Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 300051
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
851 PM EDT FRI APR 29 2016

.SYNOPSIS...
STALLED FRONTAL BOUNDARY WILL WAVER ACROSS THE AREA THROUGH
SATURDAY...THEN LOW PRESSURE MOVES THROUGH THE MID- ATLANTIC
SUNDAY AND MONDAY. ANOTHER FRONT WILL MOVE THROUGH LATER NEXT
WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A BOUNDARY REMAINS NEARLY STATIONARY ACROSS THE ALLEGHENY
HIGHLANDS SOUTHEAST INTO NORTH CAROLINA THIS EVENING. A SHORTWAVE
IS PASSING BY TO THE NORTH AS WELL.

AN EAST TO NORTHEAST FLOW WILL CONTINUE TO USHER IN COOL
CONDITIONS ACROSS OUR CWA BEHIND THE BOUNDARY. THE ONSHORE FLOW
WILL CONTINUE TO CAUSE MOISTURE TO BE TRAPPED UNDERNEATH THE
SUBSIDENCE INVERSION...RESULTING IN LOW CLOUDS ALONG WITH PATCHY
FOG. FOG MAY BE LOCALLY DENSE ACROSS THE HIGHER ELEVATIONS ABOVE
2KFT. THE SHORTWAVE HAS TRIGGERED LIGHT RAIN ACROSS NORTHERN
PORTIONS OF THE CWA...BUT RAINFALL COVERAGE IS LIMITED SINCE MOST
OF THE FORCING IS OFF TO THE NORTH. THE SHORTWAVE WILL MOVE AWAY
FROM THE AREA OVERNIGHT...BRINGING ANY STEADY RAIN WITH IT.
HOWEVER...OCCASIONAL DRIZZLE WILL CONTINUE THROUGH TONIGHT DUE TO
THE ONSHORE FLOW. MIN TEMPS TONIGHT WILL RANGE FROM THE MID TO
UPPER 40S ACROSS NORTHERN MARYLAND TO THE LOWER AND MIDDLE 50S IN
CENTRAL VIRGINIA.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
THE MOST RECENT MDL RUNS /06Z AND 12Z/ ARE TRENDING WETTER...AND
THUS HV INCREASED POPS A PINCH FOR LATE DAY SAT...AND FURTHER INTO
CAT TERRITORY FOR SAT NGT AND SUN.

SAT CULPRIT WL BE ISENT LIFT...WHICH IMPRV THRU THE DAY. BY LT
DAY...HV LKLY POPS. A SOLID SWATH OF MSTR EMINATES FM THE GLFMEX
/PWAT EXCEEDS AN INCH/...WHICH SUPPORTS DECISION TO INCR TO CAT
POPS BY SAT NGT...AS WELL AS INCR TO MDT RAFL IN OUR DATABASE.

