Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 301433 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1033 AM EDT TUE JUN 30 2015 .SYNOPSIS... LOW PRESSURE WILL SLIDE EASTWARD OVER THE EASTERN GREAT LAKES TODAY. A COLD FRONT WILL SLIDE SOUTHEAST INTO THE MID ATLANTIC ON WEDNESDAY...AND THEN STALL ACROSS THE REGION ON THURSDAY. THE STALLED FRONT WILL LINGER IN THE AREA THROUGH THE WEEKEND BEFORE LIFTING NORTHWARD AGAIN ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... SFC ANALY DEPCITS SUBTLE FETURES TODAY. TOUGH TO PIN DOWN SPECIFICALLY WHERE THE WMFNT IS...BUT CLERLY THERES CNVGNC INVOF THE BALT/DC CRRDR BASED ON SELY FLOW ACRS NERN MD VS S/SWLY FLOW ELSW WITHIN THE CWFA. THAT HAS RESULTED IN A PATCH OF CLDS IN THE METROS. A CLUSTER OF SHRA HV BEEN ABLE TO DVLP UNDER CLD DECK... WITH A HINT OF A LINE BGNG STRETCHING DOWN TO CHO. LWX 12Z RAOB DEPICTS WARM LYRS H10-8 AND AGN H6-5. HWVR...THE CURRENT RADAR SUGGESTS THAT MAY NOT BE A DETERRENT. THE MTNS/SHEN VLY SEEM TO BE GETTING ENUF HEATING...SO WUD XPCT INSTBY TO INTENSIFY. A MODIFIED SNDG...BASED ON LAMP AND A TEMP/DEWPT FCST OF 85/65F...SUGGESTS 1500-2000 J/KG SBCAPE AVBL. SHEAR MEASURED AT 30 KT...WHICH MDL PROGS RETAIN THRU THE DAY. IN TERMS OF EVOLUTION...OBVIOUSLY THE CNVGNC WL DOMINATE FOR THE MRNG. LWX WRF-ARW4 CAPTURING IT. HWVR...BELIEVE THAT TRRN CIRCUALTION SHUD DVLP IN THE BLURDG OR IN THE CRRDR OF HEATING IN THE SHEN VLY. HV POPS IN THE FORMER LOCATION FOR THE MORNING... THEN EXPAND CHC POPS ELSW BY ELY AFTN. SOME STRONG TO SEVERE STORMS COULD DEVELOP BASED ON MODIFIED RAOB AND THE MORE AGGRESSIVE MDL GDNC. THE PRIMARY THREAT WOULD BE LOCALIZED DAMAGING WIND GUSTS. HWVR THE SHEAR SUGGESTS A CPL SUPERCELLS NOT OUT OF THER QUESTION. WHILE THERE SHOULD BE AN OVERALL EASTWARD PROGRESSION AND DIURNAL WEAKENING OF ACTIVITY THIS EVENING...MODELS MAINTAIN ELEVATED INSTBY OVERNIGHT...AND MID/UPPER LEVEL TROUGH WILL BE APPROACHING TOWARD DAYBREAK. THEREFORE SOME SHOWERS AND STORMS MAY LINGER WELL INTO THE OVERNIGHT PERIOD. MIN TEMPS IN THE LOWER/MID 60S WEST AND UPPER 60S/LOWER 70S EAST. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... MID LEVEL TROUGH AXIS WILL BE LIFTING NORTH DURING THE MORNING HOURS. SFC COLD FRONT WILL BE APPROACHING FROM THE NORTHWEST BUT LIKELY WON/T ENTER THE AREA DURING THE DAYTIME HOURS. TIMING AND COVERAGE OF PRECIP QUITE UNCERTAIN WITHOUT STRONG FORCING MECHANISMS. IF FORECAST SOUNDINGS ARE CORRECT IN DECREASING INSTBY BEHIND THE TROUGH PASSAGE IN THE AFTERNOON...CONVECTION MAY BE RATHER LIMITED. HAVE MAINTAINED LOW CHANCE POPS THROUGHOUT DAY. ON WEDNESDAY NIGHT...THE COLD FRONT WILL STALL OUT OVER THE MID ATLANTIC JUST TO OUR SOUTH. SUPPORT ALOFT WILL WANE AS THE TROUGH PASSES SO EXPECT CONVECTION TO QUICKLY DISSIPATE OR MOVE AWAY. WITH THE FRONT STALLED IN THE AREA...GUIDANCE IS BEGINNING TO HONE IN ON A WAVE OF LOW PRESSURE MOVING EAST ALONG THE FRONT FROM THE MID MISSISSIPPI VALLEY THURSDAY OR THURSDAY NIGHT. HOWEVER...TIMING IS STILL MUCH IN QUESTION...SO GENERALLY KEEP CHANCE POPS AROUND WITH LIKELYS TO THE SOUTH CLOSER TO THE STALLED FRONT. WITH THE FRONT TO THE SOUTH AND INCREASED CLOUD COVER...TEMPS SHOULD BE COOLER ON THURSDAY. && .LONG TERM /FRIDAY THROUGH MONDAY/... THROUGH THE LONG TERM THE PATTERN WILL REMAIN FAIRLY STATIC WITH A BROAD TROUGH OVER CANADA...AND A STRONG RIDGE OUT WEST. THIS WILL KEEP FUNNELLING DISTURBANCES SOUTHEAST AND EAST ACROSS OUR AREA AS A FRONTAL BOUNDARY REMAINS STALLED OUT OVER THE REGION. