Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181920 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 320 PM EDT SAT APR 18 2015 .SYNOPSIS...
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LOW PRESSURE MOVES OFF THE NEW ENGLAND COAST THIS EVENING...WITH HIGH PRESSURE BUILDS OVER NEW ENGLAND TONIGHT THROUGH SUNDAY. A HIGH PRESSURE RIDGE WILL LINGER OVER THE CENTRAL MID-ATLANTIC INTO SUNDAY AFTERNOON...UNTIL LOW PRESSURE LIFTS ACROSS THE AREA FROM THE CAROLINAS SUNDAY AFTERNOON THROUGH SUNDAY NIGHT. A COLD FRONT WILL CROSS LATE MONDAY BEFORE AN UPPER LOW BRINGS COOLER THAN NORMAL TEMPERATURES TO THE NORTHEASTERN STATES FOR THE MIDDLE AND LATE PORTION OF NEXT WEEK.
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&& .NEAR TERM /THROUGH SUNDAY NIGHT/...
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AS OF 18Z...1010MB SFC LOW IS CENTERED OVER VERMONT WITH A 1027MB SFC HIGH CENTERED JUST NORTH OF LAKE SUPERIOR. A SFC RIDGE NOSES FROM THE GREAT LAKES TO WV WITH VARIABLE WIND LESS THAN 10 MPH OVER THE CWA...EXCEPT FOR THE BAY BREEZE WHICH IS SEVERAL MILES INLAND FROM THE WRN SHORE OF THE BAY AND SUSTAINED AROUND 10 MPH. SUNNY SKIES EXCEPT FOR SOME RIDGELINE AND BAY BREEZE FRONT CU HAS BEEN THE STORY SO FAR TODAY. MAX TEMPS WERE BUMPED UP TO LOW 80S FOR MUCH OF THE AREA THIS MORNING. HIGH CLOUDS OVERRIDING A RIDGE OVER THE MIDWEST WILL OVERSPREAD THE REGION THROUGH THE EVENING HOURS. TONIGHT...HIGH PRESSURE BUILDS IN FROM THE NORTH AS THE CENTER APPROACHES THE ST LAWRENCE VALLEY ENGLAND. MIXING...PARTICULARLY EAST OF THE BLUE RIDGE KEEPS TEMPS UP A BIT OVERNIGHT WITH MINS FOR SERN HALF OF CWA LOW TO MID 50S AND UPR 40S FOR NWRN HALF...PER MAV/MET/SREF BLEND. DRY WEDGE IN PLACE BY SUNDAY MORNING. AN INTENSIFYING LOW LIFTING NORTH FROM THE MID-SOUTH TO SRN LAKE MICHIGAN BRINGS A DEEP PLUME OF GULF MOISTURE EAST ACROSS THE SERN STATES TO THE MID-ATLANTIC THROUGH THE DAY SUNDAY. PRECIP WILL BE SLOW TO SCOUR OUT THE DRY WEDGE SUNDAY...THOUGH GUIDANCE CONSENSUS IS A LITTLE QUICKER THAN YESTERDAY. EXPECTATION IS FOR RAIN ONSET FOR LATE MORNING IN SWRN ZONES...AFTERNOON FOR THE PIEDMONT...AND EVENING FOR BALTIMORE. SUNDAY NIGHT...SWATH OF MODERATE WITH LOCALLY HEAVY RAIN LIFTS NORTH AND EAST ACROSS THE CWA. ENSURED 100 POPS FOR THE CWA. WENT A BIT ABOVE WPC QPF TO GIVE TWO INCHES FOR CENTRAL VA FOOTHILLS GIVEN STRONG ELY COMPONENT THAT WILL ENHANCE ON THE UPSLOPE OF THE ERN SIDE OF THE BLUE RIDGE/TO THE PIEDMONT. GENERALLY 1.0 TO 1.5 INCHES ELSEWHERE. SIX HOUR FLASH FLOOD GUIDANCE IS AROUND 1.5 INCHES FOR BALT/WASH URBAN AND THE CENTRAL VA BLUE RIDGE. THEREFORE...WILL ADD FLOOD WORDING TO THE HWO. SLY LLJ OF 50KT AROUND 2 KFT WILL SHIFT NORTH ACROSS OVERSPREAD GENERALLY EAST OF I-95 LATE IN THE NIGHT. LOW THUNDER THREAT IN THIS AREA...BUT WITH AMPLE RAIN TO MIX THIS WIND DOWN...THERE IS A LOW WIND THREAT FOR SRN MD. MIN TEMPS GENERALLY LOW TO MID 50S...UPR 50 FOR SERN PORTIONS OF THE CWA WHERE SLY FLOW PERSISTS ALL NIGHT.
