHUD CONT TO INCR SUN...WHICH IN TURN WILL
LMT SFC-BASED INSTBY. HOWEVER...FCSTD H5 TEMPS OF -22 TO -26 DEG C
SUGGEST STEEP MID-LVL LAPSE RATES WILL BE PRESENT...SPCLY SUN AFTN
AS DECAYING UPR LOW LIFTS ACRS WRN PA. GIVEN MODEST MSTR...ELEVATED
INSTBY AND STRONG FORCING FOR ASCENT PROVIDED BY BOTH THE UPR WAVE
AND ITS ASSOCIATED CDFNT...HAVE INTRODUCED TSRA SUN AFTN.

STILL A LOT OF UNCERTAINTY IN EXACT TIMING OF EXIT OF UPR LOW.
ECMWF AND SVRL OF GFS ENSEMBLE MEMBERS CONSISTENT IN SLGTLY SLOWER
DEPARTURE. EXTENDED POPS INTO SUN EVE BFR ERODING THEM LATE SUN
NGT. UPSLP SHSN PSBL AS COLD AIR MOVES INTO RGN SUN NGT-MON MRNG.

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
MVFR CIGS WILL BREAK THIS MORNING FROM NORTH TO SOUTH ACROSS THE
SOUTHERN MID-ATLANTIC WITH DRIER AIR ENTERING FROM PA...VFR WITH
ONLY FEW/SCT CLOUDS THIS AFTN. NLY FLOW 10 TO 15 KT CONTINUES
INTO THE EVENING. SOME FOG DEVELOPMENT POSSIBLE TONIGHT UNDER
MOSTLY CLEAR SKIES...THOUGH AFTERNOON DRYING MAY LIMIT COVERAGE
TO ONLY PATCHY.

HIPRES DOMINATES RMNDR OF THIS WEEK. A STRONG UPR SYSTEM WILL
IMPACT THE TERMINALS SUN IN THE FORM OF SHRA/TSRA AS A CDFNT
PASSES.

.MARINE...
LOW PRESSURE CENTER PUSHING FARTHER FROM THE MID-ATLANTIC COAST
WITH NLY FLOW OVER THE BAY. THE PRESSURE GRADIENT IS STILL TIGHT
ENOUGH FOR 25 KT GUSTS INTO THE MID MORNING HOURS...THOUGH THE
GRADIENT WILL SLACKEN ENOUGH FOR SCA GUSTS TO END BY THE EARLY
AFTERNOON. WINDS BECOME LIGHT AND VARIABLE OVERNIGHT AS HIGH
PRESSURE CENTERS OVERHEAD.

NO MARINE HAZARDS ANTICIPATED THRU RMNDR OF THIS WEEK. A CDFNT IS
XPCD TO MOVE THRU THE WATERS EARLY SUN EVE.

.HYDROLOGY...
MINOR FLOODING WILL CONTINUE FOR THE POTOMAC RIVER BELOW HARPERS
FERRY THROUGH THE REST OF THE MORNING. WATER LEVELS ACROSS THE MAIN
STEM OF THE POTOMAC WILL REMAIN ELEVATED THROUGH MID-WEEK.

.TIDES/COASTAL FLOODING...
EVEN THOUGH THE RIVER LEVEL AT LITTLE FALLS HAS DECREASED BELOW
12FT...FRESHWATER INPUT INTO THE TIDAL POTOMAC WILL BE GREAT
ENOUGH TO CONTINUE TO PRODUCE MODERATE COASTAL FLOODING IN DC /7
TO 9 FT AT WISCONSIN AVE/ AND ARLINGTON AND POSSIBLY IN ALEXANDRIA
TODAY. THE COASTAL FLOOD WARNING NOW CONTINUES ONLY FOR DC AND THE
ARLINGTON/ALEXANDRIA ZONE UNTIL MIDNIGHT.

POSITIVE DEPARTURES HAVE DECREASED TO UNDER 1.5 FEET AT LEWISETTA...
HOWEVER WITH A COMBINATION OF FRESHWATER INPUT FROM THE POTOMAC
AND INCREASING SWELL ENTERING THE MOUTH OF THE BAY...SOME MINOR
COASTAL FLOODING MAY BE POSSIBLE. A COASTAL FLOOD ADVISORY IS IN
EFFECT FOR THE REST OF THE TIDAL POTOMAC THROUGH MIDNIGHT...
CONTINUING FOR ST. MARYS THROUGH TONIGHT.

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD WARNING UNTIL MIDNIGHT EDT TONIGHT FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR MDZ013-
     016.
     COASTAL FLOOD ADVISORY UNTIL 11 AM EDT WEDNESDAY FOR MDZ017.
VA...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR VAZ052-
     053-055-057.
     COASTAL FLOOD WARNING UNTIL MIDNIGHT EDT TONIGHT FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR
     ANZ530534-537543.
     SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ535-536.

BAJ/KRAMAR