Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 050103 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 903 PM EDT SAT JUL 4 2015 .SYNOPSIS... A COLD FRONT WILL STALL TO OUR SOUTH TONIGHT INTO SUNDAY. WEAK HIGH PRESSURE WILL BUILD OVERHEAD EARLY SUNDAY BEFORE MOVING OFF THE COAST SUNDAY AFTERNOON AND EVENING. AN UPPER LEVEL DISTURBANCE IMPACTS THE AREA SUNDAY NIGHT THROUGH TUESDAY BRINGING UNSETTLED WEATHER. && .NEAR TERM /THROUGH SUNDAY NIGHT/... A WEAK BOUNDARY STRETCHES FROM THE SHENANDOAH VALLEY INTO THE VIRGINIA PIEDMONT THIS EVENING. AN UPPER-LEVEL TROUGH AXIS IS MOVING OFF TO OUR EAST DURING THIS TIME...AND SURFACE LOW PRESSURE THAT WAS ALONG THE BOUNDARY IS ALSO MOVING AWAY FROM THE AREA. THE SHOWERS AND THUNDERSTORMS THAT DEVELOPED EARLIER TODAY HAVE MOVED OUT OF THE CWA THIS EVENING. SUBSIDENCE BEHIND AND UPPER-LEVEL DISTURBANCE WILL KEEP MOST AREAS DRY THIS EVENING. HOWEVER...AN ISOLATED SHOWER CANNOT BE COMPLETELY RULED OUT WITH THE BOUNDARY NEARBY. FOR ANY AREAS THAT DO GET A SHOWER IT SHOULD ONLY LAST ABOUT TEN TO FIFTEEN MINUTES BEFORE MOVING AWAY...AND AGAIN MOST AREAS WILL NOT SEE ANY PRECIPITATION. DRY CONDITIONS WILL PERSIST OVERNIGHT AS WEAK HIGH PRESSURE SETTLES OVER THE REGION. THE BOUNDARY WILL DISSIPATE AND SHIFT SOUTH DURING THIS TIME. THERE IS LITTLE DEWPOINT OR TEMPERATURE GRADIENT ASSOCIATED WITH THE BOUNDARY...SO LOW-LEVEL MOISTURE WILL HANG AROUND. THE COMBINATION OF LOW-LEVEL MOISTURE...LIGHT WINDS AND BREAKS IN THE CLOUDS WILL RESULT IN AREAS OF FOG. SOME FOG MAY BE DENSE OVERNIGHT AND THIS WILL HAVE TO BE MONITORED. A DENSE FOG ADVISORY MAY BE NEEDED FOR PORTIONS OF THE AREA LATE TONIGHT...ESPECIALLY FOR LOCATIONS THAT RECEIVED RAINFALL AND ALSO SHELTERED VALLEYS/RURAL AREAS. HIGH PRESSURE WILL DOMINATE SUNDAY WITH PARTLY TO MOSTLY SUNNY SKIES FOR MUCH OF THE DAY ESPECIALLY OVER THE METRO. HOWEVER...FURTHER SOUTHWEST...A NEW CLOSED LOW WILL DEVELOP ALOFT TONIGHT OVER THE TENNESSEE VALLEY AND MOVE NORTHEAST TOWARD OUR REGION. CLOUDS WILL BEGIN INCREASING AGAIN...AND SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP AND ADVECT NORTHEASTWARD STARTING IN OUR SOUTHWESTERN ZONES DURING THE AFTERNOON. THESE WILL OVERSPREAD MOST OF THE CWA BY LATER SUNDAY NIGHT. AFTER HIGHS IN THE 80S SUNDAY...LOWS WILL DROP BACK INTO THE 60S ON SUNDAY NIGHT. && .SHORT TERM /MONDAY THROUGH TUESDAY/... MID/UPPER LEVEL DISTURBANCE THAT IS CUTOFF FROM THE MAIN BELT OF WESTERLIES TO THE NORTH BEGINS TO IMPACT THE AREA IN EARNEST DURING THE DAY MON. COMBINATION OF SFC WARM FRONT MOVING NORTH OVER AREA...UPPER LEVEL DIFFLUENCE...AND VERY MOIST DEEP LAYER WITH PWATS PROGGED TO BE NEAR 2 INCHES SUGGEST THE POTENTIAL FOR EFFICIENT RAIN PRODUCERS WITH MODERATE TO HEAVY RAIN POSSIBLE. SHEAR REMAINS WEAK (0-6 KM EBS AOB 20 KTS) AND INSTABILITY COULD BE LIMITED DUE TO EXTENSIVE CLOUD COVER...WHICH WOULD LIMIT OVERALL STORM ORGANIZATION/INTENSITY. TEMPS MIGHT NEED TO BE ADJUSTED A LITTLE FURTHER DOWNWARD IN SUBSEQUENT FORECASTS...AS AFOREMENTIONED CLOUD COVER COULD LIMIT INSOLATION. BULK OF ACTIVITY SHOULD MOVE AWAY FROM THE AREA DURING THE OVERNIGHT