Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 110758 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 358 AM EDT FRI APR 11 2014 .SYNOPSIS...
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A COLD FRONT OVER THE UPPER MIDWEST WILL SAG SOUTH AND MOVE INTO THE AREA THIS EVENING. HIGH PRESSURE WILL PARK OFF THE EASTERN SEABOARD THIS WEEKEND AND INTO EARLY NEXT WEEK. A SLOW-MOVING COLD FRONT WILL MOVE THROUGH THE MID-ATLANTIC REGION LATE MONDAY INTO TUESDAY.
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&& .NEAR TERM /THROUGH SATURDAY/...
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COLD FRONT STRETCHES FROM OHIO ACROSS PA EARLY THIS MORNING. SURFACE HIGH PRESSURE IS OVER THE ATLANTIC AND A WEAK SURFACE BOUNDARY IS OVER NORTHERN VA. LATEST GUIDANCE IS SLOWER MOVING COLD FRONT THROUGH. NAM HAS IT NEAR CUMBERLAND AT 21Z AND THE I-95 CORRIDOR BY 00Z. AHEAD OF THE FRONT FORECAST SOUNDINGS SHOW DRY AIR AND GOOD MIXING FOR BREEZY SW WINDS 15 TO 25 MPH. FORECAST WILL KEEP PRECIPITATION OUT OF CENTRAL VA COUNTIES UNTIL LATE AFTERNOON. ALONG THE FRONT STEEP LAPSE RATES AND A NARROW BAND OF INCREASING MOISTURE COULD TRIGGER A FEW THUNDERSTORMS. STORMS COULD HAVE GUSTY WINDS THOUGH ATMOSPHERIC INSTABILITY IS LIMITED. TEMPERATURES WILL RISE TO THE UPPER 70/S EVEN CLOSE TO 80 IN MANY AHEAD AHEAD OF THE FRONT. FLOW SHIFTS AROUND TO THE NW BEHIND THE FRONT TONIGHT WITH BREEZY WIND GUSTS TO 20 MPH AND OVERNIGHT LOW TEMPS FROM THE MID 40/S TO MID 50/S. HIGH PRESSURE REBUILDS SATURDAY AND WITH AN UPPER RIDGE OFFSHORE A SOUTHERLY SURGE OF WARM AIR WILL PUSH THROUGH. THERE WILL BE CLOUDS AROUND BUT THE MODELS ARE SHOWING LITTLE IF ANY QPF. TEMPERATURES WILL BE COOLER DUE TO THE CLOUD COVER BUT IT WILL BECOME MORE HUMID.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
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LARGE-SCALE PATTERN THRU THE REMAINDER OF THE WEEKEND WILL AMPLIFY WITH AN UPPER TROUGH ORGANIZING OVER THE ROCKIES/CENTRAL CONUS AND DOWNSTREAM RIDGE BUILDING OVER WRN ATLANTIC. DEEP AND PERSISTENT SLY FLOW BETWEEN THESE TWO SYSTEMS WILL DRAW WARM AND MOIST AIR UP THE ERN CONUS. MOISTURE ADVECTION IN BOUNDARY LAYER MAY BE SIGNIFICANT ENOUGH TO YIELD STRATUS AND/OR FOG LATE SAT NGT. AIRMASS WARMS FURTHER GOING INTO SUNDAY WITH SUBSIDENCE STRENGTHENING A BIT ON THE NWRN SIDE OF THE RIDGE. HIGHS SUNDAY RANGE FROM THE LOW/MID 70S IN THE MTS TO NEAR 80F IN CENTRAL VA. SUNDAY WILL LIKELY BE THE WARMEST DAY ACROSS THE REGION OF THE YEAR SO FAR AND MAY WIND UP BEING THE WARMEST SINCE EARLY OCTOBER. BOTH THE 00Z NAM/GFS BUFKIT SOUNDINGS INDICATE A SUBSIDENCE INVERSION THAT IS STRONG ENOUGH TO INHIBIT DEVELOPMENT OF SHOWERS OR STORMS. SLY FLOW PERSISTS SUN NGT AND SHOULD LIMIT RADIATIONAL COOLING. MIN TEMPS SUN NGT IN THE 50S WILL BE 10-15F ABOVE NORMAL.