Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 020136 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 936 PM EDT TUE SEP 1 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN CENTERED TO THE WEST THROUGH TONIGHT. 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. && .NEAR TERM /THROUGH WEDNESDAY/... SFC HIGH PRESSURE IS CENTERED OVER WEST VIRGINIA THIS EVENING WITH A WEAK LOW OFF CAPE HATTERAS. ALOFT...RIDGING IS CENTERED ALONG THE EASTERN SEABOARD WITH A CUTOFF LOW NEAR THE INDIANA/OHIO BORDER. MOST CONVECTION HAS DIMINISHED AT THIS HOUR BUT A FEW STRAY SHOWERS REMAIN WEST OF THE BLUE RIDGE. THESE SHOULD CONTINUE TO GRADUALLY WANE. LIGHT TO CALM WINDS AND ELEVATED DEW POINTS WILL RESULT IN ANOTHER NIGHT WHERE FOG IS POSSIBLE. THE UNCERTAINTY FACTOR TONIGHT WILL BE THE APPROACH OF CLOUDS FROM THE WEST AS THE WEAKENING LOW APPROACHES. AS A RESULT...THE VA PIEDMONT MAY ONCE AGAIN BE THE FAVORED LOCATION. THERE ALSO APPEARS TO BE SOME FAIRLY THICK HAZE TRAPPED UNDER THE INVERSION...WHICH IS ALSO RESULTING MINOR VISIBILITY REDUCTIONS. LOWS WILL ONLY FALL TO THE MID 60S TO LOWER 70S. THE CLOSED LOW IS FORECAST TO OPEN AND DIVE SOUTHEAST WEDNESDAY AS RIDGING BUILDS OVER THE PLAINS. THE TRACK ISN/T MUCH DIFFERENT THAN THE OVERNIGHT FORECAST BUT IS STILL FARTHER SOUTH THAN PREVIOUS DAYS. WHILE THE UPPER LEVEL TROUGH AND WEAK SFC REFLECTION WILL BE A SOURCE OF LIFT...APPEARS THE MAIN VORT MAX WILL JUST CLIP THE SOUTHWESTERN CWA. THEREFORE HAVE FOCUSED HIGHEST POPS THERE. IT IS QUITE POSSIBLE THAT DC...AND ESPECIALLY BALTIMORE...SEE LITTLE TO NO ACTIVITY. MAY SEE SHOWERS DEVELOP BEFORE TYPICAL DIURNAL TIMING DEPENDING ON TIMING OF FORCING. INSTBY AND SHEAR ARE NOT VERY IMPRESSIVE...SO DO NOT HAVE MUCH OF A SEVERE CONCERN. HIGHS MAY BE DEPENDENT ON CLOUD COVER...BUT UPPER 80S TO LOWER 90S ARE STILL SUPPORTED ACROSS MUCH OF THE AREA...AND IF CLOUDS HOLD OFF IT COULD VERY WELL BE JUST AS HOT ON WEDNESDAY AS IT WAS ON TUESDAY. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... THE TROUGH ALOFT WILL BE EAST OF THE AREA BY AROUND 06Z...SO HAVE THE LINGERING POPS IN THE SOUTHEAST CWA ENDING BY THEN. THERE SHOULD BE SOME CLEARING...ESPECIALLY IN NORTHERN AREAS. HOWEVER WITH LITTLE CHANGE TO THE LOW LEVEL AIR MASS...IT WILL AGAIN BE MUGGY WITH LOWS IN THE MID 60S TO LOWER 70S...AND FOG WILL AGAIN BE POSSIBLE. THU...WEAKENING UPPER LEVEL SHORT WAVE WILL BE SOUTH AND EAST OF CWA LEAVING US IN REGION OF HEIGHT RISES AND SUBSIDENCE. ANOTHER IN A STRING OF DAYS WITH TEMPERATURES 5-10 DEGREES ABOVE NORMAL...WITH HIGHS IN U80S/L90S. MODERATE HUMIDITY WITH DEWPOINTS IN M60S...BUT LITTLE CHANCE OF MEANINGFUL PRECIP...AS LAPSE RATES REMAIN POOR AND THERE IS LITTLE FORCING FOR ASCENT. AS SUCH...EXPECT ONLY ISOLATED AFTERNOON ACTIVITY ALONG/WEST OF BLUE RIDGE...WITH MOST AREAS REMAINING