Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201736 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 136 PM EDT Fri Apr 20 2018 .SYNOPSIS... A large high will cover much pf the eastern United States today through Saturday. Low pressure over the Lower Mississippi Valley on Sunday will track northeast to the Virginia coast by Wednesday. This will bring widespread rain and below normal temperatures to the Mid Atlantic region Monday and Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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As of 130 PM EDT Friday... Lowered dewpoints per mixing down of very dry air aloft. This will result in humidity minimums this afternoon in the 15 to 25 percent range. Other than this modification, the remainder of the forecast is unchanged which entertains cloud free skies. High pressure continues to build into the forecast area from the northwest. This will result in a light, but persistent northerly wind...with speeds averaging 5 to 10 mph. There may be a few gusts in the 14-18 mph range, but overall, expect diminishing winds as we head into the evening and overnight periods. For the overnight, the wind is expected to decouple in the valleys with ideal radiational cooling conditions under clear skies. This may permit scattered frost, although with a very dry airmass even this will be limited. Freeze watch for the Shenandoah valley where temperatures will likely reach the lower 30s. For the foothills and piedmont, the temperatures will likely dip into the 32-37 degree range. Attm think residence time near 32 degrees for the foothills/piedmont will be restricted to a few hours just before daybreak, but nothing more. As for the mountains, temperatures will again dip into the 20s, continuing to post-pone the growing season and delay green- up.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 230 AM EDT Friday... Surface high pressure centered along the Virginia coast, will weaken some on Saturday, but still keep the area dry. An inverted surface trough is expected to emerge west of the Appalachains and should only develop a few fair weather cumulus clouds Saturday afternoon across the mountains. Mostly sunny skies with a light east to southeast flow will allow for highs in the upper 50s to mid 60s areawide, coolest in the higher ridges. A back-door front will stall across north-central Virginia Saturday night. This front will bring more clouds than previously thought into the area overnight. These clouds will help keep overnight temperatures mild in the upper 30s to lower 40s. The back-door front washes out on Sunday while clouds stick around through the day. If these clouds remain thick and with a southeasterly flow, temperatures Sunday maybe similar to Saturday (upper 50s to mid 60s). A slow moving closed low is expected to track from Arkansas Sunday morning to eastern Tennessee late Sunday night. Models have a strong short wave out ahead of this low moving up the southern Appalachian Mountains Sunday night. With high pressure to the north and the low to the southwest, southeast flow will increase and transport of Gulf and Atlantic moisture should reach the southern Blue Ridge and adjacent foothills of NC into far southwest VA by dawn Monday. Latest models are coming around toward a wet Monday, but the weekend stays dry. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 200 PM EDT Thursday... Not a lot of confidence in the models as they continue to shift back and forth with track of upper and surface low across the Gulf Coast States early next week, then offshore by Wednesday followed by another front Wednesday-Wed night. Ensembles are leaning toward a wetter solution similar but not as wet as the 12z GFS. The 0z ECM appears driest early on. Will increase pops Mon-Tuesday but cap pops in the likely range with best coverage over our southern CWA. High pressure over the mid-Atlantic coast then offshore will provide an easterly fetch and in-situ wedge which could hold temps down quite a bit Monday, with 40s in the mountains of NC/far southern VA but due to uncertainty on northern shield of rain will have temps a little milder but still at or just under mex mos elsewhere. Low tracks to the GA coast by Tuesday morning, then northeast off the NC coast by Wednesday morning as northern stream wave allows another front to cross Wednesday night. So in essence most of the extended period will hold a threat of rain with best chance Mon-Monday night into early Tuesday, possibly a break Tue-Tue night but will not have sub-30 percent pops at this time. Should be drier by later Thu-Thu night. && .AVIATION /17Z FRIDAY THROUGH TUESDAY/...
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As of 130 PM EDT Friday... High confidence for VFR conditions through Sunday...high pressure promoting clear skies and light winds. Extended Aviation Discussion... Clouds will begin to creep back into the area late Sunday in advance of an approaching low in the Lower Mississippi River Valley. However, cloud bases should remain VFR until deeper moisture arrives Monday. SCT MVFR showers are possible in southern Virginia and northern North Carolina Sunday night with rain becoming more widespread across the Mid Atlantic region on Monday. MVFR/IFR ceilings and visibilities are expected Monday night and Tuesday due to widespread rain and an upslope very moist southeast wind.
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&& .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...Freeze Watch from late tonight through Saturday morning for VAZ023-024. NC...None. WV...None.
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&& $$ SYNOPSIS...AMS NEAR TERM...PM SHORT TERM...RCS LONG TERM...WP AVIATION...AMS/KK

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