Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 200114
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
914 PM EDT SUN OCT 19 2014

.SYNOPSIS...
HIGH PRESSURE WILL BRIEFLY PASS BY THE AREA TO THE SOUTH...
USHERING IN CALM WINDS AND CLEAR SKIES THROUGH EARLY MONDAY. AN
UPPER LEVEL TROUGH WILL QUICKLY DIVE DOWN THROUGH THE UPPER
MIDWEST...BUT SLOW DOWN AND RESIDE OVER THE MID-ATLANTIC AND NEW
ENGLAND REGIONS THROUGH MUCH OF THE COMING WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
HIGH PRESSURE WILL BUILD OVER THE AREA TONIGHT...ALLOWING FOR
LIGHT WINDS ACROSS THE AREA. LIGHT WINDS AND DRY CONDITIONS WILL
ALLOW FOR RADIATIONAL COOLING TONIGHT ACROSS THE ENTIRE
CWA...LEADING TO CHILLY CONDITIONS. THE FROST ADVISORY HAS BEEN
EXTENDED IN AREA TO INCLUDE THE NORTHERN AND WESTERN SUBURBS OF
WASHINGTON AND BALTIMORE. A FREEZE WARNING REMAINS IN EFFECT FOR
GRANT...PENDLETON AND HIGHLAND COUNTIES IN THE POTOMAC HIGHLANDS.
THERE WILL BE SOME HIGH CLOUDS MOVING THROUGH AHEAD OF A COLD
FRONT OVER THE GREAT LAKES. THIS DOES ADD TO THE UNCERTAINTY AS TO
HOW MUCH FROST WILL DEVELOP OVERNIGHT...BUT SINCE THE CLOUD DECK
WILL BE THIN AND WINDS WILL BE LIGHT THERE WAS ENOUGH CONFIDENCE
TO EXTEND THE ADVISORY FOR AREAS OF FROST LATE TONIGHT.

MIN TEMPS WILL RANGE FROM THE UPPER 20S TO LOWER 30S IN THE
HIGHLANDS...TO THE MIDDLE 30S ACROSS THE SHENANDOAH VALLEY INTO
THE NORTHERN AND WESTERN SUBURBS OF WASHINGTON AND BALTIMORE...TO
THE MIDDLE 40S IN DOWNTOWN WASHINGTON AND BALTIMORE.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
A ONE-DAY REPRIEVE FROM THE FALL-LIKE CONDITIONS AS THE SFC HIGH
ROLLING ACROSS THE CAROLINAS MAKES AN EXIT OFF THE COAST AND
BRINGS IN RETURN SLY FLOW. THIS WIND REGIME WILL ALLOW FOR A MINOR
WARM-UP RELATIVE TO TODAY`S CONDITIONS. AS WINDS SWITCH OUT OF THE
SOUTH FOR MUCH OF THE DAY...A FAST-MOVING CLIPPER-LIKE FEATURE
WILL DIVE DOWN TOWARD THE AREA FROM N OF THE GREAT LAKES. AS THE
APEX OF THE UPPER SHORTWAVE REACH NRN NY MON EVE...THE SYSTEM AS A
WHOLE WILL DECELERATE AND BEGIN TO CUT-OFF FROM THE MAIN UPPER
JET STREAM.

MOISTURE WILL RETURNS FROM THE TOP-DOWN AS THE SHORTWAVE
APPROACHES. THICKER MID-UPPER LEVEL CLOUD DECKS WILL ARRIVE LATE
MON AFTN/EVE ON THE ERN FRINGE OF THE INCOMING UPPER WAVE. FALLING
PRECIP WILL HAVE A SIZABLE AMOUNT OF DRY AIR TO OVERCOME BEFORE
REACHING THE SFC...BUT THIS WILL BECOME MORE PROBABLE FROM WEST TO
EAST DURING THE LATE NIGHT HRS.

