Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT SAT OCT 18 2014 .SYNOPSIS... A COLD FRONT WILL CROSS THE MID-ATLANTIC THIS MORNING. CANADIAN HIGH PRESSURE WILL THEN BUILD THROUGH SUNDAY. AN SLOW MOVING UPPER LEVEL CUT OFF LOW WILL AFFECT THE REGION TUESDAY POSSIBLY INTO FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... COLD FRONT IS ON THE DOORSTEP OF THE POTOMAC HIGHLANDS EARLY THIS MORNING...WITH A WIND SHIFT TO THE WNW AND GUSTS NOTED AT SEVERAL SPOTS IN CENTRAL AND EASTERN WV. SOME LIGHT RETURNS NOTED ON RADAR OVER ERN WV...WITH MORE COVERAGE NOTED OVER PA. MOST PRECIPITATION WILL PASS NORTH OF THE CWA...BUT WILL SOME SCATTERED SHOWERS WILL BE POSSIBLE OVER WESTERN PORTIONS OF THE CWA. SHOWER POTENTIAL CONTINUES THROUGH THE DAY OVER THE POTOMAC HIGHLANDS WITH UPSLOPE EFFECTS AS WINDS BECOME MORE NWLY. GUSTY WINDS FROM THE W-NW EXPECTED THROUGHOUT THE DAY. GUSTS GENERALLY AROUND 20-25 MPH FROM LATE MORNING THROUGH THE AFTERNOON...WITH SOME GUSTS REACHING 30 MPH POSSIBLE. SATURDAY NIGHT...HIGH PRESSURE BUILDS INTO THE OHIO VALLEY. NW WINDS CONTINUE TO ADVECT DRY AND COOL AIR INTO THE REGION. PRESSURE GRADIENT REMAINS IN TACT BETWEEN THE HIGH AND A LOW NORTH OF NEW ENGLAND. SHOWERS ARE LIKELY IN THE UPSLOPE REGION AS NW FLOW MOVES UP AGAINST THE ALLEGHENY FRONT. TEMPS WILL LIKELY DROP INTO THE 30S IN THIS REGION BY SUN MORNING...WITH 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 FRIDAY/... LINGERING LOW PRESSURE THE STORY FOR TUESDAY POSSIBLY INTO FRIDAY. 00Z GFS/ECMWF OPERATIONAL RUNS DEPICTING UPR LOW CROSSING THE CENTRAL MID-ATLANTIC TUESDAY AND WEDNESDAY...THEN LINGERING ALONG THE COAST THROUGH THURSDAY NIGHT. THIS WOULD MEAN CLOUDS AND PERIODIC RAIN...ALONG WITH BELOW NORMAL TEMPERATURES. COLD AIR DOES COME IN THE WEST SIDE...BUT NOT ENOUGH MOISTURE IS EXPECTED NOW FOR SNOW OUT WEST. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... VFR CONDS THROUGH TONIGHT. WINDS BECOME W-NW 10-15KTS WITH GUSTS UP TO 20 KTS BY LATE MORNING AND CONTINUING THROUGH THE AFTERNOON. OCCASIONAL GUSTS TO 25KT WILL BE POSSIBLE. 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... FORECAST ON TRACK AT THE MOMENT...WITH GUSTS TO NEAR 20KT NOTED IN OBSERVATIONS ALONG PORTIONS OF THE CHES BAY AND LOWER TIDAL POTOMAC WHERE A SMALL CRAFT ADVISORY IS IN EFFECT. THE SCA EXPANDS TO ALL WATERS AT 14Z THIS MORNING...WHEN A DRY COLD FRONT WILL CROSS THE WATERS AND W-NW WILL INCREASE BEHIND IT. GUSTS UP TO 25 KTS ARE EXPECTED ON THE WATERS THROUGH THE AFTERNOON. SCA HAS BEEN EXTENDED THROUGH SAT NIGHT 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... TIDAL ANOMALIES ARE RUNNING BETWEEN THREE QUARTERS AND ONE FOOT EARLY THIS MORNING. ANOMALIES WOULD NEED TO BE AROUND 1.5 FEET TO REACH MINOR FLOOD THRESHOLD...SO NO ADVISORIES ARE EXPECTED AT THIS TIME. WINDS WILL SHIFT TO THE WEST THIS MORNING...CAUSING ANOMALIES TO DECREASE FURTHER. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR ANZ530-531-535-536-538-539. SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ532>534-537- 540>543. && $$ SYNOPSIS...KCS NEAR TERM...KCS SHORT TERM...BAJ LONG TERM...BAJ AVIATION...BAJ/KCS MARINE...BAJ/KCS TIDES/COASTAL FLOODING...KCS

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