Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191439 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1039 AM EDT SUN APR 19 2015 .SYNOPSIS... HIGH PRESSURE CENTERED OVER QUEBEC WILL TRACK EAST TO MAINE TODAY. LOW PRESSURE OVER THE MID-SOUTH STATES WILL TRACK NORTHEAST TO THE OHIO VALLEY TODAY AND GREAT LAKES TONIGHT...BRINGING A WARM FRONT ACROSS 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. && .NEAR TERM /THROUGH TONIGHT/... AS OF 14Z...1029MB SFC HIGH CENTERED OVER WRN QUEBEC WITH A SFC RIDGE ARCING ACROSS NEW ENGLAND TO THE MID-ATLANTIC COAST. 1002MB SFC LOW IS OVER THE MID-SOUTH AND WILL DEVELOP AS IT LIFTS NORTH TO SRN MICHIGAN THIS EVENING. GULF MOISTURE AHEAD OF THIS LOW WILL LIFT FROM THE SERN STATES THIS MORNING TO THE MID-ATLANTIC AND ERN OHIO VALLEY THROUGH TONIGHT. THIS MOISTURE WILL OVERRUN THE RATHER DRY AIRMASS CURRENTLY BEING REINFORCED BY ELY FLOW OF 15 TO 20 MPH. RAIN IS DRIFTING NORTH TO CENTRAL VA AND WILL SLOWLY PROGRESS NORTH... REACHING DC BY 6PM OR SO. INTENSITY WILL INCREASE TO HEAVY WITHIN A COUPLE HOURS OF ONSET...ACROSS THE AREA. AS THE LOW DEEPENS INTO THE GREAT LAKES...AND A MESOLOW DEVELOPS AND LIFTS NORTH ACROSS THE AREA (ROUGHLY ALONG THE PIEDMONT) 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. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... AFTER THE WARM FRONTAL BAND PASSES EARLY MONDAY MORNING...THERE MAY BE A FAIRLY PROLONGED BREAK INTO THE MIDDAY HOURS AS THE AREA BECOMES 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. 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 SATURDAY/... 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. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... VFR CONDITIONS THROUGH MOST OF THE DAY WITH ELY WINDS GUSTING AROUND 20 KT. 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. THUNDER CHANCES LOOK BEST SOUTHEAST OF DC LATE TONIGHT. 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 REDUCTIONS 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. && .MARINE... SCA FOR ALL WATERS THROUGH TONIGHT FOR ELY FLOW CURRENTLY GUSTING TO 20 22KT...THEN FOR SELY/SLY FLOW TONIGHT THAT COULD GUST 25 TO 30 KT. MODERATE TO HEAVY RAIN TONIGHT. ISOLATED THUNDER POSSIBLE LATE TONIGHT...PARTICULARLY FOR SRN MD WATERS. STRONG GUSTS COULD MIX DOWN AND WARRANT SPECIAL MARINE WARNINGS OR A GALE WARNING. S WINDS CONTINUE MONDAY. SCA THROUGH THE DAY OR BAY/LOWER POTOMAC DUE TO CHANNELING. BREAK IN ACTIVITY EXPECTED MONDAY LATE MORNING INTO THE AFTERNOON...BUT THEN THUNDERSTORMS POSSIBLE WITH A 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. && .TIDES/COASTAL FLOODING... STRONG EASTERLY FLOW CONTINUES TODAY...THEN SELY TONIGHT. WATER LEVELS WILL INCREASE ACROSS THE BAY...PARTICULARLY TONIGHT. MINOR COASTAL FLOODING IS POSSIBLE BY THE HIGH TIDES EARLY MONDAY. && .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...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 UNTIL 8 AM EDT MONDAY FOR ANZ535-536. && $$ SYNOPSIS...BAJ/ADS NEAR TERM...BAJ/ADS SHORT TERM...ADS/DFH LONG TERM...DFH AVIATION...BAJ/ADS/DFH MARINE...BAJ/ADS/DFH TIDES/COASTAL FLOODING...BAJ EQUIPMENT...LWX

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