Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 281841 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 241 PM EDT TUE OCT 28 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OFFSHORE THROUGH TONIGHT. A COLD FRONT WILL PASS THROUGH THE AREA WEDNESDAY AND HIGH PRESSURE WILL RETURN FOR THURSDAY. LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL PASS THROUGH THE AREA FRIDAY INTO SATURDAY BEFORE CANADIAN HIGH PRESSURE BUILDS OVERHEAD EARLY NEXT WEEK. && .NEAR TERM /THROUGH WEDNESDAY/...
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HIGH PRESSURE IS WELL OFF THE MID-ATLANTIC COAST THIS AFTERNOON AS A COLD FRONT APPROACHES FROM THE OHIO RIVER VALLEY. SOUTHERLY FLOW...MIXING AND PLENTY OF SUNSHINE HAS ALLOWED TEMPERATURES TO CLIMB INTO THE 70S AND LOW 80S THIS AFTERNOON. A SHIELD OF CIRRUS IS LOCATED ACROSS THE POTOMAC HIGHLANDS AND WILL CONTINUE TO STREAM NORTHEASTWARD AHEAD OF THE ADVANCING COLD FRONT. A NARROW LINE OF SHOWERS ARE ALONG THE FRONT AND ARE EXPECTED TO MOVE EASTWARD REACHING THE HIGHLANDS LATE TONIGHT. THE LINE WILL BE FIGHTING A DRY AIRMASS SO SHOWERS ARE EXPECTED TO BE LIGHT AND SCATTERED. SHOWERS WILL SLOWLY MOVE EASTWARD OVERNIGHT REACHING THE BLUE RIDGE MTNS BY SUNRISE WEDNESDAY DUE TO THE SLOW SE FLOW ALOFT ABOUT 20-30 KTS. FCST MIN TEMPS WILL RANGE FROM THE MID 50S TO NEAR 60S ALONG AND EAST OF THE I-95 CORRIDOR. CLOUDS AND SHOWERS ARE EXPECTED WEDNESDAY AS THE FRONT SLOWLY MOVES EASTWARD REACHING SOUTHERN MARYLAND BY WEDNESDAY AFTERNOON. NW WINDS ARE EXPECTED BEHIND THE FRONT AND DRY AIR WILL MOVE INTO THE HIGHLANDS BY WED MORNING. TEMPS WILL NOT BE DIURNAL AHEAD OF THE COLD FRONT WED. MAX TEMPS AHEAD OF THE FRONT WED MORNING WILL LIKELY BE REACHED BEFORE NOON. RAINFALL AMTS ARE EXPECTED TO BE LESS THAN A QUARTER INCH.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
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A SHORTWAVE TROUGH WILL MOVE TOWARDS THE MID- ATLANTIC WEDNESDAY NIGHT AS THE COLD FRONT MOVES SOUTH AND EAST OF THE REGION. SFC HIGH PRESSURE WILL MOVE INTO THE REGION DURING THIS TIME. CLOUDS WILL LIKELY MOVE OVER THE HIGHLANDS AS THE TROUGH CROSSES THE REGION INTO THURSDAY. NRLY WINDS BEHIND THE COLD FRONT WILL CONTINUE TO BRING DRY AIR INTO THE REGION LEADING TO DRY CONDITIONS. A STRATO-CU DECK IS EXPECTED BY THURSDAY AFTERNOON. FCST MAX TEMPS WILL RANGE FROM THE UPPER 50S TO LOW 60S. HIGH PRESSURE WILL DETERIORATE OVER THE AREA THURSDAY NIGHT. BROAD TROUGHING ACROSS THE EASTERN CONUS WILL THEN INCREASE SIGNIFICANTLY IN AMPLITUDE THROUGH THE DAY FRIDAY AND FRIDAY NIGHT AS THE UPSTREAM SIDE OF THE TROUGH DIGS NEARLY MERIDIONALLY. THE ASSOCIATED SURFACE LOW WILL DEEPEN AS IT PASSES OVER THE GREAT LAKES DURING THIS TIME. AT THE BASE OF THE HIGH AMPLITUDE TROUGH...OPERATIONAL ECMWF SHOWS AN UPPER LEVEL LOW BECOMING CLOSED OVERNIGHT FRIDAY...WHILE THE GFS IS LESS INCLINED TO CLOSE THE LOW. THE PRIMARY EFFECT OF THIS DIFFERENCE LOCALLY IS UNCERTAINTY IN TRACK AND TIMING OF THE EFFECTS OF THE SURFACE LOW.