Area Forecast Discussion
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000
FXUS61 KLWX 240907
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
407 AM EST MON NOV 24 2014

.SYNOPSIS...
LOW PRESSURE INTENSIFYING OVER THE GREAT LAKES WILL BRING AN
ASSOCIATED COLD FRONT THROUGH THE MID-ATLANTIC LATE THIS AFTERNOON
AND EARLY THIS EVENING. LOW PRESSURE IS EXPECTED TO TRACK NORTH
ALONG THE COAST WEDNESDAY. HIGH PRESSURE WILL RETURN FOR THURSDAY
AND FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC WMFNT HAS JUMPED N OF CWFA. LTST TEMPS E OF THE BLURDG ARND 60F
AT 08Z. I-81 CRRDR AND FOOTHILLS LAGGING A BIT BHD...BUT A GUSTY SLY
FLOW RESIDES AREAWIDE...SO THE WARM PUSH SHUD ENCOMPASS THE ENTIRE
AREA BY DAYBREAK. THE FNT WAS THE MAIN FOCUS FOR PCPN. THUS...THE
LGT-MDT STRATIFORM RA ALREADY ACRS THE DELMARVA AND POINTS N OF
THERE. HV LGT RESIDUAL SHRA...SPCLY BTWN I-95 AND THE BLURDG DUE TO
A SLGT UPSLP COMPONENT. HWVR...THE FORCING FOR THAT WL WANE BY
SUNRISE AS WELL.

THE CWFA WL BE W/IN STRONG SLY FLOW TDA. THE CDFNT WL DROP INTO AREA
AFTR 18Z...BUT IT REMAINS MOISTURE STARVED W/ DYNAMIC FORCING ACRS
OF W OF THE OHVLY. THUS...BELIEVE IT WL COME THRU DRY...AND HV
PULLED POPS FOR THE REST OF THE DAY. RH PROFILES DO INDICATE HIGH
ENUF VALUES IN THE LLVLS FOR CONTD CLDCVR TIL MIDDAY. HWVR...MEAN
LYR RH THINS OUT DURING THE AFTN...AND XPCT INCRSG SUNSHN.

CONSIDERING THE WARM START AND H8 TEMPS RISING TO 12-14C...HV RAISED
MAXT SVRL DEGF. WL HV HIGHS AOA 70F AREAWIDE...AND A CRRDR IN THE
MID 70S BALT-DC-EZF.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
RDGG WL BLD ACRS THE CWFA FM THE W TNGT-TUE...FOR A PD OF DRY WX.
HWVR...UPR LVL CLDS WL BE INCRSG ONCE AGN TUE AFTN IN ADVC OF AN
IMPULSE OVER THE SERN CONUS. ALTHO H8 TEMPS WL BE DROPPING...THE
CORE OF THE COOLER AIR WL HANG BACK W OF THE MTNS...ALONG W/ THE
CENTER OF THE RDG. THEREFORE...ITS NOT GOING TO GET ALL THAT COLD...
JUST COOLER THAN TDA. MIN-T FCST STILL A LTL ABV CLIMO...AND MAXT
TUE RIGHT AT CLIMO.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
ACCUMULATING SNOW EXPECTED FOR PARTS OF THE MID-ATLANTIC WEDNESDAY.

A 500 MB UPPER LEVEL TROUGH WILL BE ACROSS MOST OF THE CONUS WITH
THE AXIS ACROSS THE MID-WEST TUESDAY NIGHT. SFC HIGH PRESSURE WILL
MOVE INTO THE REGION AND NRLY WINDS WILL USHER IN COOLER AIR
OVERNIGHT. THE COLD FRONT THAT WENT THROUGH THE EASTERN SEABOARD
MONDAY NIGHT WILL INTERACT WITH THE WARM WATERS OF THE GULF STREAM
TUESDAY NIGHT. A 170+KT JET WILL BE LOCATED ACROSS THE APPALACHIAN
REGION WITH THE RIGHT ENTRANCE REGION OF THE JET ACROSS THE SE
STATES. THE COLD AIR AND WARM WATER INTERACTION AND UPPER LEVEL
DIVERGENCE WILL CAUSE CYCLOGENESIS. THE 500 MB TROUGH WILL TREK
EASTWARD INTO WEDNESDAY MORNING AND LOW PRESSURE WILL MOVE UP THE
EAST COAST.

