Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 159 PM EDT FRI SEP 19 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OVERHEAD THROUGH SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A COLD FRONT WILL PASS THROUGH THE AREA SUNDAY NIGHT INTO MONDAY. HIGH PRESSURE WILL RETURN FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE NEW ENGLAND COAST THROUGH TONIGHT. A SURFACE RIDGE AXIS WILL EXTEND SOUTHWEST FROM THIS HIGH INTO THE MID-ATLANTIC DURING THIS TIME. THE LOW-LEVEL FLOW WILL CONTINUE TO TURN TOWARD THE SOUTHEAST DURING THIS TIME. THE ONSHORE FLOW WILL CAUSE MOISTURE TO GET TRAPPED UNDERNEATH THE SUBISDINCE INVERSION...RESULTING IN MORE CLOUDS ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS. HOWEVER...FOR LOCATIONS FARTHER NORTH AND EAST THERE WILL BE SOME SUNSHINE LATE THIS AFTERNOON. A COUPLE SPRINKLES CANNOT BE RULED OUT...MAINLY ACROSS CENTRAL VIRGINIA INTO THIS EVENING. HOWEVER...MOST AREAS WILL BE DRY. THE ONSHORE FLOW WILL CONTINUE TONIGHT...CAUSING LOW CLOUDS AND PATCHY FOG TO DEVELOP. MIN TEMPS WILL RANGE FROM THE 50S IN THE POTOMAC HIGHLANDS AND SHENANDOAH VALLEY TO THE LOWER 60S IN DOWNTOWN WASHINGTON AND BALTIMORE. THE SURFACE RIDGE WILL REMAIN IN PLACE FOR SATURDAY...AND AN ONSHORE FLOW WILL CONTINUE. HOWEVER...THE SUBSIDENCE INVERSION SHOULD LOWER DUE TO RISING PRESSURES OVERHEAD BETWEEN A COLD FRONT OVER THE MIDWEST AND LOW PRESSURE DEVELOPING OFF THE SOUTH CAROLINA COAST. WITH A STRENGTHENING SUBSIDENCE INVERSION...THIS MEANS THAT ANY LOW CLOUDS AND FOG SATURDAY MORNING SHOULD GIVE WAY TO SUNSHINE. MAX TEMPS WILL RANGE FROM THE 70S IN THE MOUNTAINS TO NEAR 80 ACROSS THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... A COLD FRONT WILL APPROACH FROM THE GREAT LAKES/OHIO VALLEY DURING THE SECOND HALF OF THE WEEKEND. ABOVE AVERAGE TEMPERATURES WILL PRECEDE THE COLD FRONT...BUT MOISTURE RETURN FROM THE SOUTH WILL BE MEAGER. STILL...THE UPPER-LEVEL TROUGH FORCING THE COLD FRONT IS FORECAST TO BE PRETTY STRONG BY THE MODELS AND THAT SHOULD IN TURN FORCE NARROW BANDS OF SHOWERS AND THUNDERSTORMS. GUSTY OR PERHAPS SPOTTY DAMAGING WINDS ARE POSSIBLE MAINLY ACROSS WESTERN AREAS WHERE ADDED TERRAIN FORCING COULD RESULT IN BRIEFLY MORE ROBUST UPDRAFTS. SHOWERS AND THUNDERSTORMS WILL GRADUALLY WANE AS THEY PUSH EAST OF THE BLUE RIDGE AND TOWARDS THE CHESAPEAKE BAY DURING THE EVENING. THE COLD FRONT WILL MOVE OFFSHORE AS HIGH PRESSURE REBUILDS FROM CANADA RESULTING IN DRY AND COOLER THAN NORMAL TEMPERATURES TO START THE BEGINNING OF NEXT WEEK. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A DRY AND FALL-LIKE WEEK IS FORECAST FOR MOST OF NEXT WEEK AS A LARGE AREA OF CANADIAN HIGH PRESSURE SLOWLY PUSHES ACROSS THE NORTHERN/EASTERN CONUS AND RIDGING PERSISTS ALOFT. WITH LIGHT WINDS AND MOSTLY CLEAR SKIES AND SHALLOW MOISTURE IN LIGHT EASTERLY FLOW...THE SETUP COULD BE IDEAL ON MORE THAN ONE OCCASION FOR LATE NIGHT/EARLY MORNING FOG OR STRATUS NEXT WEEK. