Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 181903
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
303 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 /THROUGH TONIGHT/...
MUCH OF ERN OH AND WRN/CNTRL PA COVERED IN NUMEROUS LIGHT SHOWERS
W/ THE LAKE EFFECT WINDS DRIVEN BY A SHARP UPPER TROUGH AXIS. ON
THE OTHER SIDE OF THE APLCNS...JUST THE LEFTOVER CLOUD FIELD WHICH
EARLIER HAD DISSIPATED E OF THE BLUE RIDGE BUT HAS NOW MADE IT TO
I-95. THE EXTRA PUSH OF THE VORT MAX ASSOCIATED W/ THE UPPER
TROUGH IS HELPING THE SOLID STRATUS DECK TO MAKE IT FURTHER EAST
OF THE MTNS - W/ ONLY SOME SUN POKING THRU THE STRANDS OF LOW
5-7KFT.

INCREASED THE HIGHS FOR THE AFTN W/ A PREV UPDATE...AS SOME MINOR
DOWNSLOPING EFFECTS AND EARLIER LACK OF CLOUD COVER ALLOWED TEMPS
ALONG I-95 FOR INCREASE INTO THE L70S. TEMPS HAVE NOW STEADIED AT
THEIR NEAR-HIGHEST LEVELS FOR THE AFTN BEFORE AN EXPECTED COOL
OVERNIGHT PERIOD. TONIGHT`S OVERNIGHT LOWS WILL END-UP A SOLID
5-10F DEG LOWER THAN LAST NIGHT`S...DROPPING WELL INTO THE 40S
ACROSS THE REGION...30S ACROSS THE HIGHER ELEVATIONS. SOME SPOTS
IN THE HIGHEST ELEVATIONS OF HIGHLAND AND PENDLETON COUNTIES
DROPPING BELOW FREEZING.

SHOWERS ARE EXPECTED TO TAPER OFF BUT BEFORE THEY DO SOME
SNOWFLAKES MAY MIX IN BEFORE SUNRISE SUNDAY MORNING. IN TERMS OF
FREEZE HEADLINE POTENTIAL...GEOGRAPHIC EXTENT SHOULD BE LESS THAN
HALF OF THESE ZONES...SO A FREEZE WATCH HAS NOT BEEN ISSUED. EAST
OF THE MOUNTAINS...OVERNIGHT LOWS WILL DROP INTO THE 40S. SOME
AREAS IN METRO BALTIMORE/WASHINGTON AND ALONG CHES BAY MAY HANG ON
TO LOWS AROUND 50.

&&

.SHORT TERM /SUNDAY 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 /18Z SATURDAY THROUGH THURSDAY/...
VFR CONDS THROUGH TONIGHT. OCCASIONAL GUSTS TO 25KT WILL BE
POSSIBLE THRU THE LATE AFTN HRS...DROPPING OFF TO MORE OF A STIFF
BREEZE IN THE 10-15KT RANGE. SOUNDINGS FOR SATURDAY NIGHT HINT AT
POSSIBLE MVFR CIGS...BUT CONFIDENCE NOT HIGH ENOUGH TO INCLUDE IN
TAFS AT THIS TIME. GUSTS WILL DIMINISH IN THE EVENING.

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...
THE SCA CONTINUES FOR ALL WATERS THRU THE REST OF THE DAY. GUSTS
UP TO 25 KTS ARE EXPECTED ON THE WATERS THROUGH THE AFTERNOON. SCA
LINGERS OVERNIGHT FOR CHES BAY SOUTH OF SANDY POINT AND THE LOWER
TIDAL POTOMAC RIVER.

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.

&&

.TIDES/COASTAL FLOODING...
THE EARLIER POSITIVE TIDAL ANOMALIES THAT WERE 0.75-1.0 FT ABOVE
NORMAL HAVE TAKEN A TUMBLE AS A SOLID WLY WIND HAS BEGUN TO PUSH
WATER BACK DOWN THE BAY. THE DC PORTION OF THE TIDAL POTOMAC
TAKING A BIT LONGER TO RESPOND. REGARDLESS...ALL COASTAL AREAS
WILL BE WELL BELOW MINOR CF POTENTIAL HEADING INTO THE NEXT FEW
H.T. CYCLES AT THE VERY LEAST W/ A COUPLE OF DAYS OF THIS STEADY
WNW WIND.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530-
     531-535-536-538-539.
     SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO MIDNIGHT EDT SUNDAY
     NIGHT FOR ANZ531-539.
     SMALL CRAFT ADVISORY FROM 6 AM TO 8 PM EDT SUNDAY FOR ANZ530-
     535-536-538.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT SUNDAY FOR ANZ542.
     SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT SUNDAY NIGHT FOR
     ANZ532>534-537-540-541-543.

&&

$$









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