Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 291951 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 351 PM EDT Sat Apr 29 2017 .SYNOPSIS... High pressure offshore will maintain a warm and humid southerly flow of air across the region through Sunday. A strong cold front will then move through the area Monday with showers and thunderstorms, followed by some cooler, but near seasonal temperatures through the first part of next week. && .NEAR TERM /THROUGH SUNDAY/...
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As of 350 PM EDT Saturday... Satellite imagery shows a Cu field along the NC/VA border with other diurnally forced convective clouds starting to sprout up. With warm air aloft providing an effective cap, do not see much potential for anything more than a stray shower/storm mainly in the mountains where orographic forcing may boost lift, though some cells have just managed to launch in the far southwest and HRRR seems to have a handle on this so will lean heavily on the latest solution for structure of POP/QPF grids though late this afternoon. It is worth noting that in this juicy airmass instability is AOA 2500J/KG, so any storms will have a good amount of energy to tap and can produce heavy downpours, gusty winds, and possibly some hail. Expect tonight to be quite similar to last night with mainly dry conditions after any evening precipitation dissipates, followed by patchy fog and a bloom of low clouds spreading up from the south. Sunday is expected to be much like today with perhaps a slightly higher chance of a shower/storm mainly later in the afternoon, with increasing chances for precipitation arriving after dark. Temperatures will remain quite warm, though with a bit more cloud cover Sunday will be a few ticks cooler. Lows tonight will be in the middle 60s east of the Blue Ridge with upper 50s/lower 60s to the west. Highs tomorrow will generally be 80 to 85 in the east, middle 70s west.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 235 PM EDT Saturday... Good consensus on the overall pattern evolution Sunday night through Tuesday. Deepening 500 MB closed low tracks from Kansas on Sunday evening to Lake Superior early Tuesday morning. Using the timing of the slightly faster GFS for the frontal passage on Monday. This puts the cold front from eastern Ohio to eastern Tennessee 8AM Monday morning and from eastern Pennsylvania to eastern North Carolina by 2AM Tuesday. Still expecting strong pre frontal winds and Convective Available Potential Energy possibly in the 1000-2000 J/kg range Monday afternoon and evening. Clouds from showers and thunderstorms upstream or from widespread low stratus in the foothills and piedmont Monday morning will have a large impact on how much heating and instability there will be later in the day. Good surge of lower 850MB temperatures on Monday night along with pressure rises around +5MB/6hrs so will keep winds gusty. Western upslope areas will stay in the clouds behind the front Monday night. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 235 PM EDT Saturday... Larger differences in the synoptic pattern show up in the different models by Wednesday. WPC leaning heavily on the ensembles with keeps a progressive amplified eastern trough. Surface low moves far enough northeast to relax the pressure gradient on lighten the winds by Tuesday night. Will have highest probability of precipitation on Wednesday night through Thursday night. Then with lower confidence due to the large spread in the guidance will have lower probability of precipitation by Saturday and Sunday. Will be keeping maximum temperatures below normal for Thursday through Saturday. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... As of 200 PM EDT Saturday... Expecting generally VFR conditions at all TAF sites through the early portion of the TAf period, though satellite imagery is showing a Cu field along the NC/VA border with other diurnally forced convective clouds starting to sprout up. With warm air aloft providing an effective cap, believe there may be a brief tempo to an MVFR cig, especially around KDAN. With orographic forcing, a stray shower/storm is possible in the mountains but minimal to no activity expected elsewhere so will only use VCTS at KBCB due to proximity to terrain. Expect tonight to be quite similar to last night with mainly dry conditions after any evening precipitation dissipates, followed by patchy fog and a bloom of low clouds spreading up from the south. Will indicate and MVFR cig at KDAN and nothing lower than a tempo to MVFR vsby at KLWB and KBCB. Sunday is expected to be much like today with perhaps a slightly higher chance of a shower/storm but mainly later in the afternoon after this TAF valid period. Winds will be light. Extended Aviation Discussion... As a low pressure system approaches from the west late Sunday night, the potential for showers and thunderstorms will increase over the western mountains by early Monday. The cold front associated with this system should reach the Appalachians Monday and depart offshore by Tuesday morning. As such, expect the best chance of MVFR conditions during the frontal passage from west to east during Monday. VFR conditions return behind the front on gusty westerly winds Tuesday followed by continued good flying weather under high pressure Tuesday night into much of Wednesday. However moisture may return to the mountains by late in the day Wednesday with local MVFR possible in isolated showers by the end of the day. && .CLIMATE... Potential for high temperature records to be broken Saturday, April 29, as well as record warm lows for the 29th Current record/year Roanoke89/1915 Lynchburg88/1974 Danville91/1981 Bluefield83/1996 Blacksburg83/1974 Current record/year Roanoke63/1956 Lynchburg66/1956 Danville65/1956 Bluefield63/1991 Blacksburg59/1962 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/MBS NEAR TERM...MBS SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/MBS CLIMATE...JR/WP

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