Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 031021 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 621 AM EDT SUN MAY 3 2015 .SYNOPSIS... HIGH PRESSURE WILL SHIFT TO OUR SOUTH TODAY BEFORE BUILDING TOWARD BERMUDA MONDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TUESDAY AND BECOME STATIONARY DURING MIDWEEK. HIGH PRESSURE IS THEN EXPECTED LATE IN THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... ...UPDATE TO CANCEL THE COASTAL FLOOD ADVISORY. PREVIOUS DISCUSSION FOLLOWS... HIGH PRESSURE WILL CONTINUE TO BUILD SOUTH TOWARD THE CAROLINAS TODAY. A RETURN FLOW AROUND THE HIGH ALONG WITH UPPER-LEVEL RIDGING AND PLENTY OF SUNSHINE WILL RESULT IN WARM CONDITIONS. LEANED TOWARD THE WARMER GUIDANCE DUE TO THE SUNSHINE AND A DEEP MIXING LAYER ANTICIPATED. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE UPPER 70S AND LOWER 80S NEAR WASHINGTON AND BALTIMORE. A SCT CU DECK WILL DEVELOP LATE THIS MORNING AND AFTERNOON DUE DAYTIME HEATING...BUT NO PRECIPITATION IS EXPECTED THANKS TO A STRONG SUBSIDENCE INVERSION. A LIGHT SOUTHWEST FLOW WILL CONTINUE AROUND HIGH PRESSURE TO OUR SOUTH TONIGHT. MILD CONDITIONS ARE EXPECTED...BUT RADIATIONAL COOLING MAY RESULT IN CHILLIER CONDITIONS FOR SHELTERED VALLEYS AND RURAL AREAS. MIN TEMPS ARE FORECAST TO RANGE FROM THE UPPER 40S IN SHELTERED VALLEYS AND RURAL AREAS TO THE LOWER AND MIDDLE 60S IN DOWNTOWN WASHINGTON AND BALTIMORE. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... HIGH PRESSURE WILL REMAIN WELL TO OUR SOUTH AND EAST...EXTENDING FROM THE CAROLINAS TOWARD BERMUDA MONDAY THROUGH TUESDAY NIGHT. A SOUTHWEST FLOW AROUND THIS SYSTEM WILL USHER IN EVEN WARMER CONDITIONS FOR MONDAY AND TUESDAY. MAX TEMPS WILL REACH THE LOWER TO MIDDLE 80S ACROSS MANY LOCATIONS. THE SOUTHWEST FLOW WILL ALSO USHER IN MORE MOISTURE DURING THIS TIME. THE INCREASED MOISTURE WILL LEAD TO INCREASED INSTABILITY. FOR MONDAY...STILL EXPECT MOST AREAS TO BE DRY DUE TO A STRONGER CAPPING INVERSION. HOWEVER...AN ISOLATED SHOWER/T-STORM CANNOT BE RULED OUT LATE IN THE AFTERNOON/EVENING ACROSS THE BLUE RIDGE MOUNTAINS INTO CENTRAL VIRGINIA AND THE POTOMAC HIGHLANDS. TERRAIN CIRCULATION WOULD BE THE PRIMARY LIFTING MECHANISM WITH AN UPPER- LEVEL DISTURBANCE LIKELY REMAINING OFF TO OUR SOUTH. CONFIDENCE IS TOO LOW AT THIS TIME TO ADD POPS IN THE FORECAST. FOR TUESDAY...A COLD FRONT IS EXPECTED TO APPROACH FROM THE NORTH. MOISTURE MAY BE A BIT DEEPER DURING THIS TIME AS WELL. TERRAIN CIRCULATION AND THE COLD FRONT WILL ACT AS THE PRIMARY