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&& .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
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THE WMFRNTL SHIELD OF RA WL BE EXITING THE CWFA AT THE START OF THE PD MON. WL BE CARRYING ELY POPS FOR ANY LINGERING SHRA. AFTER THAT...THINK THERE WL BE A DRY/RELATIVELY QUIET PD. WHAT HAPPENS DURING THIS TIME WL DICATE THE WX FOR THE REST OF THE DAY. THERE SHUD BE A FAIR AMT OF CLDCVR...LIMITING INSOLATION. THE AMT WL BE OTRW BE WARM...HUMID /DEWPTS MID-UPR 50S/ AND RELATIVELY UNSTBL. AM NOTING CAPES ARND 1000 J/KG. SEE ENUF FOR A LINE OF DIURNALLY DRIVEN SHRA/TSRA AHD OF CFP. QSTN WL BE HOW STRONG WL THEY BE. EXTENT OF DAYTIME HEATING HOLDS THE KEY. SPC HAS PAINTED AREA IN MRGL RISK... W/ SLGT RISK IN THE SERN QUAD OF THE CWFA. FROPA NEAR SUNSET. HV SCALED BACK THUNDER SOON THEREAFTR...AND POPS DWINDLE THRU THE EVNG. DECENT CAA COMING IN OVNGT...SO HV SCOURED OUT CLDS AFTR MIDNGT...XCPT FOR THE MTNS. GDNC CONSISTENT IN GOING WARMER FOR MAXT MON. HV FOLLOWED SUIT...BUT NOT AS MUCH AS MAV. THAT CUD BE AN ISSUE IF SUNSHINE REALIZED. SUSPECT THERE MAY BE A QUITE A TEMP GRADIENT ACRS THE AREA. AM NOT COMFY TRYING TO NAIL EXTREMES AT THIS POINT. REMOVED NAM FROM MDL BLEND FOR MIN-T AS IT SEEMS TOO WARM FOR THE EXTENT OF CAA PROGGED.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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A SLOW-MOVING UPPER LOW OVER THE GREAT LAKES WILL DOMINATE THE WX PATTERN THROUGH THE LONG TERM...AS SEVERAL PIECES OF ENERGY ROTATE AROUND IT AND CROSS NEAR OUR AREA. THIS WILL BRING UNSETTLED AND COOLER WX THROUGH THE WEEK. MOST GUIDANCE SUGGESTS BEST CHANCE FOR PRECIP ASSOCIATED WITH A FRONTAL PASSAGE LATE WED. SYSTEM WILL BE MOISTURE STARVED WITH LITTLE CONNECTION TO GOM/ATL MOISTURE...SO EXPECTING ONLY LIGHT PRECIP. AT THIS TIME...HIGHEST CHANCES ARE IN NORTHERN HALF OF THE CWA. CAA CONTINUES THROUGH MOST OF THE WEEK...WITH WESTERLY WINDS PREVALENT. DESPITE THE DOWNSLOPE COMPONENT...TEMPS WILL BE NOTICEABLY COOLER BY WEEKS END WITH MAX TEMPS LOW 60S/UPPER 50S AND MIN TEMPS LOW 40S/UPPER 30S. COULD EVEN BE SOME FROST BY FRI MORNING ALONG/NEAR MASON DIXON LINE WHERE GROWING SEASON HAS ALREADY BEGUN.