GUIDANCE IS IN AGREEMENT THAT LOW PRESSURE WILL RAPIDLY DEEPEN OFF
THE EAST COAST AS IT MOVES N-NE PARELLEL TO THE EAST COAST. THE
EXACT TRACK OF THE LOW MOVES IS STILL UNCERTAIN. THE ECMWF IS CLOSER
THAN THE GFS/NAM. TEMPERATURES TUESDAY NIGHT ARE EXPECTED TO REACH
THE LOW 30S ACROSS THE HIGHLANDS AND HIGHER ELEVATIONS TO THE MID TO
UPPER 30S ACROSS THE I-95 CORRIDOR AND NEAR 40 NEAR THE WATERS. USED
SREF TEMPS AS IT HAS BEEN DOING WELL WITH TEMPS FOR THE
MID-ATLANTIC. MOISTURE WILL FEED INTO THE LOW WEDNESDAY AND
PRECIPITATION WILL OCCUR WEDNESDAY. THE PRECIP SHIELD WILL
MOVE INTO THE REGION FROM THE SOUTH LATE TUESDAY NIGHT/WED MORNING.
MAX TEMPS FOR THE DAY WILL LIKELY BE REACHED WED MORNING AS PRECIP
MOVES QUICKLY INTO THE REGION. DYNAMICAL COOLING WILL ALLOW TEMPS TO
DROP FURTHER INTO THE MID 30S...A CRITICAL ZONE. SNOW SHOWERS ARE
EXPECTED TO BEGIN IN THE HIGHER ELEVATIONS SUCH AS THE BLUE
RIDGE...VA HIGHLANDS AND THE WESTERN SLOPES AS THEY WILL BE NEAR
FREEZING IF NOT BELOW. RAIN AND SNOW ARE EXPECTED FURTHER EAST AND
IN LOWER LYING AREAS. ALL RAIN IS EXPECTED ACROSS THE NRN PIEDMONT
INTO THE DC METRO AND SOUTHERN MARYLAND WED MORNING AS TEMPS WILL BE
NEAR 40.

WEAK HIGH PRESSURE WILL BE LOCATED NORTH OF THE MID-ATLANTIC
WEDNESDAY. TEMPS AROUND FREEZING WILL BE FURTHER NORTH WHILE
DEWPTS WILL BE AROUND FREEZING. NRLY WINDS WILL BE ADVECTING IN
THESE TEMPS INTO THE MID-ATLANTIC THROUGHOUT THE DAY. NOT TOO
EXCITED THAT SNOWFALL ACCUMULATIONS WILL LIKELY BE FROM DYNAMICAL
COOLING AND NOT A BELOW FREEZING AIRMASS. WITH THAT BEING SAID
WENT WITH THE LOWER SIDE OF GUIDANCE FOR SNOWFALL
ACCUMULATION...RAIN AND SNOW SHOWERS ARE EXPECTED TO CHANGE TO
SNOW SHOWERS WEDNESDAY AFTERNOON ACROSS THE NORTHWEST SUBURBS OF
BALTIMORE AND WASHINGTON DC. THIS WILL LEAD TO ACCUMULATION ACROSS
THIS AREA. TAKING THICKNESSES INTO ACCOUNT FROM SREF MEAN...3-5
INCHES OF SNOW IS EXPECTED ACROSS THE N-W SUBURBS OF BALTIMORE AND
WASHINGTON DC THROUGH WEDNESDAY. HIGHER AMTS ARE EXPECTED ALONG
THE BLUE RIDGE AND PORTIONS OF THE SHENANDOAH VALLEY. TEMPS ALONG
I-95 AND FURTHER EAST WILL BE WARMER AND THE RAIN/SNOW LINE WILL
LIKELY SETUP ACROSS THE BALTIMORE/WASHINGTON METRO AREA RESULTING
IN A SHARP GRADIENT OF SNOWFALL ACCUMULATION. LESS THAN AN INCH IS
EXPECTED FOR BALTIMORE/DC AT THIS TIME.

THIS COASTAL STORM WILL MOVE OUT QUICK AND SNOW SHOWERS WILL WRAP UP
WEDNESDAY EVENING ACROSS THE REGION. ADDITIONAL ACCUMULATION IS
EXPECTED. TEMPS WILL DROP INTO THE 20S WEDNESDAY NIGHT/THURSDAY
MORNING.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
MVFR-IFR FLGT CONDS ATTM...DUE MAINLY TO CIGS. AM XPCTG A SLGT
IMPRVMNT THRU DAYBREAK...AND THEN CIGS WL BE LIFTING TO VFR BY NOON.
VFR SHUD PREVAIL FOR THE REMAINDER OF THE TAF PD.

