Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 050750
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
350 AM EDT TUE MAY 5 2015

.SYNOPSIS...
COLD FRONT SINKS SOUTH TODAY...STALLING NEAR THE MASON-DIXON LINE
THROUGH TONIGHT BEFORE PUSHING FURTHER SOUTH ON WEDNESDAY. HIGH
PRESSURE IS EXPECTED TO RETURN TO THE REGION LATE IN THE WEEK
WHILE LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
REGION REMAINS ON THE WESTERN PERIPHERY OF HIGH PRESSURE NEAR
BERMUDA THIS MORNING. THE HIGH WILL PUSH TO THE SOUTH AND EAST
TODAY AS A COLD FRONT CURRENTLY POSITIONED OVER WESTERN NY DIPS
SOUTH...EVENTUALLY STALLING NEAR THE MASON-DIXON LINE LATER TODAY.
THIS FRONT WILL BE THE FOCUS OF PCPN DEVELOPMENT TODAY AS NEAR
ZONAL FLOW SETS UP ALOFT WITH MINIMAL ASSISTANCE OF FORCING.

THE HIGH COMBINING WITH SUBSIDENCE ALOFT KEEPING MOSTLY CLEAR SKIES
EARLY THIS MORNING. VERY LIGHT RAIN SHOWERS NOTED OVER SW PA AS OF
07Z ASSOCIATED WITH A WEAK VORT MAX. WILL MAINTAIN ISO SPRINKLES IN
FOR THE NW CORNER...BUT OVERALL NOT EXPECTING PCPN TO REACH THE CWA
TILL MID DAY AS THE FRONT NEARS THE REGION. THINKING DIURNAL HEATING
ALONG WITH THE FRONTAL BOUNDARY WILL BE THE TRIGGERING SOURCE FOR
SHOWERS AND ISO TSTMS TODAY. AS SUCH...HAVE GONE WITH LIKELY POPS
FOR NORTHERN FRINGE OF THE CWA BY LATE AFTN...THEN TAPERED POPS OFF
TO THE SOUTH. HAVE INCLUSION OF THUNDER FOR THE AFTN/EARLY
EVENING...THEN JUST SHOWERS FOR THE OVERNIGHT WITH THE LOSS OF
DAYTIME HEATING.

ANOTHER WARM DAY FOR THE ENTIRE REGION AS HIGHS REACH INTO THE 80S.
DEPENDING ON THE TIMING OF THE FRONT...COULD SEE TEMPS FLUCTUATE A
FEW DEGREES.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
COLD FRONT EXPECTED TO HAVE STALLED BY THE MASON-DIXON BY
TONIGHT...THEN BEGINS TO SINK TO THE SOUTH AGAIN AFTER 12Z WED AS
THE UPPER LVL TROUGH OVER THE NORTHEAST DEEPENS JUST ENOUGH TO
PUSH THE FRONT TO THE SOUTH. MOVEMENT TO THE SOUTH WILL BE MINIMAL
THOUGH AS THE FLOW ALOFT QUICKLY TRANSITIONS INTO A BUILDING
RIDGE.

TONIGHT LOOKS TO BRING A PERIOD OF DRY WX FOR ALMOST THE ENTIRE
AREA...WITH LINGERING SHOWERS JUST ALONG THE I-95 CORRIDOR AND EAST.
PCPN CHC INCREASES AGAIN TOMORROW WITH THE FRONTAL BOUNDARY
PROVIDING YET AGAIN A TRIGGERING MECHANISM FOR SHOWERS. WITH WINDS
TURNING E-NE BEHIND THE FRONT THOUGH INJECTING IN A MORE STABLE
ATMO...THINKING THIS WILL MINIMIZE THE THUNDER THREAT. AS SUCH...HAVE
JUST GONE WITH SLIGHT CHC AROUND MID DAY OF THUNDER...THEN TAPERED
TO THE SOUTH AND WEST TO AREAS OUT AHEAD OF THE FRONT THAT WITH A S-
E FLOW HAVE A BETTER CHC OF OF WARMING MORE/REMAINING MORE UNSTABLE.