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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VFR INTO SUNDAY AFTERNOON CWA WIDE. HIGH PRESSURE BUILDS NORTH OF THE AREA LATE TONIGHT WITH NE WINDS GUSTING 15 TO 20 KT EAST OF THE BLUE RIDGE. FLOW BECOMES ELY SUNDAY AS THE HIGH CENTER DRIFTS OFF NEW ENGLAND. STRONG LOW LIFTS INTO THE MIDWEST LATE SUNDAY THROUGH MONDAY. WARM FRONT AND DEEP MOISTURE PLUME LIFTS OVER THE AREA LATE SUNDAY AFTERNOON THROUGH SUNDAY NIGHT. HEAVY RAIN/IFR CONDS ACROSS THE DC METROS EVENING INTO LATE SUNDAY NIGHT. MON... MRNG FLGT RESTRICTIONS SHUD PART DURING THE MIDDAY. LT DAY SHRA LKLY...W/ A FEW EMBEDDED TSRA. BRIEF FLGT RESTRICTIONS PROBABLE W/IN STORMS. VFR CONDITIONS EXPECTED THROUGH MOST OF PERIOD...EXCEPT IN RAIN SHOWERS WHERE LOCALLY SUB-VFR CONDITIONS ARE POSSIBLE.
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&& .MARINE...
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NORTHEAST WINDS CHANNEL DOWN THE BAY TONIGHT THE LATE NIGHT. SCA FROM MIDNIGHT FOR NRN MD WATERS...THEN ALL BUT THE UPPER TIDAL POTOMAC 3AM TO THE MID MORNING. ALL WATERS THEN THROUGH SUNDAY NIGHT AS STRONG WIND FIELD WITH 20 TO 25 KT AS HIGH PRESSURE SHIFTS OFF THE NEW ENGLAND COAST. WARM FRONT WITH HEAVY RAIN AND GUSTY SHOWERS CROSSES THE WATERS SUNDAY NIGHT. SMW OR GALE LIKELY. RAIN TO START THE DAY MON. THEN ONCE IT DEPARTS...SLY FLOW WL RESUME...INCRSG BY MID-LT AFTN. SHUD BE ENUF INFLOW FOR MARGINAL SCA CALIBER GUSTS. IN ADDITION XPCT TSRA ALONG/AHD OF CDFNT. SOME OF THESE MAY CONTAIN STRONG GUSTY WINDS AND LARGE HAIL. SMW/S LKLY. SCA POSSIBLE TUES MORNING IN CAA REGIME ONCE BL MIXING COMMENCES. WINDS SHOULD DIMINISH TUES AFTN AS PRESSURE GRADIENT RELAXES FROM DEPARTING SFC LOW.
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&& .TIDES/COASTAL FLOODING...
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NELY FLOW INCREASES TONIGHT...ELY THROUGH SUNDAY...THEN SELY SUNDAY NIGHT. WATER LEVELS WILL INCREASE ACROSS THE BAY...PARTICULARLY SUNDAY NIGHT. MINOR COASTAL FLOODING IS POSSIBLE BY THE HIGH TIDES EARLY MONDAY.
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&& .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...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EDT MONDAY FOR ANZ530>532-538>540. SMALL CRAFT ADVISORY FROM 3 AM SUNDAY TO 6 AM EDT MONDAY FOR ANZ533-534-536-537-541>543. SMALL CRAFT ADVISORY FROM 8 AM SUNDAY TO 6 AM EDT MONDAY FOR ANZ535.
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&& $$ SYNOPSIS...BAJ NEAR TERM...BAJ SHORT TERM...HTS LONG TERM...MSE AVIATION...HTS/BAJ/MSE MARINE...HTS/BAJ/MSE TIDES/COASTAL FLOODING...BAJ EQUIPMENT...HTS

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