Area Forecast Discussion
Issued by NWS Wakefield, VA

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621 FXUS61 KAKQ 192000 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 400 PM EDT Mon Mar 19 2018 .SYNOPSIS... High pressure moves off the Mid Atlantic coast this evening. A pair of low pressure systems will impact the region tonight through Wednesday. High pressure builds into the area late in the week. && .NEAR TERM /THROUGH TUESDAY/... Current wv imagery depicts a potent low pressure system traversing the mid-Mississippi Valley this aftn. Locally, partly to mostly cloudy conditions are occurring as high clouds stream across the region. Mild with temperatures ranging from the low 50s NW to the upper 50s/low 60s elsewhere. This system will result in unsettled conditions beginning later tonight and continuing through Wednesday, with two primary events. The first event occurs tonight as a potent shortwave races ewd from the TN Valley late this evening, with a surface low tracking across NC late tonight/Tues morning before emerging off the mid-Atlantic coast on Tuesday. Rather impressive lift progged with and north of the sfc low to produce a widespread rain across the FA. Categorical PoPs prevail for all areas with some moderate to heavy rainfall possible late tonight into midday Tuesday. QPF amounts could exceed an inch in some areas. Following a blend of the models, a triple point low should track NE across NE NC and sern VA late tonight then out into the VA Capes Tuesday morning. Thus, can`t rule out thunder across those areas early Tues morning. Lows from the mid 30s north to mid-upr 40s SE. The sfc low deepens as it tracks across the VA Capes Tuesday morning. This will result in windy conditions (NE wind) along the Atlantic coast of the VA/MD Ern Shore where a wind advisory in in effect mainly for areas from Chincoteague to Ocean City. The low then lingers off the coast Tuesday aftn as weak high pressure tries to nudge in from the north. This will result in the wind becoming more northerly during the aftn. Likely to categorical PoPs Tues morning (locally heavy rain early over the Eastern Shore), then likely pops north and NE with chc PoPs south Tuesday aftn. Chilly with highs nr 40/low 40s north to 55-60 se coastal areas. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... The complex system will continue to impact the region Tuesday night into Wednesday. There is still much uncertainty on how the system evolves Tuesday night into Wednesday. However, the 19/12z GFS/NAM/ECMWF have trended toward a deepening of the surface low closer to the coast and the potential for frontogenetic banding over the Delmarva. The upper level system pulls in enough cold air to allow a transition to snow late Tuesday night into Wednesday. Chc to likely PoPs Tuesday evening ramp up to likely to categorical everywhere after midnight through midday Wednesday as the forcing from the upper level system taps into moisture. Thicknesses suggest a mixed/rain and snow event across the Piedmont Tuesday night changing to all snow, and rain/snow Tuesday night changing to all snow around daybreak Wednesday for central VA. A cold rain over the Delmarva will change to snow Wednesday morning, and a cold rain for SE VA/NE NC could mix with some snow Wednesday aftn. The current forecast is for 1-3" of snow from the NW piedmont across central VA to the Nrn Neck and the VA Ern Shore, with the potential for 3-5" over the MD Ern Shore, with possibly 4-6" over Dorchester MD. Elsewhere, expect an inch or less with no accumulation for far SE VA/coastal NE NC. This is close to the WPC forecast. Have opted to issue a Winter Storm Watch for the MD Ern Shore 10z Wed to 03z Thu. Lows Tuesday night range from 30-32F NW to the upper 30s SE, followed by highs Wednesday in the low/mid 30s where snow falls to the upper 30s/low 40s where rain prevails. Drier air arrives Wednesday night into Thursday as the system pulls to the northeast. Partly to occasionally mostly cloudy under the upper trough. Lows Wednesday night range from the mid 20s NW to the low 30s SE, with highs Thursday in the mid to upper 40s, possible cooler over the MD Ern Shore depending on snowfall Wednesday. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Remained close to WPC grids for the late week into early next week. Overall, cold high pressure building to the NW will provide a continuation of (much) below temperatures for much of the forecast period. After a cool, dry day on Friday, rain chances increase once again ahead of next system, which develops across the central plains on Fri/Friday night...then tracks east, undercutting the omega block in place over the northern tier of states through the weekend. Remaining partly to mostly cloudy through the weekend, with rain chances to increase later Sat into Sat night before becoming more widespread on Sunday. For temperatures, Highs Fri/Sat around 50F inland...m40s at the coast. Lows Fri night in the l30s inland...u30s-around 40F at the coast. Highs Sun/Mon in the 40s N to m50s S. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... VFR conditions continue for the region with mostly mid and high cloud ceilings. High pressure along the coast will gradually move east and low pressure over the TN Valley will move towards the Mid Atlantic coast over the next 24 hours. Clouds will increase and thicken through the TAF period and rain will overspread the through the evening and into the overnight. Rain could be heavy at times and ceilings and visibilities may become IFR during the overnight into Tue. Outlook: Another window of flight restrictions late Tues thru Wed. Rain for the most part may mix with or change to wet snow by Wed at RIC and SBY. There could be some accumulations of an inch or two. Gusty winds buffet the coast Tue and Wed as a coastal storm develops. && .MARINE...
