Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 122322 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 622 PM EST Mon Feb 12 2018 .SYNOPSIS...
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High pressure to the northwest will move east across New England tonight and wedge south into the Carolinas late tonight and Tuesday. Rain will then spread back into the region Wednesday as the next in a series of disturbances moves northeast along the Appalachians. Another cold front will arrive from the northwest by the end of the week with added rain chances in store.
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&& .NEAR TERM /THROUGH TUESDAY/... As of 255 PM EST Monday... A strong area of high pressure centered over the western Atlantic will continue to block/slow down weather features from moving eastward into tonight. The high pressure will weaken some and eventually move south Tuesday, allowing the weather pattern to become more progressive. A wave of low pressure tracking along a stalled front across the coast of NC/VA has move offshore this afternoon. The chance for showers will diminish as dry northerly flow increases going into this evening. A strong surface high pressure (1045 mb) centered over New England will wedge south overnight into Tuesday. This wedge will bring cooler air (upper 20s to mid 30s) into the region by Tuesday morning. Models have a Theta-E ridge over the region with the boundary north towards DC. This Theta-E ridge and weak isentropic lift will bring a chance for light precipitation to the area Tuesday. The 12Z GFS has light precipitation falling in the morning (midnight to noon), while the NAM is later after sunrise into the afternoon. HRRR also brings precipitation into the area after midnight and keeps it through the day. So, the chance for precipitation look good, especially areas south of 460, however amounts will only be a couple of hundredths of an inch. With morning surface temperatures ranging in the upper 20s to mid 30s, precipitation type will consist of rain, drizzle and/or freezing rain. Some flurries are possible north of hwy 460. Ground temperatures across the area are warm enough to not have any ice problems on roadways. Any ice (glazing) will be on elevated surfaces such as vehicle, decks and trees, therefore no headlines are expected at this time. Temperatures will warm above freezing during the afternoon for areas inside the wedge, however they will not make it out of the 40s. Areas outside of the wedge (Bluefield/Mountain Empire) will warm into the 40s. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 255 PM EST Monday... Cool high pressure will be situated from off the Northeast coast southwest to over central North Carolin Tuesday evening. Some lingering onshore moisture may keep a low threat of rain in place early in the southeast but most of the models have the area dry. Should see some clearing early in the foothills, but next warm frontal boundary/advection of moisture starts shifting northeast toward the TN valley by Wed morning and overall looking at a chance of rain that day, with best chance staying from far Southwest Virginia into Southeast West Virginia, with less threat in the NC piedmont. Upper heights build but remain fairly zonal and fast with moisture shifting a little further north by Thursday though best axis of lift and moisture convergence will be situated from TN northeastward toward the eastern Ohio Valley such that our mountains will see the higher pops Wed night-Thursday night. At the moment rainfall amounts are not amounting to too much, with higher rainfall totals staying west of the Appalachians along better upper forcing and low level warm advection ahead of storm system in the central Plains. Tuesday night starts off chilly with high pressure in place though clouds may offset the colder temps. Lows will range from the lower to mid 30s in the Alleghanys/Greenbrier to the piedmont, with lower to mid 40s out toward Chilhowie and along the NC/TN mountains, where warm advection kicks in late. Thinking non-diurnal trend with temps warming late in the west. Wednesday clouds and rain chances will keep temps down some but warm advection will at least push highs toward 60 degrees. So for those heading out for Valentines, take an umbrella. Mild temps for mid February Wed night and even warmer Thursday, but clouds may limit this. After lows in the upper 40s to lower 50s Wed night, look for highs Thursday in the mid 60s to lower 70s. Lows again Thursday night, will be mild from the upper 40s to mid 50s. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 120 PM EST Monday... Active pattern across us into the weekend, though not completely wet either. Appears models have frontal boundary shifting southeast through us Friday with a fast west-east upper flow. As the front takes on more of a west-east orientation it will slow/stop across the Gulf Coast States and Southeast. The ECMWF gives it enough of a push thanks to sharper trough over the Canadian Prairies into the Great Lakes, so may see the deeper moisture nudge south of our forecast area by late Saturday into Saturday night. Meanwhile the GFS slows it faster keeping threat of precip around Saturday over the southern half of the forecast area, and given orientation of the upper flow, leaned toward this solution. Colder air chasing the moisture may bring a changeover to snow/snow shower mainly along and west of the Blue Ridge by late Friday night into Saturday morning. High pressure situates itself over the Carolinas and mid- Atlantic Sunday, but will start to see return flow aloft as western trough ejects eastward into the Desert Southwest, turning the flow southwest over us and sending moisture our way. Looking at a warm front lifting northward across the TN and Mid MS Valley Sunday evening into the Great Lakes Monday. Some spillover of precip will likely overrun this boundary and make for a cloudier Monday with a chance of rain. If the precip arrives early enough Monday a wintry mix could occur, but models overall are keeping it milder. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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As of 615 PM EST Monday... Nose of dry air has sliced low clouds in two this evening with sub-VFR across the far western sections around KBLF and over the southeast at KDAN. Expect some of this drying to perhaps provide for brief improvement in flying conditions west with low cigs likely lingering south before perhaps edging back north along the Blue Ridge overnight. This will create quite a variation in cigs from IFR/LIFR at KBLF and MVFR around KDAN with more scattered clouds elsewhere to start. Latest short term guidance remains inconsistent in exactly how far north lower cigs will advance overnight per drier air, with trend toward keeping VFR outside of the far southwest through morning. This likely too optimistic given development of the wedge so including more clouds and at least VFR cigs south of KLWB overnight. In addition, spotty light precipitation is possible, but confidence is low on timing/location and whether or not any even affects the TAF sites. Latest HRRR/GFS models still have light precipitation starting as early as midnight, before shifting north along the southern Blue Ridge, and then across southern sections toward daybreak Tuesday. Thus may include a period of -DZ espcly around KDAN late. The surface high shifts east on Tuesday with the wedge lingering despite some drying aloft under increasing warm advection just above the surface inversion. This may tend to trap lower cigs espcly southern and western sections for much of the day although any precipitation looks quite light and spotty. However still low confidence on the expanse of sub-VFR cigs, but appears most sites will see some improvement to VFR by late in the afternoon. Extended Aviation Discussion... As the high/wedge moves east of the area by Wednesday, another disturbance will track from the south central U.S. toward the Mid-Atlantic with more rain and sub-VFR ceilings. Another front may also bring widespread rainfall and sub-VFR ceilings to the area by Friday. Brief drying behind this front may bring a return to VFR on Saturday as high pressure again wedges in from the north over the weekend.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/RCS NEAR TERM...RCS SHORT TERM...WP LONG TERM...WP AVIATION...JH/RAB/RCS

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