Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181810 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 210 PM EDT MON AUG 18 2014 .SYNOPSIS...
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A BOUNDARY WILL REMAIN STALLED OVER THE REGION THROUGH TONIGHT. LOW PRESSURE OVER THE OHIO VALLEY THIS MORNING WILL PASS THROUGH THE AREA LATER THIS AFTERNOON THROUGH TONIGHT. THE LOW WILL MOVE AWAY FROM THE AREA TUESDAY...BUT THE BOUNDARY WILL REMAIN NEARBY THROUGH THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH TUESDAY/...
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A WELL DEFINED SHORTWAVE TROUGH WILL CONTINUE TO APPROACH THE SOUTHERN MID ATLANTIC AS LOW PRESSURE TRACKS ACROSS SOUTHERN VA. A STATIONARY FRONT WILL STAY ACROSS THE REGION WITH EASTERLY WINDS ON THE COOL/STABLE SIDE AND SOUTHERLY WINDS ON THE WARM/MORE UNSTABLE SIDE. SHOWERS HAVE INCREASED IN COVERAGE THIS AFTERNOON AS LOW PRESSURE APPROACHES THE AREA. THE TRACK OF THE LOW WILL BRING IT SOUTH OF THE LWX CWA THIS AFTERNOON AND EVENING. THIS WILL LEAD TO MOST OF THE FORCING TO BE LOCATED IN SOUTHERN VA. THIS IS EVIDENT ON RADAR AS HEAVY SHOWERS AND THUNDERSTORMS MOVE ACROSS THIS REGION AND NRN NC. PWATS HAVE ALSO INCREASED TO 1.8 INCHES AND RISING IN THIS REGION. FURTHER NORTH...SHOWERS WILL INCREASE FROM SW TO NE TODAY. SHOWERS WILL BE HEAVIER CLOSER TO THE FORCING AND STATIONARY BOUNDARY THAT IS CURRENTLY SOUTH OF THE REGION. QPF WILL RANGE FROM AROUND A HALF INCH NEAR CHO TO A FEW HUNDREDTHS OF AN INCH NEAR BWI/DMH. THE SHORTWAVE TROUGH AND ASSOCIATED LOW WILL MOVE EAST TONIGHT AND EXIT THE TIDE WATER REGION TUESDAY MORNING. DUE TO THE EASTERLY FLOW ON THE NORTH SIDE OF THE SFC LOW MOISTURE ADVECTION WILL LEAD TO LOW CLOUDS ACROSS THE REGION. PATCHY FOG IS ALSO EXPECTED IN VALLEY LOCATIONS ESPECIALLY PLACES THAT SEE MORE RAIN THAN OTHERS. WESTERLY FLOW ALOFT WILL LEAD TO AN ACTIVE PERIOD THROUGH THE START OF THE WORK WEEK. A STATIONARY FRONT WILL STAY NEAR THE HIGHLANDS AND SOUTH ACROSS SOUTHERN VA. AT THIS TIME IT IS HARD TO DEFINE BUT EASTERLY FLOW FROM THE JERSEY WILL SPREAD OUT ACROSS THE REGION LEADING TO FLOW UP AGAINST THE BOUNDARY. THIS SEEMS TO BE THE ONLY FORCING MECHANISM TUESDAY AND THEREFORE LOW CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY WEST OF THE BLUE RIDGE. SFC LOW PRESSURE FROM THE SHORTWAVE TROUGH TODAY WILL BE JUST OFF THE DELMARVA COAST TUESDAY.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
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ACTIVITY SHOULD BE DIURNAL IN NATURE AND WANE TUESDAY EVENING LEADING TO MOSTLY DRY CONDITIONS. EASTERLY FLOW WILL LEAD TO LOW CLOUDS AND PATCHY FOG FOR MUCH OF THE REGION TUESDAY NIGHT AND INTO WED MORNING. A TROUGH OF LOW PRESSURE WILL ENTER THE GREAT LAKES REGION WEDNESDAY AND SHOWERS AND THUNDERSTORMS WILL APPROACH THE HIGHLANDS WED MORNING AHEAD OF A COLD FRONT MOVING ACROSS THE OHIO VALLEY. LOW PRESSURE IS STILL PROGGED TO BE LOCATED OFF THE MID ATLANTIC COAST LEADING TO NE-E WINDS ACROSS MOST OF THE REGION. WINDS SHOULD BECOME SOUTHERLY BY WED AFTERNOON AND INSTABILITY WILL INCREASE. SHOWERS AND THUNDERSTORMS WILL MOVE EASTWARD THROUGHOUT WEDNESDAY.