Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190755 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 355 AM EDT FRI SEP 19 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD THROUGH SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A STRONGER COLD FRONT WILL PASS THROUGH THE AREA SUNDAY NIGHT INTO MONDAY. HIGH PRESSURE WILL RETURN FOR THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... HIGH PRESSURE IS CENTERED ACROSS ONTARIO THIS MORNING. A WEAK FRONTAL BOUNDARY WILL CONTINUE TO MOVE TO THE SOUTH OF THE MID-ATLANTIC. HIGH PRESSURE TO THE NORTH WILL BEGIN TO WEDGE DOWN THE EASTERN SEABOARD TODAY. MOISTURE IS TRAPPED BELOW THE SUBSIDENCE INVERSION AND AGAINST THE BLUE RIDGE/VA HIGHLANDS EARLY THIS MORNING. ISO-SCT SHOWERS DUE TO MOISTURE CONVERGENCE ACROSS THE PIEDMONT MAY BRUSH NELSON- ALBEMARLE THIS MORNING. A WEAK FRONTAL BOUNDARY IS LOCATED ACROSS THE MOUTH OF THE POTOMAC AND CENTRAL PIEDMONT AND LIGHT NRLY WINDS WILL CONTINUE BEHIND THE FRONTAL BOUNDARY THIS MORNING. DRIER AIR AND SUBSIDENCE HAS LED TO CLEARING ACROSS THE NORTHEASTERN HALF OF THE CWA WITH DEWPTS IN THE UPPER 40S. NEAR AND AHEAD OF THE FRONTAL BOUNDARY DEWPTS ARE IN THE UPPER 50S LEADING TO PATCHY GROUND FOG. WINDS WILL VEER TO THE EAST THROUGHOUT THE DAY AS HIGH PRESSURE NOSES INTO THE AREA. ONSHORE FLOW WILL LEAD TO MOISTURE BANKING UP AGAINST THE RIDGE LINES ACROSS THE VA HIGHLANDS AND CENTRAL BLUE RIDGE. ELSEWHERE...PARTLY SUNNY CONDITIONS EXPECTED WITH FCST MAX TEMPS IN THE UPPER 60S TO LOW 70S TODAY. HIGH PRESSURE WILL MOVE ACROSS NEW ENGLAND LATER THIS AFTERNOON AND OUT TO SEA BY EVENING. EASTERLY FLOW WILL CONTINUE ACROSS THE REGION. COVERAGE OF LOW STRATUS WILL INCREASE AND MOVE NORTHWARD ALONG THE BLUE RIDGE...SHENANDOAH VALLEY AND POTOMAC HIGHLANDS OVERNIGHT. HIGH PRESSURE WILL BEGIN TO WEAKEN ITS HOLD ON THE MID-ATLANTIC SATURDAY AS IT MOVES FURTHER OUT TO SEA. AS WITH MANY CAD SETUPS...STRATUS WILL SLOWLY DISSIPATE ACROSS THE REGION ALTHOUGH WINDS BECOME SOUTHERLY. SUNSHINE IS EXPECTED BY SATURDAY AFTERNOON WITH FCST MAX TEMPS REACHING THE MID TO UPPER 70S. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE AXIS REMAINS IN PLACE ACROSS THE MID-ATLANTIC SATURDAY NIGHT/SUNDAY MORNING BETWEEN AN OFFSHORE TROPICAL LOW AND A STRONG COLD FRONT PUSHING ACROSS THE OHIO RIVER VALLEY. SHALLOW LOW LEVEL MOISTURE PRESENT WITH WEAK ONSHORE FLOW COULD RESULT IN PATCHY GROUND/RIVER FOG DEVELOPING OVERNIGHT...AND MAINTAINED MENTION FOR FAVORED AREAS. WARM AIR ADVECTION STRENGTHENS SUNDAY AS LOW LEVEL WINDS VEER AND H85 TEMPS CLIMB TO THE MID TEENS CELSIUS. THIS WARMER AIRMASS AHEAD OF THE APPROACHING COLD FRONT SHOULD RESULT IN TEMPS REACHING THE LOW TO MID 80S. MODELS NOW SHOWING A RELATIVELY NARROW AXIS OF MOISTURE AND INSTABILITY SUNDAY AFTERNOON...ESPECIALLY AREAS WEST OF THE BLUE RIDGE...AND HAVE MAINTAINED MENTION OF THUNDER THROUGH THE AFTERNOON PERIOD. WILL ALSO SEE INCREASING DEEP-LAYER SHEAR THROUGH THE DAY SUNDAY AS POTENT SHORT WAVE IN BASE OF LONG WAVE TROUGH SWINGS ACROSS THE SOUTHERN GREAT LAKES. THE TIMING OF THE BEST INSTABILITY AND SHEAR REMAIN DISCONNECTED HOWEVER...BUT A FEW ORGANIZED STORMS MAY BE POSSIBLE SUNDAY AFTERNOON. