Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 150915 AFDAKQ Area Forecast Discussion National Weather Service Wakefield VA 415 AM EST Wed Feb 15 2017 .SYNOPSIS...
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Low pressure lifts over the Carolinas this morning as a cold front approaches from the northwest. The cold front crosses the area this afternoon. High pressure builds into the region Thursday through Saturday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Latest GOES water vapor imagery places the potent northern stream upper low over the eastern Great Lakes Region and the deamplifying southern stream shortwave over the Tennessee Valley. Moisture plume also visible spreading from the southern stream wave northeastward over the central Appalachians. At the surface, the northern stream cold front has reached the Ohio Valley with the southern stream cold front located over the Deep South. Light rain has spread into the region ahead of an area of low pressure lifting across the Deep South. Latest high-res and NAM/RAP 290-295K isentropic analysis depicts a northward shift in the precipitation compared to previous runs, with the favored area this morning across the northern half of the forecast area. Regional radar indicates better coverage and intensity upstream over the central Appalachians. Cool cloud heights also indicated. Expect better coverage and intensity as the systems begin to phase and the surface low lifts over the Carolina around daybreak. Have increased POPs to categorical across much of the region this morning as rain spreads eastward across the local area. The low pushes offshore early afternoon as the northern stream cold front pushes across the local area this afternoon. Have kept categorical POPs across the southeast thru mid afternoon today, but expect some scattered showers along the northern stream front east of Interstate 95 this afternoon. Best moisture pushes offshore late afternoon as dry, downslope flow overspreads the region. Aside from the phasing upper level systems, a strong jet couplet will provide impressive forcing for ascent. Given the forcing and +1 standard deviation precipitable waters, have increased QPF amounts across the region. Amounts will range from one quarter to one half inch across the southeast half of the local area to a few hundredths for the northwest Piedmont. Temperatures level off this morning in the mid to upper 40`s, warming behind the precip this afternoon into the low to mid 50`s. Cloudy this morning, becoming clear inland this afternoon thanks to dry, northwest flow. Cloudy conditions remain along the coast. Winds become northwest this afternoon, increasing to 10-15 mph with gusts of 20-25 mph.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
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Deep/anomalous upper trough locates over the Northeast tonight as the trough axis pushes offshore. Additional energy on the backside of the upper trough digs over the Delmarva, but with the front well offshore and a dry air mass surging into the region, expect very little moisture to remain along the coast. However, based on the dynamics, steep lapse rates, and falling temperatures/thicknesses, will keep a mention of a slight chance for snow showers/streamers over the lower Virginia Eastern Shore through late tonight. No accumulation is anticipated. Sky becomes clear inland thanks to downslope/dry flow, but will keep a partly cloudy sky northeast. Cold, with lows in the mid to upper 20`s inland to low 30`s near the coast. The upper low lifts over the Canadian Maritimes Thursday as broad cyclonic flow prevails over the Northeast. Dry downslope flow results in dry conditions and a sunny to mostly sunny sky Thursday. 850Mb temperatures level off around -8 to -10C (-1 standard deviation). Highs Thursday in the mid to upper 40`s. Breezy, with a northwest wind of 10-15 mph inland and 15 to 20 mph Eastern Shore. Gusts 30-35 mph Eastern Shore. Deep mixing results in minimum relative humidity values in the 20-30 percent range, but precipitation today and cool temperatures expected to mitigate any fire weather concern. A shortwave progged to dig over the Ohio Valley late Thursday and into the Kentucky Valley Thursday night. Dry conditions are forecast, but expect an increase in mid to high clouds late Thursday through Thursday night. Lows in the mid to upper 20`s. High pressure slides off the Southeast coast Friday as the shortwave pushes offshore. Another shortwave drops over the Delmarva in northwest flow aloft, resulting in some mid to late afternoon clouds. Return flow and modest warm air advection pushes highs into the mid 50`s inland and upper 40`s northeast.