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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THE DOMINANT AXIS OF THE LARGE SCALE UPPER LEVEL TROUGH THAT WILL BE BRINGING THE MID-ATLANTIC ACTIVE WEATHER THIS WEEK WILL FINALLY DIG ACROSS THE EASTERN US THURSDAY AND FRIDAY. THIS WILL BRING A WEAK SURFACE COLD FRONT THROUGH THE AREA DURING THE DAY THURSDAY. SOUTHERLY FLOW AT THE SURFACE WILL ALLOW FOR ENOUGH PREFRONTAL WAA/MOISTURE ADVECTION THAT THURSDAY EVENING WILL SEE THE MOST INSTABILITY OF ANY DAY THIS WEEK...WITH POCKETS OF CAPE BETWEEN 1000 AND 1500 J. WITH JUST OVER 30 KTS OF SHEAR AND DRY LOW LEVELS/STEEP LOW LEVEL LAPSE RATES DAMAGING WINDS MAY BE A THREAT IN THUNDERSTORMS THAT DO INITIATE. COVERAGE OF STORMS WILL BE HIGHEST IN THE AFTERNOON WITH THE PEAK IN DIURNAL HEATING...THOUGH THE THREAT COULD CONTINUE THROUGH THE NIGHT DUE TO THE INCREASED UPPER LEVEL DYNAMICS IN THE AREA. AS THE UPPER LEVEL TROUGH AXIS MOVES OFF THE COAST A WAVE OF LOW PRESSURE WILL FORM OFF OF CAPE HATTERAS. ONSHORE FLOW AROUND THE NORTH SIDE OF THIS LOW WILL BRING A BACKDOOR COLD FRONT THROUGH THE AREA FRIDAY. THE SEASONABLY COOL AND MOIST AIRMASS BEHIND THIS FRONT WILL REMAIN OVER THE AREA THROUGH THE WEEKEND...BRINGING PERIODS OF LIGHT RAIN WITH A LOW CLOUD DECK. RAINFALL COULD BE ENHANCED ALONG THE BLUE RIDGE DUE TO UPSLOPING OF EASTERLY FLOW. HIGH PRESSURE WILL MOVE OVERHEAD LATE SUNDAY...ALLOWING SKIES TO BEGIN TO CLEAR AND BRINGING IN DRY CONDITIONS FOR THE BEGINNING OF THE WORKWEEK. TEMPS WILL BE IN THE LOW TO MID 80S ON THURSDAY THANKS TO PREFRONTAL WARM AIR ADVECTION. FRIDAY SATURDAY AND SUNDAY WILL ONLY SEE HIGHS INTO THE LOWER 70S AS A MARINE AIRMASS AND PLENTY OF SKY COVER WILL LIMIT DAYTIME HEATING. TEMPS WILL BEGIN TO CLIMB BACK TOWARD NORMAL TO BEGIN NEXT WEEK WITH HIGHS ON MONDAY MOSTLY IN THE LOWER 80S.
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&& .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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LOW PRESSURE WILL MOVE TO THE SOUTH OF THE TERMINALS TODAY. SHRA ARE EXPECTED AT CHO THIS AFTERNOON AND EVENING. FURTHER NORTH...SHRA WILL BE ISO-SCT. VFR CONDITIONS EXPECTED THIS AFTERNOON. EASTERLY FLOW WILL LEAD TO LOW CIGS/VSBYS TONIGHT LEADING TO IFR CONDITIONS AT THE TERMINALS. A STATIONARY FRONT WILL BE WEST OF THE TERMINALS TUESDAY AND EASTERLY WINDS WILL CONTINUE TO USHER IN MOISTURE FROM THE OCEAN. ISO-SCT SHRA AND TSRA POSSIBLE AT MRB/CHO TUESDAY AFTERNOON. IFR CONDITIONS EXPECTED TUESDAY NIGHT/WEDNESDAY MORNING FOR LOW CIGS AND VSBYS. E-SE FLOW WILL CONTINUE WEDNESDAY AS A COLD FRONT APPROACHES FROM THE WEST. SHRA AND TSRA POSSIBLE WEDNESDAY. PERIODS OF SHOWERS AND THUNDERSTORMS MAY EFFECT AVIATION THURSDAY EVENING. LOW CEILINGS ARE EXPECTED AS A MARINE AIRMASS FILLS IN TO THE AREA LATE FRIDAY NIGHT THROUGH SUNDAY.
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&& .MARINE...
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SHOWERS WILL MOVE ACROSS THE WATERS THIS EVENING AS LOW PRESSURE MOVES ACROSS SOUTHERN VA TODAY. EASTERLY WINDS WILL STAY BELOW SCA CONDITIONS BUT A FEW SHOWERS THIS EVENING MAY CAUSE NEAR 15-20 KTS ON THE WATERS. AT THIS TIME CONFIDENCE IS LOW AND THEREFORE SCA IS NOT IN EFFECT. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY MARINE HAZARDS THROUGH THE LONG TERM.
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&& .TIDES/COASTAL FLOODING...
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ONSHORE FLOW WILL INCREASE TIDAL ANOMALIES TODAY AND TONIGHT. MINOR COASTAL FLOODING WILL BE POSSIBLE LATE TONIGHT AT ANNAPOLIS AS ANOMALIES RISE TO OVER A HALF FOOT ABOVE NORMAL.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BJL NEAR TERM...HAS SHORT TERM...HAS LONG TERM...CEB AVIATION...HAS/CEB MARINE...HAS/CEB TIDES/COASTAL FLOODING...HAS

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