Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 220844
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
344 AM EST SAT NOV 22 2014

.SYNOPSIS...
HIGH PRESSURE WILL SHIFT OFFSHORE TODAY. A DEEPENING LOW PRESSURE
SYSTEM OVER THE GREAT LAKES WILL LIFT A WARM FRONT THROUGH THE
AREA SUNDAY NIGHT. AN ASSOCIATED COLD FRONT IS EXPECTED TO MOVE
THROUGH MONDAY NIGHT. THE FRONT STALLS JUST OFFSHORE AS HIGH
PRESSURE BUILDS ACROSS THE AREA TUESDAY.
&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC HIPRES ATOP CWFA ELY THIS MRNG. W/ CLR SKIES AND LTL/NO WIND...
TEMPS WUD HV AN OPPORTUNITY TO DROP TO DEWPTS IN THE TEENS. HWVR...
WAA SEEMS TO BE HVG AN INFLUENCE AS TEMPS HV LVLD OFF PAST FEW HRS.

SFC HIGH WL MOVE OFFSHORE TDA...PROVIDING SWLY FLOW TO CWFA. AS
SUCH...WAA WL INCREASE. H8 TEMPS SHUD BE IN THE NEIGHBORHOOD OF 6C
BY DAYS END. HENCE...AM REFLECTING A SHARP WARM UP IN MAXT...NEAR
MAV/MET/ECS BLEND. /ECS SOLN A COMPROMISE OF THE OTHER TWO ANYWAY./
ONLY WRINKLE WL BE ISENT LIFT INDUCING SOME CLDCVR...SPCLY DURING
THE AFTN. SEEMS LIKE ANY DECENT LIFT REMAINS CONFINED NW OF CWFA...
SO WL KEEP FCST DRY.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
RDGG WL PROTECT CWFA TNGT AS WELL. WL HV DISTURBANCES ALONG THE NWRN
PERHIPHERY AS WELL AS APPROACHING FM THE S. SHUD HV CLDS NAK/DCA/SHD
NWD...BUT OTRW NONE OF THIS WL AFFECT AREA. WL BE ABLE TO RADIATE
AFDK...BUT SUSPECT WE/LL KEEP A PINCH OF SWLY FLOW AS WELL...SO IT
WONT BE ABLE TO GET ALL THAT COLD /SPCLY ON THE RDGTOPS/. CHGS FM
GOING FCST NOT THAT SGFNT.

BY SUN...PVA FM SRN STREAM WL BEGIN TO AFFECT AREA...SPCLY DURING
THE AFTN HRS. WL START THE DAY MOSUN...BUT CLDS WL OVERSPREAD HRS
MIDDAY/ELY AFTN AND WL BRING PCPN NEWD AFT 18Z. AM MOST CONFIDENT ON
RA TWD/AFTER SUNSET DUE TO CONTD INFLUENCE OF SFC RDGG AND NEED TO
SATURATE LLVLS FIRST. MAXT ONCE AGN A BLEND OF MOS.
&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
WARM FRONT WILL MOVE THROUGH THE FORECAST AREA SUNDAY NIGHT INTO
EARLY MONDAY MORNING. MODELS CONTINUE TO INDICATE VERY STRONG LLJ
MOVING ACROSS THE REGION...ON THE ORDER OF 50-70KTS AT 850MB.
ISENTROPIC LIFT...THE LLJ AND PWATS PEAKING AROUND 1.5 INCHES WILL
SUPPORT A PERIOD OF MODERATE TO HEAVY RAINFALL FOR MOST OF THE
AREA...WITH OTHERWISE STEADY LIGHT RAIN. BASIN WIDE QPF EXPECTED TO
BE LESS THAN AN INCH...BUT LOCALLY HIGHER AMOUNTS OF RAIN POSSIBLE.
LOW TEMPS SUNDAY NIGHT WILL BE IN THE 40S...WITH LOW 50S IN SOME
SPOTS ALONG AND EAST OF I-95.

WARM FRONT IS EXPECTED TO BE ACROSS PA BY 12Z MONDAY MORNING...WITH
A COLD FRONT APPROACHING FROM THE OHIO VALLEY. PRESSURE GRADIENT
BOTH SURFACE AND ALOFT WILL BE STRONG ENOUGH FOR A BREEZY DAY...WITH
S-SW WINDS GUSTING TO AROUND 20-25 MPH. SOME MODEL OUTPUT SUGGESTS
SCATTERED OR ISOLATED SHOWERS OVER PORTIONS OF THE AREA...BUT KEPT
POPS CORRESPONDINGLY LOW. WARM AIRMASS WILL BRING A BRIEF RETURN TO
MILD TEMPERATURES...WITH HIGHS AROUND 70 EAST OF THE BLUE RIDGE AND
IN THE MID TO UPPER 60S ACROSS THE VALLEYS WEST OF THE BLUE RIDGE.

