Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 221508
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1008 AM EST SAT NOV 22 2014

.SYNOPSIS...
HIGH PRESSURE OVER EASTERN NORTH CAROLINA WILL SHIFT OFFSHORE THIS
AFTERNOON. 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 /TODAY/...

HIGH PRES HAS MIGRATED TO ERN N CAROLINA. BRILLIANT SUNSHINE OVR
THE MID ATLC AS A RESULT. COLD TEMPS B4 SUNRISE - SEE CLIMATE SXN
BLO. IT IS INTERESTING TO LOOK AT THE 12Z IAD SNDGS YDA AND THIS
MRNG. BOTH WERE VERY DRY. FRI MRNG`S 24 HR TEMPS CHG WAS NEUTRAL
AT THE SFC THEN MARKEDLY COLDER THRU 600 MB W/ A NEAR NRML LAPSE
RATE THRU 800 MB THEN ISOTHERMAL TO 500 MB. THIS MRNG SHOWED MUCH
COLDER TEMPS AT THE SFC THEN STRONG WRMG THRU 600 MB. THE TEMP
PROFILE SHOWED A STRONG RADIATIONAL INVERSION AT THE SFC.

GOING OUTSIDE AT 10 AM IT APPEARS THE INVERSION HAS BKN FM THE
MRNG SUN AS WINDS HV GONE SRLY. THIS WL LEAD TO DECENT WRMG THRU
THE AFTN HRS. HIGHS IN THE U40S/L50S LOOKS GOOD.

&&

.SHORT TERM /TONIGHT THROUGH 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 /15Z SATURDAY THROUGH WEDNESDAY/...

VFR TDA-TNGT.

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...

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.

&&

CLIMATE...
ABNORMAL EARLY SEASON COLD CONTINUES...BUT WILL GIVE WAY TO NEAR
RECORD WARMTH MONDAY.

IAD TIED A RECORD LOW OF 14 DEGREES THIS MORNING...PREVIOUSLY SET
BACK IN 1964. PERHAPS MORE TELLING IS THE FACT THAT BWI AND IAD HAVE
NOT EXCEEDED 50 DEGREES IN A WEEK. TODAY`S HIGHS ARE FORECAST TO
REMAIN IN THE 40S...WHICH WOULD BE THE 8TH CONSECUTIVE DAY WITH
TEMPERATURES BELOW 50 AT BOTH SITES...SECOND MOST ON RECORD AT IAD
IN THE MONTH OF NOVEMBER...AND THE LONGEST NOVEMBER STRETCH AT BWI
SINCE 1944.

STRONG SOUTHERLY FLOW AHEAD OF A COLD FRONT ON MONDAY WILL USHER IN
UNSEASONABLY WARM TEMPERATURES...AND HIGHS MONDAY COULD APPROACH
RECORD MAXIMUM VALUES. BELOW IS A LIST OF RECORD DAILY HIGH
TEMPERATURES FOR 11/24.

SITE   RECORD (YEAR)
DCA    74 (1958)
BWI    73 (1979)
IAD    74 (1979)

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

&&

$$
UPDATE...WOODY!/DFH
PRVS...HTS/KCS







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