Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 182016
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
316 PM EST THU DEC 18 2014

.SYNOPSIS...
AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE REGION TONIGHT AND
HIGH PRESSURE WILL BUILD OVERHEAD FRIDAY THROUGH FRIDAY NIGHT. LOW
PRESSURE WILL TRACK SOUTH OF THE AREA SATURDAY THROUGH SUNDAY. A
SECONDARY LOW IS EXPECTED TO MOVE UP FROM THE SOUTHEAST COAST EARLY
NEXT WEEK. A LARGE AREA OF LOW PRESSURE LOOKS TO DEVELOP IN THE OHIO
VALLEY DURING THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
SFC HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE GREAT LAKES
TONIGHT WHILE LOW PRESSURE PULLS AWAY FROM THE CANADIAN MARITIMES.
STRATOCUMULUS HAS BEEN STUBBORN THIS AFTERNOON...BUT APPEARS THEY
WILL GRADUALLY ERODE FROM THE SOUTH THIS AFTERNOON. MAY HANG ON
ALONG THE MD/PA BORDER INTO THE NIGHT. EVEN THOUGH PRECIP ASSOCIATED
WITH A SHORTWAVE APPROACHING FROM THE LOWER OHIO VALLEY HAS SHOWN A
WEAKENING TREND WHILE MOVING INTO A DRIER AIRMASS...THOUGHT IT WAS
WORTHWHILE TO AT LEAST MENTION A SLIGHT CHANCE OF SNOW SHOWERS IN
THE MOST FAVORED UPSLOPE AREAS TONIGHT. OTHERWISE...A BLANKET OF MID
LEVEL CLOUDS WILL SPREAD IN OVERNIGHT. THIS WILL KEEP TEMPERATURES
FROM PLUMMETING TO THE DEW POINTS...BUT LOWS WILL STILL DIP BELOW
FREEZING IN MOST LOCATIONS.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
HIGH PRESSURE WILL BE IN CONTROL FOR FRIDAY AND FRIDAY
NIGHT...LEADING TO TRANQUIL WEATHER AND LESS GUSTY WINDS. PERHAPS
SOME PASSING CLOUDS BUT EVEN OVERNIGHT WITH THE MORE SUPPRESSED
SOUTHERN STREAM SYSTEM...MOST OF THE CWA MAY ONLY SEE CIRRUS. NOT
MUCH TEMPERATURE ADVECTION...HIGHS PERHAPS A TICK WARMER BUT STILL
IN THE 40S...WITH OVERNIGHT LOWS BELOW FREEZING.

SURFACE HIGH PRESSURE WILL BUILD OVER NEW ENGLAND AND THE RIDGE AXIS
WILL EXTEND SOUTH INTO THE MID-ATLANTIC SATURDAY THROUGH SATURDAY
NIGHT. THIS WILL ALLOW FOR SEASONABLY CHILLY CONDITIONS DURING THIS
TIME.

A COUPLE SHORTWAVES...ONE IN THE NORTHERN STREAM OF THE JET AND ONE
IN THE SOUTHERN STREAM OF THE JET WILL PASS THROUGH OUR REGION
SATURDAY AFTERNOON AND NIGHT. THESE SYSTEMS WILL NOT PHASE SO THE
NORTHERN STREAM SHORTWAVE WILL REMAIN TO OUR NORTH AND THE SOUTHERN
STREAM SHORTWAVE WILL REMAIN TO OUR SOUTH. MOST OF THE MOISTURE WILL
REMAIN TO OUR SOUTH WITH THE SOUTHERN STREAM SYSTEM AS WELL.
THEREFORE...MOST AREAS ARE EXPECTED TO REMAIN DRY DURING THIS TIME.
HOWEVER...LIGHT PRECIPITATION MAY BRUSH PORTIONS OF THE POTOMAC
HIGHLANDS AND CENTRAL VIRGINIA SATURDAY INTO SATURDAY NIGHT. THERE
WILL BE ENOUGH COLD AIR FOR SNOW IF PRECIPITATION OCCURS...BUT
LITTLE OR NO SNOW ACCUMULATION IS EXPECTED WITH MOST OF THE MOISTURE
REMAINING TO THE SOUTH.

