Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210121 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 921 PM EDT SAT SEP 20 2014 .SYNOPSIS... HIGH PRESSURE CENTERED SOUTH OF THE CANADIAN MARITIMES WILL MOVE EAST INTO THE NORTH ATLANTIC OVERNIGHT. LOW PRESSURE WILL TRACK NORTH ALONG THE SOUTHEAST AND MID ATLANTIC COASTS OVERNIGHT AND SUNDAY. A COLD FRONT WILL CROSS THE REGION SUNDAY AND SUNDAY NIGHT...FOLLOWED BY A RETURN OF HIGH PRESSURE MONDAY THROUGH WEDNESDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... REGIONAL RADAR MOSAIC AT 01Z SHOWS RAIN SHIELD FROM THE LOW PRES OVER SE US COAST APPROACHING TIDEWATER VA. IR SATELLITE IMAGERY HAS HIGH CLOUDS REACHING SOUTHERN MD FROM THE SAME SYSTEM. KEEPING IN SLIGHT CHC POPS OVER SOUTHERN MD OVERNIGHT...AS THEY COULD GET SOME SPRINKLES OR VERY LIGHT RAIN AS THE SYSTEM PULLS TO THE NORTHEAST. ALL GUIDANCE SHOWS PATCHY FOG DEVELOPING OVERNIGHT IN THE USUAL SUSPECT VALLEY AND PIEDMONT LOCATIONS. OTHERWISE UNREMARKABLE WEATHER WITH MIN TEMPS IN THE UPPER 50S WEST OF I-95...LOWER 60S EAST OF I-95 DUE TO THE BAY INFLUENCE ON S/SE FLOW...AND MID 60S IN DC AND BALT METRO AREAS. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... SUNDAY...LOW PRESSURE MOVES NORTHEAST OFFSHORE AND THEN A COLD FRONT APPROACHES DURING THE DAY AND CROSSES LATE AFTERNOON THROUGH MIDNIGHT. FIVE PERCENT RISK FOR DAMAGING WIND FROM SPC ROUGHLY WEST OF THE BLUE RIDGE SEEMS REASONABLE GIVEN TIMING DURING PEAK HEATING. MAX TEMPS IN THE MID 80S (PERHAPS UPR 80S EAST OF I-95 IF MORNING CLOUDS CLEAR SOON ENOUGH) AND LIFTED INDICES FROM THE GFS AROUND -2. HIGH PRESSURE BUILDS MONDAY WITH NWLY WINDS GUSTING AROUND 20 MPH. MAX TEMPS LOW TO MID 70S. CLOUDS CLEAR THROUGH THE DAY...SUNNY BY THE AFTERNOON. CHILLY MONDAY NIGHT WITH CLEAR SKIES AND HIGH PRESSURE SETTLING OVER THE AREA. MIN TEMPS COULD BE INTO THE MID 30S IN THE ALLEGHENY HIGHLANDS WHERE FROST IS POSSIBLE. MENTIONED THIS IN THE HWO. OTHERWISE...MIN TEMPS LOW TO MID 40S...MID 50S NEAR SHORE. && .LONG TERM /TUESDAY THROUGH SATURDAY/... DEEP-LAYER RIDGING WILL ENTRENCH ITSELF OVER THE NORTH-CENTRAL AND EASTERN UNITED STATES BEGINNING TUESDAY...ACCOMPANIED BY A SEASONABLY COOL AND INITIALLY DRIER AIRMASS. BUT AS THE HIGH MIGRATES TO THE NORTH OF THE AREA DURING THE LATER PART OF THE WEEK AN ONSHORE FLOW BEGINS WHICH WILL LEAD TO GRADUALLY INCREASING MOISTURE. THIS COULD SQUEEZE OUT SOME DRIZZLE OR LIGHT RAIN BY THE END OF THE WEEK AS LOW PRESSURE MOVES INTO THE SOUTHEAST CONUS FROM THE ATLANTIC. TEMPERATURES WILL GENERALLY BE A FEW DEGREES BELOW NORMAL THROUGH MOST OF THE WEEK...BUT COULD REBOUND TO AROUND NORMAL LEVELS BY NEXT WEEKEND DEPENDING ON THE EXTENT OF CLOUD COVER AMIDST ONSHORE FLOW. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... LIGHT ONSHORE FLOW WITH VFR CONDS OVERNNIGHT AS LOW PRESSURE MOVES UP THE COAST FROM GEORGIA. A COLD FRONT CROSSES SUNDAY AFTERNOON AND EVENING WITH ISOLATED THUNDERSTORMS AS BEST EAST OF THE BLUE RIDGE. A FEW THUNDERSTORMS COULD HAVE DAMAGING WIND GUSTS WEST OF THE BLUE RIDGE. NW FLOW SUNDAY NIGHT AND MONDAY...WITH GUSTS AROUND 20 KT. HIGH PRESSURE THEN BUILDS THROUGH TUESDAY WITH CONTINUED VFR. VFR LIKELY TUE-WED NIGHT...WINDS GENERALLY NE 10 KTS OR LESS. && .MARINE... LOW PRESSURE DEVELOPING OFF GEORGIA WILL STRENGTHEN AND LIFT NORTHEAST ALONG THE CAROLINA COAST OVERNIGHT AND MOVE OFF THE MID-ATLANTIC SUNDAY. THE ONSHORE FLOW WILL CONTINUE UNTIL THE LOW PASSES MIDDAY SUNDAY. A COLD FRONT WILL CROSS THE WATERS SUNDAY NIGHT. JUST A SLIGHT CHANCE OF SHOWERS SUNDAY EVENING WITH THE PASSAGE. NWLY FLOW BEHIND THE FRONT WILL INCREASE TO 15 KT WITH SCA GUSTS TO 20 KT LATE SUNDAY NIGHT AND ALL OF MONDAY. SUB-SCA CONDITIONS EXPECTED TUESDAY AS HIGH PRESSURE MOVES ACROSS...WITH SCA GUSTS POSSIBLE AT TIMES DURING THE SECOND HALF OF THE WEEK AS THE HIGH BEGINS TO PULL AWAY AND THE GRADIENT TIGHTENS WITH LOW PRESSURE DEVELOPING WELL TO THE SOUTH. && .TIDES/COASTAL FLOODING... WATER LEVELS ACROSS MUCH OF THE MD BAY AND THE UPPER TIDAL POTOMAC REMAIN ELEVATED...W/ POSITIVE ANOMALIES STILL RANGING BETWEEN 1.3 AND 1.5FT. THE LOWER BAY ZONES HAVE SEEN A SLIGHT DECREASE...CLOSER TO A FOOT BUT STILL HEADING INTO THE HIGHER TIDE CYCLE LATE TONIGHT/EARLY SUN MRNG. A NEW COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR THE WRN SHORE MD BAY COUNTIES...MINUS HARFORD. HAVRE DE GRACE WOULD NEED A HIGHER ANOMALY VALUE THAN THE CURRENT/RECENT TRENDS SUGGEST WILL BE THERE AT HIGH TIDE DURING THE POST-DAWN HRS SUN. AFTER THE EARLY MRNG H.T. CYCLE...WINDS WILL SHIFT BRIEFLY NLY BUT THEN SWITCH TO WLY DURING THE AFTN...RESIDUAL ANOMALY MAY REQUIRE ANOTHER ROUND OF ADVISORIES BEFORE THE WINDS GO MODERATE NW SUNDAY NIGHT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY FROM 5 AM TO 9 AM EDT SUNDAY FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT SUNDAY FOR MDZ011-014- 017-018. VA...COASTAL FLOOD ADVISORY FROM 5 AM TO 9 AM EDT SUNDAY FOR VAZ054. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT MONDAY FOR ANZ530>543. && $$ SYNOPSIS...LEE NEAR TERM...LEE SHORT TERM...BAJ LONG TERM...DFH AVIATION...BAJ/DFH/LEE MARINE...BAJ/DFH/LEE TIDES/COASTAL FLOODING...GMS/LEE

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