Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 260754 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 354 AM EDT SUN OCT 26 2014 .SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL BUILD OVERHEAD THROUGH TONIGHT BEFORE MOVING OFF THE COAST MONDAY AND TUESDAY. A COLD FRONT WILL PASS THROUGH THE AREA WEDNESDAY AND HIGH PRESSURE MAY RETURN FOR THURSDAY INTO FRIDAY.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AN ATYPICAL COLD FRONTAL PASSAGE AND ATMOSPHERE OVER THE AREA ATTM. AS OF 3AM...IAD IS 61F AND LOCATIONS SOME 2-3 COUNTIES TO THE SOUTH AND EAST ARE 10-15F COOLER. SAME STORY BACK EVEN FURTHER TO THE NORTH AND WEST - THE OPPOSITE OF WHAT IS TYPICAL NOT ONLY IN A LATITUDE SENSE BUT ALSO CONSIDERING A COLD FRONT SHOULD HAVE THE COLD AIR BEHIND IT - NOT OUT AHEAD OF IT. BUT MORE IS GOING ON THAN JUST A WARM-SECTOR AHEAD OF THE FRONT AND CAA BEHIND. LOW LEVEL MOISTURE TRAPPED IN A CORRIDOR IN THE LEE OF THE BLUE RIDGE HAS HELPED CREATE A STABLE LAYER FOR THE INCOMING WINDS FROM THE WEST. DEWPOINTS W OF THE RIDGE HAVING NO TROUBLE DROPPING WELL INTO THE 30S BUT TEMPS HAVE ALSO INCREASED BEHIND THE BOUNDARY INTO THE L60S. FURTHER SOUTH AND EAST OVER THE NRN VA PIEDMONT...TEMPS HAVE SETTLED DOWN IN THE 40S. ANOTHER COUPLE OF HRS THOUGH AND TEMPS WILL BEGIN TO DROP BACK DOWN INTO THE 50S ACROSS THE ENTIRE REGION...FOR THOSE THAT ARE IN THE 60S AS WELL. A FEW WAVE-TYPE CLOUDS THAT ARE MAKING THEIR WAY ACROSS THE REGIONAL SKIES ATTM WILL DISSIPATE AND PROPAGATE WELL E OF THE AREA BY THE POST-DAWN HRS. CLEAR SKIES THRU THE DAYTIME HRS TODAY W/ A REBOUND IN TEMPS BACK TOWARD YDA`S LEVELS BUT W/ DRY AND GUSTY WINDS. BLENDED THE VARIOUS WRF DERIVATIVES FOR HOURLY WINDS FOR TODAY...SHOWING THE AREAL WAVE-LIKE PATTERN TO THE GUSTS OVER THE MTNS/FOOTHILLS. RELATIVELY HIGHER TEMPS...LOW HUMIDITIES AND GUSTY WINDS ALONG W/ FUEL MOISTURES THAT HAVE BEEN DROPPING OVER THE PAST FEW DAYS WILL CREATE AN ENHANCE FIRE THREAT...SEE THE FIRE WX SECTION BELOW FOR FURTHER DETAILS. WITH SFC DEWPOINTS FIRMLY HOLDING IN THE 30S OVERNIGHT...TEMPS WILL MAKE A SIMILAR DROP TONIGHT. MANY AREAS WILL DROP WELL INTO THE 40S AND MUCH OF THE PIEDMONT/SHELTERED VLYS WILL REACH THE M-U30S FOR OVERNIGHT LOWS. PATCHY FROST WILL BE POSSIBLE IN AREAS THAT DO REACH THESE LOWER TEMP VALUES AND CAN HAVE WINDS DECOUPLE AFTER A BREEZY DAY. MOST OF THE AREA SHOULD SEE WINDS DROP OFF SHORTLY AFTER SUNSET...BUT A FEW RESIDUAL GUSTS EXPECTED INTO THE EARLY MRNG HRS.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