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This evening the area remains sub-SCA conditions as the sfc high pressure slides offshore. Flow has become E to SE is response to the low over the TN river valley which will jump to the coast by Tuesday morning. E/SE persist this evening at 5 to 10 kt then increase overnight. Through the overnight hour tonight the pressure gradient tightens in between the approaching sfc low from the W, and sfc high centered over ontario. The dilemma for the lower Bay and Capes is models develop and deepen the surface flow somewhere between Cape Henry to Oregon Inlet. With the low forecast to develop right over the Capes this could limit the wind speeds for a time until the low pulls off the coast. If the low tracks south across NC then winds over the Bay and Capes will be stronger. This will all be a matter of timing and storm track. North of Cape Charles winds will st Gale Force no matter the storm track. Have continued Gale Warning N of Cape Charles and SCA headlines for the remainder of the marine area. NE winds will ramp up significantly by daybreak, as the initial sfc low stalls over eastern KY and transfers energy to a developing sfc low across the NC coastal Plain. Again the exact position of this will be critical as to how strong the winds get in southern portions of the marine area from the Capes south. For now, the consensus has been to rapidly intensify the sfc low in the vicinity of the VA/NC border Tue morning, then lift it NE and this would support Gales staying a little farther north. Did add a mention of gusts to 40 to 45 kt from Chincoteague north and gusts to 35 kt for portions of the Bay. This initial low will track off the VA coast and then perhaps stall off the DELMARVA Tue aftn/Tue evening. As the upper level low enters the region late Tue night/Wed, a new surface low will develop along/off the Carolina coast and lift it NE off the Virginia coast during the day Wed. models merge this second low with the initial low stalled off the coast. Another round of Gale force conditions are likely across the northern coastal waters while SCA conditions with 25 to 30 kt winds are likely over the remainder of the area. Seas will build pretty quickly as well on Tuesday into Wednesday with seas getting up to 8 to 12 ft on the coastal waters. By Wed night/Thu morning, the sfc low will be moving well off the coast and this will allow conditions to begin to relax with NW flow continuing into Friday when high pressure finally moves over the area. Seas likely to remain elevated for the coastal waters such that SCA headlines will continue through at least Thu aftn. Seas will build rapidly Tuesday and due to the nature and longevity of the event will remain high into Thursday.
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&& .TIDES/COASTAL FLOODING... Low pressure approaches from the TN Valley later today, and intensifies just off the coast on Tue before pulling off to the NE. Secondary area of low pressure lags back off the Carolina coast and tracks NE off the mid-Atlc coast Wed/Wed night. This pattern will allow for a strong and persistent NE flow into much of the local area from late tonight into Tue night, then winds shift more to the NNW on Wed. Building tidal departures and the potential for at least minor coastal flooding over locations adjacent to the lower Bay and the Atlc coast from Ocean City to Currituck NC. Current forecast projections give the greatest chance for flooding Late Tue night into midday Wed as the anomalies will take awhile to build tonight through Tue. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...Wind Advisory from 8 AM to 8 PM EDT Tuesday for MDZ024-025. Winter Storm Watch from Wednesday morning through Wednesday evening for MDZ021>025. NC...None. VA...Wind Advisory from 8 AM to 8 PM EDT Tuesday for VAZ099. MARINE...Small Craft Advisory from 1 AM Tuesday to 8 PM EDT Wednesday for ANZ630>632-634>638. Small Craft Advisory from 4 AM Tuesday to 8 PM EDT Wednesday for ANZ633-656-658. Gale Warning from 4 AM Tuesday to 2 PM EDT Wednesday for ANZ650-652-654. && $$ SYNOPSIS...AJZ/JDM NEAR TERM...AJZ/JDM SHORT TERM...AJZ/JDM LONG TERM...ALB AVIATION...JDM/JEF MARINE...LKB/JAO TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.