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE EACH DAY WITH THE FRONT NEARBY BUT TIMING DISTURBANCES WILL BE INCREASINGLY DIFFICULT AS WE GO FURTHER OUT. RIGHT NOW ONE SYSTEM MAY AFFECT US SATURDAY...AND ANOTHER MONDAY...BUT CONFIDENCE ON TIMING IS NOT HIGH. SO...GENERALLY HAVE KEPT TEMPS A BIT BELOW NORMAL...WITH A CHANCE OF SHOWERS AND THUNDERSTORMS IN THE FORECAST EACH DAY. AS WE GET CLOSER...WE SHOULD HAVE BETTER CLARITY AS FAR AS DAYS WHICH WILL TURN OUT MOSTLY RAIN-FREE...AND THOSE WHICH WILL BE PRETTY WET. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... SOUTHERLY WINDS WILL INCREASE DURING THE MIDDAY WITH OCNL GUSTS TO 20 KT. THUNDERSTORM COVERAGE AND TIMING STILL LOWER CONFIDENCE TODAY. CONVERGENCE DVLPG SOME STORMS INVOF DCA/IAD/BWI THIS MRNG. THINK THE ACTIVITY SHUD JUMP TO THE BLURDG DURING THE AFTN. HWVR...CANNOT RULE ANYTHING OUT IN TERMS OF TIMING AND PLACEMENT. RESTRICTIONS WUD BE BRIEF...BUT MVFR/IFR POTL EXISTS. STRONG WIND GUSTS COULD ACCOMPANY ANY STORM. DISTURBANCE CROSSES AREA LATE TONIGHT/WED MORNING...SO A SHOWER OR STORM WILL REMAIN POSSIBLE...BUT LOWER POTENTIAL FOR CIG/VSBY REDUCTIONS. QUESTIONABLE HOW MUCH OF THIS ACTIVITY LINGERS/REDEVELOPS WED AFTERNOON...LOW CHANCE OF IMPACTS. MAIN CONCERN THROUGH EXTENDED IS POTENTIAL FOR SCATTERED THUNDERSTORMS EACH DAY. WINDS WILL BE UNCERTAIN GIVEN THE FRONT WILL CONTINUE TO MEANDER IN THE AREA AFTER ARRIVING WEDNESDAY. WAVE OF LOW PRESSURE MAY PROVIDE A MORE CONCENTRATED PERIOD OF RAIN AND IFR CIGS/VIS AT SOME POINT THURSDAY...FRIDAY OR SATURDAY BUT LOW CONFIDENCE RIGHT NOW ON WHEN THIS IS...OR IF IT EVEN HAPPENS. && .MARINE... S/SE CHANNELING OCCURING OVER THE WATERS. SCA IN EFFECT. THUNDERSTORMS WILL DEVELOP WITH THE POTENTIAL FOR STRONG WIND GUSTS-- SOME SMW/S ARE POSSIBLE. GRADIENT WINDS WILL DIMINSH OVERNIGHT. SW FLOW THROUGH WED AROUND 10 KT...ALTHOUGH MAY BE SLIGHTLY STRONGER TOWARD TANGIER SOUND. LOWER CHANCE OF STORMS THROUGH WED. WINDS EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH THE EXTENDED...THOUGH WILL NEED TO MONITOR AS FRONT WILL BE NEAR AREA EACH DAY. SHOWERS AND TSTMS ARE ALSO POSSIBLE EACH DAY...WHICH COULD IMPACT MARINE CONCERNS. && .TIDES/COASTAL FLOODING... WATER LVLS WL BE INCREASING THRU MID WEEK. THE WATER LVLS TOPPED OUT ON THE EDGE OF ADVY CRITERIA THIS MORNING AT WASD2 AND AXTV2. BETTER CHC TMRW DURING THE SAME TIME CYCLE...MIDNGT THRU NOON. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT WEDNESDAY FOR ANZ531>534- 536-537-539>543. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530- 535-538. && $$ SYNOPSIS...RCM NEAR TERM...ADS/HTS SHORT TERM...ADS/RCM LONG TERM...RCM AVIATION...ADS/RCM/HTS MARINE...ADS/RCM/HTS TIDES/COASTAL FLOODING...HTS

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