Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 190103
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
903 PM EDT SAT OCT 18 2014

.SYNOPSIS...
AN UPPER TROUGH AXIS WILL CLEAR THE AREA LATER TONIGHT...WITH
CANADIAN HIGH PRESSURE BUILDING TROUGH MONDAY. A SLOW MOVING
CUT OFF UPPER LEVEL LOW PRESSURE SYSTEM WILL HOVER AROUND THE EAST
COAST THROUGH MUCH OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
HIGH PRESSURE WILL BUILD INTO THE GREAT LAKES AND TENNESSEE VALLEY
OVERNIGHT WHILE A COLD FRONT CONTINUES TO MOVE OFF THE COAST. A
NORTHWEST FLOW IN BETWEEN THESE SYSTEMS WILL CONTINUE TO USHER IN
CHILLIER AIR DURING THIS TIME.

AN UPPER-LEVEL TROUGH WILL SWING THROUGH THE AREA...BRINGING SOME
CLOUDS WITH IT BUT ANY PRECIPITATION WILL BE LIGHT AND CONFINED TO
LOCATIONS ALONG AND WEST OF THE ALLEGHENY FRONT WHERE THERE IS AN
UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW. THERE MAY BE ENOUGH COLD
AIR FOR A FEW FLURRIES OR SNOW SHOWERS ALONG THE RIDGE TOPS...BUT
LITTLE OR NO SNOW ACCUMULATION IS EXPECTED. MIN TEMPS WILL RANGE
FROM THE UPPER 20S AND LOWER 30S ALONG THE RIDGE TOPS OFF THE
ALLEGHENY HIGHLANDS...TO THE LOWER AND MIDDLE 40S ACROSS MOST
OTHER LOCATIONS.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
SFC HIGH PRESSURE CENTER ENTERS THE CWA FROM THE WEST SUNDAY
AFTERNOON...MOVING OFFSHORE MONDAY MORNING. GUSTY NWLY FLOW THROUGH
SUNDAY...EXPECT 30 MPH GUSTS THROUGH MUCH OF THE DAY. DOWNSLOPING
FLOW WILL WARM AS IT DESCENDS WITH MORNING CLOUDS OVER THE MOUNTAIN
QUICKLY DISSIPATING (ALONG WITH ANY LIGHT WINTRY MIX PRECIP WEST OF
THE ALLEGHENY FRONT). MAX TEMPS GENERALLY MID TO UPR 50S AT LOWER
ELEVATION. 60F POSSIBLE EAST OF THE BLUE RIDGE.

SUNDAY NIGHT...HIGH PRESSURE CROSSES THE MOUNTAINS IN THE
EVENING...TO THE CHESAPEAKE BAY BY SUNRISE. CLEAR...CALM...AND DRY
WILL MAKE FOR AN IDEAL RADIATIONAL COOL NIGHT. MIN TEMPS AROUND
FREEZING LIKELY PIEDMONT AND VALLEYS WEST OF THE BLUE RIDGE
(INVERSION FOR RIDGES). COULD NEED A FROST OR FREEZE HEADLINE FOR
NEARLY ALL OF THE CWA (GRIDDED GUIDANCE GENERALLY HAS A WARM BIAS
FOR INTERIOR SOUTHERN MARYLAND ON CLEAR/CALM NIGHTS). LOW TO MID 40S
FOR URBAN/NEAR SHORE.

RETURN FLOW MONDAY AS HIGH PRESSURE MOVES OFFSHORE AND LOW PRESSURE
APPROACHES FROM THE GREAT LAKES. MOISTURE RETURNS WITH RAIN CHANCES
INCREASING FROM THE WEST MONDAY AFTERNOON AHEAD OF AN AMPLIFYING
TROUGH. UPR TROUGH AXIS CROSSES THE CWA MONDAY NIGHT WITH LOW
CHANCES FOR LIGHT RAIN ACROSS THE CWA.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
ECMWF HAS 500MB CUT-OFF LOW OVER WESTERN PA TUESDAY NIGHT WITH VORT
MAX DROPPING DOWN WEST SIDE OF TROUGH. VORT MAX WILL ROUND THE
BOTTOM OF THE TROUGH WEDNESDAY MORNING AND MOVE OFFSHORE BY
WEDNESDAY EVENING. UPPER LEVEL LOW WILL CROSS CWA LATE TUESDAY INTO
WEDNESDAY AND MOVE OFFSHORE WEDNESDAY EVENING. BROAD UPPER LEVEL LOW
PRESSURE PATTERN WILL SET UP OVER CANADA AND NEW ENGLAND THROUGH THE
REST OF THE PERIOD. CWA WILL BE ON THE SOUTHERN EDGE OF THE TROUGH
WITH SHORTWAVE CROSSING AREA FRIDAY.

ALTHOUGH ANTICIPATED PATH OF THE SURFACE LOW WILL KEEP THE STRONGEST
OF ITS ASSOCIATED PRECIPITATION IN PA...OUR CWA LOOKS TO GET WET ALSO.
GREATEST OPPORTUNITY FOR PRECIPITATION APPEARS TO BE TUESDAY NIGHT
THROUGH THURSDAY.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
VFR CONDS THROUGH TONIGHT. NORTHWEST WINDS WILL NOT BE AS GUSTY AS
TODAY...BUT GUSTS AROUND 15 TO 20 KNOTS ARE STILL POSSIBLE DUE TO
A RELATIVELY STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE TO THE
WEST AND A COLD FRONT OFF THE COAST.

GUSTY VFR SUNDAY WITH NWLY FLOW GUSTING 25 KT AS HIGH PRESSURE
BUILDS FROM THE WEST. GUSTS EASE THROUGH THE EVENING AS THE HIGH
CENTER CROSSES INTO THE AREA. VFR CONTINUES THROUGH MONDAY AS THE
HIGH SHIFTS OFFSHORE. LOW PRESSURE APPROACHES TUESDAY WITH RAIN
CHANCES INCREASING. LOW LINGERS INTO LATE IN THE WEEK.

&&

.MARINE...
A NORTHWEST FLOW WILL CONTINUE THROUGH SATURDAY. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE WATERS DURING THIS TIME. THERE MAY
BE A BREAK IN THE GUSTY WINDS THIS EVENING FOR PORTIONS OF THE
UPPER TIDAL POTOMAC RIVER AND THE NORTHERN CHESAPEAKE BAY...BUT
ANOTHER PRESSURE SURGE OVERNIGHT SHOULD CAUSE MORE GUSTS AROUND 20
KNOTS. FOR SATURDAY...WIDESPREAD GUSTS AROUND 20 TO 25 KNOTS ARE
EXPECTED.

SCA FOR SUNDAY AND SUNDAY EVENING AS HIGH PRESSURE BUILDS FROM THE
WEST. NWLY FLOW GUSTS 25 TO 30 KT SUNDAY...EASING THROUGH THE NIGHT
AS HIGH PRESSURE CENTER CROSSES THE BAY LATE IN THE NIGHT. RETURN
FLOW MONDAY AS HIGH PRESSURE MOVES OFF SHORE. LOW PRESSURE DRIFTS
OVER THE REGION THEN INTO THURSDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT SUNDAY NIGHT FOR
     ANZ531>534-537-539>541-543.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT SUNDAY FOR ANZ530-535-536-
     538-542.

&&

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







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