MONDAY AS THE DISTURBANCE IS ENGULFED INTO THE NORTHERN STREAM. LIKELY A PERIOD OF SUBSIDENCE BEHIND DISTURBANCE PROVIDING SOME CLEARING DURING THE EARLY PART OF TUE. LITTLE IN THE WAY OF FORCING MECHANISM TUE...THOUGH COULD GET SOME ACTIVITY MOVING EAST OFF HIGHER TERRAIN OR ALONG LEE TROUGH. STARTS GETTING A LITTLE WARMER TUE...WITH TEMPS GETTING BACK TO NEAR NORMAL (U80S). && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... DISTURBANCE LINGERS IN THE AREA TUES NIGHT INTO WED AS A COLD FRONT APPROACHES LATE ON WED. COLD FRONT SLOWLY DRIFTS SOUTH OVER THE CWA AND LINGERS THROUGH THE END OF THE WEEK...DRIER CONDITIONS ARRIVE FOR THE WEEKEND. UNCERTAINTY ON LOCATION OF THE FRONT MAY AFFECT POPS...BUT DIURNAL EFFECTS ALLOWS FOR THE RISK OF ISOLATED/SCATTERED SHOWERS AND/OR TSTMS EACH DAY. HIGH TEMPS WILL BE IN THE 80S...LOW TEMPS IN THE 70S FOR MOST OF THE CWA...AND IN THE MID TO UPR 60S AT HIGHER ELEVATIONS. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... THE STORMS HAVE MOVED AWAY FROM THE TERMINALS THIS EVENING. A STRAY SHOWER CANNOT BE RULED OUT THIS EVENING...BUT MOST AREAS WILL BE DRY. AREAS OF FOG ARE EXPECTED LATE TONIGHT INTO SUNDAY MORNING. FOG MAY BE LOCALLY DENSE WITH IFR/SUBIFR CONDITIONS POSSIBLE. SUNDAY AFTER ANY FOG BREAKS SHOULD BE MOSTLY VFR...THOUGH LATE IN THE DAY ANOTHER ROUND OF STORMS LOOKS TO MOVE INTO CHO AND THEN NORTHEAST TOWARD THE REST OF THE TERMINALS SUNDAY NIGHT...WITH MORE CONCERNS ABOUT GUSTY WINDS AND REDUCED VIS. OUTSIDE OF STORMS...WINDS SHOULD REMAIN BELOW 10 KNOTS THROUGH SUNDAY NIGHT. IFR CIGS APPEAR POSSIBLE THROUGH THE DAY MON IN MODERATE/HEAVY RAIN SHWRS AND STORMS. IMPROVING TO MVFR LATE MON AND VFR BY TUESDAY MORNING AS UPPER LEVEL DISTURBANCE PULLS AWAY FROM THE AREA. VFR CONDITIONS EXPECTED FOR TUES NIGHT AND WED. SUB-VFR DUE TO PSBL SHOWERS AND TSTMS WED AFTN. && .MARINE... THUNDERSTORMS WILL MOVE THROUGH THE LOWER TIDAL POTOMAC RIVER AND MARYLAND CHESAPEAKE BAY SOUTH OF DRUM POINT EARLY THIS EVENING. ELSEWHERE...DRY CONDITIONS ARE EXPECTED MOST OF THE TIME BUT A STRAY SHOWER CANNOT BE RULED OUT. NORTH TO NORTHEAST WINDS WILL REMAIN BELOW SCA CRITERIA THIS EVENING. WINDS WILL BE LIGHT OVERNIGHT AS WEAK HIGH PRESSURE BUILDS OVERHEAD. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND AN EAST TO SOUTHEAST FLOW WILL DEVELOP. WIND SPEEDS WILL REMAIN BELOW SCA CRITERIA...BUT SHOWERS AND A FEW THUNDERSTORMS ARE POSSIBLE SUNDAY NIGHT. WINDS EXPECTED TO REMAIN LIGHT AND VARIABLE MON....BUT COULD STRENGTHEN SOME ON TUE DUE TO CHANNELING SRLY FLOW. COULD BE SOME ISOLATED TSTMS MON AND AGAIN TUE AFTERNOON. SUB-SCA CONDITIONS EXPECTED FOR TUES NIGHT AND WED. PSBL SHOWERS AND TSTMS ACROSS THE WATERS ON WED AFTN. && .TIDES/COASTAL FLOODING... THE FLOW WILL REMAIN LIGHT THROUGH SUNDAY. NO TIDAL FLOODING IS EXPECTED...DESPITE ANOMALIES BEING A BIT ABOVE NORMAL. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...MSE NEAR TERM...BJL/RCM SHORT TERM...MSE/RCM LONG TERM...IMR AVIATION...BJL/IMR/MSE/RCM MARINE...BJL/IMR/MSE/RCM TIDES/COASTAL FLOODING...BJL

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