Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 210121
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
921 PM EDT SAT SEP 20 2014

.SYNOPSIS...
HIGH PRESSURE CENTERED SOUTH OF THE CANADIAN MARITIMES WILL MOVE
EAST INTO THE NORTH ATLANTIC OVERNIGHT. LOW PRESSURE WILL TRACK NORTH
ALONG THE SOUTHEAST AND MID ATLANTIC COASTS OVERNIGHT AND SUNDAY.
A COLD FRONT WILL CROSS THE REGION SUNDAY AND SUNDAY NIGHT...FOLLOWED
BY A RETURN OF HIGH PRESSURE MONDAY THROUGH WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
REGIONAL RADAR MOSAIC AT 01Z SHOWS RAIN SHIELD FROM THE LOW PRES
OVER SE US COAST APPROACHING TIDEWATER VA. IR SATELLITE IMAGERY
HAS HIGH CLOUDS REACHING SOUTHERN MD FROM THE SAME SYSTEM. KEEPING
IN SLIGHT CHC POPS OVER SOUTHERN MD OVERNIGHT...AS THEY COULD GET
SOME SPRINKLES OR VERY LIGHT RAIN AS THE SYSTEM PULLS TO THE NORTHEAST.

ALL GUIDANCE SHOWS PATCHY FOG DEVELOPING OVERNIGHT IN THE USUAL
SUSPECT VALLEY AND PIEDMONT LOCATIONS. OTHERWISE UNREMARKABLE
WEATHER WITH MIN TEMPS IN THE UPPER 50S WEST OF I-95...LOWER 60S
EAST OF I-95 DUE TO THE BAY INFLUENCE ON S/SE FLOW...AND MID 60S
IN DC AND BALT METRO AREAS.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
SUNDAY...LOW PRESSURE MOVES NORTHEAST OFFSHORE AND THEN A COLD FRONT
APPROACHES DURING THE DAY AND CROSSES LATE AFTERNOON THROUGH
MIDNIGHT. FIVE PERCENT RISK FOR DAMAGING WIND FROM SPC ROUGHLY
WEST OF THE BLUE RIDGE SEEMS REASONABLE GIVEN TIMING DURING PEAK
HEATING. MAX TEMPS IN THE MID 80S (PERHAPS UPR 80S EAST OF I-95
IF MORNING CLOUDS CLEAR SOON ENOUGH) AND LIFTED INDICES FROM THE
GFS AROUND -2.

HIGH PRESSURE BUILDS MONDAY WITH NWLY WINDS GUSTING AROUND 20 MPH.
MAX TEMPS LOW TO MID 70S. CLOUDS CLEAR THROUGH THE DAY...SUNNY BY
THE AFTERNOON.

CHILLY MONDAY NIGHT WITH CLEAR SKIES AND HIGH PRESSURE SETTLING
OVER THE AREA. MIN TEMPS COULD BE INTO THE MID 30S IN THE
ALLEGHENY HIGHLANDS WHERE FROST IS POSSIBLE. MENTIONED THIS IN THE
HWO. OTHERWISE...MIN TEMPS LOW TO MID 40S...MID 50S NEAR SHORE.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
DEEP-LAYER RIDGING WILL ENTRENCH ITSELF OVER THE NORTH-CENTRAL AND
EASTERN UNITED STATES BEGINNING TUESDAY...ACCOMPANIED BY A
SEASONABLY COOL AND INITIALLY DRIER AIRMASS. BUT AS THE HIGH
MIGRATES TO THE NORTH OF THE AREA DURING THE LATER PART OF THE WEEK
AN ONSHORE FLOW BEGINS WHICH WILL LEAD TO GRADUALLY INCREASING
MOISTURE. THIS COULD SQUEEZE OUT SOME DRIZZLE OR LIGHT RAIN BY THE
END OF THE WEEK AS LOW PRESSURE MOVES INTO THE SOUTHEAST CONUS FROM
THE ATLANTIC.

