Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 120755 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 355 AM EDT SAT APR 12 2014 .SYNOPSIS...
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HIGH PRESSURE WILL MOVE ACROSS THE REGION TODAY AND PUSH OFFSHORE THIS EVENING. A WARM FRONT WILL LIFT NORTH ACROSS THE REGION TONIGHT AND SUNDAY. A COLD FRONT WILL SLOWLY MOVE THROUGH THE REGION MONDAY NIGHT THROUGH TUESDAY NIGHT. CANADIAN HIGH PRESSURE BUILDS INTO THE AREA WEDNESDAY AND THURSDAY.
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&& .NEAR TERM /THROUGH SUNDAY/...
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PATCHY DENSE FOG DUE TO RADIATIONAL COOLING AND RESIDUAL MOISTURE FROM EARLIER RAINS HAS DEVELOPED IN VALLEY AREAS OF EAST OF THE BLUE RIDGE AND INTO THE WESTERN DC METRO. THIS FOG SHOULD LIFT SHORTLY AFTER SUNRISE WHEN DAYTIME HEATING AND MIXING ENSUE. WILL MONITOR FOR POSSIBLE DENSE FOG ADVISORY IF COVERAGE OF <1/4SM INCREASES EARLY THIS MORNING. RIDGE OF SURFACE HIGH PRESSURE WILL SLOWLY PUSH ACROSS THE CWA AND OFFSHORE TODAY AS SURFACE WINDS VEER AND THERMAL RIDGE BEGINS ITS RETURN NORTH. TEMPERATURES WILL BE A BIT COOLER THAN YESTERDAY YET STILL WELL ABOVE NORMAL TODAY. WEAK ISENTROPIC LIFT ALONG WITH DAYTIME HEATING CONVERGENCE AND A FEW HUNDRED JOULES OF MLCAPE MAY RESULT IN SOME AFTERNOON POP-UP SHOWERS OVER THE SOUTHERN POTOMAC HIGHLAND. HAVE GONE WITH LOW CHANCE POPS AS OVERALL MOISTURE AND LIFT REMAIN LOW. AS LEADING EDGE OF SOUTHWEST 30KT LOW LEVEL JET NUDGES EAST OVER THE REGION TONIGHT AFTER 03Z...FORECAST SOUNDINGS ARE SHOWING INCREASING LOW LEVEL MOISTURE WITH STRONG WAA PUSH. COULD SEE SOME STRATUS...ESPECIALLY CLOSER TO ONSHORE WINDS NEAR NORTHERN SIDE OF THE BAY. HAVE ALSO INCREASED LOW TEMPS FOR TONIGHT WITH FULL DECOUPLING NOT EXPECTED. MID-ATLANTIC IS WELL INTO THE WARM SECTOR FOR SUNDAY WITH AND INCREASING SOUTHWEST FLOW/WIND FAVORING GOOD MIXING. DEWPOINTS WILL BE A BIT HIGHER...BUT SHOULD STILL SEE TEMPERATURES AROUND OR INTO THE 80S.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
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FLOW THRUOUT THE TROPOSPHERE BECOMES INCREASINGLY MERIDIONAL/SLY OVER THE ERN SEABOARD SUN NGT AND MON AS AN AMPLIFYING UPPER TROUGH AND SFC COLD FRONT APPROACH FROM THE CENTRAL CONUS AND DOWNSTREAM RIDGE BUILDS OVER THE WRN ATLANTIC. WARM CONDITIONS WILL CONTINUE AS A RESULT. FCST LOWS IN THE 50S SUN NGT AND HIGHS IN THE 70S MON ARE MORE REPRESENTATIVE OF CLIMO FOR LATE MAY THAN FOR MID APRIL. THE COLD FRONT WILL PROGRESS EWD TOWARD THE WRN SIDE OF THE APPALACHIANS ON MON. CLOUDS WILL INCREASE THRUOUT THE DAY AS A 40-50KT SLY LLVL JET AHEAD OF THE FRONT TRANSPORTS DEEPER MOISTURE UP THE ERN SEABOARD. THE GREATEST LIFT WILL STILL REMAIN UPSTREAM OF THE AREA ON MON SO COVERAGE OF SHOWERS WILL BE LOW DURING THE AFTN.