Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300138 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 938 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/... As of 930 PM EDT Saturday... Showers and storms continue to fade this evening, with main area of convection further west over the VA/KY border. As we head into the overnight, a few high-res models showing some sfc convergence in the mountains of NC around midnight-3am, so have added a few showers, possibly thunder there. Otherwise, some high clouds in the north to move out, while some lower clouds work in from the south overnight. A summerlike night with lows in the 60s. Fog a possibility over the river valleys. Previous early evening discussion... Overall seeing a decreasing trend in stronger storms, though still enough instability per mesoanalysis and high-res models to keep a few strong storms around til 00-01z, mainly in WV, far SW VA. Coverage will erode by midnight with mainly high clouds overnight, with patchy fog in the west, where it rained. Previous discussion from the afternoon... 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. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... 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 /WEDNESDAY 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 /02Z SUNDAY THROUGH THURSDAY/... As of 700 PM EDT Saturday... Expect VFR through the period. Will have to watch BLF/LWB for another 1-2 hrs for potential shower/storm activity but most of that is moving west of BLF and northeast of LWB as of 7pm EDT. Expect overnight to be quite similar to last night with mainly dry conditions followed by patchy fog and a bloom of low clouds spreading up from the south. Will keep it scattered at DAN for now, but will have to see how far north this plume makes it. Will indicate MVFR vsby at KLWB and KBCB. Sunday is expected to be much like today with perhaps a slightly higher chance of a shower/storm in the afternoon, but still scattered at best to keep out of tafs at this time. 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. By Thursday next system should be impacting us with showers and a few storms, so sub-VFR is likely. && .CLIMATE... Record highs were broken at Bluefield and Blacksburg today. Details in RERRNK product. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/MBS NEAR TERM...MBS/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/MBS/WP CLIMATE...JR/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.