Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 170100 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 800 PM EST Tue Jan 16 2018 .SYNOPSIS... High pressure will slide offshore today into tonight. A cold front crosses the area Wednesday morning with low pressure moving northeast along the coast Wednesday afternoon and night. A second surge of arctic air pushes across the area Wednesday night into Thursday before temperatures moderate into next weekend. && .NEAR TERM /THROUGH WEDNESDAY/... Current WV imagery and model analysis depicts a positively tilted, potent upper level trough digging SE across the Ohio Valley/Mid-south, with broad SW flow aloft from the Gulf coast across the Mid- Atlantic and into coastal New England. At the surface, 1030+ mb surface ridge axis continues to linger across the coastal northeast down into the Mid- Atlantic. The coastal trough is now oriented just offshore of the NA/NC coast with some light returns on mosaic radar imagery indicating some showers well offshore. The light NE flow associated with this feature allowed for a marine layer to push across coastal zones, which continues across coastal NE NC and SE VA with Stratocu and lingering fog. Temperatures early this morning range from the upper teens over the Piedmont to the low 30s along the coast. The potent upper trough will pivot sewd tonight across the Ohio Valley and into the Cumberland plateau, with the cold front pushing across the mountains and into the Piedmont by 06-12z Wednesday. The vigorous upper level feature will continue to trundle ewd across the region Wednesday as the cold front gradually pushes through the region with snow overspreading the region and affecting the commute Wednesday morning across wrn and central portions. Pcpn could briefly begin as rain, especially toward the coast. 16/00z GFS/ECMWF/NAM/CMC demonstrate decent agreement with this feature, with some slight timing differences in the latter stages, mainly 18-00z Wednesday with the ECMWF/CMC slightly slower. Given this, PoPs have been increased to categorical across the Piedmont after 06z tonight into midday Wednesday, and for central and s- central VA Wednesday morning. Likely PoPs have been maintained for SE VA/NE NC, with likely PoPs for the Middle Peninsula/Northern Neck/Lower Ern Shore tapering to chc for the Lower MD Ern Shore. Overall, not much has changed with the synoptic weather details/preferences in the near and short term. Have gone ahead and extended Winter Weather Advisories east to include all zones west of the Chesapeake Bay, including for the Hampton Roads area for their evening commute. Have held out Accomack/Northampton for now with accumulations ~1" and some mixed pcpn expected. 12z/16 suite once again have trended slightly slower and upward with QPF. Have nudged forecast snow totals up slightly from the peninsula into Tidewater/Hampton Roads areas. Model consensus supports QPF of 0.25-0.35" across the Piedmont and s-central VA and Northampton NC, bordered by ~0.1 to 0.2" from central VA to E VA and NE NC, with 0.1" or less over the lower eastern shore. Expect some variability in SLRs, but generally ratios of 12-15:1 are expected during the highest PoPs, which supports 2-4" of snow across the Piedmont, with 1-3" for the I-95 corridor of central and s-central VA into Northampton NC. Confident in period of moderate snow inland, given well-modeled narrow band of negative EPV dropping over the SW zones in the Piedmont (I-85 corridor). There could be a very narrow corridor of 4-6" of snow in this band. However, expect this would be very localized and hard to pin- down, so there is no need for a watch or warning at this time. Slightly less confident into SE VA. To reiterate...we have issued a Winter Weather Advisory over Hampton Roads for the late morning and afternoon. However, we are still a bit concerned with sharpening axis of F-Gen/OPRH depicted by the 12z (and now 18z) high-res NAM. Issue will be that we will have a very narrow window within which to receive moderate snows into Tidewater area, before best axis of moisture slides offshore. Potential is there for warning criteria snows (and criteria is 3" for SE VA). However, after collaboration with neighboring offices and WPC, will hold off with warning for now. Narrow window of potential snowfall is the primary issue. Should later model runs continue to depict this potential, an upgrade to a Winter Storm Warning for all or part of the Hampton Roads area may be needed. High temperatures will generally be 30-35F, but will likely fall into the mid/upper 20s across the NW half of the area during the aftn. