Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 231849 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 249 PM EDT SUN AUG 23 2015 .SYNOPSIS... HIGH PRESSURE WEAKEN OVER THE AREA TONIGHT. A COLD FRONT WILL APPROACH FROM THE WEST EARLY MONDAY AND CROSS THE REGION BY LATE MONDAY NIGHT. HIGH PRESSURE WILL GRADUALLY BUILD SOUTHEASTWARD INTO THE AREA DURING THE MIDDLE OF THE WEEK AND SETTLE DIRECTLY ON TOP OF OUR AREA FOR THE START OF NEXT WEEKEND. && .NEAR TERM /THROUGH MONDAY/... SFC HIGH PRESSURE RETREATING TO THE NORTH AS THE REGION REMAINS POSITIONED BETWEEN TWO AREAS OF LOW PRESSURE...ONE DEEPENING TO THE EAST OFFSHORE AND ANOTHER TREKKING THROUGH THE GREAT LAKES...DRAGGING ITS ASSOCIATED COLD FRONT CURRENTLY THRU INDIANA. WEAK SFC TROUGH HAS DEVELOPED ACROSS WV...WITH 18Z RADAR REFLECTIVITY SHOWING SCT CONVECTION HAVING FORMED WHERE A VORT MAX IS PASSING THIS TROUGH. STILL ANTICIPATING ISO-SCT SHOWERS AND TSTMS TO MOVE INTO THE SOUTHWESTERN CORNER OF THE CWA WHERE THE THETA-E RIDGE HAS NUDGED IN. EXPECTING LACK OF SFC/UPPER LVL FORCING COMBINED WITH A MAINLY STABLE AIRMASS WILL PRECLUDE ANY OF THE STORMS FROM PUSHING FURTHER EAST. STORMS TAPER OFF AFTR SUNSET...WITH DRY CONDITIONS FOR THE NIGHT. 12Z MODELS STILL CONSISTENT ON KEEPING THE FRONT WELL ENOUGH TO THE WEST...AND AS SUCH PCPN WILL MOVE IN AFTR 12Z MON. TEMPS CLOSE TO NORMAL FOR TONIGHT. INITIALLY DRY CONDITIONS MON MORNING WITH 12Z MODEL CONSENSUS SHOWING COLD FRONT GENERALLY EXTENDING THROUGH CENTRAL WV AT 12Z MON. A WEAK WARM FRONT IS NOTED ON THE LATEST RUNS EXTENDING THROUGH CENTRAL VA...WITH PSBL MORNING DEVELOPMENT TO THE SOUTH AND WEST. INCRSG CHC AND COVERAGE OF SHOWERS AND TSTMS INTO THE AFTN AS THE COLD FRONT SWINGS THRU. AXIS OF INSTABILITY LINING UP EAST OF THE BLUE RIDGE MON AFTN INTO THE EVENING WITH MOISTURE ADVECTION ON THE CONTINUAL SLY FLOW AIDING IN PUSHING SBCAPE VALUES TO AROUND 1000 J/KG. OVERALL NOT EXPECTING MUCH IN TERMS OF ORGANIZED CONVECTION WITH LACK OF MID/UPPER LVL FORCING. AS SUCH...EXPECTING FORMATION RIGHT ALONG THE FRONTAL BOUNDARY. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... COLD FRONT PUSHES THROUGH BY MON EVENING...WITH PCPN TAPERING OFF FROM THE WEST. NOT EXPECTING THE FRONT TO COMPLETELY CLEAR THE REGION AS ASSOCIATED CLOSED LOW LINGERS OVER THE GREAT LAKES REGION...THUS RESULTING IN THE NEAR STALLING OF THE BOUNDARY. THIS COULD KEEP PSBL SHOWERS OVER THE FAR EASTERN PORTIONS OF THE CWA THRU LATE MON NIGHT. HOWEVER...THE DRIER AIR WILL BE QUICK TO MOVE IN...WITH DEW