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000
FXUS61 KLWX 190010
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
810 PM EDT SAT MAY 18 2013

.SYNOPSIS...
A WARM FRONT OVER THE CENTRAL APPALACHIANS AND SOUTHERN MID-ATLANTIC
WILL DRIFT NORTH ACROSS THE AREA THROUGH SUNDAY NIGHT AS SURFACE
HIGH PRESSURE BUILD OFF THE NORTHERN MID-ATLANTIC COAST. HIGH
PRESSURE WILL BUILD INTO THE REGION DURING MIDWEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
BLOCKED PATTERN THIS WEEKEND WITH AN UPR TROUGH DRIFTING EAST TO THE
NRN GREAT PLAINS AND AN AMPLIFYING TROUGH OVER THE CANADIAN
MARITIMES AND A RIDGE IN BETWEEN OVER THE MIDWEST. AT THE SFC...HIGH
PRESSURE CONTINUES TO BUILD OFF THE NRN MID-ATLANTIC COAST WITH THE
STALLED BOUNDARY DRIFTING NORTH AS A WARM FRONT OVER SRN VA.

ONSHORE FLOW WILL PERSIST IN THE MID ATLANTIC THROUGH SUNDAY
NIGHT. RAIN/DZ WL SPREAD NORTHEAST ACROSS THE BALT- WASH METRO
LATE THIS EVENING/OVERNIGHT AS MOIST SLY LLVL FLOW EXPANDS ACROSS
THE CWA. MIN TEMPS IN THE UPR 50S TO LOW 60S.

SUNDAY IS A WEDGE DAY WITH ONSHORE FLOW...LOW CLOUDS...AND
WIDESPREAD PRECIP. ONLY FLOOD THREAT IS WHERE NW MOVING ACTIVITY
STALLS AND REPEATS OVER THE SAME AREA. THIS WOULD MOST LIKELY BE
OVER THE SWRN ZONES WHERE THUNDERSTORMS ARE ONCE AGAIN EXPECTED TO
BE LIMITED TO (FAR SW OF DC). WENT A COUPLE DEGREES UNDER
GUIDANCE TO HAVE MAX TEMPS AROUND 70F.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
WMFNT WL CROSS THE AREA SUN NGT...BRINGING FVRBL MSTR INFLOW AND
GOOD UPGLIDE. SHUD BE A WET EVNG...BUT ANY INSTBY SHUD BE LMTD
AND ELEVATED. GNLY STAYED W/ SHRA INSTEAD OF TSRA.

H5 EAST COAST RDGG WL BE MAINTAINED MON-TUE...WHICH WL KEEP THE
QSTNRY/WMFNT N OF THE CWFA. THEREFORE THE AMS ACRS MD/VA WL BE WARM
AND AT LEAST MARGINALLY UNSTBL. SINCE THERE WL BE A LTL MID-LVL PVA
ARND AND PERHAPS TEMPS SLGTLY COOLER...AREAL CVRG OF TSRA SHUD BE A
BIT BETTER MON VS TUE. HWVR...BOTH DAYS TRENDS SHUD FAVOR DIURNALLY
DRIVEN CNVCTN. ALSO ADDED A PINCH OF AN OROGRAPHIC COMPONENT ON THE
TUE PM ACTIVITY.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
TROF/CUTOFF H5 LOW IN THE ROCKIES WL GRDLY MIGRATE EWD FOR THE 2ND
HALF OF THE WK...PUSHING A SFC CDFNT INTO AND EVENTUALLY THRU CWFA.
TSRA WED WL ONCE AGN BE DIURNALLY-DRIVEN WITH A FAIR TRRN-BASED
COMPONENT. MAXT MID-UPR 80S...BUT A FEW 90F READINGS NOT OUT OF THE
QSTN.

DETAILS ON PCPN TIMING GETS HARDER TO DISTINGUISH THU-FRI...ALTHO
FROPA ITSELF SHUD BE ON/NEAR FRI. WL NEED TO SEE HOW SUBSEQUENT RUNS
SHAKE OUT. FNT SHUD BE ABLE TO CLR AREA BEFORE STALLING OUT SAT...
BUT IT/LL BE AWFULLY CLOSE AND ATTAINING AN E-W ORIENTATION WRT
MID-LVL FLOW. GOTTA KEEP POPS GOING AT THIS PT...BUT MAXT WL BE BACK
INTO THE 70S.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
IFR CIGS SPREAD NORTHEAST ACROSS THE DC METROS THIS EVENING AS
COVERAGE OF SHOWERS...ALONG WITH DRIZZLE...INCREASES. LIFR BY LATE
TONIGHT CONTINUING INTO SUNDAY WITH LITTLE CONDITION IMPROVEMENT
THROUGH TOMORROW. E/SE FLOW 5-10 KT. ANY THUNDER CHANCES LOOK TO BE
THIS EVENING INVOF KCHO AND SUNDAY AFTERNOON AGAIN BY KCHO.
STABILITY FROM THE ONSHORE FLOW IS EXPECTED TO KEEP THUNDER
SOUTHWEST OF THE DC METROS THROUGH THE REST OF THE WEEKEND.

OUTLOOK...
FLGT RESTRICTIONS LKLY SUN EVE DUE TO PCPN/RESIDUAL MSTR INVOF
WMFNT. AOB IFR QUITE PSBL...SPCLY INVOF BWI/MTN.

VFR SHUD PREVAIL FOR A MAJORITY OF THE TIME MON-THU...WITH TWO
EXCEPTIONS...
1...DIURNALLY DRIVEN TSRA WL RESULT IN BRIEF IFR RESTRICTIONS
WHEN/WHERE THEY OCCUR.
2...THERE MAY BE PATCHES OF ELY MRNG MVFR DUE TO FOG.

&&

.MARINE...

SCA IN EFFECT FOR THE LWR PTMC AND LWR CHES BAY OVRNGT.

SLY FLOW WL PREVAIL FOR MOST OF THE OUTLOOK PD. CHANNELING WL
RESULT IN SCA CONDS SUN AFTN-EVE. LLJ SHUD CONT BYD THAT...BUT AM
HAVING DOUBTS WHETHER IT/LL MAKE IT TO THE WATERS EDGE. SIMILARLY...
SHUD HV ANOTHER SLY CHANNELING EVENT MON NGT.

&&

.TIDES/COASTAL FLOODING...
DEPARTURES REMAIN HALF TO 3/4 FOOT ABOVE ASTRO PREDICTION THROUGH
THIS EVENING. NO FLOODING IS EXPECTED. FLOW SLACKENS OVER NIGHT
THROUGH SUNDAY MORNING...SO NO INCREASES ARE EXPECTED. SLY FLOW
INCREASES SUNDAY LATE AFTERNOON...WILL HAVE TO WATCH THAT HIGH
TIDE FOR POSSIBLE MINOR INUNDATION AT SENSITIVE SITES...BUT AS OF
NOW NO COASTAL FLOODING IS ANTICIPATED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM SUNDAY TO MIDNIGHT EDT SUNDAY
     NIGHT FOR ANZ531-532-539-540.
     SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR ANZ533-
     534-536-537-543.
     SMALL CRAFT ADVISORY FROM 3 PM SUNDAY TO MIDNIGHT EDT SUNDAY
     NIGHT FOR ANZ533-534-537-541-543.

&&

$$
UPDATE...WOODY!
PRVS...BJL/HTS