Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT SAT APR 18 2015 .SYNOPSIS... HIGH PRESSURE ACROSS THE REGION TODAY WILL BE REPLACED BY A BACK DOOR COLD FRONT TONIGHT AS LOW PRESSURE MOVES FROM QUEBEC TO THE GULF OF MAINE. WEAK HIGH PRESSURE WILL BUILD BACK INTO THE REGION BRIEFLY SATURDAY NIGHT...AS LOW PRESSURE APPROACHES THE AREA FROM THE CAROLINAS SUNDAY AND SUNDAY NIGHT. A COLD FRONT WILL PASS THROUGH LATE MONDAY BEFORE HIGH PRESSURE BRINGS COOLER THAN NORMAL TEMPERATURES FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SUNDAY/... A WEAK BOUNDARY BISECTS THE AREA EARLY THIS MORNING...MARKED MOST NOTABLY IN THE DEW POINT FIELD. IN CENTRAL VA/SOUTHERN MD WHERE THE DEW POINTS ARE HIGHER...AND RAIN FELL EARLIER...PATCHY FOG HAS DEVELOPED. THERE HAVE BEEN A FEW FLEETING OBSERVATIONS OF 1/4 SM...BUT FOR THE MOST PART THE FOG HAS BEEN LIGHT. AS LONG AS THE LOWER DEW POINTS CONTINUE TO ADVECT IN...THE CHANCE OF WIDESPREAD DENSE FOG IS LOW...BUT WILL MONITOR. HIGH PRESSURE OVER SOUTHERN CANADA WILL SPREAD INTO THE REGION TODAY. MOSTLY SUNNY SKIES...A DRIER AIRMASS AND SUFFICIENT MIXING WILL ALLOW TEMPERATURES TO ONCE AGAIN RISE ABOVE NORMAL...WITH HIGHS IN THE 70S TO NEAR 80. CANNOT TOTALLY RULE OUT A SPRINKLE IN THE SOUTHERN HIGHLANDS DUE TO LOW LEVEL EASTERLY FLOW AND A LITTLE MORE MOISTURE IN PLACE...BUT HAVE LEFT THE FORECAST DRY FOR NOW. AS THE HIGH SLIPS EAST THIS EVENING...AN EFFECTIVE BACK DOOR COLD FRONT WILL PUSH DOWN EAST OF THE APPALACHIANS. COOLER AND DRIER AIR WILL SETTLE IN WITH LOWS DROPPING INTO THE 40S...WITH 50S IN THE METROS AND NEAR THE BAY. THE NEXT SYSTEM OF NOTE WILL APPROACH FROM THE SW ON SUNDAY. ENERGY DIGGING INTO THE CENTRAL CONUS WILL TURN THE MID/UPPER FLOW TO THE SW. EXPECT INCREASING CLOUDS AND RAIN TO BEGIN TO SPREAD IN FROM THE SW DUE TO ISENTROPIC PROCESSES. THE TIMING MAY BE A LITTLE FASTER...BUT THE HIGHEST RAIN CHANCES REMAIN IN CENTRAL VA...AND AREAS NE OF DC MAY REMAIN DRY UNTIL EVENING. WHILE IT WILL TAKE SOME TIME FOR THE AIRMASS TO SATURATE...MOISTURE RETURN WILL BE STRONG FROM GULF AND ATLANTIC TRAJECTORIES. TEMPERATURES WILL BE COOLER WITH HIGHS RANGING FROM THE MID 50S IN THE SW TO MID 60S EAST. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... ACTIVE 24 HOUR PERIOD OF WEATHER STARTING SUNDAY NIGHT THROUGH MONDAY NIGHT. THE FIRST ROUND OF PCPN WILL BE STEADY RAIN MOVING INTO THE REGION FROM THE SW IN RESPONSE TO AN AREA OF LOW PRESSURE. THIS IS DEPICTED WELL ON BOTH THE 00Z GFS AND 00Z ECMWF. THEN A COLD FRONT WILL CROSS THE REGION LATE MONDAY AFTERNOON...BRINING SHOWERS AND TSTMS TO THE AREA. POTENTIAL FOR SEVERE WILL BE LIMITED BY THE CLOUD COVER...BUT DESPITE THIS THE 00Z GFS IS STILL GIVING ABOUT 1000 J/KG OF CAPE FOR MONDAY AFTERNOON AND EVENING WITH THE FROPA. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AN UPPER LOW OVER GREAT LAKES WILL DOMINATE THE WEATHER FOR THE LONG TERM AS SEVERAL VORT MAXES AROUND THE LOW WILL IMPACT THE MID-ATLANTIC AND NE US...GIVING UNSETTLED WEATHER FOR MID TO LATE WEEK. DAYTIME HIGHS WILL BE ABOUT 10 DEG BELOW AVERAGE STARTING ON THURSDAY AND CONTINUING INTO THE WEEKEND. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... PATCHY FOG HAS DEVELOPED IN CENTRAL VA EARLY THIS MORNING...WITH VARIABLE VSBY AT CHO. AM NOT SURE IF THEY WILL SETTLE INTO ONE CATEGORY...BUT IFR OR LOWER WILL BE POSSIBLE AT TIMES UNTIL AFTER SUNRISE. OTHERWISE EXPECTING VFR CONDITIONS THROUGH THE TAF PERIOD. WIND WILL BE HAVE A NORTHERLY COMPONENT AT LESS THAN 10 KT...BECOMING EASTERLY ON SUNDAY AND INCREASING SLIGHTLY. MVFR CIGS LATE SUNDAY AFTERNOON FOLLOWED BY IFR CONDITIONS FOR BOTH CIGS AND VSBYS EXPECTED AT ALL TERMINALS FROM 00Z MON THROUGH 12 MON...IMPROVING MONDAY MORNING. && .MARINE... EXPECT LIGHT NORTHERLY WINDS TO CONTINUE TODAY AND TONIGHT OVER THE WATERS AS HIGH PRESSURE PASSES TO THE NORTH. DO NOT SEE EVIDENCE OF INCREASING WINDS FOR TONIGHT IN THE LATEST GUIDANCE...SO HAVE CANCELED THE SCA FOR TONIGHT. HOWEVER WINDS WILL INCREASE OUT OF THE EAST FOR SUNDAY...AND HAVE RAISED AN SCA FOR ALL WATERS BEGINNING AT 6 AM AS LOW PRES APPROACHES FROM THE CAROLINAS. EXPECTING TO SEE SCA WINDS FROM EARLY SUNDAY THROUGH MIDNIGHT MONDAY AS SHOWN BY BOTH THE 00Z GFS AND NAM BUFKIT PROFILES. && .EQUIPMENT... AUDIO DEGRADATION AT THE NOAA WEATHER RADIO CHARLOTTESVILLE TRANSMITTER IS EXPECTED TO CONTINUE THROUGH THIS WEEKEND. TECHNICIANS ARE SCHEDULED TO PERFORM MAINTENANCE AT THE TRANSMITTER SITE MONDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO 2 AM EDT MONDAY FOR ANZ530>543. && $$ SYNOPSIS...LEE NEAR TERM...ADS SHORT TERM...LEE LONG TERM...LEE AVIATION...ADS/LEE MARINE...ADS/LEE

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