Area Forecast Discussion
Issued by NWS Sterling, VA

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781 FXUS61 KLWX 050801 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 401 AM EDT THU MAY 5 2016 .SYNOPSIS... UPPER LEVEL LOW PRESSURE OVER KENTUCKY WILL SWING SOUTHEAST INTO THE CAROLINAS TODAY...BEFORE MOVING UP THE MID-ATLANTIC COAST TONIGHT. THIS LOW WILL STALL OVER THE AREA FRIDAY INTO SATURDAY BEFORE SHIFTING OUT TO SEA. A COLD FRONT WILL CROSS THE AREA SATURDAY NIGHT INTO SUNDAY BEFORE A WARM FRONT LIFTS OVER THE AREA MONDAY NIGHT INTO TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3AM...UPR LOW IS OVER IN/KY BORDER PER WATER VAPOR IMAGERY WITH THE DEVELOPING SFC LOW OFF CAPE HATTERAS. ONSHORE FLOW IS ACROSS THE AREA WITH PATCHY RAIN WEST OF A LINE FROM MARTINSBURG WC TO DAHLGREN VA. NOTABLE LOCALLY MODERATE RAIN HAS PERSISTED ALONG ALLEGANY/MORGAN CO BORDERS THE PAST FEW HOURS...THIS SHOULD EVENTUALLY DISSIPATE/DRIFT. KEY FEATURE TODAY WILL BE DEVELOPMENT AND PERSISTENCE OF CONVERGENCE ALONG THE TROUGH AS THE UPR LOW TRANSLATES ENERGY TO THE COASTAL SFC LOW. LATEST GUIDANCE HAS SHIFTED THIS SLIGHTLY SOUTH...ESSENTIALLY ALONG THE SRN BORDERS OF HIGHLAND/AUGUSTA/ NELSON COUNTIES THEN UP THE ALLEGHENY FRONT. WITH THIS SOUTH SHIFT...HAVE DECIDED TO NOT ISSUE A FLOOD WATCH. SIX HOUR FLASH FLOOD GUIDANCE IS GENERALLY AROUND TWO INCHES. HIGHER REFLECTIVITY IS CURRENTLY SOUTH OF NELSON COUNTY. THIS ACTIVITY WILL NEED TO BE MONITORED. LITTLE RAIN OUTSIDE THIS CONVERGENCE AREA INTO THE AFTERNOON. DIURNAL HEATING AND LOW HEIGHTS ALONG WILL ALLOW INSTABILITY SHOWERS. THUNDER LOOKS ISOLATED AT BEST AND ONLY IN CNTRL VA/JUST WEST OF THE ALLEGHENY FRONT. MAX TEMPS GENERALLY MID TO UPR 50S WITH PERSISTENT LOW CLOUDS. FORTUNATELY THIS IS NOT MAY 5 1917 WHEN IT WAS 46F IN BOTH BALTIMORE AND WASHINGTON. MIN TEMPS AROUND 50F TONIGHT AS THE UPR LOW CENTER SHIFTS TO CAPE HATTERAS. RAIN GENERALLY INCREASES IN COVERAGE OVERNIGHT. QUARTER TO HALF INCH QPF OVERNIGHT. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... DEEP UPR LOW STALLS/LOOPS OVER THE AREA FRIDAY THROUGH MIDDAY SATURDAY PER 00Z GFS/ECMWF. CONTINUED LOW CLOUDS AND RAIN FRIDAY WITH AN ADDITIONAL HALF TO ONE INCH QPF AS THE LOW BECOMES VERTICALLY STACKED. LOW SLOWLY FILLS FRIDAY NIGHT THROUGH SATURDAY WITH LOWER POPS AND LIGHT RAIN RATES. TEMPERATURES 5-10 DEGREES HIGHER SATURDAY OVER FRIDAY AS CLOUD COVER STEADILY DISSIPATES THROUGH SATURDAY. COLD FRONT BEHIND THE EJECTING WHOLE SYSTEM APPROACHES SATURDAY NIGHT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... SOME IMPROVEMENT EXPECTED IN THE EXTENDED PERIOD OF THE FORECAST...HOWEVER RELATIVELY UNSETTLED WEATHER LIKELY TO CONTINUE. WILL BE LOOKING AT A COLD FRONT CROSSING