Area Forecast Discussion
Issued by NWS Blacksburg, VA

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587 FXUS61 KRNK 260548 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 148 AM EDT Fri Aug 26 2016 .SYNOPSIS... High pressure will be the dominant weather feature through the upcoming weekend...becoming centered directly overhead by Saturday. && .NEAR TERM /THROUGH TODAY/... As of 845 PM EDT Thursday... Despite the return of ample low level moisture per dewpoints/pwats, convection has remained quite isolated into early this evening given only a weak residual surface trof along the Blue Ridge to focus on. Also subsidence aloft across the west in the wake of the passing wave very efficient in removing most cloudiness as evidenced via the very dry air aloft over a weak mid level cap off the RNK evening sounding. This along with building heights under the ridge aloft and forecast subsidence seen off latest models in conjunction with loss of heating supports going dry overnight. Still might see an isolated low topped shower redevelop from outflow along the VA/NC border given lingering instability but overall mostly clear. This along with low level moisture and favorable fog parameters off guidance raobs should allow for more widespread fog in the valleys by dawn, and espcly southern sections that saw earlier heavy downpours. Otherwise will be back to the warm and muggy scenario overnight with lows mid/upper 60s mountains to around 70/low 70s east. Previous discussion as of 330 PM EDT Thursday... A few showers and storms across the foothills of VA/NC shown by the high-res models to shift eastward through late afternoon. As such will keep very low chance pops mainly from just east of the Blue Ridge through early evening, then should see dry wx. As we head overnight skies should be mostly clear. With dewpoints in the upper 60s to lower 70s and a light wind, should see some fog mainly in river valleys, and where it rained this afternoon. Low temps will be in the mid to upper 60s west to lower 70s east. Friday will be drier as upper center of high moves across Virginia. Slight chance of storms will be mainly over the southern Blue Ridge. A hotter day but heat indices in the Piedmont should stay just below the century mark. Highs will be in the lower to mid 90s east of the Blue Ridge including Roanoke and Lexington, VA, with the mountains reaching the mid to upper 80s. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 350 PM EDT Thursday... Strong subtropical ridge of high pressure (5H heights advertised near 597 dm) will be centered over the region this weekend. This feature will ensure that summertime heat will prevail with daytime temperatures of 4 to 7 degrees above normal and overnight lows averaging a full 10 degrees above normal. There will be an isolated threat for diurnally driven showers/storms, but this activity is expected to be mainly confined to the mountains west of the Blue Ridge. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 450 AM EDT Thursday... The upper-level ridge will begin to weaken as we progress into the mid part of next week but will also be the key to steering a tropical system that is forecast by most models to track into south Florida early in the week. Although the track is now relatively similar among the models, there are vast differences in the intensity. While the GFS shows a weak tropical low drifting slowly north to northeast across FL into southeast GA and eventually the Carolinas through the week, the ECMWF develops a tropical storm/hurricane, which it similarly moves northeast, albeit much quicker than the weaker GFS system. Meanwhile, as the upper high weakens and shifts south of our area, another weak front is progged to drift into the region by midweek. Much of the time, our region will likely remained sandwiched in between the frontal precipitation to our north/west and the tropical system to our south. However during the later part of the week, the tropical system could begin to impact at least the southeastern parts of our CWA and with the pattern in place, there is always at least some concern of a predecessor rain event. At any rate, considerably uncertainty remains and such considerations still remain just beyond this forecast period. Therefore, will continue the trend established in the short term period of slight chance to low chance diurnally driven pops and well above normal temperatures moderating only slightly closer to normal by the end of the period as cloud cover and moisture increase, the upper high weakens, and 850mb temps drop back a few degrees. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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As of 148 AM EDT Friday... High pressure both surface and aloft will control our weather today and tonight. Outside of morning fog and isolated convection, great flying weather is expected. This morning, the combination of light winds and low level moisture has produced patches of fog. Patchy dense fog and localized IFR- LIFR vsbys/cigs may occur especially KLWB and perhaps KBCB. KLYH and KDAN along with KBLF may also see a period of MVFR fog. morning low clouds and fog will burn off by mid morning, expecting mainly scattered cumulus through the afternoon with any convection very isolated at best. This will be too isolated to include mention in any taf site. winds will remain light and variable Friday afternoon. Clear to partly cloudy conditions are expected Friday night with another round of late night patchy fog in the valleys. KLWB could drop to IFR/LIFR once again Saturday morning. High confidence in ceilings,winds and winds during the taf period. Extended aviation discussion... Strong ridging to hold tight on Saturday with continued VFR and again only isolated late day mountain shra/tsra resulting in possible brief MVFR. A weak front will drift into the area Sunday. Isolated to scattered diurnal showers and thunderstorms still possible into Sunday evening. Coverage will be limited in area and duration. Monday high pressure bubbles in but still a very humid airmass to keep isolated mountain storms around in the afternoon, but mainly VFR. Another front situated north of us Tuesday could enhance convective threat, mainly over the mountains and north of ROA/LYH.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...JH/WP SHORT TERM...PM LONG TERM...RAB AVIATION...JH/KK

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