Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271012 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 512 AM EST THU NOV 27 2014 .SYNOPSIS... AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE AREA TODAY AND HIGH PRESSURE WILL BUILD OVERHEAD FRIDAY. THE HIGH WILL MOVE OFF THE COAST DURING THE WEEKEND. A COLD FRONT IS EXPECTED TO MOVE THROUGH MONDAY. && .NEAR TERM /THROUGH TONIGHT/... UPDATE...EXPANDED DENSE FOG ADVISORY TO INCLUDE FREDERICK VA AND HAMPSHIRE WV. COASTAL LOW PRESSURE THAT BROUGHT RAIN AND SNOW TO THE MID-ATLANTIC WEDNESDAY WILL CONTINUE TO DEEPEN OFF THE MAINE COAST THIS MORNING. HIGH PRESSURE HAS RIDGED INTO THE REGION FROM THE SOUTH THIS MORNING AHEAD OF A WEAK AREA OF LOW PRESSURE. SUBSIDENCE HAS LED TO AREAS OF CLEARING EARLY THIS MORNING. PATCHY FOG HAS DEVELOPED AS CALM WINDS LEAD TO RADIATIONAL COOLING ACROSS THE WET GROUND. DENSE FOG HAS BEEN OBSERVED IN VALLEY LOCATIONS ESPECIALLY IN THE SHENANDOAH VALLEY. A DENSE FOG ADVISORY IS IN EFFECT THIS MORNING FOR THE SHENANDOAH VALLEY. CLOUDS FROM THE APPROACHING DISTURBANCE WILL CONTINUE TO MOVE INTO THE MID-ATLANTIC FROM THE TN VALLEY. THIS SHOULD HALT FOG DEVELOPMENT FURTHER EAST BUT DUE TO THE SNOWPACK WEST OF THE BLUE RIDGE...DENSE FOG WILL CONTINUE ACROSS THE SHEN VALLEY. TEMPS WILL REACH THE UPPER 20S AND LOW 30S ACROSS THE REGION. ICY CONDITIONS FROM REFREEZE ARE POSSIBLE THIS MORNING. A SHORTWAVE TROUGH HAS MOVED INTO THE TN VALLEY THIS MORNING. WEAKENING LOW PRESSURE AHEAD OF THE TROUGH WILL CROSS SW VA THIS MORNING AND OFF THE CAROLINA COAST BY THIS AFTERNOON. SHOWERS HAVE BEEN OBSERVED ACROSS THE TN VALLEY/APPALACHIAN REGION OVERNIGHT. THEY WILL PIVOT NORTHWARD THIS MORNING AS THE TROUGH AXIS SWINGS APPROACHES THE REGION. THE TRACK OF THE LOW WILL KEEP MOST OF THE ACTIVITY SOUTH OF THE LWX REGION. LIGHT SHOWERS MAY SKIRT THE CENTRAL FOOTHILLS AND PIEDMONT TODAY. MAINLY RAIN SHOWERS ARE EXPECTED IN THIS AREA WITH THE EXCEPTION OF THE PRE DAWN HRS WHERE TEMPS DROPPING TO AROUND FREEZING WILL LEAD TO SNOW SHOWERS THIS MORNING. TEMPS WILL RISE INTO THE UPPER 30S TO 40S TODAY. AS LOW PRESSURE MOVES SOUTH OF THE REGION AND THE UPPER LEVEL TROUGH AXIS MOVES ACROSS THE REGION WESTERLY WINDS WILL INCREASE. UPSLOPE SNOW SHOWERS ARE POSSIBLE LATE THIS MORNING THROUGH TONIGHT. UP TO THREE INCHES IS POSSIBLE TODAY AND TONIGHT ACROSS THE WESTERN SLOPES. FURTHER EAST...COLD AIR ADVECTION WILL LEAD TO A STRATO-CU DECK AND SPRINKLES/FLURRIES ARE EXPECTED AS THE UPPER LEVEL TROUGH PASSES OVERHEAD TODAY. HIGH PRESSURE WILL MOVE INTO THE REGION TONIGHT. SNOW SHOWERS ON THE WESTERN SLOPES WILL TAPER OFF BY FRIDAY MORNING. FCST MIN TEMPS WILL RANGE FROM THE LOW 20S IN THE MTNS TO THE LOW 30S NEAR THE CITIES. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... STILL MAY HAVE A FEW UPSLOPE SNOW SHOWERS ONGOING TO START FRIDAY OTHERWISE SURFACE HIGH BUILDS IN FROM THE WEST FOR DRY CONDITIONS/SOME SUNSHINE BUT BELOW NORMAL TEMPERATURES. SURFACE HIGH SHIFTS OFFSHORE FRIDAY NIGHT. SHORTWAVE IN 500 MB FLOW WILL BRING INCREASING CLOUDS FRIDAY NIGHT INTO EARLY SATURDAY. MUCH OF THE CWA SHOULD BE DRY ALTHOUGH THERE WILL BE A SLIGHT CHANCE OF SNOW SHOWERS OVER THE ALLEGHENY/POTOMAC HIGHLANDS. TEMPERATURES START TO MODERATE A LITTLE FOR SATURDAY. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... RETURN FLOW AROUND HIGH PRESSURE LOCATED OFFSHORE WILL MODERATE TEMPERATURES MORE SATURDAY NIGHT INTO SUNDAY. A WARM FRONT WILL LIKELY PUSH NORTH FOR SUNDAY. THERE WILL BE SOME CLOUDS BUT CHANCE OF PRECIP APPEARS MINIMAL. ABOVE NORMAL TEMPERATURES ARE LIKELY TO PERSIST INTO MONDAY. A COLD FRONT WILL MOVE ACROSS THE AREA WITH A CHANCE OF RAIN SHOWERS. COLDER AIR IS THEN EXPECTED TO MOVE IN BEHIND THE FRONT FOR THE MID-WEEK PERIOD. && .AVIATION /10Z THURSDAY THROUGH MONDAY/... MVFR/IFR CONDITIONS DUE TO FOG DEVELOPMENT HAS LED TO SUDDEN DROPS IN VSBYS AT CHO THIS MORNING. THIS IS POSSIBLE AT MRB-IAD THROUGH THE DAWN HOURS. LIGHT SW WINDS WILL BECOME NW 5-10 KTS THIS AFTERNOON AT THE TERMINALS. VFR CONDITIONS EXPECTED LATER TODAY AND TONIGHT. HIGH PRESSURE BUILDS IN FOR FRIDAY THEN MOVES OFFSHORE FOR THE WEEKEND. NO SIGNIFICANT WX IS EXPECTED. && .MARINE... NRLY WINDS HAVE SUBSIDED ON THE WATERS OVERNIGHT AS THE COASTAL LOW MOVES FURTHER AWAY. WEAK LOW PRESSURE WILL MOVE SOUTH OF THE WATERS TODAY LEADING TO NW WINDS 10-15KTS TODAY. NRLY WINDS BEHIND THE LOW WILL INCREASE AND SCA CONDITIONS WILL BE POSSIBLE TONIGHT FOR PORTIONS OF THE WATERS BECOMING ALL THE WATERS FRIDAY. NORTHWEST WINDS BEHIND A SHORTWAVE SHOULD BE ABLE TO MIX DOWN FOR SCA CONDITIONS ON FRIDAY. HIGH PRESSURE BUILDS IN FOR LESS WIND FRIDAY NIGHT. RETURN FLOW ON SATURDAY COULD THEN INCREASE INTO SCA TERRITORY. && .CLIMATE... && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR VAZ025>030- 504. WV...DENSE FOG ADVISORY UNTIL 9 AM EST THIS MORNING FOR WVZ050-055- 502-506. MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 6 PM EST FRIDAY FOR ANZ530>534-536-537-539>541-543. SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EST FRIDAY FOR ANZ535- 538-542. && $$ SYNOPSIS...BPP/HAS NEAR TERM...HAS SHORT TERM...BPP LONG TERM...BPP AVIATION...BPP/HAS MARINE...BPP/HAS CLIMATE...

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