WNDS WL BE THE OTHER ISSUE. SLY WINDS 15-25 KT ATTM AT THE SFC. LWX
VWP INDICATES 40 KT AT 2K FT. HV LLWS GROUP CONTG...ALTHO THE JET
AXIS SHUD BE PASSING NE OF TERMINALS SHORTLY /BTWN 09-10Z/. WINDS WL
STILL BE STRONG THRUT THE DAY...W/ MEAN LYR MIXING SUGGESTING A FEW
GUSTS SHUD REACH AOA 30KT ELY TAFTN. WNDS WL BECOME WLY TNGT..AND
DIMINISH TO ARND 10-15 KT.

VFR TUE. WLY WINDS CONTG 10-15 KT.

RAIN AND SNOW ARE EXPECTED AT THE TERMINALS TUESDAY NIGHT AND
THROUGH WEDNESDAY. MVFR/VFR CONDITIONS WILL LIKELY BECOME IFR BY
WEDNESDAY AFTERNOON AS RAIN OR SNOW WHICH MAY BE HEAVY AT TIMES
RESULT IN LOW VSBYS. N WINDS 10-15 KTS ARE EXPECTED WEDNESDAY
BECOMING NW 10-15 KTS WED NIGHT. CONDITIONS WILL IMPROVE THURSDAY
MORNING BUT ADDITIONAL -SN IS POSSIBLE. AT THIS TIME VFR CONDITIONS
ARE EXPECTED.
&&

.MARINE...
SCA ACRS ALL WATERS ATTM...W/ STRONG SCA UP THE BAY. RECENTLY SAW A
33KT GUST AT NAK...WHICH IS ALSO REFLECTED AT TPLM2. WL MONITOR THAT
CLOSELY. IF ITS A TREND AND NOT AN OUTLIER...WL EITHER NEED TO RAISE
GLW OR ADD A MWS. SUSPECT THE LATTER WL BE THE COURSE OF ACTION.

THERE WL BE ANOTHER PEAK IN THE MIXED PROFILE ELY TAFTN WHERE WNDS
MAY REACH 30-35 KT. HV CAPPED WNDS AT 30 KT ATTM DUE TO WATER TEMPS
IN THE 40S. IF WE NEED TO CHANGE COURSE OF ACTION THIS MRNG...WL
NEED TO ADJUST REST OF DAY AS WELL.

WNDS WL VEER WLY TNGT AS CDFNT CROSSES WATERS. FNT WL BE LOSING
SUPPORT...AND THUS WONT BE XTNDG ONTO CURRENT SCA...WHICH ENDS 01Z
MID-UPR PTMC AND 06Z ELSW.

A LIGHTER WLY FLOW WL CONT INTO TUE...10-15 KT.

N-NE WINDS 10-15KTS ARE EXPECTED TUESDAY NIGHT AS A COASTAL LOW
APPROACHES THE BAY REGION. WINDS WILL BECOME STRONGER AS THE LOW
GETS CLOSER AND SCA CONDITIONS WILL BE LIKELY WEDNESDAY. THE
COASTAL LOW WILL MOVE OUT TO SEA AND WINDS WILL BECOME NWLY WED
NIGHT. A TIGHT PRESSURE GRADIENT WILL CONTINUE DURING THIS TIME AND
SCA CONDITIONS WILL BE LIKELY.
&&

.TIDES/COASTAL FLOODING...
IN SPITE OF A STRONG SLY FLOW...WATER LVLS HAVE REMAINED NEAR OR BLO
ASTRO NORMS. THEREFORE...NO ISSUES EXPECTED TODAY OR TOMORROW.

&&

.CLIMATE...
FORECAST HIGH TEMPERATURES TODAY FOR DCA/IAD/BWI WOULD ALL COME
VERY NEAR CURRENT RECORDS. HERE ARE THE RECORD HIGHS AND THE YEAR
THEY OCCURRED...

DCA...74 IN 1958.
IAD...74 IN 1979.
BWI...73 IN 1979.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ530>534-
     537>543.
     SMALL CRAFT ADVISORY UNTIL 8 PM EST THIS EVENING FOR ANZ535-
     536.

&&

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







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