Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261728 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 128 PM EDT Wed Oct 26 2016 .SYNOPSIS... Cool high pressure will remain wedged along the eastern slopes of the Appalachians today before weakening and sliding east tonight. Low pressure crossing the Great Lakes will push a cold front through the region later Thursday and offshore Thursday night. High pressure follows the front for the end of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 245 AM EDT Wednesday... Weak wedge of high pressure along the eastern slopes of the mountains will linger today before slowly weakening and pushing east tonight in advance of the next upstream cold front. This should continue to keep overall quiet weather in place today although the degree of cloud cover espcly north/west remains iffy despite dry air in place. Latest guidance tending to gradually lift the shear axis responsible for the ongoing streak of mid deck across the north out of the area this afternoon as deepening warm advection aloft works in from the southwest. However as this canopy erodes, expect to see more in the way of sheared mid/high clouds advect in from the west as weak shortwave ridging across the region slowly breaks down. This looks to translate to more periodic cloudiness north and west with more sun southern/eastern sections overall. With the low level wedge deeper across the east under the lingering cooler 850 mb cool pool, but weaker far west per increasing warm advection, appears warmer highs west/southwest sections where likely to reach well into the 60s. Otherwise should be cooler than the last few days given light east/southeast flow, with potential for northeast sections to stay in the 50s, while slowly recovering into the low 60s elsewhere pending clouds. Weak surface warm front will be lifting northeast through the area overnight allowing deeper southwest flow aloft to take shape as the eastern wedge slowly departs late. Models show much of the region still removed from deep moisture which will remain west of the ridges and closer to the cold front that will lag back in the Ohio Valley around daybreak. Also little in the way of lift with perhaps some warm advection driven low clouds developing over the south/east, with more in the way of a mid deck canopy over the west after midnight per latest forecast soundings. However much of the sub cloud layer over the mountains appears quite dry, so removing most going pops overnight and trending more in the way of increasing clouds at this point. Low temps tricky with potential to see readings quickly drop over the west this evening before rising with clouds/mixing increasing. Expect the overall coldest lows out east where still under the residual surface ridge and likely to see less overall cloud cover until late. Therefore trending toward a more non diurnal temp curve mountains where the ridges could bounce back into the 50s overnight. Otherwise overall lows in the 40s except a few 30s valleys early, and outlying areas in the east during the early morning hours. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 330 AM EDT Wednesday... A fairly vigorous short wave will move through the Great Lakes and into the middle Atlantic region on Thursday. This will push a surface low from the Lakes well into New England with the trailing cold front moving through the Appalachians. A bit of a spread has developed in solutions with this system, but there is still consensus in keeping the best dynamics well off to our west and north. The overall trend is for lower POPs on Thursday with the best chances for precipitation west of the Blue Ridge mainly up towards western Greenbrier county. Mid level lapse rates have cooled a bit more since previous runs so a slight chance for thunder seems reasonable especially west. All in all this looks like a rather dry FROPA that will continue our overall dry pattern. The low level wind field will be energized and good mixing with the front will make for some blustery conditions Thursday into early Friday before winds relax Friday afternoon. A quasi zonal upper pattern will then keep high pressure in place at the surface with quite warm conditions expected into the first part of the weekend. Temperatures east of the Blue Ridge will start the period near normal, then steadily warm to well above normal with highs generally in the middle 70s by Saturday. Locations west of the Ridge will see a brief cool down behind the front on Friday, but then warm to above normal on Saturday with highs in the low/mid 70s. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 250 PM EDT Tuesday... Low pressure over the Great Lakes will travel northeast across New England Sunday and push off into the Atlantic Sunday night. A nearly dry cold front associated with low center will move south across our area. The richest moisture along with most of the convections remains north of our area. The ECMWF remains stronger further south with shortwave compared to GFS. This difference effect the timing of frontal passage. High pressure will settle south for the end of the weekend into early next week. Temperatures may cool behind the front Sunday especially in the northwest, but for most areas will remain above normal into early next week. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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As of 125 PM EDT Wednesday... Upper low moves east across the Great Lakes tonight and Thursday.The tail end of this short wave will reach the Mid Atlantic region with slightly lower heights on Thursday. Will be slowing down the arrival time of the probability of precipitation until after 6AM on Thursday in the mountains. There may be some pre-frontal showers in the morning which will help saturate the air mass but the surface cold front will just be into the mountains of West Virginia by late Thursday afternoon. NAM/GFS were similar with this timing. Like the NAM depiction of the eastern extent of the light precipitation by 00Z Friday/8PM Thursday. At the surface high pressure moves off the Mid Atlantic coast which will bring southwest surface and low level winds to the area by this evening. As a warm front lifts northeast through the Tennessee Valley tonight...the high clouds will move out of southeast West Virginia as well as southern and central Virginia. Ceilings will lower after midnight but high confidence they will remain VFR through the 18Z/2PM end of the TAF forecast period. Southwest low level jet gradually increases tonight. Expect winds to decouple in the valleys this evening, so have added LLWS in for KLWB late tonight. Extended aviation discussion... Thursday night... Threat for showers and sub-VFR will be possible along this front which would impact the central Appalachians by Thursday afternoon. However given best support passing to the north and limited moisture, expecting best potential for lower cigs/vsbys to occur across the western mountains and across northern portions of the area in the late afternoon and evening. High pressure builds in from the northwest Friday, with potential MVFR ceilings at KBLF/KLWB Thursday night before the high arrives. Another cold front will approach from the north on Saturday and pass through the region Sunday with possible showers and MVFR ceilings mainly in the mountains. However, models were still showing differences in the timing of the weekend system with potential for showers to stay mainly north of the region. High pressure and dry weather with VFR conditions are expected on Monday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...MBS LONG TERM...KK/MBS AVIATION...AMS/JH is the U.S. government's official web portal to all federal, state and local government web resources and services.