Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT SUN APR 19 2015 .SYNOPSIS...
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HIGH PRESSURE CENTERED OVER ONTARIO WILL TRACK TOWARD THE EAST COAST TONIGHT TODAY. LOW PRESSURE DEVELOPING IN THE GULF OF MEXICO WILL TRACK NORTHEAST INTO THE MID ATLANTIC TONIGHT. A COLD FRONT WILL MOVE THROUGH THE AREA LATE MONDAY. AN UPPER LOW BRINGS COOLER THAN NORMAL TEMPERATURES TO THE NORTHEASTERN STATES FOR THE MIDDLE AND LATE PORTION OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SFC HIGH PRESSURE CENTERED OVER ONTARIO EARLY THIS MORNING. A BACKDOOR FRONT IS SLIPPING THROUGH THE AREA...WITH THE MOST NOTICEABLE MARKER BEING A WIND SHIFT TO THE N/NE. THE HIGH WILL MOVE OFF TO THE EAST TODAY AS MID/UPPER LEVEL TROUGHING DIGS INTO THE NATION/S MID SECTION AND A SFC LOW TAKES SHAPE OVER THE MID MS VALLEY. MOISTURE WILL BEGIN TO OVERRUN THE DRY AIRMASS CURRENTLY IN PLACE. EXPECT RAIN TO APPROACH CENTRAL VA BY THE MIDDAY HOURS. THIS WILL PROBABLY BE LIGHT INITIALLY AS THE AIRMASS SATURATES. AS THE LOW DEEPENS INTO THE GREAT LAKES...A STRONG SE LLVL JET WILL DEVELOP BY THIS EVENING...TRANSPORTING COPIOUS MOISTURE INTO THE REGION. PWATS WILL CLIMB TO NEAR MAXIMUM CLIMO VALUES FOR THIS TIME OF YEAR (UPWARDS OF 1.5 INCHES) AND WARM CLOUD DEPTHS ARE FORECAST TO AOA 3 KM...ESPECIALLY EAST OF THE BLUE RIDGE. COMBINED WITH THE UPSLOPE COMPONENT...EXPECT HIGHEST RAIN TOTALS APPROACHING 2 INCHES TO BE FOCUSED NEAR THE CENTRAL BLUE RIDGE. WILL BE RAISING A FLOOD WATCH IN THIS AREA AS 6 HR FFG IS AROUND 1.5 INCHES IN SPOTS. HOWEVER THE ENTIRE AREA WILL GET A GOOD SOAKING RAIN AS THE WARM FRONTAL BAND LIFTS THROUGH TONIGHT...WITH MANY SPOTS TOPPING AN INCH. WILL ALLOW THE DAYSHIFT TO ASSESS THE NEED TO EXPAND THE WATCH...WITH THE MOST LIKELY CANDIDATES BEING INTO THE URBAN AREAS. HOWEVER...WOULD EXPECT PONDING OF WATER WOULD BE THE MAIN CONCERN. INCREASING CLOUDS TODAY LIMIT TEMPS TO THE UPPER 50S/LOWER 60S. TEMPS HOLD STEADY OR PERHAPS RISE A LITTLE IN EASTERN AREAS TONIGHT WITH THE RAIN. LOWS IN THE 50S.
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&& .SHORT TERM /MONDAY/...
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AFTER THE WARM FRONTAL BAND PASSES EARLY MONDAY MORNING...THERE MAY BE A FAIRLY PROLONGED BREAK INTO THE MIDDAY HOURS AS THE AREA BECOME WARM SECTORED...AND THERE MAY BE A CAP IN PLACE AS WELL. TEMPERATURES WILL WARM INTO THE 70S...AND FAIRLY GOOD AGREEMENT ON 60S DEW POINTS ESPECIALLY EAST OF BLUE RIDGE. DECENT PROBS OF MUCAPE GREATER THAN 1000 J/KG AND DEEP LAYER SHEAR AOA 30 KT. HI-RES GUIDANCE SUGGEST STORMS FIRST FIRE ALONG THE MOUNTAINS NEAR A PRE- FRONTAL TROUGH...WITH ADDITIONAL STORMS ALONG THE COLD FRONT TO THE WEST. SPC HAS HIGHLIGHTED MOST OF THE AREA FOR A SLIGHT RISK OF SEVERE STORMS. UNIDIRECTIONAL WINDS SUGGEST POTENTIAL FOR LINEAR FEATURES. GIVEN SOME MID LEVEL DRYING AND STEEP LLVL LAPSE RATES...THINK DMG WINDS WILL BE MORE LIKELY THAN LARGE HAIL.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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COLD FRONT SWEEPS OFFSHORE OVERNIGHT...BRINGING AN END TO ANY SHOWERS AND THUNDERSTORMS FROM WEST TO EAST...LIKELY BY AROUND MIDNIGHT. SLIGHT CHANCE A FEW SHOWERS LINGER NEAR THE BAY INTO THE WEE HOURS OF THE MORNING TUESDAY. OTHERWISE...BREEZY AND DRIER OVERNIGHT BEHIND THE FRONT. PRESSURE SURGE BEHIND THE COLD FRONT COULD BRING DOWN STRONG GUSTY WINDS NEAR ADVISORY LEVELS ESPECIALLY OVER THE RIDGELINES MONDAY NIGHT. LONG TERM /TUESDAY THROUGH SUNDAY/... A LARGE AND DEEP UPPER-LEVEL LOW PRESSURE SYSTEM WILL DIVE OUT OF CANADA AND SET UP SHOP ACROSS THE NORTHEASTERN CONUS FOR MUCH OF THE MIDDLE AND LATER PART OF THE WEEK. A REINFORCING COLD FRONT WILL MOVE ACROSS THE AREA WEDNESDAY. MOISTURE MAY BE SOMEWHAT LIMITED SO KEPT POPS AT CHANCE FOR NOW. SEEMS LIKE A SCATTERED SHOWER/ISOLATED THUNDERSTORM DAY ENHANCED OVER TERRAIN AREAS...MORE ISOLATED FURTHER EAST. BEHIND THIS FRONT WILL COME A MUCH COOLER AND DRIER DURING THE SECOND HALF OF THE WEEK. TEMPERATURES WILL BE AROUND 10 DEGREES BELOW NORMAL...WITH HIGHS STRUGGLING TO GET OUT OF THE 50S THURSDAY THROUGH NEXT WEEKEND.