TEMPERATURES WILL GENERALLY BE A FEW DEGREES BELOW NORMAL THROUGH
MOST OF THE WEEK...BUT COULD REBOUND TO AROUND NORMAL LEVELS BY NEXT
WEEKEND DEPENDING ON THE EXTENT OF CLOUD COVER AMIDST ONSHORE FLOW.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
LIGHT ONSHORE FLOW WITH VFR CONDS OVERNNIGHT AS LOW PRESSURE
MOVES UP THE COAST FROM GEORGIA. A COLD FRONT CROSSES SUNDAY
AFTERNOON AND EVENING WITH ISOLATED THUNDERSTORMS AS BEST EAST OF
THE BLUE RIDGE. A FEW THUNDERSTORMS COULD HAVE DAMAGING WIND GUSTS
WEST OF THE BLUE RIDGE.

NW FLOW SUNDAY NIGHT AND MONDAY...WITH GUSTS AROUND 20 KT. HIGH
PRESSURE THEN BUILDS THROUGH TUESDAY WITH CONTINUED VFR.

VFR LIKELY TUE-WED NIGHT...WINDS GENERALLY NE 10 KTS OR LESS.

&&

.MARINE...
LOW PRESSURE DEVELOPING OFF GEORGIA WILL STRENGTHEN AND LIFT
NORTHEAST ALONG THE CAROLINA COAST OVERNIGHT AND MOVE OFF THE
MID-ATLANTIC SUNDAY. THE ONSHORE FLOW WILL CONTINUE UNTIL THE LOW
PASSES MIDDAY SUNDAY.

A COLD FRONT WILL CROSS THE WATERS SUNDAY NIGHT. JUST A SLIGHT
CHANCE OF SHOWERS SUNDAY EVENING WITH THE PASSAGE. NWLY FLOW
BEHIND THE FRONT WILL INCREASE TO 15 KT WITH SCA GUSTS TO 20 KT
LATE SUNDAY NIGHT AND ALL OF MONDAY.

SUB-SCA CONDITIONS EXPECTED TUESDAY AS HIGH PRESSURE MOVES
ACROSS...WITH SCA GUSTS POSSIBLE AT TIMES DURING THE SECOND HALF OF
THE WEEK AS THE HIGH BEGINS TO PULL AWAY AND THE GRADIENT TIGHTENS
WITH LOW PRESSURE DEVELOPING WELL TO THE SOUTH.

&&

.TIDES/COASTAL FLOODING...
WATER LEVELS ACROSS MUCH OF THE MD BAY AND THE UPPER TIDAL POTOMAC
REMAIN ELEVATED...W/ POSITIVE ANOMALIES STILL RANGING BETWEEN 1.3
AND 1.5FT. THE LOWER BAY ZONES HAVE SEEN A SLIGHT DECREASE...CLOSER
TO A FOOT BUT STILL HEADING INTO THE HIGHER TIDE CYCLE LATE
TONIGHT/EARLY SUN MRNG. A NEW COASTAL FLOOD ADVISORY HAS BEEN ISSUED
FOR THE WRN SHORE MD BAY COUNTIES...MINUS HARFORD. HAVRE DE GRACE
WOULD NEED A HIGHER ANOMALY VALUE THAN THE CURRENT/RECENT TRENDS
SUGGEST WILL BE THERE AT HIGH TIDE DURING THE POST-DAWN HRS SUN.

AFTER THE EARLY MRNG H.T. CYCLE...WINDS WILL SHIFT BRIEFLY NLY BUT
THEN SWITCH TO WLY DURING THE AFTN...RESIDUAL ANOMALY MAY REQUIRE
ANOTHER ROUND OF ADVISORIES BEFORE THE WINDS GO MODERATE NW SUNDAY NIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY FROM 5 AM TO 9 AM EDT SUNDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT SUNDAY FOR MDZ011-014-
     017-018.
VA...COASTAL FLOOD ADVISORY FROM 5 AM TO 9 AM EDT SUNDAY FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT MONDAY FOR
     ANZ530>543.

&&

$$
SYNOPSIS...LEE
NEAR TERM...LEE
SHORT TERM...BAJ
LONG TERM...DFH
AVIATION...BAJ/DFH/LEE
MARINE...BAJ/DFH/LEE
TIDES/COASTAL FLOODING...GMS/LEE







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