Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 290555 AFDAKQ AREA FORECAST DISCUSSION National Weather Service Wakefield VA 1255 AM EST Sat Feb 29 2020 .SYNOPSIS... Cooler weather will prevail across the region through Saturday night as high pressure slowly builds toward the area from the southwest. A warming trend begins on Sunday as the area of high pressure moves offshore. Rain chances increase by the middle part of next week as low pressure and an associated cold front approach from the west. && .NEAR TERM /THROUGH TODAY/... As of 620 PM EST Friday... Only minor tweaks to the near term sky cover and pops. Surface obs confirm that radar returns are not reaching the ground as the lower atmosphere is still too dry. However, still expect the lower atmosphere to moisten up enough this evening to allow for a few widely scattered light rain showers/sprinkles, with little to no accumulation. As the boundary layer continues to cool off overnight, wouldn`t be surprised if there are a few stray flurries out there in the hours leading up to sunrise, however available moisture will be limited with PWAT values around 0.25 inches. Previous Discussion. As of 330 PM EST Friday... Late afternoon weather analysis continues to show a vertically stacked low pressure system over southern Quebec, with broad upper troughing over the ern CONUS. An upper shortwave and associated weak sfc trough are approaching the area from the west. Clouds have increased ahead of the system, with radar mosaic showing some light echoes west of I-95. However, none of this is reaching the ground as the layer below 5000 feet is very dry (sfc dew points are still in the low-mid 20s on average). Low-level SW flow prevails across the area, and temperatures range from the mid 40s W to the low 50s SE. Still think these showers will increase some in coverage/intensity as the move eastward later this aftn through this evening, but the dry low-levels may inhibit some pcpn potential (what falls may be less than what some of the 12z CAMs were forecasting). Given steep low level lapse rates (~9 degrees C/km)/freezing levels around 3000 ft AGL, there is a chance that some mixing with graupel/a few snowflakes will occur if the showers become strong enough. Will maintain PoPs of around 30% across srn zones, 20-30% PoPs in central zones, and 15-20% PoPs across the north. The most likely timing for pcpn is from now to 6 PM across from the VA Piedmont to Dorchester County (MD), 5-8 PM for the central third of the area, and 7 PM-midnight for SE VA/NE NC. Will keep pcpn type as rain in the grids, since mixing w/ graupel will likely be confined to a few areas. Even if the rain mixes with graupel/snow, temperatures at the surface will be well above freezing so there will be no impacts or accumulations. Drying out after midnight with a brief period of partial clearing before clouds increase closer to sunrise as a secondary shortwave tracks ESE from wrn VA to ern North Carolina Saturday morning. Cannot rule out a flurry or two across southern zones Saturday morning, but kept PoPs in the 10-14% range since it is very unlikely that the pcpn will be measurable. Have a mention of sprinkles/flurries in the grids from 09-15z Sat. The HRRR would suggest a little bit more than just flurries Saturday morning, but am reluctant to go with its solution considering that it was too aggressive w/ the showers this aftn at this time yesterday. Overnight lows will be in the upper 20s-low 30s in most areas, with some mid 20s across the far NW. The aforementioned vertically stacked low will slowly track eastward toward New Brunswick/Newfoundland on Saturday, w/ dry WNW-NW flow at the surface and aloft across the area. 850 mb temperatures will only be in the -8 to -13C range on Saturday as a secondary CAA surge is progged to moves across the area. Highs Saturday range from ~40F over the Lower Ern Shore, with only low-mid 40s elsewhere. SCT CU likely develops across ern zones on Saturday, with gradual clearing across the SW. && .SHORT TERM /TONIGHT THROUGH MONDAY/... As of 330 PM EST Friday... Surface high pressure builds from the Deep South to GA and the Carolinas Saturday night as the upper trough axis moves offshore. With clear skies and diminishing winds, temperatures will fall into the low-mid 20s in most areas, with mainly upper 20s in coastal SE VA/NE NC. A rather significant warming trend takes place from Sunday-Monday as the high moves offshore and the flow aloft becomes zonal across the ern CONUS while a srn stream upper low slowly moves eastward from California to Arizona. 850 mb temperatures are progged to warm to -4 to +2C by Sunday afternoon before rising to 3 to 6C on Monday. Cannot rule out a stray shower west of I-95 Monday afternoon, but rainfall amounts will be a few hundredths at best. Highs Sunday range from the upper 40s on the Lower Ern Shore to the low-mid 50s elsewhere. Lows will be in the 30s Sunday night. Warmer on Monday with highs mainly in the low-mid 60s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 330 PM EST Friday... Unsettled period next week as the upper level flow becomes zonal to southwest over the Mid-Atlantic region. Air mass becomes moist with PWAT values increasing to 1-1.25 inches. Several disturbances will move across the area increasing rain chances. Timing differences between models exist from mid week on in regards to how fast the upper level trough moves through the area, with the GFS about a day or so faster than the ECMWF. This will have implications for when the precip will come to an end. For now kept chance pops in for Thursday and Friday due to the uncertainty. Temperatures will be well above normal next week with high and low temps running about 10-20 degrees above normal. Warmest day of the week will be Wednesday, where temps will range from the upper 60s N/NW to mid 70s SE. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... As of 630 PM EST Friday... VFR condition are expected to prevail through the 06z TAF period. SCT CIGs 080-150 are moving offshore of southeastern VA and northeastern NC. Skies will become clear for the entire area for the remainder of the night. Mid-level clouds will move in early Saturday morning. CIGs will be SCT-BKN around 5000 ft. There is a chance that ceilings may drop to MVFR late Saturday morning across extreme southeastern VA and northeastern NC, but confidence is low, therefore kept out of TAFs. Skies will clear once again during Saturday afternoon. Winds will remain WNW-NW tonight and tomorrow. Winds will remain light overnight (5-10 kt). Northwest winds will increase mid- morning Saturday to around 15 kt with gusts up to 25 kt. Gusty winds will remain into the evening before decreasing for Saturday night. Outlook...VFR and dry conditions will continue through the remainder of the weekend as high pressure slowly builds into the area. Shower chances increase by the middle of next week with the possibility of degraded flight conditions. && .MARINE... As of 1020 PM EST Friday... SCA`s remain up through 06Z for the Ches Bay/ Currituck Sound and lwr James river for the few hr surge progged behind the trof as it crosses the area late this eve. No headlines along the coast as wind speeds should remain below 25 kts overnight. Yet another CAA surge and deep mixing progged Sat aftrn and nite behind a secondary trof that crosses the area. This will likely need SCA`s over most of the marine area with gusts 25-30 kts over the coastal waters. Waves build 2-4 ft, seas build 3-5 ft. Winds diminish Sun then become SW Mon and Tue as high pressure moves offshore. Speeds aob 20 kts. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 AM EST early this morning for ANZ630>634-638. && $$ SYNOPSIS...ERI NEAR TERM...CMF/ERI SHORT TERM...CP/ERI LONG TERM...CMF AVIATION...CMF/CP MARINE...JDM/MPR

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