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Area Forecast Discussion

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FXUS61 KLWX 200141
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
941 PM EDT SAT APR 19 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE AREA...AND WILL REMAIN IN
CONTROL OF THE REGION'S WEATHER THROUGH MONDAY. A COLD FRONT WILL
BRING SHOWERS TO THE AREA TUESDAY INTO TUESDAY EVENING BEFORE HIGH
PRESSURE BUILDS BACK IN FOR THE SECOND HALF OF THE WORKWEEK. NEXT
UP IS ANOTHER COLD FRONT LATER FRIDAY OR SATURDAY.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
AS HAS BEEN THE CASE FOR THE DAYTIME HRS...MAIN FCST ISSUE FOR THE
EVNG HAS BEEN HI CLDS. NOT ONLY HV THEY NOT BEEN DSPTG...BUT
THEYVE ACTUALLY BEEN INCRSG...BLOWOFF FM UPR LOW. GDNC KEEPING H3
RH HIGH THRU THE NGT...AND HV BEEN BUMPING UP SKYCVR IN THE
GRIDS.

SINCE CLDS HV BEEN IN PLACE ALL PM...TEMPS HVNT DROPPED MUCH FM
DAYTIME HIGHS. HWVR...DEWPTS QUITE LOW...SPCLY ALONG THE PA BRDR.
HV MADE AN UPWD ADJUSTMENT...BUT NOT AS LARGE AS OTRW GIVEN POTL
FOR QUICK RADL COOLING.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
EXPECTING HIGH CLOUDS TO START EASTER SUNDAY BUT DIMINISH THROUGH 
THE DAY.  SLIGHTLY LOWER MAX TEMPERATURES AS HIGH PRESSURE GETS 
ESTABLISHED OVER SOUTHERN NEW ENGLAND AND OUR AREA RECEIVES A DEEP 
LLVL MARINE/NE INFLOW ORIGINATING FROM THE GULF OF MAINE.  TEMPS WILL 
REACH THE LOWER 60S IN MOST AREAS EXCEPT DIRECTLY ON THE WESTERN 
SHORE OF THE CHESAPEAKE WHERE THEY'LL BE IN THE UPPER 50S TO NEAR 60.

NOTHING MUCH OF A CHANGE FOR SUN NIGHT AS MARINE FLOW CONTINUES.  
NIGHTTIME MINS ON SUN NIGHT WILL BE FLIRTING ONCE AGAIN WITH FROST 
ADVISORIES AS DRYER AIR WORKS IN AND CALMER WINDS.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
MONDAY THROUGH TUESDAY...
NORTHERN JET STREAM GETS A BIT MORE AMPLIFIED BETWEEN MON AND TUE. 
WE START WITH AN AXIS OF SURFACE HIGH PRESSURE OVER THE EAST MONDAY 
MORNING. BUT A NORTHERN STREAM 500MB TROUGH WILL DIP DOWN INTO THE 
NE AND BRING A COLD FRONT IN FROM THE WEST. THERE IS SOME 
DISAGREEMENT BETWEEN THE VARIOUS MODELS AS TO TIMING AND HOW QUICKLY 
IT WILL PASS THRU. WENT WITH THE SREF ENSEMBLE FOR POPS AND CLOUDS 
TO ACCOUNT FOR THE POSSIBLE DIFFS. IN ANY CASE...EXPECT THE COLD 
FRONT TO CROSS THE APPALACHIANS TUESDAY MORNING AND MOVE THRU THE 
FORECAST AREA DURING THE DAY TUESDAY. HOW QUICKLY IT WILL CLEAR IS 
IN QUESTION...PARTIALLY DUE TO ITS INTERACTION WITH THE LIFTING AREA 
OF LOW PRESSURE MOVING SLOWLY NE OFFSHORE. FOR TEMPS RELIED ON THE 
BIAS CORRECTED SREF AND BIAS CORRECTED ADJUSTED NAM MOS...BOTH OF 
WHICH HAVE BEEN DOING WELL RECENTLY.

SHOWERS WITH THE COLD FRONT ARE NOT EXPECTED TO LEAVE A LOT OF 
RAIN...FORECAST IS FOR 0.15 TO A QUARTER OF AN INCH. HOWEVER LOOKING 
AT A SMALL AMOUNT OF FORECAST ATMOSPHERIC INSTABILITY...THERE IS A 
CHANCE FOR A THUNDERSTORM EMBEDDED WITH THE SHOWERS IN OUR SOUTHERN 
HALF WHICH COULD BOOST RAINFALL IN TARGETED AREAS IF IT COMES TO 
PASS.

