Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 281914
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
314 PM EDT SAT MAR 28 2015

.SYNOPSIS...
AN UPPER-LEVEL TROUGH WILL MOVE ACROSS THE EASTERN UNITED STATES
TONIGHT. HIGH PRESSURE WILL BUILD OVERHEAD ON SUNDAY. A COLD FRONT
WILL DROP THROUGH THE AREA ON MONDAY...WITH ANOTHER COLD FRONT
ARRIVING ON WEDNESDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
LTST WATER VAPOR IMAGERY DEPICTS A SHARP UPR TROF AXIS ACRS THE NERN
CONUS TAFTN. EMBEDDED W/IN THIS AXIS IS A S/WV ENTERING WRN PA. A
CONCENTRATION OF CLDS EVIDENT ON VSBL SATPIX...AND IT APPEARS AS THO
THERE ARE ACCOMPANYING FLURRIES ON RGNL RADARS. 12Z NAM/GFS IN GOOD
AGREEMENT SWINGING THIS FEATURE ACRS MD LT TAFTN INTO ELY THIS EVNG.
WHERE DIFFS LAY RELATE TO THE AMT OF ASSOCD MSTR.

ITS TRUE THAT IN THE WAKE OF THE MRNG TROF DEWPTS HV DROPPED...AND
HV VALUES NEAR 10F ACRS A SIZEABLE PORTION OF THE CWFA ATTM.  THAT
WL DO A GOOD JOB EATING AWAY AT ANY PCPN THAT ATTEMPTS TO FALL.
HWVR...PVA IMPRESSIVE AND ITS TIMED IN SYNCH WITH BEST DAYTIME
HEATING. THUS WOULD BE INCLINED TO BELIEVE THAT SOMETHING WL REACH
THE GRND. THE MORE GENEROUS GFS QPF FIELDS KEEPING TRUE TO ITS
TENDENCY TO BE WETTER...WHICH THIS MRNG PROVED TO BE THE BETTER
FCST. STATISTICAL GDNC ON THE OTHER HAND WUD TEND TO WASH OUT SUCH
SMALL SCALE FEATURES. THEREFORE...NEW DATABASE GRIDS ALIGNED WITH
THIS MORE AGGRESSIVE SOLN.

TEMPS TAFTN WARMER THAN THE MRNG ROUND...BUT BY NO MEANS WUD IT BE
CONSIDERED WARM-- JUST ABOUT EVERYWHERE TRAPPED IN THE 30S.
THEREFORE ANY FALLING PCPN WUD LIKELY BE PARTIALLY IF NOT COMPLETELY
FROZEN. TIME OF YEAR AND TEMP OF AMS ALOFT SUGGEST GRAUPEL A
CONSIDERATION. WL STICK W/ SHSN OR SHRASN FOR SIMPLICITY. BEST
TIMING WOULD BE 20-00Z BASED ON MEAN VORT POSN. AFTR SUNSET...POTL
SHUD WANE.

IN THE WAKE OF THE VORT...EXPECT MEAN LYR RH TO THIN...WHICH WHEN
FACTORED W/ LOSS OF DIURNAL CLDS AND NVA...CLDS SHUD RAPIDLY
DECREASE. STILL A DECENT P-GRAD SO WINDS SHUD BECOME LESS BUT WL
STILL BE A FACTOR. CONSIDERING IMPACT OF CAA AND CURRENT TEMPS...
WENT ON THE COOL SIDE OF MOS MEAN EVEN W/O GOOD DCPLG. THUS MIN-T IN
THE TEENS COMMONPLACE BLURDG WWD.

WL BE UNDER TRANSITORY SFC HIPRES SUNDAY W/ BLDG HGTS ALOFT. THAT
SHUD BE A FVRBL COMBO...MOSUN SKIES AND WARMER TEMPS. MOS MEAN NOT
FAR OFF FM PRVS FCST...SO A BLEND WAS TAKEN. MAXT MAY EXCEED 50F IN
OUR VA CNTYS...STILL MORE THAN 10 DEGF BLO AVG BUT 10+ DEGF WARMER
THAN TDA. IN ADDITION...WNDS ARND 5 KT WUD MEAN NOT MUCH OF A WIND
CHILL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...