DRY MOST OF THE TIME. FRI...AFTER SEVERAL DAYS OF TEMPERATURES IN THE U80S/L90S...THERE COULD BE A LITTLE RELIEF BY FRIDAY...AS WEAK BACK DOOR COLD FRONT NUDGES INTO THE AREA. CURRENT FRONTAL AND THUNDERSTORM TIMING OCCURS EARLY ENOUGH THAT DAYTIME HIGHS MIGHT BE A FEW DEGREES LOWER THAN PREVIOUS DAYS...GENERALLY IN M/U80S...THOUGH STILL ABOVE NORMAL. HEAT AND HUMIDITY REMAIN IN PLACE AHEAD OF THE FRONT AND MID-LEVEL TEMPS COOL SLIGHTLY...WHICH WILL LEAD TO AT LEAST LOW-END SHOWER AND THUNDERSTORM CHANCES ACROSS THE ENTIRE AREA AS LAPSE RATES STEEPEN EVER SO SLIGHTLY. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... UPR LEVEL DISTURBANCE IN ADDITION TO A WILL BRING THE CHANCE FOR SCATTERED SHOWERS AND TSTMS FRI NIGHT INTO SAT... MAINLY WEST OF THE BLUE RIDGE AND IN THE SOUTHERN PART OF OUR CWA. AFTER A BACKDOOR COLD FRONT SLIPS DOWN THE MID-ATLANTIC COAST...HIGH PRESS BUILDS IN ON SAT THROUGH TUE BRINGING DRIER CONDITIONS. APPROACHING COLD FRONT MAY BRING SHOWERS AND TSTMS ON TUE AFTN. TEMPS WILL BE NEAR NORMAL DURING THE WKND...BECOMING ABOVE NORMAL MON AND TUE. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... MAINTAINED OVERALL FORECAST CONSISTENCY IN REGARDS TO FOG OVERNIGHT. CLOUD COVER IS THE MAIN UNCERTAINTY AND POTENTIAL LIMITING FACTOR. HAVE NOT INCLUDED BR AT IAD FOR NOW...BUT GROUND FOG IS A POSSIBILITY. TROUGH OF LOW PRESSURE PASSES THROUGH REGION WEDNESDAY...BRINGING A LITTLE BETTER PROB OF STORMS...ESPECIALLY IN THE AFTERNOON. CHO WILL BE THE MAIN TARGET...WITH MUCH MORE UNCERTAINTY IN COVERAGE WITH NE EXTENT (ESPECIALLY BALTIMORE AREA). ANY IMPACTS SHOULD BE SHORT- LIVED. MAY BE SOME FOG AGAIN IN PRONE LOCATIONS WEDNESDAY NIGHT. AFTER LIGHT/VRB WINDS THROUGH TONIGHT...A MORE NW COMPONENT SHOULD BE OBTAINED WED...BUT STILL GENERALLY LESS THAN 10 KNOTS. VFR CONDITIONS EXPECTED THURSDAY UNDER HIGH PRESSURE. AFTERNOON AND EVENING SHOWER/THUNDERSTORM CHANCES RETURN FRIDAY WITH BRIEF PERIODS OF SUB-VFR POSSIBLE NEAR ANY ACTIVITY. VFR CONDITIONS EXPECTED FRI NIGHT AND SAT. SUB VFR CONDITIONS PSBL DUE TO SCATTERED SHOWERS AND TSTMS. && .MARINE... ONSHORE COMPONENT TO WINDS THIS AFTERNOON...PERHAPS BECOMING SW TONIGHT. WINDS BECOME W TO NW WED. SPEEDS REMAIN UNDER 10 KT MOST OF THE TIME THROUGH WED NIGHT. ISOLATED TO SCATTERED STORMS A LITTLE BETTER POSSIBILITY ON WEDNESDAY...MORE SO OVER THE SOUTHERN WATERS. WINDS EXPECTED TO REMAIN SUB-SCA THURSDAY AND FRIDAY. THUNDERSTORM CHANCES INCREASE ALONG THE WATERS FRIDAY AS FRONT MOVES INTO THE REGION. SUB-SCA CONDITIONS EXPECTED FOR FRI NIGHT INTO SAT. SOME SHOWERS AND TSTMS PSBL OVER THE WATERS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...ADS/RCM NEAR TERM...ADS/RCM SHORT TERM...ADS/MSE LONG TERM...IMR AVIATION...ADS/IMR/MSE/RCM MARINE...ADS/IMR/MSE

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