Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191310 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 910 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/...
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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. HIGH PRESSURE OVER NEW ENGLAND THIS MORNING WILL SHIFT TOWARD THE NEW ENGLAND COAST THIS AFTERNOON. THE SURFACE RIDGE AXIS ASSOCIATED WITH THE HIGH CURRENTLY EXTENDS SOUTH INTO OUR AREA...AND THIS IS EXPECTED TO SHIFT TOWARD THE MID-ATLANTIC COAST THIS AFTERNOON. NORTHEAST WINDS THIS MORNING WILL SHIFT TO THE EAST-SOUTHEAST THIS AFTERNOON. THE ONSHORE FLOW WILL RESULT IN PLENTY OF CLOUDS ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS...BUT THE DRIER AIR CLOSER TO THE HIGH SHOULD ALLOW FOR SOME SUNSHINE ACROSS THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS AS WELL AS FOR LOCATIONS NEAR THE MARYLAND CHESAPEAKE BAY. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS AS WELL AS THE CENTRAL SHENANDOAH VALLEY WHERE MORE CLOUD COVER IS EXPECTED...TO THE LOWER AND MIDDLE 70S NEAR WASHINGTON AND BALTIMORE INTO SOUTHERN MARYLAND. HIGH PRESSURE WILL MOVE OFF THE NEW ENGLAND COAST TONIGHT. 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.
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&& .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 /13Z FRIDAY THROUGH TUESDAY/...
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VFR CONDITIONS ARE EXPECTED TODAY ACROSS MOST AREAS...BUT DEEPER MOISTURE WILL RESULT IN MVFR CONDITIONS ACROSS KCHO. HIGH PRESSURE WILL CONTINUE TO WEDGE ACROSS THE EASTERN SEABOARD AND MVFR CIGS WILL EXPAND TONIGHT REACHING MRB AND POSSIBLY KIAD BY SATURDAY MORNING. CIGS MAY BECOME IFR AT KCHO. WINDS WILL VEER TO THE SOUTH BY SATURDAY MORNING AND LOW CLOUDS SHOULD BURN OFF LATER IN THE MORNING OR PERHAPS EARLY AFTERNOON. 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...
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NORTHEAST WINDS WILL SHIFT TO THE EAST THIS AFTERNOON AS A SURFACE RIDGE AXIS BUILDS ALONG THE MID-ATLANTIC COAST. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER THIS MORNING. WINDS SHOULD DIMINISH A BIT THIS AFTERNOON AS THE PRESSURE GRADIENT WEAKENS...BUT GUSTS WILL BE CLOSE TO SCA CRITERIA FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. EASTERLY WINDS WILL CONTINUE TONIGHT. 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.
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&& .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...BJL/HAS SHORT TERM...AEB LONG TERM...AEB AVIATION...BJL/HAS/AEB MARINE...BJL/HAS/AEB TIDES/COASTAL FLOODING...HAS

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