Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | 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 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 311901 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 301 PM EDT MON AUG 31 2015 .SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL REMAIN OFFSHORE THROUGH TUESDAY. AN UPPER- LEVEL DISTURBANCE ALONG WITH ITS ASSOCIATED SURFACE TROUGH WILL PASS THROUGH THE REGION WEDNESDAY. WEAK HIGH PRESSURE WILL BUILD OVERHEAD THURSDAY BEFORE A BACKDOOR COLD FRONT MOVES INTO THE AREA LATE FRIDAY INTO THE WEEKEND.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TUESDAY/...
-- Changed Discussion --
SEVERAL COMPETING FACTORS IN REGARDS TO CONVECTION THIS AFTERNOON. VORT MAX IS LIFTING NE ACROSS THE AREA...WITH RAPID CLEARING IN THE SUBSIDENCE BEHIND IT. HOWEVER...CUMULUS HAVE FILLED IN OVER THE HIGHER TERRAIN. THIS FEATURE HAS ONLY PROVIDED A FEW LIGHT SHOWERS AS MOST MOISTURE IS IN THE MID LEVELS. MEANWHILE LOW LEVEL CONVERGENT BOUNDARY IS SINKING SOUTH AND THIS IS WHERE SCATTERED CONVECTION HAS FORMED IN SOUTHERN PA/WESTERN MD. ALL TOLD...THINK THIS WILL LEAD TO MOST OF THE CONVECTION REMAINING MAINLY N AND W OF DC...WHERE BETTER INSTBY IS ALSO LOCATED. CAN/T RULE OUT ISOLATED DEVELOPMENT ELSEWHERE THOUGH. PRECIP CHANCES WILL SINK SOUTH WITH DEEPER MOISTURE THIS EVENING...EVENTUALLY DISSIPATING. SKIES WILL LIKELY BECOME MOSTLY CLEAR ACROSS THE MAJORITY OF THE AREA...ALTHOUGH SOME CLOUDS COULD LINGER IN THE S/W. WITH WINDS CALM AND ELEVATED DEW POINTS...SOME PATCHY FOG COULD DEVELOP DEPENDENT ON CLOUD COVER. FAVORED AREAS WOULD BE S/W OF METROS. LOWS IN THE 60S WITH LOWER 70S ALONG AND EAST OF I-95. BROAD SFC RIDGING REMAINS IN PLACE ON TUESDAY. MID AND UPPER LEVEL RIDGING WILL ALSO BUILD...AND A CLOSED LOW OVER THE OHIO VALLEY WILL REMAIN TO THE WEST. ATMOSPHERE WILL LIKELY BE CAPPED OVER MOST OF THE AREA...SO HAVE LEFT THE SMALL CHANCE OF DIURNAL CONVECTION LIMITED TO THE WESTERN TERRAIN. WITH MOSTLY SUNNY SKIES EAST OF THE MOUNTAINS...HIGHS SHOULD BE ABLE TO NEAR OR EXCEED 90 IN MANY LOCATIONS. HEAT INDICES SHOULD REMAIN BELOW 100 THOUGH.