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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A COLD FRONT WILL APPROACH FROM THE WRN SIDE OF THE APPALACHIANS ON MONDAY. A WAVE OF LOPRES ALONG THE FRONT WILL TRACK NEWD INTO THE GREAT LAKES. FOLLOWED THE TREND IN THE LATEST MODEL GUIDANCE WHICH WAS TO SLOW DOWN ARRIVAL OF THE PRECIP WITH THE FRONT UNTIL MON NGT. THIS SCENARIO MAKES SENSE UNDER THE SETUP OF STEERING FLOW ALOFT BECOMING INCREASINGLY PARALLEL TO THE BOUNDARY AS THE COLD FRONT APPROACHES THE EAST COAST. POPS FOLLOW WPC CLOSELY AND WERE INCREASED TO LIKELY/CATEGORICAL MON NGT INTO TUE WITH FAVORABLE ULVL JET DYNAMICS IN RIGHT ENTRANCE REGION OF JET STREAK...DEEP MOISTURE TRANSPORT FROM THE GULF OF MEXICO AND WAVES OF LOPRES RIDING ALONG THE FRONTAL BOUNDARY. EXTENDED-RANGE MODELS HAVE BEEN FAIRLY PERSISTENT IN SHOWING THE POTENTIAL FOR HVY RAIN BUT QPF AMOUNTS VARY SIGNIFICANTLY BETWEEN GUIDANCE (WHICH IS NOT A SURPRISE THIS FAR OUT INTO THE FCST PERIOD). FUTURE SHIFTS MAY NEED TO INTRODUCE THE POTENTIAL FOR FLOODING ISSUES WITH THIS SYSTEM IN THE HWO AS WE GET CLOSER TO THE EVENT AND THE DETAILS BECOME CLEARER. ANOMALOUS LATE SEASON COLD AIR MOVES IN BEHIND THE COLD FRONT LATE TUE NGT AND WED. ALTHOUGH NOT LIKELY...CANNOT RULE OUT THE POSSIBILITY OF PRECIP BRIEFLY MIXING IN OR CHANGING TO SNOW BEFORE ENDING WITH H8 TEMPS CRASHING TO BETWEEN -5C TO -10C. TEMPS 10-15 DEG BELOW NORMAL FOR THE MIDDLE OF NEXT WEEK.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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INCREASING W-SW WINDS ALOFT WILL CAUSE LOW LEVEL WIND SHEAR AT THE DCA...IAD AND BWI TERMINALS UNTIL 10Z. VFR INCREASING HI CLOUDS FL250 THROUGH THE MORNING AND EARLY AFTERNOON. LOWER CIGS OVC090 AFTER 23Z WITH PERIODS -SHRA AND LESS THAN A 10 PERCENT CHANCE OF TS. WINDS SHIFT AROUND TO THE N THIS EVENING. VFR EXPECTED FRIDAY NIGHT AND SATURDAY A BKN CLOUD DECK FL110 IS POSSIBLE. LOW CLOUDS AND FOG MAY DEVELOP SAT NGT/SUN MRNG. VFR SUN AND MON. SLY WINDS 10-20 KT DURING THE AFTN BOTH DAYS. RAIN ASSOCIATED WITH A SLOW-MOVING COLD FRONT MOVES INTO THE TERMINALS MON NGT AND TUE. FLGT RESTRICTIONS LIKELY DURING THIS TIME.
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&& .MARINE...
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SCA FOR ALL WATERS UNTIL 10 AM. WILL NEED TO WATCH FOR NWLY GUSTS IN EXCESS OF 20 KT FRIDAY EVENING BEHIND THE COLD FRONT. SLY FLOW WILL STRENGTHEN SUN AND MON AHEAD OF A COLD FRONT. MULTIPLE SCA HEADLINES MAY BE REQUIRED DURING THIS TIME. COLD FRONT APPROACHES FROM THE WEST MON NGT INTO TUE. NW WINDS IN WAKE OF FROPA TUE NGT AND WED WILL LIKELY REACH SCA LVLS.
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&& .FIRE WEATHER...
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SLOWER PROGRESSION OF THE COLD FRONT AND W-SW WINDS 15 TO 25 MPH WILL CAUSE HUMIDITY TO DROP TO 25 TO 35 PERCENT ACROSS PORTIONS OF CENTRAL VIRGINIA LATER THIS MORNING AND EARLY THIS AFTERNOON. LOW FUEL MOISTURE IN THIS AREA WILL COMBINE WITH THE BREEZY WINDS AND DRY AIR MASS TO CAUSE A LIMITED PERIOD WHERE WILDFIRES / BRUSH FIRES COULD SPREAD RAPIDLY. HUMIDITY WILL INCREASE LATE IN THE AFTERNOON AS A COLD FRONT APPROACHES. WILL ISSUE A SPS TO HIGHLIGHT THE ENHANCED WILDFIRE THREAT AFTER COORDINATION WITH SURROUNDING WFOS AND VA FIRE OFFICIALS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EDT THIS MORNING FOR ANZ530>534-537-539>541-543.
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&& $$ SYNOPSIS...SDG/JRK NEAR TERM...SDG SHORT TERM...JRK LONG TERM...JRK AVIATION...SDG/JRK MARINE...SDG/JRK FIRE WEATHER...SDG

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