Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 090845 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 345 AM EST Sat Dec 9 2017 .SYNOPSIS... A frontal boundary remains nearly stationary off the Mid Atlantic coast through Saturday. A series of low pressure systems will track northeast along this boundary through Saturday. Cold high pressure builds into the area Saturday night into Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The current regional radar mosaic indicates a band of moderate to heavy pcpn from the S-central VA Piedmont to the Lower MD Ern Shore associated with a potent nearly 170kt jet over Srn New England. Pcpn is mainly SN along and NW of an AVC-RIC-SBY line with a narrow zone of RA/PL/SN mix immediately SE of this line and then all RA farther SE. T/Td values are 32/32F for most areas receiving SN, with 32-34F T values co-located with areas receiving a mix or a chilly RA and then temperatures in the upper 30s/around 40F for coastal SE VA/NE NC. Expect temperatures to be mainly steady overnight. All signs are pointing to mainly snow generally NW of a South Hill to Richmond to Salisbury MD line overnight, as even the GFS which is now the warmest model keeps the entire column below freezing in these areas. Just on the cold side of the rain/snow line, there will likely be a moderate to locally heavy snow where is is juxtapositioned with the best upper f-gen forcing and associated banding features. As such, have opted to go with a winter storm warning for Dorchester/Wicomico County, southwest to Caroline, and then through the western RIC metro and SW to Mecklenburg County. Could see 6 inches of snow in this area, although the evening shift will need to watch for how long this heavier snow burst lasts tonight which may inflate totals even more. Additional snow expected into Saturday with the deformation axis associated with the upper trough moving overhead. The snow should diminish west to east Saturday aftn into evening. Overall, will go with storm totals of 4 to 6 inches in the warning area with locally higher amounts especially in the MD. Since the snow started even earlier than anticipated, it would not shock me to see 7 inch amounts in a narrow corridor west of RIC as well. In the advy areas, will go with 2 to 4 inches, although the eastern advy may see some lesser amts due to more rain mixing in. The rain/snow line may actually shift westward a little bit as the low develops along the coast as the upper short wave approaches. Do not think this will be of huge consequence to snow totals in the warning area, but none the less it should be noted it could lower totals slightly on the eastern side of RIC into the Tri Cities. Thus, the reason this area stays in the winter weather advy. To the southeast of the snow, expect rain to fall locally heavy at times tonight especially in NE NC and the VA Tidewater. Rainfall amounts of 1-2 inches tonight into Saturday are certainly possible causing some ponding of water on roadways. Temps tonight will stay in the lower 30s west and upper 30s east. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... After Saturday evening, skies will quickly clear out as the upper trough axis moves through and westerly flow kicks in. The clearing combined with the strong cold advection will allow temps to drop into the 20s everywhere. Roads may become slick even if they melted during the day on Saturday, and any snow that remains on the ground will become quite compacted. Sunday should be a cool day with temps only in the upper 30s/lower 40s. && .LONG TERM /MONDAY THROUGH FRIDAY/... The long term period will be characterized by below normal temperatures and mainly dry wx as a long wave trough sets up over the eastern CONUS. A vigorous shortwave is shown to rotate through the mean trough and pivot across the local area late Tuesday into Wednesday. This feature will reinforce the already chilly air in place and probably bring our coldest readings so far this season. In addition, widely scattered snow showers may occur especially over eastern areas as the upper trough pivots through Tuesday night/Wednesday. Highs Mon/Tues from the mid 40s to around 50. Highs Wed in the mid to upper 30s. Highs next Thurs in the low to mid 40s. Similar into Fri. Low temps Sunday night in the 20s, to near 30 coast. Lows Mon night from the upr 20s Piedmont to the mid 30s coast. Lows Tues/Wed nights from around 20 Piedmont to nr 30 coast. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... As the winter storm moves into the area, expect widespread IFR at all the sites tonight into Saturday. RIC and SBY may see moderate to locally heavy snow tonight into Saturday morning with vsbys AOB 1/2sm. Rain mainly at the other terminals tonight but still IFR conditions. Improving conditions expected mainly into Saturday afternoon/evening. Quiet Saturday night through early next week. && .MARINE...
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An active period expected for the next several days with sfc low pressure currently along a frontal boundary from the eastern gulf of Mexico to off the NE FL Atlc coast. N/NE winds currently range from 15 to 25 knots over the waters with waves of 3-5 feet and seas of 4- 7 feet. Small Craft Advisories remain in effect for all of the waters minus the upper rivers through Sunday. A strong cold front passes through tonight, shifting winds to the WNW, and allowing for Small Craft conditions to prevail for all zones (including the upper rivers). Small Craft Advisories have been extended for much of Sunday with the passage of the front. While there may be a brief gust to near gale force Sunday morning it will be limited and Gales are not expected. Elevated westerly flow of 15-20 kt to continue Mon- Tue and will increase to 20-30 kt late Tue night and Wed.
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&& .TIDES/COASTAL FLOODING... Water levels in the lower Bay and NC Outer Banks may approach minor flood thresholds during late morning/early aftn Sat high tide, but do not anticipate headlines being needed attm. && .CLIMATE... Avg 1st Date with Measurable Snowfall at Sites (Data based on 1981-2010): * Richmond: Dec 25th * Norfolk: Jan 12th * Salisbury: Dec 25th * Wallops: Dec 26th * Louisa: Dec 18th * Farmville: Dec 24th && .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...Winter Weather Advisory until 4 PM EST this afternoon for MDZ024. Winter Storm Warning until 7 PM EST this evening for MDZ021>023. NC...None. VA...Winter Weather Advisory until 4 PM EST this afternoon for VAZ048-078>083-085-509-510-514-516-518-520-522. Winter Storm Warning until 4 PM EST this afternoon for VAZ060>062-064>069-075>077-511>513-515-517-519-521. MARINE...Small Craft Advisory until 6 PM EST Sunday for ANZ650-652-654. Small Craft Advisory until 1 PM EST Sunday for ANZ633-638-656- 658. Small Craft Advisory until 4 PM EST Sunday for ANZ630>632-634.
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&& $$ SYNOPSIS...MRD NEAR TERM...AJZ/MRD SHORT TERM...ALB/MRD LONG TERM...MAS AVIATION...ALB MARINE...AJB/LKB TIDES/COASTAL FLOODING... CLIMATE...

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