Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 120154 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 854 PM EST Wed Jan 11 2017 .SYNOPSIS... A weak warm front to the northwest of the area will continue to lift north and weaken overnight. Warmer southwest flow behind this boundary will increase later tonight and continue into Thursday. Another cold front will approach the region from the north by Thursday night, before spilling south through the area Friday into Friday night. && .NEAR TERM /THROUGH THURSDAY/...
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As of 845 PM EST Wednesday... Patchy earlier rainfall in advance of a warm front passing to the west has exited the region this evening leaving a varying degree of residual cloud cover in place. Latest evening soundings show quite a bit more moisture than last night but most forcing overnight looks to stay to the north/west of the region. Thus have removed most lingering measurable rain chances overnight with focus more on spotty drizzle along with areas/patchy fog pending just how much of the strong jet aloft can mix down. Latest short term guidance also showing less cloudiness across the east overnight, so appears this likely the region that could see more fog and eventually some stratus. Otherwise mainly cloudy and a bit gusty at elevation under the southwest jet aloft. Expect temps to remain about steady for a while longer with some quick drops where clouds thin before slowly rising later as warm advection deepens from above. Did lower some spots espcly valleys where have dropped off into the 30s, and below previous forecast lows, with most likely to stay in the 40s overnight. Previous discussion as of 320 PM EST Wednesday... Low pressure will move from the Midwest this afternoon into eastern Canada tonight into Thursday and an upper ridge builds across the Southeast States. The frontal boundary will stall this afternoon and return fairly quickly as a warm front tonight. Rain associated with the front will lift north this afternoon into evening back across the northern parts of the CWA. The warm frontal associated rainfall will then drift north into northern VA/WV overnight. For pops initially started with blend of HRRR and HiResW-arw-east and trended towards the Nam for tonight into Thursday. