Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 260006 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 806 PM EDT SAT JUL 25 2015 .SYNOPSIS...
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HIGH PRESSURE WILL MOVE OFF THE COAST TONIGHT INTO SUNDAY. A COLD FRONT WILL APPROACH THE REGION SUNDAY AFTERNOON BEFORE DISSIPATING TO OUR NORTH SUNDAY NIGHT THROUGH MONDAY. HIGH PRESSURE BUILDS OVERHEAD FOR TUESDAY AND WEDNESDAY. A COLD FRONT WILL CROSS THE AREA THURSDAY NIGHT.
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&& .NEAR TERM /THROUGH SUNDAY NIGHT/...
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A SOUTHERLY FLOW AROUND DEPARTING HIGH PRESSURE WILL ALLOW FOR SOME MORE HUMIDITY COMPARED TO RECENT NIGHTS...BUT DRY CONDITIONS WILL PERSIST. MIN TEMPS WILL RANGE FROM THE LOWER TO MIDDLE 60S IN THE POTOMAC HIGHLANDS TO THE LOWER AND MIDDLE 70S IN DOWNTOWN WASHINGTON AND BALTIMORE. SOUTHERLY FLOW CONTINUES FOR SUNDAY...CAUSING A RETURN OF SEASONABLY HOT AND HUMID CONDITIONS. LEE- SIDE TROF BECOMES ESTABLISHED IN THE AFTERNOON WITH BETTER MOISTURE AND INSTABILITY TO SUPPORT ISOLD- SCT T-STORMS. ACTIVITY EXPECTED TO MOVE TOWARD THE CHESAPEAKE BAY SUNDAY EVENING POSSIBLY INTO THE OVERNIGHT HOURS.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY/...
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A WEAK COLD FRONT WILL STALL OVER THE AREA MONDAY. WITH THIS BOUNDARY IN PLACE...LOW-LEVEL CONVERGENCE AND FORCING FROM SUBTLE SHORTWAVES ALOFT WILL LIKELY TRIGGER SHOWERS AND SCATTERED THUNDERSTORMS DURING THE AFTERNOON HOURS. MODEL SOUNDINGS INDICATE MLCAPE IN EXCESS OF 1000 J/KG BUT WITH ONLY MODEST SHEAR. A STRONG THUNDERSTORM CANNOT BE RULED OUT BUT AT THE MOMENT IT APPEARS ANY SEVERE RISK WOULD BE MINIMAL. GUIDANCE IS IN DECENT AGREEMENT FOR HIGH TEMPS SO PRETTY MUCH JUST STUCK WITH A STRAIGHT BLEND...BUT CLOUDS COULD KEEP THINGS A COUPLE DEGREES COOLER IN A FEW SPOTS. CONVECTION SHOULD DWINDLE PRETTY QUICKLY WITH THE LOSS OF DAYTIME HEATING AND AS THE FRONT PUSHES SOUTH AND DISSIPATES. NOT MUCH IN THE WAY OF COOLER OR DRIER AIR WORKS INTO THE REGION SO LOW TEMPS SHOULD BE SIMILAR TO THOSE OBSERVED SUNDAY NIGHT...MID 60S TO LOW 70S. SEASONABLY WARM WEATHER CONTINUES TUESDAY BUT WITH SLIGHTLY LOWER HUMIDITY IN LIGHT NORTHERLY FLOW.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... HIGH PRES OVER OUR REGION DOMINATES CONDITIONS TUE NIGHT AND WED... THEN IT MOVES OFF THE COAST THU... BRINGING DRY CONDITIONS DURING THIS PERIOD. A COLD FRONT APPROACHES FROM THE NW LATE ON THU AND STALLS CLOSE TO OUR CWA THROUGH FRI. SHOWERS AND TSTMS ARE PSBL BOTH THU AND FRI. THERE IS UNCERTAINTY ON THE POSITION OF THIS BOUNDARY FRI NIGHT INTO SAT... SO KEPT A CHANCE OF POPS FOR THE SOUTHERN PART OF THE CWA. HIGH TEMPS WILL BE IN THE LOW TO MID 90S WED AND THU... AND IN THE UPR 80S FRI AND SAT. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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VFR AT MOST AIRPORTS TONIGHT XCPT FOR SOME PATCHY FOG POSSIBLE AT KCHO. RISK OF T-STORMS SUN AFTERNOON EVERYWHERE BUT THEY SHOULD REMAIN SCT AT BEST. ACTIVITY SHOULD CLEAR THE CHESAPEAKE SUNDAY NIGHT. SUB-VFR POSSIBLE MON AFT IN SHWRS/SCTD TSTMS. SLY FLOW 10 KT MON BECOMING NLY TUE. VFR CONDITIONS EXPECTED TUE NIGHT INTO WED.
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&& .MARINE...
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SRLY WINDS MAY APPROACH SCA CRITERIA TONIGHT ALONG THE MIDDLE PORTION OF THE BAY AND THE LOWER TIDAL POTOMAC RIVER. HAVE CAPPED GUSTS AROUND 15 KNOTS FOR NOW DUE TO THE RELATIVELY WEAKER GRADIENT. THE GRADIENT WILL INCREASE SUNDAY...CAUSING THE SOUTHERLY WINDS TO INCREASE TO AROUND 15G20KT SUNDAY AFTERNOON INTO EARLY MONDAY. SLY CHANNELING POSSIBLE MON AFT DEPENDING ON GRADIENT/POSITION OF WEAK FRONT NEAR THE WATERS. SUB-SCA CONDITIONS EXPECTED FOR TUE NIGHT INTO WED.
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&& .TIDES/COASTAL FLOODING...
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SOUTHERLY FLOW INCREASES THROUGH SUNDAY...PUSHING ANOMALIES HIGHER AND CAUSING WATER LEVELS TO APPROACH MINOR FLOOD AT A FEW VULNERABLE LOCATIONS...MAINLY FOR THE SUNDAY NIGHT HIGH TIDE CYCLE. LARGELY DISCOUNTING ESTOFS GUIDANCE AT THIS TIME AS IT HAS BEEN RUNNING TOO HIGH /ABOUT HALF A FOOT HIGHER THAN OTHER AVAILABLE GUIDANCE/.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON SUNDAY TO 4 AM EDT MONDAY FOR ANZ530>534-537>543. && $$ SYNOPSIS...BJL/LFR NEAR TERM...BJL/LFR SHORT TERM...DFH LONG TERM...IMR AVIATION...BJL/IMR/LFR/DFH MARINE...BJL/IMR/LFR/DFH TIDES/COASTAL FLOODING...DFH/BJL

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