Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 070742 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 242 AM EST Thu Dec 7 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 /THROUGH TODAY/...
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Frontal boundary remains (well) S and E (off the coast) today. Initial weak s/w aloft in SW flow exits early this morning...w/ a general trend to RA (now mainly invof NE NC) settling a bit farther SE. Otherwise...expecting widespread mid-high clouds to stream NE over much of the FA today. PoPs (blo 20% - highest invof NE NC) after 12Z/07. Near seasonable temps w/ winds VRB blo 10 mph. Highs within a degree or two either side of 50F.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY/... Frontal boundary will remain offshore nearly parallel to the SSW upr flow through early Saturday. A series of disturbances will move through the region Thursday night through Saturday morning. Thursday should be a mainly dry day, although have maintained chc/slgt chc POPs for light rain across NE NC, near the deepest moisture. Upper flow begins to back Thursday night/Friday, allowing moisture to pull NWWD, and increase precipitation chances back toward the I-95 corridor. Surface temperatures through 00Z Saturday expected to be warm enough for all liquid precipitation. The 00Z Friday through 15Z Saturday is the time period where potential snow could occur across the region. 12Z NAM/Canadian are most aggressive with snow potential Friday night/saturday morning, with GFS/ECMWF nearly identical through 00Z Sunday with regard to precip trends and snowfall potential. GFS/ECMWF would suggest limited precip west of the I-95 corridor, with the best chance for snow across interior southeast Virginia northeastward toward the MD Eastern Shore. Lots of factors limiting snow potential, including a marginal temperature profile, and relatively weak forcing. Thus, while some snow is likely, precipitation rates are expected to be low enough to prevent much accumulation. A small area of around an inch of snow has been forecast south of a South Hill to Petersburg to Suffolk area, mainly before 12Z Saturday. Lighter amounts extend northeastward into the Lower MD Eastern Shore. Given warm temperatures recently, and warm road temperatures, expect little impact from the snow, which will likely melt within a few hours of sunrise Saturday. Precipitation, mainly in the form of rain or a rain/snow mix, gradually moves offshore by early Saturday afternoon, with a surge of colder air moving into the area Saturday afternoon/evening. Temperatures return to below normal levels Thursday through Saturday. Lows Thursday night in the near 30 NW to the upper 30s at the immediate coast in SE VA-NE NC. Highs Friday low to mid 40s. Lows Friday night from the upper 20s to low 30s away from the Bay/Ocean the upper 30s near the coast. Highs Saturday generally in the low to mid 40S. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Long term period characterized by a broad (and amplifying) Eastern U.S. trough. In general, 12Z/06 suite of models, and their respective ensemble means, continue to be in good agreement with the overall setup. However, temporal/spatial differences remain and become greater later in the period. The period begins with deep/cold upper level low pressure centered over the NE CONUS Sat night/Sunday, with shortwave energy aloft brushing NE zones of the CWA. Cold Saturday night with temperatures most areas dropping well into the 20s. Partly cloudy except mostly cloudy NE where will have a ~20 PoP for snow showers. Flow becomes temporarily less amplified Sunday through Monday, with a slow moderation in temperatures starting Sunday night, under clear to partly cloudy skies. High temperatures Sunday only around 40-45 F (highest SE), with low temps Sunday night again mostly in the 20s (with some upper teens possible well inland). Highs Monday in the upper 40s NW to lower 50s SE. Next shortwave trough amplifies the flow Monday night through Tuesday, with the attendant Arctic cold front moving through the area late Tuesday/Tuesday night. This front is expected to be accompanied at least scattered showers, with enough low level warm air intrusion ahead of the system to keep the precipitation mainly in liquid form initially. Lows Monday night in the lower 30s, with highs Tuesday mid/upper 40s to lower 50s (SE). By Tue night into Wed, any lingering moisture will change to snow as much colder air moves in from the NW. This is period where the models diverge, the GFS developing sfc low pressure later and farther south than the ECWMF. Latest WPC guidance and model consensus will be followed for now, with a chance for snow into the forecast late tue night/wed morning, but not as high as what the 12Z GFS would suggest. Turning very cold Wed with highs only in the 30s. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... Frontal boundary remains (well) S and E of the local area through the 06Z/07 TAF forecast period. BKN-OVC VFR CIGS (mainly aoa 10kft) continuing. Area of -RA now in far SE VA-NE NC settles a bit SE through today into tonight. Winds mainly VRB blo 10 kt. The frontal boundary remains off the coast through Sat with a series of weak low pressure areas tracking ENE along it but remaining offshore. BKN-OVC CIGS/occasional pcpn expected at KORF/KECG, and possibly KPHF (by late) tonight/Fri. Pcpn may trend NWWD Fri afternoon/night and reach KRIC/KSBY. Pcpn...possibly as a mix of rain/snow...is expected to move offshore by 18Z Sat. VFR conditions are expected for the upcoming weekend after Saturday morning. && .MARINE... Cold front now SE of the area, and pressure gradient has weakened with winds now mainly NNE at 10-15 kt or less. Only SCA headline still in effect is for NC coastal waters for 5 ft seas. Light onshore winds shift to the WSW and then WNW overnight at 10 to 15 knots and will continue through Thursday, before winds turn northerly as low pressure develops off the southeast coast Friday/Friday night. The consensus forecast still keeps low pressure not intensifying until it is well offshore Fri night through Sat, which means winds will generally remain below Small Craft Advisory criteria Friday through Saturday. Did however ramp the winds up a bit across the far southern VA and NC coastal waters where low end SCA conditions will be possible Sat. Strong cold front passes through sat night ans SCA conditions look to prevail for all zones Sunday (potential for a few brief gusts to Gale force Sun morning). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...None. && $$ SYNOPSIS...ALB/MPR NEAR TERM...ALB SHORT TERM...WRS LONG TERM...LKB AVIATION...ALB MARINE...AJB/LKB

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