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Long term period will feature mainly dry weather with slowly increasing temps through the period. For Fri night, an upr-level shortwave ridge builds into the area with sfc high pres remaining in the vicinity. Expect low temps in the 30s under a mostly clear sky with light southerly flow. Winds remain southerly into Sat as low- level thicknesses rise, allowing for well above normal temps...highs in the low/mid 60s most areas; upr 50s Lwr Ern Shore. Southern stream trough approaches the region Sat night, pushing across the region Sun. An associated weak area of low pres is progged to lift along the SE coast. Clouds increase Sat night along with a slight chance of rain over the srn half of the FA. The trough pushes offshore Sun night with dry and clearing conditions. High temps Sun and Mon in the mid 60s most areas; near 60 Lwr Ern Shore. && .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... VFR conditions to begin the 06Z TAF period as low pressure develops south of the region. A few obs around central Virginia indicate light rain, but low levels remain quite dry so expect the brunt of the precip to remain west of the region through 09Z. Thereafter, expect light rain to increase in coverage as a potent upper level disturbance approaches the region. Light rain develops across central Virginia, then spreads south and east through early to mid afternoon. Rain may become moderate to locally heavy at times, reducing visibilities to MVFR/localized IFR. Ceilings lower to MVFR mid morning, with IFR expected across southeast Virginia and northeast North Carolina late morning/early afternoon. Conditions improve late today as the cold front pushes across the region. Some lingering precip possible across the Eastern Shore as the disturbance tracks across the region. Westerly winds this morning become northwest this afternoon generally around 10 knots. Gusts to 20 knots expected along the coast late today and this evening. Outlook: VFR conditions are expected tonight through Saturday. Winds will be gusty behind the front on Thursday, winds could occasionally gust in excess of 20 knots out of the NW. The next potential for sub-VFR conditions will be Saturday night and into Sunday as weak low pressure lifts along the southeast coast. && .MARINE...
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Sub-SCA conditions currently with light winds across the area and seas of 2-4 ft, waves 1-2 ft or less. A slowly developing surface low tracks E from the Great Lakes and then rapidly intensifies off the New England coast tonight and Thu. Will have SCA headlines for all zones starting either late this aftn or this evening. Appears that this system will be a little stronger than earlier anticipated, and have bumped winds up a few KT from previous forecast, with a fairly strong SCA event expected for the Bay and coastal waters. Expect a brief surge of higher gusts to 30 KT or perhaps a little higher with the initial push of CAA early this evening, then winds may diminish a bit later tonight. However, as the sfc low continues to intensify off the New England coast/Canadian Maritimes (down to ~980 mb) on Thu, expect winds to ramp back up and a period occasional gusts to Gale force will be possible over the coastal waters (especially over the N). Still do not think this warrants a Gale Warning, but if the sfc low were to be a little farther S than guidance, may need to upgrade to Gales over the northern coastal waters. Seas will not be excessive despite the strong winds as the flow will be offshore (will avg 4-6 ft). High pressure builds in for the end of the week and winds and seas/waves subside slowly Thu night (have extended the SCA`s through 06Z/Fri northern coastal zones, 03Z Bay and southern areas). Lighter winds and sub-SCA conditions Fri-Sun.
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&& .AKQ WATCHES/WARNINGS/ADVISORIES...
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MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 4 PM this afternoon to 4 PM EST Thursday for ANZ635>638. Small Craft Advisory from 4 PM this afternoon to 10 PM EST Thursday for ANZ630>632-634. Small Craft Advisory from 7 PM this evening to 7 PM EST Thursday for ANZ633. Small Craft Advisory from 7 PM this evening to 10 PM EST Thursday for ANZ654-656-658. Small Craft Advisory from 7 PM this evening to 1 AM EST Friday for ANZ650-652.
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&& $$ SYNOPSIS...MPR/SAM NEAR TERM...SAM SHORT TERM...SAM LONG TERM...MAS AVIATION...AJB/SAM MARINE...LKB

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