HIGH PRESSURE BUILDS SOUTH BEHIND THE FRONT BY WED NIGHT...RESULTING
IN A MAINLY DRY NIGHT. ANY LINGERING SHOWERS WED EVENING WILL TAPER
OFF BY MIDNIGHT. TEMPS STILL WELL ABV NORMAL...GENERALLY IN THE 50S
FOR OVERNIGHT LOWS...WITH POCKETS OF NEAR 60 IN THE METRO ARES.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
RDGG REASSERTS ITSELF THU...NOT JUST AT THE SFC BUT ALSO ALOFT. THAT
SETUP SHUD MAKE IT DFCLT FOR TSRA TO DVLP. HWVR...RESIDUAL MSTR WL
LINGER...NOT JUST IN THE FORM OF DEWPTS IN THE UPR 50S/LWR 60S...BUT
ALSO W/IN THE LYR. THEREFORE...XPCT A DECENT AMT OF CLDCVR. INSTBY
PUSHED BACK TWD THE MTNS...WHERE OF COURSE TRRN BASED FORCING EXISTS
TOO. IN THE END...OPTED TO KEEP A CHC SHRA/TSRA FOR THE VA PIEDMONT/
BLURDG CNTYS AS WELL AS APLCNS. CONFIDENCE NOT ALL THAT GREAT
THOUGH. GIVEN LMTD INSTBY/FORCING...ANY ACTIVITY SHUD BE IN RAPID
DECAY BY SUNSET.

ITLL BE A SIMLR SETUP FRI-SAT. GIVEN SUCH A SMALL OPPORTUNITY...WL
BE GOING W/ A DRY FCST FOR THESE TWO DAYS. INSTBY INCREASES SUN-MON
AS RDGG SHIFTS OFFSHORE AND CDFNT APPROACHES FM THE WEST. THAT WL BE
WHEN POPS /TSTMS/ APPEAR IN THE FCST...THO ITS A SLOWER PROGRESSION
THAN FCST YDA.

PTTN WL BE WARM THRUT THE XTNDD...W/ MAXT LWR-MID 80S. THU WL BE THE
COOLEST DAY...AND TOOK FCST DOWN BY A DEGF OR TWO. GIVEN DEWPTS...
MIN-T FOR A NUMBER OF DAYS.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
MAINLY VFR CONDITIONS FOR THE PERIOD. INCRSG HIGH LVL CLOUDS THIS
MORNING...WITH SCT-BKN CU BY THIS AFTN WITH PCPN. BKN-OVC
CONDITIONS CONTINUE TONIGHT THRU WED.

WIND DIRECTION HARD TO PINPOINT TODAY WITH FRONTAL BOUNDARY OVER THE
REGION. HOWEVER...WINDS WILL BE LIGHT...GENERALLY 7 KTS OR LESS.

SCT-NUM SHRA MAINLY AFTR 18Z. ISO TSTM PSBL LATE AFTN...WILL MENTION
WITH VCTS FOR NOW WITH LOW CONFIDENCE OF TIMING/LOCATION. BEST CHC
FOR TSTM 19-23Z. CHC RW TONIGHT INCRSG IN COVERAGE ON WED. LESS CHC
OF TSTM ON WED WITH ELY FLOW.

MAINLY VFR THU-SAT. LOW CHC FOR A LTL PREDAWN FOG AT CLIMO FAVORED
LOCATIONS.

&&

.MARINE...
SCA REMAINS IN PLACE FOR SOUTHERN TIDAL POTOMAC AND CENTRAL
CHESAPEAKE BAY THRU 10Z WITH GUSTS 18-22KTS. WINDS DIMINISH AFTR
DAYBREAK...SO ONLY KEEPING CHESAPEAKE BAY ZONES THRU THE MORNING.
SUB-SCA CONDITIONS EXPECTED EVERYWHERE BY THIS AFTN...AND LASTING
THRU WED NIGHT.

FLOW WL BE LIGHT /10 KT OR LESS/ THRU THE END OF THE WEEK--ELY
THU...SELY FRI...AND EVENTUALLY SLY BY SAT. NO FLAGS XPCTD.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
     ANZ533-537.
     SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ534-543.

&&

$$
SYNOPSIS...SEARS/HTS
NEAR TERM...SEARS
SHORT TERM...SEARS
LONG TERM...HTS
AVIATION...SEARS/HTS
MARINE...SEARS/HTS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.