-- Changed Discussion --
MONDAY WILL BE MUCH LIKE SATURDAY - A PLEASANT TRANSITION DAY W/ HIGH PRESSURE REBOUNDING FROM THE DEEP SOUTH AFTER GETTING PUSHED OUT OF THE AREA TODAY. A CHANGE IN THE WIND FIELD WILL TURN OUR SFC WINDS TO SLY...BRINGING BACK SOME WARMTH AND INCREASING LOW LEVEL MOISTURE. THE HIGHLANDS WILL BENEFIT THE MOST FROM THIS REGIME...W/ TEMPS CLIMBING WELL INTO THE 70S - SOME LOCALES NEAR 80F IN THE SHELTERED APLCN VLYS. A BIT MORE OF A COMPLEX SOLUTION FOR THE PIEDMONT/COASTAL AREAS...W/ TEMPS ALSO CLIMBING INTO THE SEASONAL AVG`S BUT THE COOLER AIR WILL RESIDE OVER EXTREME NERN MD. BIAS-CORRECTED MAV/MEX SEEMED TO HAVE THE BEST HANDLE ON THIS - W/ SOME EURO CONTRIBUTIONS AS WELL. CLOUD-FREE AND DRY FOR THE MONDAY...W/ SOME CIRRUS MOVING IN FROM THE NW LATER IN THE DAY. HIGH PRESSURE WILL MOVE INTO THE ATLANTIC OCEAN MONDAY NIGHT AND TUESDAY WHILE A COLD FRONT APPROACHES FROM THE WEST. A SOUTHERLY FLOW WILL INCREASE BETWEEN THESE SYSTEMS. THIS WILL ALLOW FOR MILDER CONDITIONS MONDAY NIGHT COMPARED TO SUNDAY NIGHT...AND TUESDAY WILL TURN OUT QUITE WARM FOR THIS TIME OF YEAR AS THE SOUTHERLY FLOW STRENGTHENS. MAX TEMPS TUESDAY WILL RANGE FROM THE MID AND UPPER 70S NEAR WASHINGTON AND BALTIMORE...TO THE LOWER 80S IN CENTRAL VIRGINIA.
-- End Changed Discussion --
&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
THE COLD FRONT WILL SLOWLY PASS THROUGH THE AREA LATE TUESDAY NIGHT AND WEDNESDAY. CLOUDS WILL INCREASE AHEAD OF THIS SYSTEM AND A FEW SHOWERS ARE POSSIBLE DURING THIS TIME. HOWEVER...PRECIPITATION AMOUNTS SHOULD BE LIGHT SINCE LITTLE MOISTURE WILL BE ASSOCIATED WITH THE BOUNDARY. HIGH PRESSURE WILL RETURN FOR WEDNESDAY NIGHT AND THURSDAY...BRINGING A RETURN OF DRY AND SEASONABLY COOL CONDITIONS. AN UPPER-LEVEL TROUGH WILL SWING THROUGH THE AREA FRIDAY INTO SATURDAY. UNCERTAINTY IN THE STRENGTH AND TIMING OF THIS SYSTEM REMAIN HIGH. THERE WILL BE A CHANCE FOR SHOWERS DURING THIS TIME...AND THERE MAY BE ENOUGH COLD AIR FOR SOME SNOW SHOWERS ALONG THE RIDGE TOPS.
