Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 280120 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 920 PM EDT WED AUG 27 2014 .SYNOPSIS... A WEAK COLD FRONT OVER SOUTHERN PENNSYLVANIA WILL MOVE INTO THE AREA TONIGHT. HIGH PRESSURE WILL BUILD ACROSS THE NORTHERN MID-ATLANTIC THURSDAY NIGHT...LINGERING OFF THE COAST INTO THE WEEKEND. THE NEXT COLD FRONT WILL APPROACH THE MID-ATLANTIC EARLY NEXT WEEK. && .NEAR TERM /THROUGH THURSDAY/... WK CD FNT NOW ACROSS SRN PA WL CONT TO SINK THRU THE CWA OVRNGT. IT IS APPEARING LK ONLY THE FAR WRN SXN OF THE CWA WL XPRNC ANY PCPN W/ THIS. NW FLOW AND DRIER AIR WILL MOVE IN BEHIND THE FRONT. THE FRONT SHOULD BE IN SRN VA BY THURSDAY MORNING AND CLOUDS WILL CLEAR FROM NORTH TO SOUTH EARLY THURSDAY MORNING. THURSDAY...NW FLOW WILL DROP DEWPTS INTO THE 50S. FCST MAX TEMPS ARE IN THE LOW 80S NEAR THE MASON DIXON LINE TO THE MID 80S IN CENTRAL VA...WITH MID TO UPPER 80S IN DC/BALTIMORE. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... NLY FLOW FROM HIGH PRESSURE MOVING EAST ACROSS THE NRN MID- ATLANTIC SHOULD LIMIT FOG THURSDAY NIGHT. MIN TEMPS MID 50S NW TO LOW 60S SE (MID 60S URBAN). FRIDAY...MID LEVEL RIDGE AXIS LIFT OVER THE AREA WITH A RETURN OF MOISTURE BY THAT EVENING. ISO WORDING FOR THUNDERSTORMS IN MOUNTAINS OF THE SOUTHWEST ZONES. MAX TEMPS GENERALLY MID 80S IN SELY ONSHORE SFC FLOW. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... SURFACE HIGH PRESSURE WILL MOVE OFF OF THE NEW ENGLAND COAST OVER THE COURSE OF THE WEEKEND. GRADUALLY INCREASING WARM AND MOIST SOUTHERLY FLOW COMBINED WITH HEIGHT FALLS ALOFT WILL LEAD TO INCREASED INSTABILITY DURING THIS TIME. THUNDERSTORM ACTIVITY SATURDAY SHOULD BE LIMITED TO THE HIGH TERRAIN ALONG THE POTOMAC HIGHLANDS AND WESTERN MD WHERE UPSLOPE FLOW WILL PROVIDE THE BEST TRIGGER FOR CONVECTION. LITTLE STEERING FLOW SHOULD ENSURE THAT THESE STORMS REMAIN WEST OF THE METRO AREAS UNTIL THEY DIE OUT SHORTLY AFTER SUNSET SATURDAY NIGHT. HIGH PRESSURE OFF THE COAST WILL SETTLE INTO A MORE TYPICAL BERMUDA HIGH LOCATION BY SUNDAY EVENING...ALLOW LEE TROUGHING TO SET UP LOCALLY AHEAD OF AN APPROACHING WEAK COLD FRONT SUNDAY. THIS LIFTING MECHANISM WILL LEAD TO AN INCREASE IN SHOWERS AND THUNDERSTORM COVERAGE AHEAD OF THE FRONT BY SUNDAY AFTERNOON. INSTABILITY LESS THAN 1000 J AND RELATIVELY WEAK SHEAR SUNDAY SHOULD LIMIT THE SEVERE POTENTIAL OF THUNDERSTORMS THAT DO FORM. THE FRONTAL BOUNDARY WILL ESSENTIALLY STALL AND DETERIORATE OVER THE AREA THROUGH MONDAY...SO CHANCE POPS AND THUNDERSTORMS WILL REMAIN IN THE FORECAST FOR MONDAY WITH SLIGHTLY MORE INSTABILITY THAN ON SUNDAY. MONDAY NIGHT SHOULD BE DRY AS LITTLE DYNAMIC ENHANCEMENT WILL REMAIN OVER THE AREA AS THE FRONT WILL HAVE MOSTLY DETERIORATED. SOUTHERLY FLOW AROUND THE BERMUDA HIGH AND THE RESULTING LEE TROUGH WILL RESUME TUESDAY AND AFTERNOON THUNDERSTORMS WILL BE POSSIBLE ONCE AGAIN. A REINFORCING COLD FRONT SHOULD MOVE THROUGH WEDNESDAY...BRINGING SHOWERS AND THUNDERSTORMS FOR THE MIDDLE OF THE WORKWEEK. HIGH TEMPS WILL BE NEAR 90 SATURDAY...SUNDAY AND TUESDAY...AS PREFRONTAL SOUTHERLY FLOW AND LEE TROUGHING SET UP LOCALLY. HIGHS ON MONDAY AND WEDNESDAY WILL BE IN THE MID TO UPPER 80S AS FRONTS APPROACH AND CROSS THE AREA. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... VFR TONIGHT FOR MOST TERMINALS. DC METROS SHOULD BE DRY TONIGHT IN SPITE OF A COLD FRONTAL PASSAGE. NWLY FLOW AROUND 10 KT BEHIND THE FRONT LATE TONIGHT. HIGH PRESSURE THROUGH THURSDAY NIGHT WITH VFR CONDS THROUGH FRIDAY. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY HAZARDS TO AVIATION IN THE LONG TERM. && .MARINE... NWLY WINDS TONIGHT BEHIND A DRY COLD FRONT. 10 TO 15 KT NWLY FLOW THURSDAY AS HIGH PRESSURE BUILDS FROM THE GREAT LAKES. LIGHTER NLY FLOW THURSDAY NIGHT...BECOMING ONSHORE FOR FRIDAY. A SMALL CRAFT ADVISORY MAY BE NECESSARY SUNDAY IN BREEZY PREFRONTAL SOUTHERLY FLOW. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ UPDATE...WOODY! PRVS...BAJ/CEB

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