AFTER YET ANOTHER REMINDER WINTER HASN`T COMPLETELY LEFT...THE START
OF THE WORK WEEK WILL HAVE MORE OF A SPRING-LIKE REBOUND. LOWS SUN
NIGHT INTO MON MORNING WILL BE COLD...NEAR FREEZING IN MOST AREAS
BRIEFLY - AND ALSO STARTING OFF CLOUDY W/ AN UPPER WAVE PASSAGE. A
BRIEF PERIOD OF UPSLOPE PRECIP...AND SOME LIGHT SNOW AND/OR RAIN
SHOWERS FOR PORTIONS OF THE SRN FRINGE OF THE AREA. GOOD GUIDANCE
AGREEMENT THAT THE APLCNS EFFICIENTLY DISPERSE MUCH OF THE PRECIP AS
THE UPPER WAVE AND SFC COLD FRONT QUICKLY PASSES OVERHEAD. SOME WEAK
LLJ DYNAMICS AND SOME LIMITED  THE WINDS WILL THEN KICK-IN SHORTLY
AFTER SUNRISE...LOW LEVEL - BUT INCREASING - MOISTURE SHOULD ALSO
ALLOW FOR SOME PRECIP DEVELOP ACROSS OUR SRN FRINGE BRIEFLY EARLY
MON. A LIGHT AND BRIEF RAIN/SNOW MIX POSSIBLE OVER SRN MD/DELMARVA
BEFORE DAWN...THEN THIS ACTIVITY QUICKLY MOVES OFF THE COAST.

IN ITS WAKE WILL BE CLEARING SKIES OVER THE AREA AND A BREEZY WLY
WIND THAT WILL KEEP THE HIGHER TERRAIN COOLER BUT THE DOWNSLOPING
EFFECT IN THE VLYS/LOWLANDS WILL HELP HIGH TEMPS REACH THE M-U50S BY
AFTN. WINDS WILL GUST IN THE 20-30KT RANGE ACROSS THE AREA...ESPEC
ALONG THE MASON-DIXON LINE AND ACROSS THE HIGHER TERRAIN. NOT
ANTICIPATING WIND ADVISORY CONDS BUT IT COULD BE WARRANTED FOR
HIGHER TERRAIN. MON NIGHT...TEMPS WILL AGAIN DROP TOWARD THE
FREEZING MARK...EVEN W/ A RELATIVELY HIGHER DEWPOINT FIELD ACROSS
THE REGION.

AS WINDS DROP OFF FROM THE MONDAY COLD FRONTAL PASSAGE...TUE WILL
START OFF MUCH MORE CALM BUT STILL COLD. TEMPS WILL QUICKLY CLIMB
BACK THRU THE 40S AND 50S ON THE WAY TO HIGHS IN NEAR 60F BEFORE YET
ANOTHER UPPER WAVE PASSAGE. ODDLY THE 12Z VERSIONS OF THE EURO AND
GFS TRADED SOLUTIONS FROM THEIR 06Z RUNS. THE LATEST GFS TOOK THE
MINOR UPPER WAVE ELONGATED MORE LATITUDINALLY AND MADE IT THE
FURTHER NORTH COMPACT LOW SPREADING DIRECTLY OVER PA AND TOUCHING
OUR NRN FRINGE. THE 12Z EURO IS THE OPPOSITE. THEIR ALGORITHMS ALSO
MAKE A DECENT PERCENTAGE OF THE MODEL PRECIP INTO SNOW...ESPEC OVER
THE NRN REACHES OF THE PRECIP BATCH. THE TROUBLE W/ THE STRONGER OF
THE SOLUTIONS - WHICH WOULD BE THE POTENT AND MORE COMPACT SYSTEM TO
THE NORTH IS THAT IT WOULD ILLICIT A STRONGER WAA REGION OUT AHEAD
OF THE SYSTEM. THE WARMER AIR ENTRAINED INTO THE PORTION OF THE
SYSTEM SPREADING ACROSS OUR REGION WOULD HAVE A LOWER POTENTIAL FOR
FROZEN PRECIP W/ HIGHS REACHING THE 50S/L60S JUST AHEAD OF THE
SYSTEM. NOT AN INTENSE TEMP PLUNGE EXPECTED W/ THIS FEATURE EITHER
WAY...W/ TEMPS DROPPING AT AN AVERAGE PACE INTO THE U30S/L40S. THE
ADVECTION PATTERN ALSO NOT PARTICULARLY STRONG ACCORDING TO THESE
SAME MODELS...WHICH KEEPS THE SFC WINDS FAIRLY LIGHT THROUGHOUT THIS
EPISODE.
&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A FEW RAIN SHOWERS COULD LINGER ALONG THE MASON DIXON REGION TUESDAY
NIGHT AS A COLD FRONT WORKS ITS WAY SOUTHWARD AND HIGH PRESSURE
BUILDS SOUTHEASTWARD FROM THE GREAT LAKES REGION. LOW TEMPERATURES
WILL BE MAINLY IN THE UPPER 30S TO NEAR 40...NEAR NORMAL FOR EARLY
APRIL.

