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000
FXUS61 KLWX 181934
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
334 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 THROUGH 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.

SHOWERS AND ELEVATED THUNDERSTORMS ARE EXPECTED TO DRIFT INTO THE
SWRN LWX ZONES LATE THIS AFTERNOON. NORTH OF THIS IS AN ONSHORE FLOW
THAT WILL PERSIST THROUGH SUNDAY NIGHT. WIDESPREAD SHOWERS WILL
SPREAD NORTHEAST ACROSS THE BALT-WASH METRO LATE THIS
EVENING/OVERNIGHT AS MOIST SLY LLVL FLOW EXPANDS ACROSS THE CWA.
CLOUDS AND ONSHORE FLOW MAKE FOR A MILD TONIGHT WITH MIN TEMPS 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). GUIDANCE STILL SUGGESTS WAA OVERRIDES
THE LOW CLOUDS AND DRIZZLE/RAIN MAKING MAX TEMPS LOW 70S. WENT A
COUPLE DEGREES UNDER GUIDANCE TO HAVE MAX TEMPS AROUND 70F.
EXPERIENCE WOULD SAY TAKE THE TEMPS LOWER STILL...BUT THE FLOW DOES
LOOK TO VEER SSELY WHICH MAY BRING THE PROGGED WAA.
&&

.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 /20Z SATURDAY 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...
SELY FLOW PICKS UP AGAIN THIS AFTERNOON WITH GUSTS 20 TO 22 KT INTO
THIS EVENING. SCA FOR MD WATERS SOUTH OF NORTH BEACH UNTIL 6PM...
EXPANDING UP TO SANDY PT UNTIL 10PM.

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. WITH HALF MOON JUST PASSED...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.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ532.

&&

$$
SYNOPSIS...BAJ/HTS
NEAR TERM...BAJ
SHORT TERM...HTS
LONG TERM...HTS
AVIATION...BAJ/HTS
MARINE...BAJ/HTS
TIDES/COASTAL FLOODING...BAJ