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... INSTABILITY DROPS OFF RAPIDLY SUNDAY EVENING AS FRONT PROGRESSES EASTWARD. HOWEVER SHEAR INCREASES SO GUSTY SHOWERS ARE POSSIBLE THROUGH THE EVENING ALONG AND AHEAD OF THE COLD FRONT. GOOD COLD AIR ADVECTION LOOKS TO BEGIN A BIG EARLIER /NOW ON LATE SUNDAY NIGHT/ AND CONTINUES THROUGH MONDAY AS UPPER SHORT WAVE TROUGH MOVES OVERHEAD. WILL SEE INCREASING NORTHWEST WINDS AND MUCH COOLER/DRIER AIR MONDAY. SHOULD ALSO SEE DOWNSLOPING TEMPERATURE EFFECT FOR AREAS EAST OF THE RIDGES ON MONDAY. TEMPS WILL BE CHILLY MONDAY NIGHT AS HIGH PRESSURE BUILDS IN FROM THE WEST. THIS COOL AND DRY AIRMASS WILL CONTINUE FOR THE FIRST FULL DAY OF ASTRONOMICAL FALL -TUESDAY...AS WELL AS WEDNESDAY/THURSDAY. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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LIGHT NRLY WINDS WILL BECOME EASTERLY TODAY AND ONSHORE FLOW WILL ALLOW STRATUS TO BANK AGAINST THE BLUE RIDGE TODAY. MVFR CIGS ARE EXPECTED AT CHO THROUGH TONIGHT. ELSEWHERE...VFR SCT- BKN CIGS ARE EXPECTED. HIGH PRESSURE WILL CONTINUE TO WEDGE ACROSS THE EASTERN SEABOARD AND MVFR CIGS WILL EXPAND TONIGHT REACHING MRB AND POSSIBLY IAD BY SATURDAY MORNING. CIGS MAY BECOME IFR AT CHO THIS EVENING. WINDS WILL VEER TO THE SOUTH BY SATURDAY MORNING AND CIGS WILL BECOME VFR FROM SOUTH TO NORTH SATURDAY. A HIGH PRESSURE WEDGE WILL BE IN PLACE FOR SATURDAY NIGHT WITH AREAS OF FOG POSSIBLE LATE. A COLD FRONT WILL BRING THE CHANCE OF SHOWERS AND STORMS AS IT CROSSES THE AREA FROM WEST TO EAST SUNDAY AFTERNOON THROUGH LATE SUNDAY EVENING. WINDS WILL SHIFT OUT OF THE NORTHWEST AND INCREASE BEHIND THE FRONT FOR MONDAY. COOL HIGH PRESSURE WILL RETURN FOR TUESDAY AND WEDNESDAY.
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&& .MARINE... NRLY WINDS WILL INCREASE BEHIND AN EXITING FRONTAL BOUNDARY THIS MORNING. WINDS WILL INCREASE FROM NORTH TO SOUTH ACROSS THE BAY AND LOWER TIDAL POTOMAC AND A SCA IS IN EFFECT FOR THESE ZONES. E-SE WINDS WILL CONTINUE THROUGH SATURDAY. SOME GUSTS MAY APPROACH SCA AT TIMES THIS AFTERNOON BUT DUE TO THE WEAK PRESSURE GRADIENT ACROSS THE WATERS KEPT THEM BELOW AT THIS TIME. HIGH PRESSURE WILL SHIFT SOUTH OF THE REGION SATURDAY NIGHT INTO SUNDAY AS WINDS VEER SOUTH. A COLD FRONT WILL PUSH ACROSS THE WATERS SUNDAY EVENING...BRINGING THE CHANCE OF SHOWERS OR STORMS WITH GUSTY WINDS. NORTHWEST WINDS WILL INCREASE EARLY MONDAY BEHIND THE COLD FRONT...AND A SCA MAY BE NEEDED FOR PORTIONS OF THE WATERS. HIGH PRESSURE WILL RETURN TO THE REGION FOR TUESDAY AND WEDNESDAY. && .TIDES/COASTAL FLOODING... ANOMALIES HAVE DROPPED BELOW A FOOT THIS MORNING AND COASTAL FLOODING IS NOT EXPECTED AT THIS TIME. AN ONSHORE FLOW IS EXPECTED TO CONTINUE LATE TONIGHT THROUGH SUNDAY...CAUSING ELEVATED WATER LEVELS AND THE POSSIBILITY OF MINOR TIDAL FLOODING. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ530>534-537- 539>541-543. && $$ SYNOPSIS...HAS NEAR TERM...HAS SHORT TERM...AEB LONG TERM...AEB AVIATION...HAS/AEB MARINE...HAS/AEB TIDES/COASTAL FLOODING...HAS

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