Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 290056
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
856 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/...
LATEST WATER VAPOR IMAGERY SHOWING VORT MAX CENTERED OVER SOUTH-
CENTRAL PA...SWINGING THROUGH AND OFFSHORE BY 06Z TONIGHT. DESPITE
FORCING ALOFT...WITH THE LOSS OF DAYTIME
HEATING/INSTABILITY...SEEING SNOW SHOWERS DCRSNG IN COVERAGE OVER
NORTHEASTERN MD. HAVE MENTION OF FLURRIES STILL THRU 02Z THEN DRY
THE REMAINDER OF THE NIGHT.

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 PCPN...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 PCPN 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 PCPN 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 PCPN INTO SNOW...ESPEC OVER
THE NRN REACHES OF THE PCPN 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 PCPN 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 /01Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS THRU SUN. NW FLOW WITH GUSTS...ENDING 01-03Z
EVERYWHERE EXCEPT KBWI/KMTN. MIGHT BECOME MORE OCNL IN NATURE
OVERNIGHT BEFORE ENDING BY 12Z. LIGHT NW FLOW WILL SHIFT TO W
MIDDAY...THEN SW FOR TOMORROW EVENING.

DCRSNG CLOUDS TONIGHT...MAINLY MID LVL IF ANY. FEW HIGH LVL CLOUDS
PSBL DURING THE DAY SUN AHEAD OF NEXT LOW PRESSURE SYSTEM.

INCRSNG MID LVL CLOUDS SUN NIGHT AS PCPN APPROACHES FROM THE
WEST. A FAST-MOVING COLD FRONT WILL SLIDE THRU EARLY MON MRNG...W/
LITTLE IF ANY PCPN BUT A BRIEF PERIOD OF OVC MID CLOUDS THAT
BREAK UP AND MOVE E QUICKLY AFTER SUNRISE. LOW LVL WINDS 35-45
KTS...WITH GUSTS 20-30 KTS AT THE SFC MONDAY.

VFR CONDITIONS...AND LIGHT WINDS MON NIGHT-TUE. MVFR CONDITIONS
PSBL AT KMTN AND KBWI TERMINALS TUES NIGHT WITH LINGERING PCPN.
OTHERWISE...VFR CONDITIONS TUESDAY NIGHT AND WEDNESDAY. WINDS
LIGHT AND VARIABLE TUESDAY NIGHT BECOMING NORTHWEST AND GUSTING TO
15 KNOTS WEDNESDAY.

&&

.MARINE...
SCA REMAINS IN EFFECT ALL WATERS WITH 00Z OBS SHOWING GUSTS 20-25
KTS. SCA IS DROPPED UPPER TIDAL POTOMAC AT MIDNIGHT...UPPER
CHESAPEAKE BAY MIDDAY SUNDAY...AND THE REMAINING AREAS SUN AFTN.
THE SCA MAY END EARLIER FOR THE SOUTHERN PORTION OF THE
BAY...THOUGH WILL HOLD WITH TIMING FOR NOW.

SCA WILL LIKELY BE NEEDED AGAIN LATER SUN NIGHT AS A COLD FRONT
CROSSES OVER THE AREA EARLY MON MRNG. 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.

&&

.CLIMATE...
A LATE SEASON SHOT OF COLD AIR IS CURRENTLY MOVING OVER THE REGION.

IF TEMPERATURES DO NOT SPIKE ANY HIGHER THIS EVENING...DULLES
INTERNATIONAL AIRPORT (IAD) WILL BE ON TRACK TO BREAK A RECORD DAILY
LOW MAXIMUM TEMPERATURE. THE RECORD DAILY LOW MAXIMUM TEMPERATURE
FOR MARCH 28TH IS 39 DEGREES WHICH WAS SET IN 1996. SO FAR TODAY
THEY HAVE REACHED 37 DEGREES...WHICH WAS SHORTLY AFTER MIDNIGHT
LOCAL STANDARD TIME LAST NIGHT.

SUNDAY MORNING (MARCH 29TH)...LOW TEMPERATURES MAY APPROACH RECORD
MINIMUM VALUES FOR THE DATE.

SITE...3/29 RECORD MIN T...FORECAST MIN T...
DCA......18 (1923)............28............
BWI......18 (1923)............21............
IAD......20 (1982)............19............

&&

.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...SEARS/HTS
SHORT TERM...GMS
LONG TERM...KLW
AVIATION...SEARS/GMS
MARINE...SEARS/GMS
CLIMATE...DFH



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