INCREASE POPS FOR THE CNTRL APLCNS LATE MON AND KEPT A LOW CHANCE
FURTHER EAST TO THE BLUE RIDGE. THE SFC TROUGH CROSSES THE CWA
MONDAY NIGHT. THE LOW CROSSES THE CWA TUESDAY NIGHT. LOW CHANCES
FOR LIGHT RAIN ACROSS THE CWA AS DOWNSLOPING FLOW WILL GREATLY
LIMIT THE COVERAGE OF RAIN. TEMPERATURES NEAR NORMAL WITH
DOWNSLOPING FLOW COUNTERACTING CLOUD COVER FROM KEEPING
TEMPERATURES TOO LOW.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
AN UPPER LEVEL TROUGH WILL DIG ACROSS THE EASTERN UNITED STATES
THROUGH THE FIRST HALF OF THE WORKWEEK. LOW PRESSURE ASSOCIATED
WITH THIS TROUGH WILL JUMP SOUTHWARD FROM OVER THE GREAT LAKES TO
THE MID-ATLANTIC THROUGH THE FIRST PART OF THE WORKWEEK AS HIGH
PRESSURE MOVES OFFSHORE. THE LOW WILL LOOSE SOME OF ITS
ORGANIZATION...LIKELY DUE TO THE PASSAGE OVER THE MOUNTAINS...BUT
POPS WILL ENTER THE HIGH END CHANCE RANGE BEGINNING TUESDAY.
PRECIP TYPE SHOULD MOSTLY BE LIGHT RAIN WITH LIMITED INSTABILITY.

THE UPPER LEVEL LOW WILL OCCLUDE FROM THE BACKGROUND WESTERLIES AS
THE ASSOCIATED SURFACE LOW DEEPENS OFF OF THE NORTHEAST COAST
THROUGH THE DAY WEDNESDAY. OPERATIONAL EURO AND GFS ARE IN PRETTY
GOOD AGREEMENT IN THE HIGHEST QPF ASSOCIATED WITH THIS SYSTEM BEING
IN THE SOUTHEASTERN QUADRANT OF THE LOW WELL OFF OF THE COAST...BUT
LIGHT PRECIPITATION COULD CONTINUE LOCALLY THROUGH WEDNESDAY
AFTERNOON.

COOL AND BREEZY NORTHERLY FLOW WILL FILL IN AS THE LOW SLOWLY MOVES
UP THE COAST THROUGH THE SECOND HALF OF THE WORKWEEK. THIS WILL LEAD
TO CLEARING SKIES AND TEMPS 5 TO 10 DEGREES BELOW NORMAL THURSDAY
AND FRIDAY. HIGH PRESSURE WILL SETTLE OVERHEAD FOR THE WEEKEND
ALLOWING TEMPS TO BEGIN TO SLOWLY REBOUND TOWARD NORMAL.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
WINDS WILL REMAIN LIGHT TONIGHT BEFORE TURNING TO THE SOUTH MONDAY
WITH GUSTS AROUND 15 TO 20 KNOTS DURING THE LATE MORNING AND
AFTERNOON HOURS. WINDS WILL DIMINISH MONDAY NIGHT. VFR CONDITIONS
ARE EXPECTED THROUGH MONDAY EVENING. PATCHY BR IS POSSIBLE
OVERNIGHT MONDAY.

CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS THROUGH
THE LONG TERM PERIOD.

&&

.MARINE...
WINDS WILL CONTINUE TO DIMINISH OVER THE WATERS TONIGHT AS HIGH
PRESSURE BUILDS OVERHEAD. THE SMALL CRAFT ADVISORY HAS BEEN
CANCELLED. WINDS WILL SHIFT TO THE SOUTH MONDAY AND GUSTS MAY
APPROACH SCA CRITERIA DURING THE LATE MORNING AND AFTERNOON HOURS.
HAVE CAPPED GUSTS AT 15 KNOTS FOR NOW DUE TO THE RELATIVELY COOLER
WATERS.

A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE CHESAPEAKE
BAY AND LOWER TIDAL POTOMAC IN GUSTY NORTHERLY WINDS AS LOW PRESSURE
MOVES UP THE NORTHEAST COAST BEGINNING WEDNESDAY MORNING AND
CONTINUING THROUGH FRIDAY NIGHT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR MDZ003>007-009-
     010-501-502.
VA...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR VAZ025>031-
     036>040-042-050>053-501-502.
     FREEZE WARNING FROM 2 AM TO 9 AM EDT MONDAY FOR VAZ503-504.
WV...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR WVZ050>053-055-
     502>504.
     FREEZE WARNING FROM 2 AM TO 9 AM EDT MONDAY FOR WVZ501-505-506.
MARINE...NONE.

&&

$$
SYNOPSIS...GMS
NEAR TERM...BJL
SHORT TERM...GMS
LONG TERM...BJL/CEB
AVIATION...BJL/GMS/CEB
MARINE...BJL/GMS/CEB






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