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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 201427
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1027 AM EDT MON MAY 20 2013

.SYNOPSIS...
-- Changed Discussion --
A WARM FRONT WILL PASS THROUGH THE AREA TODAY WHILE AN UPPER-LEVEL
DISTURBANCE MOVES THROUGH THE AREA. HIGH PRESSURE OVER THE ATLANTIC
WILL PROVIDE A SOUTHERLY FLOW FOR TUESDAY THROUGH THURSDAY...
BRINGING WARM AND HUMID CONDITIONS. A COLD FRONT WILL PASS THROUGH
THE AREA LATE IN THE WEEK AND COOLER CONDITIONS WILL RETURN FOR
NEXT WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...

-- Changed Discussion --
WK WMFNT ALONG OR NEAR THE PTMC RIVER THIS MRNG. LWX RAOB MOIST
BUT NOT SATD. LIKE SNDGS FM SIMLR SECTOR YDA...ITS ALSO MARGINALLY
UNSTBL. CNVCTV TEMPS UP IN THE UPR 70S...WHICH PER LAMP WUD BE
REACHABLE. IN ADDITION...AN UPR LOW MVG THRU THE TN VLY TWD WRN
VA/SRN WVA CAN BE A TRIGGERING MECHANISM.

THEREFORE...XPCT SHRA/TSRA TO DVLP TAFTN IN THE WARM AMS. PWAT
ARND 1.40 IN AND CAPE VALUES 500-1000 J/KG SUGGESTS THAT HVY
RAINERS WL BE THE BIGGER CONCERN...NOT WND GUSTS. IN FACT...SHEAR
LESS THAN 10 KT. HELD ONTO GLIMMER OF LKLY POPS FOR CENTRL VA AND
UPR PTMC HIGHLANDS...OTRW CVRG WL BE SCT AT BEST. RADAR DEPICTION
WL BE PRTLY CONTROLLED BY MESOSCALE FEATURES SUCH AS THE DIFF
HEATING BNDRY PRESENT IN SHEN VLY/PTMC HIGHLANDS ATTM.

WARM AND HUMID CONDITIONS WILL PERSIST OVERNIGHT WITH MIN TEMPS
HOLDING IN THE 60S FOR MOST AREAS. PLENTY OF MOISTURE UNDERNEATH THE
NOCTURNAL INVERSION WILL RESULT IN AREAS OF LOW CLOUDS/FOG.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
MID-ATLANTIC WILL RESIDE IN A WARM SECTOR DURING THE MID-WEEK. THIS
WILL ALLOW FOR A WARM UP TUESDAY THROUGH WEDNESDAY...WITH MAXIMA IN
THE MID 80S. IF THERE IS MORE SUNSHINE...THEN MAXIMA COULD EVEN
REACH UPPER 80S IN SOME LOCATIONS.

TUESDAY MORNING MAY START OFF WITH SOME FOG/STRATUS...BUT CLOUDS
SHOULD BREAK FOR SOME SUNSHINE DURING THE AFTERNOON. MODELS SHOW
MOISTURE IN PLACE...AND SOME INSTABILITY AS WELL HOWEVER AM HAVING
TROUBLE FINDING ANY GOOD FORCING/FOCUSING MECHANISMS FOR CONVECTION
THEREFORE CONTINUE TO FAVOR A DRY FORECAST FOR TUESDAY WITH ONLY
ISOLATED CONVECTION ACROSS THE NORTHWEST.

AIR MASS REMAINS THE SAME ON WEDNESDAY. MODELS HINT AT A BETTER
CHANCE OF DIURNAL CONVECTION SO HAVE INCLUDED CHANCE POPS IN THE
FORECAST FOR SCATTERED THUNDERSTORMS ACROSS THE CWA.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
SLIGHT HEIGHT FALLS ARE FORECAST TOWARD THE END OF THE WEEK AS AN
UPPER TROUGH APPROACHES...IN TANDEM WITH A COLD FRONT. THERE IS SOME
QUESTION REGARDING TIMING OF THE FROPA...LATEST GUIDANCE SUGGESTING
LATE THURSDAY INTO EARLY FRIDAY. DUE TO UNCERTAINTY HAVE CHANCE POPS
IN THE THURSDAY THROUGH FRIDAY TIME FRAME...AND WE CAN FINE TUNE THE
TIMING AS WE GET CLOSER.

THERE IS GOOD AGREEMENT THAT THE FRONT WILL HAVE MOVED THROUGH THE
AREA BY THE WEEKEND...FAVORING A COOLER/DRIER AIR MASS. FORECAST
REFLECTS MOSTLY CLEAR SKIES AND TEMPERATURES NEAR CLIMATOLOGY.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
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IFR CONDS REMAIN ACROSS DCA/IAD/BWI. AT LEAST MVFR ELSW. MAY
INSOLATION WL ERODE LLVL MSTR...PERMITTING CONDITIONS TO IMPROVE
BY EARLY AFTERNOON. SCATTERED SHOWERS AND THUNDERSTORMS ARE
EXPECTED...MAINLY THIS TAFTN AND EVENING. HWVR...LOW CONFIDENCE ON
DIRECT IMPACT FOR ANY AIRFIELD.

THERE IS THE POTENTIAL FOR SOME FOG/STRATUS EARLY TUESDAY...
PARTICULARLY IF SOME OVERNIGHT CLEARING TAKES PLACE AS LOW LEVEL
MOISTURE REMAINS. BUT CONFIDENCE REMAINS ONLY LOW-MODERATE ON
OCCURRENCE ATTM. VFR EXPECTED TO PREVAIL THE BALANCE OF TUESDAY.
CHANCE OF THUNDERSTORMS RETURNS FOR WEDNESDAY AFTERNOON...AND
SHRA/TSRA REMAIN POSSIBLE UNTIL A COLD FRONT MOVES THROUGH LATE
THURSDAY INTO EARLY FRIDAY.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
SOUTHERLY WINDS ARE EXPECTED TODAY THROUGH TONIGHT AS A WMFNT MVS
NWD. HOWEVER...WIND SPEEDS WILL REMAIN BELOW SCA CRITERIA.
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED...MAINLY THIS
AFTERNOON AND EVENING.

SOUTHERLY WINDS ARE EXPECTED DURING THE MID WEEK UNTIL A COLD FRONT
MOVES THROUGH TOWARD THE END OF THE WEEK SWITCHING WINDS TO THE
NORTHWEST. SOUTHERLY FLOW CHANNELLING UP THE BAY COULD BRING
MARGINAL SCA CONDITIONS UP THE BAY PARTICULARLY DURING THE LATE
AFTERNOON/EVENINGS.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES REMAIN NEAR NORMAL EARLY THIS MORNING. SOUTHERLY
WINDS ARE WILL DEVELOP OVER THE WATERS TODAY AND ANOMALIES ARE
EXPECTED TO INCREASE. HOWEVER...THE HIGH TIDE THIS AFTERNOON WILL BE
THE LOWER OF THE TWO. WILL HAVE TO WATCH SOUTHERLY FLOW DURING THE
MID-WEEK AS IT MAY SUPPORT AN INCREASE IN DEPARTURES AGAIN. BUT
CBOFS KEEPS WATER LEVELS BELOW MINOR THRESHOLDS THROUGH HIGH TIDES
TUESDAY AFTERNOON.

&&

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

&&

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