THE REGION SUNDAY MORNING WITH A CHANCE OF RAIN SHOWERS...FOLLOWED SOME BRIEF DRYING OCCURRING BEHIND IT LATER SUNDAY AND INTO SUNDAY NIGHT. HOWEVER...THIS WILL BE QUICKLY FOLLOWED BY A WARM FRONT ON MONDAY...USHERING IN SOUTHWEST FLOW...WARMTH...AND ADDITIONAL MOISTURE. SOME VARIATIONS IN MODEL SOLUTIONS...BUT THERE ARE INDICATIONS OF A COLD FRONT NEARING THE REGION ON WEDNESDAY. WHILE WIDESPREAD RAIN IS NOT EXPECTED...THE INCREASING WARMTH AND MOISTURE COMBINED WITH THE PRESENCE OF FRONTAL BOUNDARIES WILL KEEP CHANCES FOR SCATTERED SHOWERS AND/OR THUNDERSTORMS IN THE FORECAST FOR THE BEGINNING OF NEXT WEEK. TEMPERATURES WILL REBOUND TO NEAR AND EVENTUALLY ABOVE NORMAL WITH HIGHS REACHING BACK UP INTO THE 70S AND 80S BY NEXT WEEK. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... PERIODIC IFR CONDS THROUGH FRIDAY NIGHT AS LOW PRESSURE SHIFTS SOUTHEAST ACROSS THE CAROLINAS TONIGHT AND STALLS OVER THE DC METROS FRIDAY THROUGH SATURDAY. HEAVIEST RAIN TODAY SOUTHWEST OF DC METROS...WITH MODERATE RAIN ACROSS THE DC METROS TONIGHT THROUGH FRIDAY. SYSTEMS EJECTS EAST SATURDAY WITH A COLD FRONT CROSSING LATE SATURDAY NIGHT INTO SUNDAY. VFR CONDITIONS ARE EXPECTED SUNDAY THROUGH MONDAY. && .MARINE... ONSHORE FLOW 10 TO 15 KT CONTINUES THROUGH TONIGHT AS LOW PRESSURE SWINGS THROUGH THE CAROLINAS. NORTH WINDS 10 TO 15 KT THEN THROUGH SATURDAY AS LOW PRESSURE STALLS OVER THE AREA. A SMALL CRAFT ADVISORY MAY BE NEEDED ON SUNDAY WITH GUSTY NORTHWEST WINDS BEHIND FRONTAL PASSAGE. SUB-SCA CONDITIONS THEN FOLLOW ON MONDAY. && .HYDROLOGY... LOCALLY HEAVY RAIN OVER CNTRL VA AND THE SHENANDOAH VALLEY AND ALLEGHENY HIGHLANDS. NO WATCH AS OF NOW...BUT WILL NEED TO MONITOR PROGRESS OVER LARGE SCALE CONVERGENCE AS AN UPPER LOW PRESSURE SYSTEM DEVELOPS AS IT MOVES OVER THE REGION THROUGH TONIGHT. && .TIDES/COASTAL FLOODING... MINOR FLOODING FROM ONSHORE FLOW. WIDESPREAD MINOR AT PREFERRED HIGH TIDE AND FOR EACH HIGH TIDE AT STRAITS POINT AND SW WATERFRONT DC/ALEXANDRIA THROUGH SATURDAY. ADVISORIES IN EFFECT THROUGH TONIGHT. AMENDMENTS TO THIS AS NEEDED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 4 AM EDT EARLY THIS MORNING FOR MDZ018. COASTAL FLOOD ADVISORY FROM 10 PM THIS EVENING TO 6 AM EDT FRIDAY FOR MDZ018. COASTAL FLOOD ADVISORY UNTIL 7 AM EDT THIS MORNING FOR MDZ014. COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EDT FRIDAY FOR MDZ014. COASTAL FLOOD ADVISORY UNTIL 6 AM EDT FRIDAY FOR MDZ017. VA...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR VAZ054. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BAJ NEAR TERM...BAJ SHORT TERM...BAJ LONG TERM...MM AVIATION...BAJ/MM MARINE...BAJ/MM HYDROLOGY...BAJ TIDES/COASTAL FLOODING...BAJ

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