Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 160522 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 122 AM EDT Wed Aug 16 2017 .SYNOPSIS... A weak stationary front across the region will weaken overnight prior to dissipating on Wednesday. Weak high pressure builds north of the area Wednesday afternoon before giving way to increasing moisture ahead of another cold front approaching from the northwest on Thursday. This cold front will work slowly southeast toward the area Friday before sliding into the Carolinas during the weekend. && .NEAR TERM /THROUGH TODAY/... As of 245 PM EDT Tuesday... Scattered showers and a few thunderstorms will continue to progress eastward across mainly eastern sections of the region heading into the early evening hours. This upper level disturbance responsible for this activity is progged to be east of the area by the late evening. Very little, if any, precipitation is expected to survive across the area by midnight. Coverage will decrease from northwest to southeast. An upper level ridge will start to build into the region tonight, and continue to do so on Wednesday. This will allow for milder temperatures aloft, as well as drier air aloft working its way into the area. This will not preclude lingering cloud cover during the overnight as moisture in the lowest level gets trapped under a developing inversion across the mountains. Also anticipate fog development, especially in areas that have received measurable rainfall the past couple of days. Low temperatures tonight will range from around 60 to the mid 60s. Across the Piedmont lows will range from the upper 60s to near 70 degrees. For Wednesday, expect a slightly less humid day with more sun than clouds, especially in areas along and north of route 460. Precipitation chances will be low, limited to isolated showers/storms across the Northern Mountains, eastward into the NC Piedmont. With more sunshine, higher heights aloft, and milder 850mb temperatures, look for high temperatures to range from the low to mid 80s across the mountains with mid to upper 80s across the Piedmont. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... As of 230 PM EDT Tuesday... Weak shortwave ridging will remain across the region Wednesday night into Thursday as a weak warm front aloft slides back through the area from the southwest. This should act to return deeper moisture north espcly by Thursday when will see a bit stronger southwest flow within the low levels by the afternoon. However forcing remains quite weak until later Thursday when some of the ridging aloft breaks down and moist PWATS surge back north. Since models show the column quickly moistening Wednesday night, will include some slight chance pops from southwest to northeast by daybreak Thursday. Better convergence develops by Thursday afternoon espcly Blue Ridge as capping aloft fades, while guidance shows quite an increase in instability as whats left of the boundary lifts across during max heating. Therefore boosting pops to medium/high chance over the region Thursday afternoon. Will also become quite muggy with highs surging back into the 80s to near 90 out east under some insolation. A few showers and storms may linger into Thursday evening before loss of heating and exodus of the weak boundary takes place. Could even see a period of dry weather overnight between the front to the north and the next upstream pre-frontal band of showers ahead of the next cold front. This front should slowly pivot toward the region Friday afternoon preceded by a lead band of residual showers that could jump into the eastern lee trough during the afternoon where deeper convection possible. However most guidance not very impressive with only weak lift ahead of the boundary, given most upper support shearing out to the northeast with the passing weak 500 mb low. This while seeing the boundary layer flow turn more westerly espcly mountains behind the passing pre-frontal axis early on. However progged instability still quite strong east of the mountains and if timing is slower then could see better thunder coverage eastern half. Thus staying with decent chance pops most sections with trend for earlier higher pops west, and mostly afternoon timing out east. Highs again mainly 80-85 mountains to near 90 east pending timing of any convection at this point. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 130 PM EDT Tuesday... Transition to more of an upper troughing regime will again occur over the weekend allowing another surface cold front to push into and perhaps south of the region by early next week. Latest models again have differences on the southward push of drier air behind the front espcly given another upper disturbance that looks to pass just north by later Sunday. However appears passage of this feature may be enough to briefly shunt deeper moisture to the south/east before the trough flattens into broad ridging early next week. Therefore will leave in some low pops mainly southeast third later Saturday where the front may slow up during heating, and slight to low end chance pops espcly southern/southwest sections Sunday as the wave/trough passes. Monday into Tuesday look drier but rather hot with surface high pressure building in from the north behind the front resulting in better subsidence under a weak wedge. Thus limiting any pops to start the week to mainly the southern Blue Ridge, with overall more sunshine elsewhere for now. Despite the frontal passage, will actually see warmer high temps given heating of somewhat drier air and warming aloft to start next week. This supports overall above normal highs with low/mid 80s mountains to near 90 east through much of the period. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
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As of 120 AM EDT Wednesday... Mainly clear skies and a wet ground will allow for fog to develop at most TAF sites early this morning. Expect IFR/LIFR conditions at KLWB and KBCB with generally a tempo to MVFR/IFR elsewhere. After fog dissipates Wednesday morning expect VFR conditions through the rest of the taf period. However, the front to our south will start to feel the influence of a low moving through the Mississippi valley and buckle back into the region from the southwest. This may generate some late day showers/thunderstorms from the mountains of NC into the southern Blue Ridge but TAF sites look to remain dry. Winds will be light through the period. Extended Aviation Discussion... Thursday through Sunday, we will be in an active weather pattern with a series of disturbances or fronts crossing the area. The most active periods will be Friday afternoon and evening, and then again on Sunday. While during the bulk of this time period VFR conditions are anticipated, sub-VFR conditions are expected under any of the heavier showers or storms.
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&& .EQUIPMENT... As of 755 PM EDT Saturday Aug 12th... KFCX doppler radar will continue to be down for the rest of the month due to a failing bull gear. It will only be operational during this time frame for brief periods if an imminent significant widespread severe weather and/or hydrologic event occurs. Operating the system for any amount of time until the bull gear is replaced risks a catastrophic failure that would further extend system downtime. From the 17th through the 27th the radar will most likely be down completely as the repairs are expected to be made during this period. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...DS SHORT TERM...JH LONG TERM...JH AVIATION...DS/MBS/WP EQUIPMENT...RAB/WERT is the U.S. government's official web portal to all federal, state and local government web resources and services.