THE HIGH PRESSURE WILL BRING DRY CONDITIONS AND NEAR NORMAL
TEMPERATURES TO THE REGION WEDNESDAY. EXPECT HIGH TEMPERATURES TO BE
NEAR 60 TO THE MIDDLE 60S.

AS THE HIGH MOVES TO THE EAST COAST AND OFFSHORE WEDNESDAY NIGHT...A
SOUTHERLY FLOW WILL DEVELOP AND INCREASE DURING THE DAY THURSDAY
AHEAD OF AN APPROACHING COLD FRONT. LOW TEMPERATURES SHOULD REACH
THE MIDDLE 40S WEDNESDAY NIGHT AS HIGHS ARE EXPECTED TO APPROACH 70
DEGREES ACROSS MUCH OF THE REGION THURSDAY.

A COLD FRONT SHOULD PUSH ACROSS THE LOWER GREAT LAKES THURSDAY
BEFORE SLOWING DOWN AND DRAGGING ACROSS THE MID ATLANTIC REGION
THURSDAY NIGHT AND FRIDAY. THIS FRONT WILL BE THE FOCAL ZONE OF
DEVELOPING RAIN SHOWERS AND PERHAPS A RUMBLE OF THUNDER OR TWO
LATE THURSDAY THROUGH FRIDAY. TEMPERATURES SHOULD REMAIN MILD
THURSDAY NIGHT AND FRIDAY WITH HIGHS REACHING THE MIDDLE 60S FRIDAY.

BY FRIDAY NIGHT AND POSSIBLY AS LATE AS SATURDAY AFTERNOON...A
LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THE COLD FRONT
AND PUSH ACROSS THE REGION...BRINGING PROLONGED CHANCES OF RAIN
SHOWERS OR EVEN A THUNDERSTORM. TIMING IS UNCERTAIN AS TO THIS
LOW`S DEVELOPMENT AND ITS LOCATION OR PROGRESS...NONETHELESS...THE
RAIN CHANCES LINGER ONCE AGAIN ACROSS THE MID ATLANTIC.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...

VFR CONDS WL GENERALLY PREVAIL THRU TMRW. HWVR...CANNOT GUARANTEE A
DRY FCST. THERE MAY BE A FEW SHOWERS...OF RAIN OR SNOW OR EVEN
GRAUPEL...LATE THIS AFTN TO NEAR SUNSET SPCLY NEAR BWI/MTN. HWVR
CONFIDENCE AND AREAL CVRG PRECLUDE ANY RESTRICTIONS IN TAFS. DID
PLACE WX IN TAF FOR MTN/BWI NEAR TIME OF MOST LKLY OCCURENCE...20-
23Z. ANY RESTRICTIONS WUD BE BRIEF AND LIMITED...MOST LKLY NO LWR
THAN MVFR.

WINDS WL BE THE LARGER SCALE ISSUE...WITH NW WINDS 15 KT GUSTING UP
TO 25-30 KT. THE GUSTS WL SUBSIDE SOMEWHAT THIS EVNG...BUT WL STILL
HV 10-15 KT WINDS INTO TMRW.

