Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281917 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 317 PM EDT Sun Aug 28 2016 .SYNOPSIS... High pressure at the surface and aloft will remain over the region today. A weak cold front will begin to approach from the north Monday, then stall near the North Carolina border awaiting another front that will arrive from the north Thursday as high pressure aloft weakens. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 1000 AM EDT Sunday... Wedge of high pressure will bring a pleasant Sunday to the majority of the area, with drier and more comfortable conditions expected through this afternoon. However, moisture will continue to pool along the western boundary of the wedge which is lingering just to our west. This will create a bit of instability and combine with some weak short wave energy rotating around the upper ridge over the mid Atlantic region to bring a low chance for widely scattered showers or a thunderstorm mainly from western Greenbrier in WV back through the Mountain Empire of VA into the mountains of NC. Highs today will range from around 90 degrees east of the Blue Ridge to the low/middle 80s west. Previous AFD... High pressure along the northern Mid-Atlantic coast has pushed a backdoor cold front toward the Alleghany front and northwest North Carolina Blue Ridge. The location of the backdoor frontal boundary will be further west today as compared to Saturday. Thus, expecting any afternoon showers/storms to be confined to areas mainly west of the RNK CWA, but a few could develop or creep into the western periphery of the CWA, especially where the wedge normally tends to be weaker, say west of the I-77 corridor. Will maintain low pops in those areas, otherwise looking at a precipitation free day for the vast majority of the CWA along with mostly sunny skies. Any convection in the western areas will dissipate quickly with the loss of daytime heating. Temperatures will be slightly cooler today as 850mb temps fall back closer to +20C and the drier/slightly cooler air mass spreads southwest into the region from the northern Mid-Atlantic. The drop in dewpoints/RH values will likely be more noticeable than any temperature drop as the sun will still feel quite warm/hot this afternoon at any rate temperatures will still average about 8-10 degrees above normal. Overnight, a weak tropical low off the NC coast will drift northwest toward the coast and this will likely result in increasing RH values after midnight along with mid/high clouds into the Piedmont. To the north, a weak front will be nearing the PA/WV/MD border. Expect partly cloudy skies most areas with increased likelihood of patchy fog development as the wedge weakens and moisture begins to encroach from the southeast. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/... As of 145 AM EDT Sunday... A persistent upper ridge will continue to rest across the Ohio River Valley eastward into northern Virginia through Monday. This will help maintain a prevailing easterly flow into and through the region that will bring with some Atlantic moisture. Trajectories will have their origin initially across New England before skirting the far western Atlantic then coming onshore once again. Look for the development of isolated to scattered afternoon showers and a few thunderstorms across western portions of the area. Here the impacts of any capping inversion will be least and orographical impacts and differential heating will lead to convection development. Any activity is anticipated to wane through the Monday evening hours. More of the same is expected on Tuesday. However, even a greater fetch of moisture off the Atlantic is anticipated. This will allow for a increased coverage of showers and storms as compared to 24 hours prior. The far southeast portion of the area may be hard pressed however to experience any convection. Convection will again wane through the evening hours, with some isolated coverage in the west into the early morning hours of Wednesday. Wednesday into Wednesday night, a cold front is progged to move southeast into, through and out of the area. Look for a trend of increasing showers and storms during the day Wednesday, with lingering showers across the eastern portion of the area during the evening and overnight hours. Temperatures during this portion of the forecast will trend slightly cooler each day. However, readings will still be above average for this time of the year. Highs will average around five degrees above average with the lows close to ten degrees above average. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 400 AM EDT Sunday... General model consensus for the second half of the week is for the upper ridge to give way to some weak upper level troughing over the eastern CONUS, progressive flow across the northern tier states gradually whittling away at the eastern ridge. This should allow for another front to come through from the northwest during the period, although model uncertainty is high with respect to timing per unresolved solutions ongoing in the tropics. As such will keep the forecast pretty close to persistence with respect to precip probabilities, but shave a degree or two off the temperature per potential for drier air to infiltrate from the north later in the week, temperature trending closer to normal. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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As of 315 PM EDT Sunday... Wedge of high pressure will bring quiet conditions to TAF sites through this period, with chances for showers/storms west of the Blue Ridge on Monday holding off until after this valid period. Lingering convective precipitation far west of the Ridge will be tapering off early this evening and coverage will remain sparse. Conditions overnight appear favorable for radiational cooling and moisture profiles indicated by model soundings favor some fog/stratus development late especially for KBCB and KLWB. There is also a strong signal from the NAM soundings for a layer of strato cu developing in a similar manner to last night. Will include a mention of these clouds but will leave them as scattered and not create a cig. Any fog/stratus will burn off early Monday morning with VFR conditions expected through the end of this valid period. Winds will be light. Extended aviation discussion... A weak west-east oriented front will drift south through the forecast area later on Mon. Isolated diurnally driven convection will be possible along the front toward the I-64 corridor Mon afternoon, then toward the NC/SC border by Tue. Coverage will be limited in duration and area on all days and have minimal impact on the TAF sites. Another front will move into the region Wed into Thu with a better chance for showers/thunderstorms, followed by cooler and drier air for Friday. Most of the period looks VFR at this point, outside of the usual late night/early morning fog/low clouds. At this time, it does not appear that any tropical systems will impact the CWA.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...MBS/RAB SHORT TERM...DS LONG TERM...DS/PM AVIATION...MBS/RAB

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