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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FORECAST REFLECTS EXPECTATION THAT THE LOW WILL BEGIN TO WORK PRECIP INTO THE FORECAST AREA FRIDAY BUT THE BEST CHANCES WILL BE FRIDAY NIGHT AND INTO SATURDAY AS THE LOW PASSES OVER OR JUST WEST OF THE CWA ON A SOUTHEASTWARD TRACK. GIVEN THE TRACK OF THE LOW AND THE HIGH AMPLITUDE TROUGH OVERHEAD SATURDAY AND SUNDAY COULD SEE TEMPS 10 TO 20 DEGREES BELOW NORMAL. SOME SNOWFALL ACROSS THE HIGHEST ELEVATIONS...SPECIFICALLY THE POTOMAC HIGHLANDS...IS POSSIBLE...ELSEWHERE SHOULD SEE MOSTLY LIGHT RAIN SHOWERS. GUSTY WINDS ARE POSSIBLE SATURDAY AND SUNDAY AS THE SURFACE LOW MOVES OFF THE CAROLINA COAST AND THEN RETURNS NORTHEASTWARD UP THE COAST. HIGH PRESSURE WILL FILL IN BEHIND THE LOW AND TEMPS WILL REBOUND CLOSER TO NORMAL BY THE MIDDLE OF NEXT WEEK.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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VFR CONDITIONS EXPECTED TODAY AND TONIGHT. A SLOW MOVING COLD FRONT WILL APPROACH THE TERMINALS LATE TONIGHT AND INTO WEDNESDAY. -SHRA ARE EXPECTED AS THE FRONT PASSES BUT DUE TO A DRY AIRMASS...RESTRICTIONS ARE NOT EXPECTED AT THIS TIME. LIGHT S WINDS ARE EXPECTED TONIGHT. WINDS WILL BECOME NW BEHIND THE FRONT EARLY WED MORNING FOR MRB AND BY WEDNESDAY EVENING FOR THE REST OF THE TERMINALS. NW WINDS 5-10KTS ARE EXPECTED BEHIND THE FRONT. HIGH PRESSURE MOVES INTO THE REGION WEDNESDAY NIGHT THROUGH THURSDAY. VFR CONDITIONS EXPECTED AT THIS TIME. CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS THROUGH THE LONG TERM PERIOD.
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&& .MARINE...
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&& .TIDES/COASTAL FLOODING...
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SOUTHERLY FLOW IS CAUSING TIDAL ANOMALIES TO INCREASE TODAY. WATER LEVELS MAY APPROACH MINOR FLOODING THRESHOLDS FOR SENSITIVE AREAS NEAR HIGH TIDE TONIGHT MAINLY FOR ANNAPOLIS. ANOMALIES WILL NEED TO RISE TO 0.8 FEET AND AT THIS TIME THEY ARE AROUND 0.6 FEET. SW FLOW IS EXPECTED TO BECOME MORE S WHICH SHOULD INCREASE ANOMALIES. ANOMALIES WILL DECREASE WEDNESDAY AS THE FLOW TURNS OFFSHORE.
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&& .CLIMATE... MAX TEMPS TODAY WILL BE UNUSUALLY WARM FOR THIS TIME OF YEAR. THE RECORD AT DULLES MAY BE TIED OR BROKEN TODAY. BELOW IS A LIST OF THE PREVIOUS RECORDS AT IAD...DCA AND BWI. IAD...83 IN 1984 DCA...87 IN 1919 BWI...87 IN 1919. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ530- 531-535-536-538-539. SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ532>534- 537-540>543.
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&& $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...HAS/CEB LONG TERM...CEB AVIATION...HAS/CEB MARINE...HAS/CEB TIDES/COASTAL FLOODING...HAS CLIMATE...LWX

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