Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 241909 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 309 PM EDT WED SEP 24 2014 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL DEVELOP OFF THE DELMARVA PENINSULA TONIGHT...AND MOVE ACROSS THE WATERS SOUTH OF NEW ENGLAND ON THURSDAY. HIGH PRESSURE WILL FORM OVER THE GREAT LAKES REGION THURSDAY NIGHT...AND REMAIN ACROSS THE NORTHEAST UNITED STATES THROUGH THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... 19Z KNHK AND KEZF OBS FINALLY SHOWING LIGHT RAIN IN THE CWA. THE ANTICYCLONIC FLOW AROUND THE INVERTED RIDGE HAS HELD TOUGH OVER THE AREA SO FAR TODAY. THE 12Z ECMWF CAME IN WITH MUCH LESS QPF THAN 00Z RUN...MAKING THE 12Z GFS AND NAM THE WETTEST MODEL SOLNS. STILL ANTICPATING ABOUT AN INCH TO 1.5 INCHES OF RAINFALL TONIGHT ALONG AND EAST OF I-95 ONCE THE INVERTED RIDGE BREAKS DOWN EARLY THIS EVENING. STILL TOO MUCH UNCERTAINTY WITH THE DIFFERING MODEL SOLUTIONS TO CONSIDER TAKING DOWN FLOOD WATCH...BUT WILL PASS ON TO THE EVENING SHIFT TO MAKE THAT FINAL DECISION. STILL A VERY STRONG LLVL JET CENTERED AT 950 MB TO CONTEND WITH OFF THE GULF STREAM CONVERGING INTO THE CWA. MIN TEMPS TONIGHT WILL BE IN THE LOWER 60S IN URBAN AREAS AND IN THE MID TO UPPER 50S ELSEWHERE IN A WELL MIXED ENVIROMENT AS A NE 35KT LLVL JET PER THE 12Z GFS MAKES IT WAY THROUGH THE CHESAPEAKE BAY REGION OVERNIGHT. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... RAIN WILL CONTINUE TO LINGER INTO THE MORNING HOURS ACROSS MUCH OF THE AREA BEFORE PULLING OFF TO THE NORTHEAST IN THE EARLY AFTERNOON. WINDS SHOULD CONTINUE TO BE GUSTY FROM THE NE AGAIN ON THURSDAY AS THE LOW DEEPENS AS IT MOVES TOWARDS CAPE COD AND HIGH PRESSURE STARTS TO BUILD OVER THE GREAT LAKES. HIGHS ON THURSDAY WILL BE IN THE UPPER 60S BUT WITH A GUSTY NE WIND WILL MAKE IT FEEL COOLER. THURSDAY NIGHT AND FRIDAY WILL BE FAIR WITH NEAR NORMAL TO SLIGHTLY ABOVE NORMAL TEMPS. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGH PRESSURE WILL DOMINATE THE REGION FRIDAY NIGHT THROUGH SUNDAY MORNING...PROVIDING PLENTY OF SUNSHINE THAT WILL LEAD TO WARM AFTERNOONS AND COMFORTABLE NIGHTS. HIGHS SHOULD REACH 80 IF NOT A FEW DEGREES ABOVE DURING EACH AFTERNOON. A WEAK COLD FRONT COULD DROP IN ACROSS THE REGION LATE SUNDAY INTO SUNDAY NIGHT. LITTLE OR INSUFFICIENT MOISTURE COULD LEAD TO NO PRECIPITATION AHEAD OF AND ALONG THE FRONT. A REINFORCING AREA OF HIGH PRESSURE WILL BUILD BEHIND THE FRONT MONDAY THROUGH TUESDAY. THIS WILL LEAD TO HIGHS REACHING THE UPPER 70S TO NEAR 80. SOME UPPER LEVEL ENERGY MONDAY NIGHT INTO TUESDAY COULD TRY TO WORK SOUTHEASTWARD ACROSS THE REGION. THERE MAY BE JUST ENOUGH UPPER ENERGY TO SUPPORT A COUPLE OF RAIN SHOWERS IN A FEW AREAS...MAINLY IN THE UPSLOPE PORTIONS OF OUR REGION. WE HAVE SLIGHT CHANCE OR CHANCE POPS TO ACCOUNT FOR THIS. SURFACE WINDS COULD BE EAST TO SOUTHEAST WITH HIGH PRESSURE OVER NEW ENGLAND. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... CLOUD COVER WILL CONTINUE TO SPREAD INTO THE AREA THIS AFTERNOON AHEAD OF LOW PRESSURE ALONG THE COAST OF THE CAROLINAS. CIGS MAY VARY BETWEEN HIGHER MVFR AND LOWER VFR AT KCHO AND BALTIMORE/WASHINGTON METRO TERMINALS. LOW PRESSURE WILL MOVE NORTH INTO THE MID-ATLANTIC TONIGHT. ASSOCIATED RAINFALL WITH MVFR/IFR CIGS AND VSBYS WILL MOVE INTO THE AREA BY THIS EVENING AND CONTINUE OVERNIGHT. CONDITIONS WILL BE SLOW TO IMPROVE THURSDAY...WITH LINGERING MVFR CIGS EXPECTED MOST OF THE DAY. SHORT-TERM AMENDMENTS LIKELY FOR PERIODS OF HEAVY RAIN AND REDUCED CIGS/VSBYS THIS EVENING AND OVERNIGHT. GENERALLY NE WINDS AROUND 10KT THROUGH THURSDAY AFTERNOON. SOME GUSTS TO 20KT AT TIMES...MOSTLY AT KBWI/KDCA/KMTN. VFR CONDITIONS AT ALL TERMINALS FRIDAY NIGHT THROUGH SATURDAY. WINDS NORTH BECOMING VARIABLE 5 TO 10 KNOTS GUSTS 15 KNOTS FRIDAY NIGHT THROUGH SATURDAY. && .MARINE... GUSTY NE WINDS ACROSS ALL THE WATERS THROUGH THE NEXT 36 HOURS CAUSING SCA TO BE EXTENDED THROUGHOUT THE DAY ON THURSDAY. WINDS AND SEAS SHOULD SUBSIDE THURSDAY NIGHT INTO FRIDAY. NO MARINE HAZARDS EXPECTED FRIDAY NIGHT THROUGH SATURDAY. && .HYDROLOGY... THE THOUGHT ON QPF HAS SHIFTED A BIT THE PAST COUPLE OF HOURS AS THE 12Z ECMWF CAME IN LESS WET THAN THE PREVIOUS RUN. THIS MAKES THE GFS AND THE NAM THE WETTEST SOLNS AND SHOULD GIVE THE REGION BETWEEN 1.0 AND 1.5 INCHES OF RAIN ALONG AND E OF I-95 OVERNIGHT...WITH 0.5 TO 1 INCH BETWEEN I-95 AND THE SHEN VALLEY. THIS MAY NOT BE QUITE ENOUGH FOR FLOODING BUT STILL ENOUGH UNCERTAINTY NOT TO TAKE DOWN THE FLOOD WATCH ATTM. && .TIDES/COASTAL FLOODING... ESTOFS GUIDANCE FROM 06Z SHOWS TIDAL ANOMALIES AOB 1.2 FT IN THE TIDAL POTOMAC AND MD BAY. THUS NOT EXPECTING ANY TIDAL FLOODING ATTM. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR DCZ001. MD...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR MDZ006-007-009>011-013-014. VA...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR VAZ053-054. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ530>543. && $$ SYNOPSIS...LEE NEAR TERM...LEE SHORT TERM...LEE LONG TERM...KLW AVIATION...KS/KLW MARINE...LEE/KLW HYDROLOGY...LEE TIDES/COASTAL FLOODING...LEE

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