TUESDAY NIGHT THROUGH SATURDAY...
PRECIP WILL EXIT THE EASTERN EXTENT OF THE CWA OVERNIGHT TUES AS
COOL DRY AIR FILLS IN IN BREEZY NW FLOW BEHIND THE FRONT. SKIES
WILL BE PARTLY TO MOSTLY SUNNY FOR SUNRISE ON WED AND SHOULD
CONTINUE TO CLEAR THROUGH THE MORNING. A WEAK VORT MAX MAY LEAD TO
A SLIGHT INCREASE IN CLOUD COVER NEAR THE MASON DIXON LINE FOR WED
AFTERNOON/EVENING...BUT EVERYWHERE WILL STAY DRY. MODEST COLD AIR
ADVECTION WILL KEEP HIGHS 5 TO 10 DEGREES COOLER THAN TUES...IN
THE UPPER 50S TO MID 60S.

HIGH PRESSURE WILL FILL IN OVER THE AREA BEGINNING OVERNIGHT 
WED AND THURS WILL BE A COOL BUT PLEASANT SPRING DAY. LOWS THURSDAY 
MORNING WILL BE NEAR 40 WITH HIGHS REACHING INTO THE MID 60S UNDER 
MOSTLY SUNNY SKIES. 

THE HIGH WILL MOVE OFF THE COAST ON THURS NIGHT AND WE WILL SEE 
WARMING IN THE SOUTHERLY RETURN FLOW FOR THE DAY ON FRI AS A COLD 
FRONT APPROACHES FROM THE WEST. DETERMINISTIC MODELS DISAGREE ON THE 
EXACT TIMING OF THE COLD FRONTAL PASSAGE WITH THE EURO BRINGING RAIN 
THROUGH THE DAY FRI AND THE GFS KEEPING US WARM AND DRY DURING 
THE DAY BUT WET OVERNIGHT ON FRI. LARGE SPREAD AMONGST ENSEMBLE 
MEMBERS JUSTIFIED KEEPING CHANCE POPS IN THE FORECAST THROUGH THE 
DAY AND NIGHT ON FRI AND INTO SAT. TIMING OF THE FRONTAL PASSAGE 
WILL DETERMINE HIGHS SAT...BUT FAVORING SLOWER PROGRESSION OF FRONT 
EXPECT HIGH TEMPS SLIGHT COOLER THAN FRI...MID 70S FRI AND LOWER 
70S SAT.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS XPCTD THRU VALID TAF PD. ONLY ISSUE HIGH CLDS...NOT
OF OP IMPACT. NE WNDS AOB 10 KT.

VFR CONDS ARE XPCTD FOR MONDAY AND MONDAY NIGHT. LARGELY VFR ON TUE 
AS WELL BUT IFR POSSIBLE FOR FEW HOURS AROUND COLD FRONTAL PASSAGE.

IFR CONDITIONS ARE POSSIBLE IN LINGERING LOW CEILINGS AND RAIN 
SHOWERS AS A COLD FRONT DEPARTS THE AREA TUESDAY NIGHT.

&&

.MARINE...
WNDS MAINLY AOB 10 KT...W/ A HINT OF VRBL ONSHORE FLOW. WRF-ARW4
SUGGESTS INCRSG NELY FLOW LT TNGT...AND FLLWD ALONG SINCE PRVS
FCSTS BASED ON THAT TOO. GREATEST WNDS TMRW MRNG-MIDDAY...BUT SHUD
START A LTL SOONER AND LAST A LTL LONGER MAIN CHANNEL OF BAY/LWR
PTMC/MID BAY INLETS.

WIND SHIFT ON TUESDAY INTO TUE NIGHT...BUT NO HAZARDS DURING THAT 
TIME.

A SMALL CRAFT ADVISORY MAY BE NECESSARY TUESDAY NIGHT THROUGH 
THURSDAY MORNING IN BREEZY POST FRONTAL NORTHWEST FLOW.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 2 PM EDT SUNDAY FOR ANZ530-
     535-536-538>540.
     SMALL CRAFT ADVISORY FROM 4 AM TO 8 PM EDT SUNDAY FOR 
     ANZ531>534-537-541>543.

&&

$$
SYNOPSIS...HTS/CAS
NEAR TERM...HTS
SHORT TERM...LEE
LONG TERM...CAS/CEB
AVIATION...HTS/LEE/CAS/CEB
MARINE...HTS/CAS/CEB






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