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... The sky will clear quickly Wednesday night as well-advertised quick shot of arctic air surges into the region. Shallow mixing is expected to persist overnight, which should inhibit temperatures from plummeting too far. Still cold nonetheless with lows in the teens inland to the upper teens/low 20s for coastal SE VA/NE NC. Mid-level WAA resumes rather quickly Thursday with 850mb temperatures of -2 to -4C at 12z warming to +4-6C by 21z. A cold start to the day, limited mixing, and mid- level WAA should result in rather stable lapse rates and surface high temperatures Thursday should only reach the upper 30s to low 40s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... Pattern change looks to occur during the medium range period with a significant warmup expected through the upcoming weekend/early next week. It will still be on the cold side early Fri morning with sfc high pressure centered across the deep south, and one last upper trough moving ESE to the New England coast. Latest GFS/ECMWF/CMC depict the upper trough moving well off the New England coast Fri with a broad upper level ridge building over the eastern CONUS Fri aftn through the weekend. Expect continued dry conditions with warming temperatures, highs in the upper 40s/lower 50s Fri, rising well into the 50s (possibly near 60F) Sat, and into the upper 50s to lower 60s for Sun. Lows Fri night/Sat am in the mid 20s to mid 30s, and Sat night/Sun am in the 30s to around 40F. Minor timing differences arise by Mon between the models, but the overall trend is for a slower arrival of the cold front and with the upper pattern amplifying quite a bit this makes sense. Expect increasing clouds ahead of the next front Sun night but have genly slowed down the main chance for for showers until Mon aftn/Mon night. Mild with lows in the 40s Sun night/Mon am and highs Mon mainly in the 60s (could even be near 70F in the SE if more sun develops and the precip is slower to arrive). High chc PoPs for now/40-50% all zones mon night. The ECMWF is slower by this time than the GFS/CMC so will linger PoPs through 12Z. Drying out/becoming partly-mostly sunny Tue with highs mainly in the 50s. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
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Complex scenario this evening with patchy fog/low stratus becoming confined mainly to the waters and the eastern shore (vsbys having recently improved at KORF). Mainly VFR conditions inland for the time being. However, expect conditions near the coast to again deteriorate by around 03Z and persist overnight (though probably not to the level of what occurred last night). Expect widespread flight restrictions on Wed in snow as clipper and associated cold front crosses the region. KRIC will likely experience the worst conditions from 12-18Z while KORF/KPHF/KECG will lag behind by several hrs with worst conditions not starting until between 15-18Z and lasting through most of the remainder of the TAF period. KSBY will overall see only light snow showers with vsbys down to about 2SM. Winds will be from the N and gust to 20-25kt near the coast by aftn. Outlook: Clearing Wed night with breezy N winds near the coast. Predominate VFR then likely Thu-Sat as the trough ejects NE offshore.
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&& .MARINE... Light winds and saturated conditions this evening over portions of the Bay and southern VA coastal waters. Cams show limited vsbys over these waters and raised a Marine Dense Fog Advisory through the evening hrs. High pressure will slide into the Atlc this evening. A surface cold front crosses the the coast late tonight into Wed morning, with strong CAA lagging behind until the upper trough arrives Wed evening into Thu. NNW winds increase to 15 to 25 knots Wed aftn/evening with gusts up to or arnd 30 kt, esply later Wed evening and Wed night, as the storm system moves out to sea and high pressure starts to build back in fm the west. SCAs are in effect over the coastal waters into Thu aftn, with SCAs for the Ches Bay and Currituck Snd now in effect fm Wed morning (7-10 am) into Thu morning (7-10 am). High pressure settles over the area later Thu aftn into Sat, then slides off the SE coast Sun. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...Winter Weather Advisory from 6 AM to 6 PM EST Wednesday for NCZ012>014-030. Winter Weather Advisory from 10 AM to 9 PM EST Wednesday for NCZ015>017-031-032-102. VA...Winter Weather Advisory from midnight tonight to 3 PM EST Wednesday for VAZ048-060>062-069-509-510. Winter Weather Advisory from 6 AM to 6 PM EST Wednesday for VAZ084-086>090-092-093-096-523>525. Winter Weather Advisory from 10 AM to 9 PM EST Wednesday for VAZ095-097-098. Winter Weather Advisory from 3 AM to 6 PM EST Wednesday for VAZ064>068-075>083-085-511>522. MARINE...Small Craft Advisory until 1 PM EST Thursday for ANZ650-652- 654-656-658. Dense Fog Advisory until 1 AM EST Wednesday for ANZ631-632-634- 656. Small Craft Advisory from 7 AM Wednesday to 7 AM EST Thursday for ANZ630>632. Small Craft Advisory from 7 AM Wednesday to 10 AM EST Thursday for ANZ634. Small Craft Advisory from 10 AM Wednesday to 10 AM EST Thursday for ANZ633. && $$ SYNOPSIS...MAM NEAR TERM...AJZ/MAM SHORT TERM...MAM LONG TERM...LKB AVIATION...LKB MARINE...LKB/TMG

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