-- End Changed Discussion --
&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
ANY MOUNTAIN CONVECTION WILL WANE DURING THE EVENING. OTHERWISE CONTINUED MUGGY CONDITIONS ARE EXPECTED AS WEATHER PATTERN CHANGES VERY LITTLE. LOWS COULD EVEN BE A DEGREE OR TWO HIGHER...WITH MORE LOCATIONS IN THE UPPER 60S TO LOWER 70S. AN UPPER-LEVEL DISTURBANCE AND ITS ASSOCIATED SURFACE TROUGH WILL PASS THROUGH THE REGION LATER WEDNESDAY INTO WEDNESDAY EVENING. MORE UNUSUALLY WARM AND HUMID CONDITIONS WILL CONTINUE...BUT THERE WILL BE AN INCREASED CHANCE FOR A SHOWER OR THUNDERSTORM. THE BEST CHANCE FOR CONVECTION WILL BE ACROSS THE POTOMAC HIGHLANDS INTO CENTRAL VIRGINIA...CLOSER TO TRACK OF THE UPPER-LEVEL DISTURBANCE. MOST CONVECTION SHOULD DISSIPATE WEDNESDAY EVENING AS THE UPPER- LEVEL DISTURBANCE AND SURFACE TROUGH MOVE OFF TO OUR SOUTH AND EAST. A NORTHWEST FLOW IS EXPECTED BEHIND THE TROUGH...BUT WITH NO TEMPERATURE OR DEWPOINT GRADIENT MORE WARM AND HUMID CONDITIONS ARE EXPECTED. WEAK HIGH PRESSURE WILL BUILD TOWARD THE AREA THURSDAY. A NORTHWEST FLOW WILL CONTINUE...BUT AGAIN MORE HOT AND HUMID CONDITIONS ARE EXPECTED DUE TO SUNSHINE AND A DOWNSLOPING FLOW. AN ISOLATED SHOWER OR THUNDERSTORM MAY POP UP ACROSS THE HIGHER TERRAIN...BUT MOST OF THE TIME WILL BE DRY.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
WARM AND HUMID CONDITIONS WILL CONTINUE THURSDAY NIGHT...BUT MOST AREAS WILL TURN OUT DRY. A BACKDOOR COLD FRONT WILL APPROACH THE REGION FRIDAY BEFORE MOVING INTO THE AREA SATURDAY. THE BOUNDARY MAY TRIGGER A FEW SHOWERS AND THUNDERSTORMS. COOLER AND LESS HUMID CONDITIONS ARE POSSIBLE BEHIND THE BOUNDARY LATER THIS WEEKEND. THERE IS STILL SOME UNCERTAINTY THOUGH AS TO HOW FAR SOUTH AND WEST THE BOUNDARY WILL MAKE IT. HIGH PRESS BUILDS IN SUN THROUGH MON BRINGING DRIER CONDITIONS.
-- End Changed Discussion --
&& .AVIATION /19Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF MID-AFTERNOON...TRENDS SUGGEST MOST SHOWERS AND STORMS WILL REMAIN NW OF THE METRO AREAS THROUGH THIS AFTERNOON. HOWEVER CANNOT RULE OUT AN ISOLATED SHOWER AFFECTING A TERMINAL BY LATE AFTERNOON. IMPACTS WOULD BE BRIEF IF THIS WERE TO OCCUR. CHANCE WILL DIMINISH WITH SUNSET. ASSUMING SKIES CLEAR TONIGHT...BR WILL LIKELY DEVELOP AT MRB/CHO. CONFIDENCE TO LOW TO INCLUDE AT IAD FOR NOW. FOR TUESDAY...STORMS SHOULD REMAIN WEST OF THE TERMINALS. WINDS REMAIN UNDER 10 KT THROUGH THE TAF PERIOD. VFR CONDITIONS ARE EXPECTED MOST OF THE TIME WEDNESDAY AND THURSDAY. A POPUP THUNDERSTORM IS POSSIBLE WEDNESDAY AFTERNOON AND EVENING. PATCHY BR MAY BRIEFLY REDUCE VSBYS EARLY WEDNESDAY MORNING AND AGAIN EARLY THURSDAY MORNING. VFR CONDITIONS EXPECTED THU NIGHT. SUB VFR CONDITIONS PSBL DUE TO SHOWERS AND TSTMS ON FRI.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
SOUTHWEST FLOW WILL CONTINUE ACROSS THE WATERS THROUGH TONIGHT. SPEED COULD INCREASE THIS EVENING...BUT HAVE CAPPED AT 15 KT GIVEN THE SW COMPONENT. AN ISOLATE SHOWER OR STORM IS POSSIBLE NEAR THE DC/BALTIMORE AREA THROUGH EVENING...BUT THESE SHOULD BE WEAK IF THEY OCCUR. HIGH PRESSURE BECOMES REESTABLISHED TUESDAY AND FLOW WILL BE VARIABLE AND UNDER 10 KT. WINDS SHOULD REMAIN BELOW SCA CRITERIA WEDNESDAY AND THURSDAY. A BACKDOOR COLD FRONT WILL PASS THROUGH THE WATERS LATE FRIDAY INTO SATURDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS DURING THIS TIME. HIGH PRESSURE WILL RETURN FOR EARLY NEXT WEEK.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BJL NEAR TERM...ADS SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/ADS/IMR MARINE...BJL/ADS/IMR

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