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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VFR CONDITIONS THROUGH MOST OF THE DAY WITH NE WINDS BECOMING EASTERLY. RAIN WILL SPREAD S TO N THIS AFTERNOON AND EVENING...WITH FLIGHT CONDITIONS DETERIORATING FIRST AT CHO. AS THE RAIN SPREADS THROUGH TONIGHT...MDT TO LOCALLY HEAVY RAIN IS POSSIBLE. IFR OR LOWER CIGS AND IFR VSBYS ARE LIKELY. CONDITIONS WILL IMPROVE MONDAY MORNING AS THE RAIN EXITS AND WINDS BECOME SOUTHERLY. THUNDERSTORMS WILL BE POSSIBLE MONDAY AFTERNOON AND EVENING AHEAD OF AN APPROACHING COLD FRONT. STRONG WIND GUSTS AND BRIEF CIG/VSBY CONDITIONS POSSIBLE. WINDS TURN WLY BEHIND COLD FRONT MON NIGHT...10-20 KT W/ VFR LIKELY BY AROUND MIDNIGHT. GUSTY TUE IN CONTINUED WLY FLOW AND VFR. SWLY FLOW 10-15 KT TUE NIGHT-WED...W/ SUB-VFR POSSIBLE IN ISO SHOWER/TSTM...HIGHEST PROBABILITY N&W OF BLUE RIDGE WED PM. VFR THU WLY FLOW 10 KT.
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&& .MARINE...
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COLD FRONT HAS MOVED THROUGH THE WATERS BRINGING N WINDS. WILL LEAVE SCA IN EFFECT AS A FEW HIGHER GUSTS MAY REACH THE WATERS. AFTER DAYBREAK EXPECT E WINDS TO INCREASE...WITH SCA FOR ALL WATERS THROUGH TONIGHT. WINDS SHIFT TO THE S EARLY MONDAY MORNING. HAVE EXTENDED SCA FOR BAY/LOWER POTOMAC DUE TO CHANNELING. MODERATE TO HEAVY RAIN TONIGHT. POSSIBLE A FEW STRONG GUSTS MIX DOWN. BREAK POSSIBLE THROUGH EARLY MONDAY AFTERNOON...BUT THEN THUNDERSTORMS POSSIBLE WITH A GOOD CHANCE OF STRONG WIND GUSTS AND SMW/S. SCA CONDITIONS LIKELY IN WESTERLY SURGE MONDAY NIGHT INTO TUESDAY...WITH GALE GUSTS POSSIBLE DURING THIS TIME. SCA GUSTS POSSIBLE AGAIN WEDNESDAY AHEAD OF A SECONDARY COLD FRONT.
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&& .TIDES/COASTAL FLOODING...
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EASTERLY FLOW INCREASE TODAY...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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&& .CLIMATE...
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SATURDAY WAS THE WARMEST DAY OF 2015 SO FAR AT OUR THREE MAJOR CLIMATE SITES. WASHINGTON DC /REAGAN NATIONAL AIRPORT...DCA/ HAD A HIGH TEMPERATURE OF 84 DEGREES...THE WARMEST READING SINCE SEPTEMBER 27 2014 WHEN THE HIGH TEMPERATURE WAS 85. BALTIMORE MD /BALTIMORE-WASHINGTON THURGOOD MARSHALL INTERNATIONAL AIRPORT...BWI/ HAD A HIGH TEMPERATURE OF 80 DEGREES...THE WARMEST READING AND FIRST 80-DEGREE DAY SINCE OCTOBER 28 2014 WHEN THE HIGH TEMPERATURE WAS ALSO 80. DULLES INTERNATIONAL AIRPORT /IAD/ HAD A HIGH TEMPERATURE OF 80 DEGREES...THE WARMEST READING AND FIRST 80-DEGREE DAY SINCE OCTOBER 28 2014 WHEN THE HIGH TEMPERATURE WAS 82 DEGREES.
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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...FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT FOR VAZ025-026-029-036>040-507-508. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT MONDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 8 AM EDT MONDAY FOR ANZ535. SMALL CRAFT ADVISORY UNTIL 8 AM EDT MONDAY FOR ANZ536.
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&& $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS/DFH LONG TERM...DFH AVIATION...ADS/DFH MARINE...ADS/DFH TIDES/COASTAL FLOODING...ADS CLIMATE...DFH EQUIPMENT...LWX

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