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AN ONSHORE FLOW WILL CONTINUE THROUGH SATURDAY. LOW CLOUDS ACROSS CENTRAL VIRGINIA MAY SPREAD NORTH AND EAST TONIGHT. CERTAINTY IS LOW AS TO HOW WIDESPREAD THE LOW CLOUDS WILL BE. FOR NOW...MVFR CONDITIONS ARE FORECAST OVER THE TERMINALS TONIGHT INTO SATURDAY MORNING...BUT IFR CONDITIONS ARE POSSIBLE. IFR CONDITIONS ARE LIKELY AT KCHO DURING THIS TIME. ANY LOW CLOUDS AND FOG WILL BURN OFF LATER SATURDAY MORNING AND VFR CONDITIONS ARE EXPECTED IN THE AFTERNOON. SUB-VFR PSBL SUN IN SPARSE COVERAGE SHWRS/TSTMS IN AFTN/EVE. WINDS SW 10 KTS SUN. VFR LIKELY SUNDAY NIGHT THROUGH TUESDAY NIGHT BEHIND FRONT W/ W WINDS 10-15 KTS W/ GUSTS TO 20 KTS PSBL SUN NIGHT-MON...THEN N LESS 10 KTS OR LESS MON NIGHT-TUE NIGHT. MODERATELY HIGH CONFIDENCE FORECAST IN OVERALL SETUP AS MODELS ARE IN AGREEMENT WITH TYPICAL TIMING DIFFERENCES REVOLVING AROUND THE WIND SHIFT IMMEDIATELY FOLLOWING THE FRONT AND THE TIMING OF HIGHER GUSTS. && .MARINE... AN ONSHORE FLOW WILL CONTINUE THROUGH SATURDAY AS HIGH PRESSURE REMAINS NEAR THE MID-ATLANTIC COAST. A PRESSURE SURGE WILL CAUSE WINDS TO INCREASE A BIT OVER THE WATERS TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER...BUT IT WILL BE MARGINAL. WINDS SHOULD BE A BIT WEAKER SATURDAY AS THE GRADIENT SUBSIDES A BIT. S FLOW AROUND 10 KTS OR SO AHEAD OF COLD FRONT SAT NIGHT-SUN ALONG W/ CHC OF SHWRS/TSTMS WHICH COULD BE ACCOMPANIED BY GUSTY WINDS SUN EVE. FRONT AND PRECIP CLEARS THE COAST SUN NIGHT AND WINDS BECOME W OR NW 10-15 KTS GUSTS 20 KTS. WINDS BECOME N 10 KTS MON NIGHT-WED BEFORE VEERING AROUND TO THE E LATER IN THE WEEK AS HIGH PRESSURE SLOWLY MIGRATES TO THE NORTH OF THE REGION. && .TIDES/COASTAL FLOODING... TIDAL ANOMALIES ARE AROUND ONE-HALF FOOT ABOVE NORMAL THIS AFTERNOON. THE SURFACE FLOW WILL CONTINUE TO TURN TOWARD THE SOUTHEAST THIS AFTERNOON AND A SOUTHEASTERLY FLOW WILL CONTINUE THROUGH SATURDAY. LOW PRESSURE WILL MOVE UP THE MID-ATLANTIC COAST SATURDAY NIGHT INTO SUNDAY...AND THIS MAY ENHANCE THE THREAT FOR ELEVATED WATER LEVELS. MINOR TIDAL FLOODING CANNOT BE RULED OUT WITH THE HIGH TIDE CYCLE LATE TONIGHT INTO EARLY SATURDAY MORNING...BUT CONFIDENCE IS NOT HIGH ENOUGH TO ISSUE A COASTAL FLOOD ADVISORY AT THIS TIME. THERE IS A BETTER CHANCE FOR MINOR TIDAL FLOODING WITH THE HIGH TIDE CYCLES LATER SATURDAY INTO SUNDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL/DFH LONG TERM...BJL/DFH AVIATION...BJL/DFH MARINE...BJL/DFH TIDES/COASTAL FLOODING...BJL

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