COLD FRONT MOVES THROUGH MONDAY EVENING. 00Z NAM SUGGESTS POTENTIAL
FOR ORGANIZED SHOWERS...BUT IS NOT SUPPORTED BY GFS OR ECMWF. WINDS
WILL SHIFT TO THE NW BEHIND THE FRONT. LOWS PRIMARILY IN THE
40S...WITH SOME 30S IN THE SHENANDOAH VALLEY AND HIGHLANDS.

CONFIDENCE DECREASES WITH SYNOPTIC SETUP FROM TUESDAY ONWARD.
GENERAL SCENARIO IS THAT HIGH PRESSURE ATTEMPS TO BUILD IN FROM THE
WEST...BUT A COASTAL LOW DEVELOPS OFF THE CAROLINA COAST AND MOVES
THROUGH THE OFFSHORE WATERS. 00Z GFS AND ECMWF DIFFER IN
TIMING...LOCATION AND STRENGTH OF THE LOW. FCST AT THIS POINT CALLS
FOR POTENTIAL SHOWERS TUESDAY EAST OF I-95...FOLLOWED BY LIGHT RAIN
OR A RAIN/SNOW MIX TUESDAY NIGHT. PRECIPITATION POTENTIAL INCLUDES
MOST OF THE CWA WEDNESDAY INTO WEDNESDAY NIGHT. HIGH TEMPS WEDNESDAY
SHOULD BE IN THE 40S...SO ANY PRECIP SHOULD BE LIQUID. WEDNESDAY
NIGHT TEMPS START ABOVE FREEZING AND DROP BELOW LATE AT NIGHT FOR
MOST OF THE CWA...SO A PERIOD OF SNOW OR A RAIN/SNOW MIX POSSIBLE.
HOWEVER...WITH CWA BEING ON THE BACKSIDE OF THE LOW...PRECIP AMOUNTS
WILL BE HIGHLY DEPENDENT ON THE EXACT TRACK OF THE STORM.

BY LATE WEEK...MODEL DIVERGENCE INCREASES WITH ECMWF FAVORING AN
UPPER LOW DROPPING INTO THE GREAT LAKES WHILE GFS FAVORS THE UPPER
LOW FURTHER NORTH AND A COLD FROPA ACROSS THE MID-ATLANTIC. HIGH
PRESSURE BUILDS IN FOR THE START OF THE WEEKEND.
&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
VFR TDA-TNGT. MOST CLDS WL BE MID-DECK.

WL HV LWRG CIGS SUN AFTN AS PCPN APPROACHES. NO RESTRICTIONS XPCTD
DURING MOST OF THE DAY...BUT DETERIORATING CONDS WL BE APPRCHG FM
THE SW...POTENTIALLY AFFECTING AFTN PUSH.

MVFR/IFR CONDITIONS EXPECTED SUNDAY NIGHT WITH RAIN...WITH POTENTIAL
FOR A PERIOD OF HEAVY RAIN. CONDITIONS IMPROVE TO VFR MONDAY
MORNING...WITH GUSTY S-SW WINDS. FLIGHT CONDITIONS UNCERTAIN MIDWEEK
WITH POTENTIAL FOR SOME PRECIPITATION FROM A COASTAL SYSTEM.
&&

.MARINE...
WL HV SLY WINDS ON THE WATERS THIS WKND. WHILE THERE WL PDS W/
DECENT FLOW...MIXING WL BE QUITE POOR OVER LWR-MID 40S WATER TEMPS.
HV CAPPED WINDS AOB 15 KT.

SMALL CRAFT CONDITIONS LIKELY SUNDAY NIGHT THROUGH MONDAY AS A
WARM FRONT MOVES THROUGH...FOLLOWED BY A COLD FRONT MONDAY
EVENING. GUSTY WINDS POSSIBLE MIDWEEK WITH A COASTAL LOW...BUT
STRENGTH AND TRACK OF THE SYSTEM IS UNCERTAIN AT THIS TIME.
&&

.TIDES/COASTAL FLOODING...
STILL HV WATER LVLS 1/2 TO 1 FT BLO ASTRO TIDES. WINDS WILL BECOME
SLY AFTER DAYBREAK...WHICH WL BRING WATER BACK TO NORMAL LVLS. MAY
EVEN BE A PINCH ABV NORMAL BY THIS EVENING.
&&

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

&&

$$
SYNOPSIS...HTS
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...KCS
AVIATION...HTS/KCS
MARINE...HTS/KCS
TIDES/COASTAL FLOODING...HTS







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