Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 202148 AAA
AFDLWX

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

.SYNOPSIS...
A SURFACE HIGH PRESSURE RIDGE WILL CONTINUE TO EXTEND SOUTHWEST
ACROSS THE MID-ATLANTIC INTO TONIGHT. A SURFACE LOW OFF THE
GEORGIA COAST WILL MOVE NORTHEAST BY CAPE HATTERAS SUNDAY.
MEANWHILE...ANOTHER LOW WILL MOVE EAST ACROSS THE NORTHERN GREAT
LAKES...WITH AN ASSOCIATED COLD FRONT MOVING THROUGH THE MID-
ATLANTIC SUNDAY AFTERNOON AND NIGHT. CONTINENTAL HIGH PRESSURE
WILL MOVE IN MONDAY AND PERSIST THROUGH THE REST OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
HEADLINE UPDATE. SEE TIDES/COASTAL FLOODING SECTION. SMALL CRAFT
ADVISORY IN EFFECT FOR THE MD BAY AND TIDAL POTOMAC RVR FROM SUN
NIGHT INTO MONDAY.

PREV DISCUSSION...
AS OF 18Z...SFC RIDGE IS DRAPED WSW TO ENE ACROSS THE CWA WITH
THE AXIS OVER DC. AN ASSOCIATED ONSHORE FLOW (WITH A BIT OF A BAY
BREEZE) WILL CONTINUE UNTIL EVENING. A TROUGH IN ADVANCE OF A LOW
OFF THE GEORGIA COAST EXTENDS NORTHEAST OFF THE MID- ATLANTIC
COAST WHERE SCATTERED SHOWERS/THUNDERSTORMS ARE PRESENT. THIS
ACTIVITY COULD APPROACH MD WATERS...WITH SLIGHT CHANCES FOR LOWER
ST MARYS AND EAST. LOW/MID CLOUDS SHOULD MOVE IN FROM THE
EAST...PERHAPS REACHING AS FAR WEST AS I-95.

OTHERWISE...CLEAR TONIGHT WITH VALLEY AND PIEDMONT FOG. GUIDANCE
IS SUGGESTING SOME FOG FOR THE METRO AREAS TOO...BUT THE
CLOUD/CLEAR LINE WILL DETERMINE THAT. MIN TEMPS MID TO UPR 50S
WEST OF BALT-WASH...LOW TO MID 60S FOR THE COASTAL LOWLANDS...NEAR
70F URBAN AND NEAR SHORE.

&&

.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 /22Z SATURDAY THROUGH THURSDAY/...
LIGHT ONSHORE FLOW WITH VFR CONDS THROUGH TONIGHT 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...COULD GUST 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...
LIGHT ONSHORE FLOW FROM SFC HIGH RIDGE OVER THE AREA WITH A BAY
BREEZE THAT WILL ENDS THIS EVENING. LOW PRESSURE DEVELOPING OFF
GEORGIA WILL STRENGTHEN AND LIFT NORTHEAST ALONG THE CAROLING
COAST TONIGHT 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 OR SO. SCA GUSTS TO 20 KT
CURRENTLY LOOK TO WAIT UNTIL MONDAY MORNING...THOUGH THEY COULD
ARRIVE WITH THE COLD FRONT LATE SUNDAY NIGHT. LATER SHIFTS WILL
NEED TO MONITOR THAT.

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...
COASTAL FLOOD ADVISORY REMAINS IN EFFECT FOR ANNE ARUNDEL COUNTIES
UNTIL 7 PM. WILL MISS THE MARK AT BALTIMORE/FT MCHENRY...THOUGH
THEIR LEVELS ARE ELEVATED WELL ABOVE NORMAL FOR THE EVE`S HIGH
TIDE. DEPARTURES WILL REMAIN ELEVATED...UP TO 1.5 FT ABOVE
NORMAL...SO MORE COUNTIES ARE ANTICIPATED TO BE IN THE ADVISORY
FOR THE HIGH TIDE TONIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL 9 PM EDT THIS EVENING FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 7 PM EDT THIS EVENING FOR MDZ014.
VA...COASTAL FLOOD ADVISORY UNTIL 9 PM EDT THIS EVENING FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT MONDAY FOR
     ANZ530>543.

&&

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








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