-- End Changed Discussion --
&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
VFR CONDS THRU THE CURRENT TAF PERIOD...BUT A CHALLENGING SITUATION CREATED BY AN INCOMING COLD FRONT. WEST OF THE BLUE RIDGE...BOUNDARY LAYER WINDS HAVE BEEN ABLE TO NEAR-FULLY FIX DOWN...CREATING THE 20-30KT GUSTS THAT HAVE BEEN APPEARING IN MANY POTOMAC HIGHLAND OBS IN RECENT HRS. EAST OF THE BLUE RIDGE...A MORE STABLE ATMOS HAS CUT DOWN SUBSTANTIALLY ON THESE GUSTS BUT MORE RECENTLY THIS LAYER HAS SHOWN SIGNS OF MIXING-OUT. THRU 12Z...LOCALES ACROSS THE I-95 CORRIDOR AND NEARBY TAF SITES SHOULD PREPARE FOR BRIEF GUSTS IN THE 20-30KT RANGE W/ INTERMITTENT PERIODS OF LIGHTER WINDS. POST-SUNRISE...THE MORE STEADY AND WIDESPREAD GUSTS IN THE 20-30KT RANGE WILL BEGIN AND CONTINUE WELL INTO THE AFTN HRS. BY LATE THIS AFTN/EVE...THE TOP-END GUSTS WILL SUBSIDE BACK TOWARD 15-20KT THEN DROP OFF AFTER SUNSET. HIGH PRESSURE WILL BUILD BACK INTO THE AREA ON MONDAY...ALLOWING SFC WINDS TO SWITCH TO SLY THRU THE DAYTIME HRS AND CLEAR SKIES FOR ALL SITES TODAY INTO MONDAY. VFR CONDITIONS ARE EXPECTED MOST OF THE TIME MONDAY NIGHT THROUGH THURSDAY. GUSTY SOUTHWEST WINDS ARE POSSIBLE TUESDAY AFTERNOON. A COLD FRONT WILL BRING A CHANCE FOR SHOWERS LATE TUESDAY NIGHT AND WEDNESDAY. CIGS/VSBYS MAY APPROACH MVFR LEVELS DURING THIS TIME.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
A COLD FRONT PUSHING ACROSS THE AREA WILL EVENTUALLY SPREAD SOLID SCA GUSTS ACROSS THE WATERS IN THE COMING HRS AND CONTINUE THROUGHOUT THE DAY. A FEW NEAR-GALE GUSTS IN THE U20KT RANGE WILL BE POSSIBLE AT ISOLATED LOCALES DURING THIS TIME PERIOD BUT THE OVERWHELMING RANGE WILL BE A GENERAL 20-25KT. HIGH PRESSURE WILL BUILD INTO THE AREA AGAIN STARTING LATER THIS AFTN...SLOWLY DROPPING WINDS BACK DOWN INTO THE 5-10KT AND SWITCH THE FLOW TO SLY HEADING INTO MONDAY. A COLD FRONT WILL APPROACH THE WATERS MONDAY NIGHT AND TUESDAY. SOUTHERLY WINDS WILL INCREASE TUESDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS TUESDAY INTO TUESDAY NIGHT. THE COLD FRONT WILL PASS THROUGH THE WATERS WEDNESDAY. HAVE CAPPED GUSTS AROUND 15 KNOTS FOR NOW DUE TO THE RELATIVE WEAK PRESSURE GRADIENT. HOWEVER...A PRESSURE SURGE MAY CAUSE WIND GUSTS TO EXCEED SCA CRITERIA WEDNESDAY NIGHT INTO THURSDAY FOR PORTIONS OF THE WATERS.
-- End Changed Discussion --
&& .FIRE WEATHER...
-- Changed Discussion --
GUSTY WINDS ARE EXPECTED BEHIND A COLD FRONT TODAY. THE GUSTY WINDS ALONG WITH LOW RELATIVE HUMIDITY AND LOW FUEL MOISTURE WILL ENHANCE THE THREAT FOR THE SPREAD OF WILDFIRES LATE THIS MORNING AND AFTERNOON. WILL CONTINUE WITH A SPECIAL WEATHER STATEMENT FOR THE ENHANCED THREAT ACROSS THE CENTRAL SHENANDOAH VALLEY INTO THE POTOMAC HIGHLANDS OF VIRGINIA. THE RELATIVE HUMIDITY WILL BE LOWEST ACROSS THESE AREAS. ELSEWHERE...THE RELATIVE HUMIDITY MAY BE A BIT HIGHER BUT WINDS WILL BE GUSTY.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT MONDAY FOR ANZ530>534-537- 539>541-543. SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ535- 536-538-542. && $$ SYNOPSIS...BJL NEAR TERM...GMS SHORT TERM...BJL/GMS LONG TERM...BJL AVIATION...BJL/GMS MARINE...BJL/GMS FIRE WEATHER...BJL/GMS

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.