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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MODELS INDICATE A WEAK REX BLOCK FORMING OVER THE ATLANTIC NEAR 60W NEXT WEEK...WHICH WOULD WILL CAUSE THE COLD FRONT TO SLOW DOWN AS IT MOVES EWD TOWARD THE ERN SEABOARD. AN EXTENDED PERIOD OF CLOUDY AND WET CONDITIONS ARE IN THE FCST MON NGT THRU TUE NGT WITH THE FRONT LOCATED OVER THE AREA. COVERAGE OF PRECIP SHOULD BE WIDESPREAD WITH FAVORABLE JET DYNAMICS IN RIGHT ENTRANCE REGION OF ULVL JET STREAK AND A PERSISTENT FEED OF MOISTURE FROM THE GULF OF MEXICO AND ATLANTIC ALONG THE FRONTAL BOUNDARY. 00Z GUIDANCE HAS GENERALLY BACKED OFF ON HIGHER QPF AMOUNTS A BIT COMPARED TO YDA/S RUNS BUT THE POSSIBILITY FOR A HEAVY RAINFALL EVENT STILL CANNOT BE DISMISSED GIVEN THE AFOREMENTIONED SYNOPTIC SETUP. THE COLD FRONT MOVES OFF THE EAST COAST WED. CANADIAN HIPRES EVENTUALLY BUILDS INTO THE AREA DURING THE SECOND HALF OF THE WEEK. WELL-BELOW NORMAL TEMPS ARE FCST FOR WED WITH HIGHS ONLY IN THE 40S AND LOW WED NGT NEAR FREEZING. FROST/FREEZE HEADLINES MAY BE NEEDED EAST OF THE BLUE RIDGE WHERE THE GROWING SEASON HAS STARTED.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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IFR/LIFR VSBYS IN AREAS OF FOG ACROSS VALLEY AREA AFFECTING MRB/IAD WILL LIFT AFTER SUNRISE. VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE DAY. HIGH PRESSURE WILL MOVE OFFSHORE LATER TODAY AS WINDS VEER TO THE SOUTHEAST. WINDS WILL INCREASE TONIGHT INTO SUNDAY AS A WARM FRONT PUSHES NORTH. AREAS OF MVFR STRATUS MAY DEVELOP LATE TONIGHT...MAINLY EXPECTED TO AFFECT BWI/MTN. CONFIDENCE ON DEVELOPMENT AND COVERAGE OF STRATUS IS LOW. PATCHY FOG OR LOW STRATUS MAY DEVELOP SUN NGT UNDER MOIST SLY FLOW. SLY WINDS WILL BE BREEZY ON MON WITH GUSTS 25-30 KT POSSIBLE DURING THE AFTN BUT VFR CONDITIONS. COLD FRONT SLOWS DOWN AS IT MOVE THRU THE TERMINALS MIDWEEK...RESULTING IN A PROLONGED RISK OF FLGT RESTRICTIONS AND SHOWERS LATE MON THRU ERY WED.
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&& .MARINE...
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HIGH PRESSURE WILL MOVE ACROSS THE WATERS TODAY AS LIGHT WINDS VEER FROM NORTH TO SOUTHEAST. WINDS WIND WILL INCREASE OVERNIGHT AND SCA CONDITIONS ARE EXPECTED SUNDAY BEHIND A WARM FRONT. SCA MAY NEED TO BE EXTENDED INTO SUN NGT FOR THE MAIN STEM OF THE CHSPK BAY WHERE SLY WINDS WILL CHANNEL. SCA CONDITIONS LIKELY ACROSS ALL MARINE ZONES ON MON INTO TUE AS SLY WINDS INCREASE AHEAD OF A COLD FRONT. A STRONG PRESSURE GRADIENT LOOKS TO DEVELOP BEHIND THE FRONT DURING MIDWEEK AS THE FRONT MOVES OFFSHORE AND HIPRES BUILDS IN FROM THE GREAT LAKES. NW WINDS DURING THIS TIME SHOULD CONTINUE TO PRODUCE SCA CONDITIONS WITH GALES POSSIBLE BRIEFLY BEHIND THE FRONT SOMETIME EITHER LATE TUE OR ERY WED.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON TO 6 PM EDT SUNDAY FOR ANZ530>543.
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&& $$ SYNOPSIS...AEB NEAR TERM...AEB SHORT TERM...JRK LONG TERM...JRK AVIATION...JRK/AEB MARINE...JRK/AEB

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