LIFTING MECHANISMS...AND WITH A LITTLE MORE INSTABILITY TO WORK WITH THERE IS A BETTER CHANCE FOR A SHOWER/THUNDERSTORM...MAINLY ACROSS NORTHERN MARYLAND...NORTHERN VIRGINIA AND FOR LOCATIONS NEAR AND WEST OF THE BLUE RIDGE MOUNTAINS. HAVE CHANCE POPS IN THE FORECAST FOR THESE AREAS TUESDAY AFTERNOON/EVENING. THE COLD FRONT WILL MOVE INTO NORTHERN MARYLAND OVERNIGHT TUESDAY. THE BOUNDARY WILL BE WEAK WITH LITTLE TEMPERATURE GRADIENT ASSOCIATED WITH IT. THEREFORE...MILD CONDITIONS WILL CONTINUE BUT THERE MAY BE A COUPLE SHOWERS ACROSS NORTHERN PORTIONS OF THE CWA DURING THIS TIME. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... PERIOD OF UNSETTLED WX CONTINUING INTO THE SECOND HALF OF THE WEEK WITH THE COLD FRONT DROPPING SOUTH TUES NIGHT STALLING ACROSS THE MID ATLANTIC. ANY PCPN INITIALLY WED MORNING CONFINED NEAR THE MASON DIXON LINE...CLOSER TO THE FRONTAL BOUNDARY. PCPN INCREASES IN COVERAGE TO THE SOUTH DURING THE DAY AS THE FRONT SLIDES SLIGHTLY TO THE SOUTH AS SFC HIGH PRESSURE TO THE NORTH BUILDS SOUTH. THE COMBINATION OF RIDGING BUILDING IN ALOFT AND A DEVELOPING LOW OFF THE SOUTHEAST US WILL KEEP THE MOVEMENT OF THE FRONT MINIMAL THRU THE END OF THE WEEK. TSTMS MENTIONED ON WED WITH DECENT INSTABILITY...THOUGH LAPSE RATES ARE THE WEAKER SIDE. ELY FLOW COULD KEEP ANY THUNDER MORE CONFINED TO SOUTHWESTER PORTIONS OF THE CWA. ANY PCPN MENTION ENDS WED EVENING. SLIGHT CHC FOR PCPN AGAIN ON THURS...MAINLY WEST OF THE BLUE RIDGE AS THE FRONT ALIGNS ALONG THE VA/MD BORDER. WITH THE REGION UNDER RIDGING ALOFT...FEEL BEST PCPN CHC COMES FROM THE UPSLOPING FACTOR FROM THE ELY FLOW. HAVE MENTION YET AGAIN OF THUNDER ON THURS. RIDGE AXIS NUDGES EAST FRIDAY HEADING INTO THE WEEKEND...ALLOWING FOR THE SFC LOW IN SOUTHERN CANADA IN WHICH THE FRONTAL BOUNDARY IS ASSOCIATED WITH TO PROGRESS TO THE EAST. THIS WILL LIFT THE FRONT TO THE NORTHEAST AS A WARM FRONT SOMETIME FRIDAY...CLEARING THE AREA BY SAT MORNING. PCPN ASSOCIATED WITH THE FRONT PSBL DURING THIS TIME MAINLY OVER WESTERN AND NORTHERN AREAS. ANOTHER THING TO KEEP WATCH ON IS THE DEVELOPING LOW WELL TO THE SOUTH OFF THE SOUTHEASTERN US COAST. MODELS HAVE DIVERGING SOLUTIONS ON THE PATH AND STRENGTH OF THIS SYSTEM...BUT IF IT PUSHES FAR ENOUGH NORTH...COULD RESULT IN PCPN TO THE SOUTH AND EASTERN AREAS OF THE CWA TO END THE WEEK AS WELL. THE BUILDING RIDGE AND RISING HEIGHTS WILL BRING WELL ABV NORMAL TEMPS FOR THE SECOND HALF OF THE WEEK...WITH MANY AREAS HAVING MULTIPLE DAYS OF 80+ HIGHS. FOR WED AND THURS...DID KEEP THE EASTERN AREAS A BIT ON THE COOLER SIDE TO ACCOUNT FOR ELY FLOW...BUT STILL REACHING INTO THE MID TO UPPER 70S. LOWS THRU THE PERIOD IN THE 50S AND 60S. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT. LIGHT AND VARIABLE WINDS WILL TURN NORTHWEST AFTER SUNRISE BEFORE SHIFTING TOWARD THE SOUTHWEST BY SUNSET. WIND SPEEDS AROUND 5 TO 10 KNOTS ARE EXPECTED. WINDS WILL BECOME LIGHT AND VARIABLE TONIGHT. VFR CONDITIONS WILL PERIST FOR MOST OF THE TIME MONDAY THROUGH TUESDAY NIGHT. HOWEVER...AN AFTERNOON/EVENING THUNDERSTORM IS POSSIBLE TUESDAY. COVERAGE IS EXPECTED TO BE SCATTERED AT THIS TIME. GENERALLY EXPECTING VFR CONDITIONS TUES-SAT. PSBL SUB-VFR CONDITIONS WITH ANY SHOWERS/TSTMS THRU THE PERIOD. && .MARINE... HIGH PRESSURE WILL BUILD TO OUR SOUTH TODAY THROUGH TUESDAY. A COLD FRONT WILL MOVE INTO THE NORTHERN PORTIONS OF THE WATERS TUESDAY NIGHT. A SOUTH TO SOUTHWEST FLOW IS EXPECTED DURING THIS TIME. HOWEVER...THERE MAY BE A BRIEF PERIOD OF WESTERLY WINDS LATER THIS MORNING INTO THE MIDDAY HOURS. WIND SPEEDS WILL REMAIN BELOW SCA CRITERIA THROUGH MONDAY. THE PRESSURE GRADIENT MAY STRENGTHEN A BIT MONDAY NIGHT AND WIND GUSTS MAY APPROACH SCA CRITERIA FOR PORTIONS OF THE WATERS. A SHOWER OR THUNDERSTORM CANNOT BE RULED OUT TUESDAY AFTERNOON INTO TUESDAY EVENING...ESPECIALLY FOR NORTHERN PORTIONS OF THE WATERS. CONFIDENCE IS LOW AT THIS TIME. SOUTH TO SOUTHWEST WINDS MAY COME CLOSE TO SCA CRITERIA TUESDAY...BUT GUSTS HAVE BEEN CAPPED AROUND 15 KNOTS FOR NOW DUE TO THE RELATIVELY COOLER WATERS. SUB-SCA CONDITIONS EXPECTED TUES-THURS WITH PERSISTENT ELY FLOW GENERALLY 10 KTS OR LESS. PSBL SCA GUSTS FRI...DEPENDING ON THE TRACK OF THE LOW. && .TIDES/COASTAL FLOODING... THE MINOR TIDAL FLOODING HAS ENDED AT ANNAPOLIS WITH WATER LEVELS FALLING DUE TO THE APPROACHING LOW TIDE THIS AFTERNOON. TIDAL ANOMALIES SHOULD BE LOW ENOUGH TO PREVENT MINOR TIDAL FLOODING FOR THE NORTHERN CHESAPEAKE BAY AND UPPER TIDAL POTOMAC RIVER LATER THIS MORNING. THE NEXT HIGH TIDE WILL BE THE LOWER OF THE TWO ASTRONOICAL NORMS THIS AFTERNOON AND EVENING. ALSO...A LIGHT OFFSHORE WILL LIKELY CAUSE ANOMALIES TO DECREASE A BIT. THEREFORE...NO MINOR TIDAL IS FLOODING. ALSO WITH THE DECREASED ANOMALIES...MINOR TIDAL FLOODING IS UNLIKELY WITH THE HIGHER OF THE TWO HIGH TIDES LATE TONIGHT INTO MONDAY MORNING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...BJL/SEARS AVIATION...BJL/SEARS MARINE...BJL/SEARS TIDES/COASTAL FLOODING...BJL

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