SFC LOPRES AND H5 VORT TRACK ALONG THE STALLED BNDRY UP THE OHVLY
SUN INTO SUN NGT. THIS PATH TAKES THE BNDRY N OF THE CWA...AND
DISLODGES LLVL WEDGE. AM A BIT SKEPTICAL OF FULL SCOURING DUE TO
CLIMO...BUT AT THE VERY LEAST IT APPEARS AS THOUGH THERE WL BE AN
ELEVATED UNSTBL LYR. ISENT LIFT/MSTR ADVCTN WL CONT TO FUEL THIS
SYSTEM. AM ATTEMPTING TO PROVIDE A LTL DEFINITION BY CAPTURING A
DIURNAL MIN /RELATIVELY SPEAKING/ IN THE MRNG...FLLWD BY CAT POPS
WHEN DAYTIME HEATING WL HV THE BIGGER IMPACT. IN ADDITION...AM A
LTL MORE EXPANSIVE IN AREA OF CHC THUNDER...AT LEAST FM AN
ELEVATED SENSE. SHEAR LOOKS GOOD...BUT AM CHALLENGED TO SEE TOO
MUCH SFC BASED INSTBY.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
LOW PRESSURE DEPARTS TO THE NORTHEAST MONDAY...BUT THE FRONTAL
BOUNDARY IT RODE IN ON WILL REMAIN STALLED NEAR THE REGION THROUGH
MUCH OF NEXT WEEK. MULTIPLE AREAS OF LOW PRESSURE WILL CONTINUE TO
DEVELOP AND MOVE ALONG IT...AS THE LARGE SCALE TROUGH RESPONSIBLE
FOR THIS ACTIVE PATTERN PERSISTS OVER EASTERN NORTH AMERICA. THIS
WILL ALSO LEAD TO BELOW NORMAL TEMPERATURES THROUGH MUCH OF NEXT
WEEK...WITH HIGHS STRUGGLING TO REACH 70.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
LOW CLOUDS AND DRIZZLE WILL CONTINUE BEHIND A BOUNDARY OVER THE
ALLEGHENY HIGHLANDS TONIGHT. IFR CIGS ALONG WITH MVFR AND IFR
VSBYS ARE EXPECTED DURING THIS TIME. CONDS WL GRDLY IMPRV
SAT...ALTHO FLGT RESTRICTIONS REMAIN. THERE IS A CHC AT BRIEF
VFR PRIOR TO RAFL ARRIVING. ATTM CONFIDENCE TOO LOW TO CARVE OUT A
WINDOW OF VFR IN THE TAFS.

LT AFTN OR EVE SAT CONDS WL DROP AS RA OVERSPREADS THE AREA. RA
MAY BE MDT TO BRIEFLY HVY SAT NGT INTO SUN. FLGT RESTRICTIONS WL
BE WIDESPREAD.

POOR FLYING CONDS CARRY OVER INTO SUN...THO BREAKS IN THE OVC PSBL
AS BDRY ATTEMPTS TO WIGGLE N OF THE TERMINALS. HWVR THAT ALSO
YIELDS A THUNDER RISK.

SUB-VFR PSBL MON-TUE IN ANY LWR CIGS/-RA W/ FRONT STALLED NEARBY.
WINDS GENERALLY NELY 10 KTS.

&&

.MARINE...
PREV FCST REMAINS ON TRACK. ONSHORE FLOW WILL CONTINUE THROUGH
SATURDAY. GENERALLY EXPECTING 5- 10 KT WITH OCCASIONAL INCREASES
TO 15 KT. LIGHT FOG AND DZ WILL CONTINUE AT TIMES.

NEXT ROUND OF RAIN AND ASSOCIATED LLJ REACHES WATERS BY ELY SAT
EVNG. AM KEEPING WINDS UNDER SCA CRITERIA THRU SAT NGT EVEN THO
WINDS ALOFT INCREASE DUE TO POOR MIXING. MIXING MAY IMPROVE ON
SUN...PSBLY AFTN/EVE...BUT CONFIDENCE ON THAT RATHER LOW.

THUNDERSTORMS WILL BE POSSIBLE SUNDAY AFTERNOON AND EVENING. SCA
CONDITIONS ALSO REMAIN POSSIBLE SUN-MON WITH LOW PRESSURE PASSING
ON MONDAY.

A FRONTAL BOUNDARY STALLED NEAR OR JUST SOUTH OF THE WATERS
SHOULD RESULT IN A WEAK ENOUGH GRADIENT TO PRECLUDE SMALL CRAFT
ADVISORIES MONDAY INTO TUESDAY.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES ARE AROUND ONE-HALF TO THREE QUARTERS OF A FOOT
ABOVE NORMAL. A PERSISTENT ONSHORE FLOW WILL CAUSE ANOMALIES TO
HOLD NEARLY STEADY OR EVEN INCREASE A BIT THROUGH SATURDAY.
HOWEVER...THE FLOW SHOULD BE LIGHT ENOUGH FOR WATER LEVELS TO
REMAIN BELOW MINOR FLOODING THRESHOLDS. THE FLOW MAY STRENGTHEN A
BIT SUNDAY...CAUSING WATER LEVELS TO APPROACH MINOR FLOODING
THRESHOLDS BUT CONFIDENCE REMAINS LOW AT THIS TIME.

&&

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

&&

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



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