MAX TEMPS SATURDAY WILL RANGE FROM THE 30S IN THE MOUNTAINS TO THE
LOWER AND MIDDLE 40S ACROSS MOST OTHER LOCATIONS. MIN TEMPS SATURDAY
NIGHT WILL BE IN THE MID TO UPPER 20S ACROSS MOST LOCATIONS...BUT
LOWER AND MIDDLE 30S IN DOWNTOWN WASHINGTON AND BALTIMORE.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
UPPER LEVEL CUT-OFF LOW CENTERED OVER THE UPPER MISSISSIPPI VALLEY
SUNDAY WILL SLOWLY DRIFT TO THE EAST AND FILL BY WEDNESDAY NIGHT.
A SHORTWAVE MOVING THROUGH THE PATTERN WILL SUPPORT DEVELOPMENT OF A
SURFACE LOW OVER EASTERN NORTH CAROLINA AND VIRGINIA WEDNESDAY.
SURFACE LOW WILL MOVE ON TO NEW ENGLAND BY WEDNESDAY NIGHT.

MOISTURE WILL INCREASE OVER MID ATLANTIC REGION WILL INCREASE ON
SOUTHWEST WINDS DURING EARLY HALF OF PERIOD. MARGINAL 1000-500 MB
THICKNESS VALUES AND AIR TEMPERATURES AROUND FREEZING MAY SUPPORT
SNOW...OR WINTRY MIX. MORE MOISTURE WILL FOLLOW AT MID WEEK AHEAD OF
LOW APPROACHING FROM THE MID WEST. TEMPERATURES SHOULD STAY HIGH
ENOUGH THAT PRECIPITATION SHOULD BE RAIN.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
BKN CIGS NEAR 4KFT SHOULD ERODE BY LATE AFTERNOON BUT GIVE WAY TO
INCREASING MID LEVEL CIGS OVERNIGHT. HOWEVER VFR CONDITIONS EXPECTED
THROUGH THE TAF PERIOD. WINDS REMAIN OUT OF THE NW BUT BECOME LESS
GUSTY TONIGHT AND FRIDAY.

VFR CONDITIONS ARE EXPECTED ACROSS MOST OF THE TERMINALS SATURDAY
THROUGH SATURDAY NIGHT. A PERIOD OF LIGHT SNOW OR RAIN MAY IMPACT
KCHO. SUBVFR CONDITIONS ARE POSSIBLE IF ANY PRECIPITATION DEVELOPS.

HIGH PRESSURE WILL BUILD OVER THE TERMINALS SUNDAY...BUT LOW
PRESSURE MAY IMPACT THE AREA TUESDAY AND WEDNESDAY WITH
PRECIPITATION AND SUBVFR CONDITIONS.

&&

.MARINE...
HIGH PRESSURE AFFECTS THE WATERS THROUGH FRIDAY NIGHT. EXTENDED BOTH
SEGMENTS OF THE SCA INTO THIS EVENING AS NOT SURE THE GUST WILL
DECREASE TOO QUICKLY. WINDS INCREASE AGAIN FOR THE DAYTIME OF
FRIDAY...WITH A SCA GOING INTO EFFECT FOR MOST OF THE WATERS. WINDS
WILL DIMINISH FRIDAY EVENING.

HIGH PRESSURE WILL REMAIN OVER THE WATERS SATURDAY THROUGH
SUNDAY. LOW PRESSURE WILL IMPACT THE WATERS EARLY NEXT WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EST THIS EVENING FOR
     ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 7 AM TO 3 PM EST FRIDAY FOR
     ANZ531>534-537>543.
     SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR ANZ535-
     536.

&&

$$
SYNOPSIS...BJL
NEAR TERM...ADS
SHORT TERM...BJL/ADS
LONG TERM...BJL/CEM
AVIATION...BJL/ADS
MARINE...BJL/ADS






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