DURING THE DAY SUNDAY WINDS WL SUBSIDE TO LESS THAN 10 KT AND
VEERING SW. FEW IF ANY CLDS XPCTD.

A FAST-MOVING COLD FRONT WILL SLIDE THRU EARLY MON MRNG...W/ LITTLE
IF ANY PRECIP BUT A BRIEF PERIOD OF OVC MID CLOUDS THAT BREAK UP AND
MOVE E QUICKLY AFTER SUNRISE. SFC AND BOUNDARY LAYER WINDS EXPECTED
IN THE 30-40KT RANGE W/ SOME 20-25KT GUSTS AT THE SFC DURING THE
DAYTIME HRS.

MVFR CONDITIONS POSSIBLE AT MTN AND BWI TERMINALS TUESDAY NIGHT
DUE TO LINGERING RAIN SHOWERS NEAR A FRONT...OTHERWISE...VFR
CONDITIONS ELSEWHERE TUESDAY NIGHT AND WEDNESDAY. WINDS LIGHT AND
VARIABLE TUESDAY NIGHT BECOMING NORTHWEST AND GUSTING TO 15 KNOTS
WEDNESDAY.

&&

.MARINE...

SOLID SCA CONDS ATTM CONTG THRU THIS EVNG. WINDS WL BE SLOWLY
SUBSIDING OVNGT AND SUNDAY MRNG. HV SCALED BACK SCA AT MIDNGT FOR
THE MID-UPR PTMC. CONTD THE REST INTO SUN MRNG...AND CONTD MID BAY
INTO SUNDAY AFTN. PASSING HIPRES WL BE RESPONSIBLE FOR DIMINISHING
WINDS DURING THE DAY.

A COLD FRONT CROSSES OVER THE AREA EARLY MON MRNG...W/ SCA CONDS
POSSIBLE OVERNIGHT. BEHIND THE FRONT...WEST WINDS WILL AGAIN PICK UP
INTO SOLID SCA RANGES AND POSSIBLE GALES FOR THE DAYTIME HRS MON.
WINDS WILL GRADUALLY SUBSIDE OVERNIGHT INTO TUE. ANOTHER COLD FRONT
WILL CROSS THE REGION LATE TUE...W/ A PERIOD OF LOW-END SCA GUSTS
POSSIBLE.

NO MARINE HAZARDS EXPECTED TUESDAY NIGHT AND WEDNESDAY. WINDS MAY
GUST TO 15 KNOTS WEDNESDAY.

&&

.TIDES/COASTAL FLOODING...

WATER LVLS AS LOW AS A FOOT BELOW ASTRO PREDICTIONS IN THE NRN BAY
AND 1.5 FT IN THE UPPER TIDAL POTOMAC ATTM. THIS NEGATIVE DEPARTURE
WILL ONLY INCREASE AS STRONG NW WINDS RESULT IN BLOW-OUT CONDS.

&&

.CLIMATE...

TEMPERATURES SUNDAY MORNING MAY APPROACH THE RECORD LOWS FOR THE
DATE. CURRENTLY THE FORECAST LOWS ARE ABOVE THESE RECORDS...ASIDE
FROM DULLES. IF THE LOW DROPS TO 21 OR LESS AT DULLES IT WOULD BE
THE COLDEST SO LATE IN THE SEASON SINCE 1987...AND IF THE LOW
DROPS TO 24 OR LESS AT BWI IT WOULD BE THE COLDEST SO LATE IN THE
SEASON SINCE 1985.

SITE...3/29 RECORD MIN T...
DCA......18 (1923).........
BWI......18 (1923).........
IAD......20 (1982).........

&&

.EQUIPMENT...
NWR PIKESVILLE HAS RETURNED TO SERVICE AFTER TOWER WORK TODAY.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT SUNDAY FOR ANZ530>532-
     537>540-542.
     SMALL CRAFT ADVISORY UNTIL 4 PM EDT SUNDAY FOR ANZ533-534-541-
     543.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ535-536.

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...GMS
LONG TERM...KLW
AVIATION...HTS/GMS/KLW
MARINE...HTS/GMS/KLW
TIDES/COASTAL FLOODING...HTS
CLIMATE...DFH/JE/HTS
EQUIPMENT...HTS



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