Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 231407 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1007 AM EDT SAT AUG 23 2014 .SYNOPSIS... A WEAK COLD FRONT WILL PUSH WESTWARD THROUGH THE APPALACHIANS TODAY. HIGH PRESSURE WILL BUILD FROM THE CANADIAN MARITIMES DOWN THE COAST...REACHING THE DELMARVA BY SUNDAY...AND REMAINING THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... LATEST ANALYSIS SHOWS HIGH PRESSURE EXTENDING THROUGH NEW ENGLAND. A WEAK COLD FRONT IS LOCATED NEAR THE APPALACHIAN MOUNTAINS AND AN EASTERLY FLOW BEHIND THE BOUNDARY HAS CAUSED MOISTURE TO MOVE IN FROM THE ATLANTIC. THE EASTERLY FLOW WILL CONTINUE ACROSS MOST OF THE AREA AS THE COLD FRONT SLOWLY MOVES WEST INTO THE APPALACHIAN MOUNTAINS TODAY. PLENTY OF MOISTURE WILL REMAIN OVERHEAD DUE TO THE ONSHORE FLOW. ALSO...THE FRONT IS RELATIVELY SHALLOW WHICH MEANS THE 850 MB FRONT IS STILL OVERHEAD. THIS IS PROVIDING ENOUGH FORCING FOR SHOWERS DESPITE DRIER AIR MOVING IN ALOFT. SHOWERS ARE LIKELY FOR THE REST OF TODAY WITH THE 850MB BOUNDARY REMAINING OVERHEAD. THERE IS SOME CONCERN FOR LOCALLY HEAVY RAINFALL. PWATS ARE DROPPING A BIT AS DRIER AIR MOVES IN ALOFT...BUT PLENTY OF LOW- LEVEL MOISTURE REMAINS. ALSO...WARM RAIN PROCESSES ARE EXPECTED WITH THE LOW-TOPPED CONVECTION. DO NOT FEEL THE THREAT IS WIDESPREAD ENOUGH TO WARRENT A FLASH FLOOD WATCH AT THIS TIME SINCE ANY HEAVY RAIN WILL BE LOCALIZED AND FLASH FLOOD GUIDANCE REMAINS HIGH ACROSS MOST AREAS. THE HIGH WILL CONTINUE PUSH SOUTH AND WEST...CAUSING LOWER DEWPT AIR AND SUBSIDENCE TO INFILTRATE FM THE NE. THE AXIS OF PCPN WL BE PUSHED WWD LATER TONIGHT. WL START THE EVNG HRS W/ POPS AREAWIDE /40-60 PCT... BUT WL BE CARVING AWAY AT THAT FM E TO W OVERNIGHT. FEW CHGS TO TEMPS REQD. KEPT GOING MAXT FCST LOWER TO MIDDLE 70S ACROSS NORTHERN MARYLAND TO NEAR 80 IN THE CENTRAL SHENANDOAH VALLEY. IF PCPN HAS ENUF STAYING POWER...IT/LL BE TUFF TO SEE MUCH OF A TEMP RISE. KEPT MIN-T TNGT LWR-MID 60S...AS DEWPTS WL BE A LTL BIT SLOW TO DROP. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... H5 HGTS WL BE RISING SUN AS SFC HIPRES BLDS DOWN THE COAST. AS A RSLT...CLDS SHUD BE BREAKING APART...1ST IN THE NE...BUT EVENTUALLY AREAWIDE. MTNS WL BE LAST. HV KEPT FCST DRY...BUT RECOGNIZE THERE MAY BE A LINGERING MRNG SPRINKLE OR TWO IN THE APLCNS S OF W99. MOS IN GOOD AGREEMENT ON MAXT /NEAR 80/...AND SEE NO REASON TO ARGUE. DEWPTS WL BE DROPPING...AND SHUD BE IN THE UPR 50S SUN NGT. HENCE... MON MRNG MIN-T COOLER...MID 50S TO LWR 60S. && .LONG TERM /MONDAY THROUGH FRIDAY/... POSITIVELY TILTED UPPER RIDGE AND SURFACE HIGH PRESSURE WILL THEN DOMINATE THROUGH MID NEXT WEEK WITH SLOWLY MODERATING TEMPERATURES AND HUMIDITY. POSITION OF UPPER FLOW LOOKS TO KEEP ANY TROPICAL SYSTEM ACTIVITY OFFSHORE THE MID-ATLANTIC NEXT WEEK AS WELL. RETURN FLOW SETS IN WITH TEMPS BACK TO NORMAL FOR THURSDAY AHEAD OF A PROGRESSIVE UPPER TROUGH MOVING ACROSS THE NORTHERN CONUS. THIS DEEPENING TROUGH DRAGS A SEASONABLY STRONG COLD FRONT THROUGH THE REGION FOR THE END OF THE WORK WEEK...WITH FRIDAY LOOKING TO BE BACK IN THE UPPER 70S/LOW 80S ATTM. DEEP-LAYER WIND SHEAR AND INSTABILITY MAY BE FAVORABLE FOR SOME ORGANIZED CONVECTION WITH THIS COLD FROPA. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... SHOWERS ARE LIKELY TODAY WITH MVFR CIGS FOR MOST OF THE TIME. BRIEF IFR CONDITIONS CANNOT BE RULED OUT IN HEAVIER SHOWERS. MAY HV FLGT RESTRICTIONS AGN LT TNGT NEAR MRB/CHO. OTRW...DRIER AIR WL BE COMING DOWN FM THE NE...WHICH SHUD MAINTAIN VFR OVNGT FOR THE METROS. SKIES CLEAR FROM INCREASING HIGH PRESSURE SUNDAY. HIGH PRESSURE/VFR WILL PREVAIL THROUGH MIDWEEK. && .MARINE... AN EASTERLY FLOW WILL CONTINUE THROUGH TONIGHT. A WEAK PRESSURE SURGE MAY CAUSE GUSTS NEAR SCA CRITERIA TONIGHT...BUT GUSTS HAVE BEEN CAPPED AROUND 15 KNOTS FOR NOW SINCE THERE WILL BE LITTLE TO NO MIXING. HIPRES BLDS DOWN THE COAST TMRW. ELY FLOW WL CONT...BUT AT 5-10 KT SUSTAINED /MAYBE CLSR TO 10 KT FOR THE MID BAY/OPEN WATERS/...AND THEN DIMINISHING SUN NGT. HIGH PRESSURE WILL THEN BUILD ACROSS THE AREA SUNDAY THROUGH MID WEEK. NO FLAGS ANTICIPATED. && .TIDES/COASTAL FLOODING... A PERSISTENT ONSHORE FLOW WILL CAUSE TIDAL ANOMALIES TO RISE TO AROUND ONE FOOT ABOVE NORMAL. THE PM TIDE TODAY IS THE LOWER OF THE TWO ASTRONOMICALLY...BUT WITH THE FCST WATER LVL INCREASE SHOULD END UP BEING SIMILAR TO THE MRNG TIDE...IF NOT A PINCH HIGHER. THE CONCERN COMES LATE TNGT INTO ELY SUN MRNG...WHEN DEPARTURES OF A FOOT WL CAUSE WATER TO APPROACH MINOR THRESHOLDS FOR SENSITIVE LOCATIONS ON THE WESTERN SHORE AND TIDAL POTOMAC. ELY FLOW WILL CONTINUE INTO MONDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...HTS NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...AEB AVIATION...BJL/AEB/HTS MARINE...BJL/AEB/HTS TIDES/COASTAL FLOODING...BJL/HTS

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