PTS IN THE LOWER 50S ADVECTING IN BY TUES MORNING. COLD FRONT WILL CONTINUE SLOWLY SLIDING SOUTHEAST AWAY FROM THE AREA TUESDAY AND WEDNESDAY AS HIGH PRESSURE TRIES TO NOSE INTO THE AREA FROM THE WEST. TEMPERATURES WILL REMAIN SEASONABLE WITH HIGHS IN THE 80S WIDESPREAD. HOWEVER...DEW POINTS WILL DROP INTO THE LOW- MID 50S TUESDAY AND REMAIN THERE WEDNESDAY ACROSS THE BULK OF THE AREA. A TROUGH WILL BE LOCATED OVER OUR AREA ALOFT WITH A CLOSED LOW WELL TO OUR NORTH IN SOUTHERN CANADA. WILL NEED TO KEEP AN EYE ON PASSING VORT LOBES TO SEE IF A STRAY SHOWER MIGHT TRY TO DEVELOP WITH ONE OF THEM...BUT THE AIR MASS WILL PROBABLY BE DRY ENOUGH TO RETARD ANY SHOWER DEVELOPMENT. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HIGH PRESS CONTINUES TO DOMINATE DURING THIS PERIOD KEEPING DRY CONDITIONS OVER OUR REGION. HIGH TEMPS WILL BE GRADUALLY INCREASING FROM THE UPR 70S TO LOW 80S ON THU TO THE MID 80S TO LOW 90S ON SUN. LOWS TEMPS WILL BE IN THE 50S TO UPR 60S. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... GENERALLY VFR CONDITIONS THRU THE TAF PERIOD. ISO TSTMS THIS AFTN SHOULD REMAIN WEST OF ALL TAF SITES. WINDS LIGHT AND VRB. A COLD FRONT WILL SWING THRU MON AFTN-EVENING...BRINGING A CHC FOR SHOWERS AND TSTMS. PSBL SUB-VFR CONDITIONS WITH ANY STORM. WINDS SLY AHEAD OF THE FRONT WILL BECOME NW BY MON NIGHT. WITH HIGH PRESSURE EXPECTED TO BUILD IN TUESDAY AND PERSIST THROUGH THE LONG TERM...VFR CONDITIONS WITH LIGHT WINDS SHOULD PREVAIL. && .MARINE... SUB-SCA CONDITIONS THRU MON MORNING. HAVE ISSUED A SCA FOR THE CHESAPEAKE BAY WATERS AND LOWER TIDAL POTOMAC MON AFTN-NIGHT TO ACCOUNT FOR INCRSG SLY FLOW AHEAD OF THE FRONT...AS WELL AS A PRESSURE SURGE RESULTING IN ELEVATED WINDS MON NIGHT. WITH HIGH PRESSURE EXPECTED TO DOMINATE TUESDAY NIGHT ONWARD...SUB-SCA CONDITIONS SHOULD PREVAIL THROUGH THE LONG TERM. && .TIDES/COASTAL FLOODING... PERSISTENT SOUTHERLY FLOW WILL LEND TO INCREASING ANOMALIES TONIGHT THROUGH MONDAY NIGHT. GENERALLY EXPECTING FORECAST SITES TO REMAIN BELOW MINOR FLOOD LEVELS...BUT THERE IS THE POTENTIAL WITH AN ANOMALY OF AROUND HALF AN INCH THAT ANNAPOLIS COULD BARELY REACH MINOR FLOOD LEVELS WITH THE HIGH TIDE CYCLE MONDAY NIGHT. WITH THE WIND SHIFT WITH THE COLD FROPA...THIS WOULD BE THE ONLY PROBLEMATIC CYCLE. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...RCM NEAR TERM...SEARS SHORT TERM...SEARS/RCM LONG TERM...IMR/RCM AVIATION...SEARS/IMR/RCM MARINE...SEARS/IMR/RCM TIDES/COASTAL FLOODING...SEARS

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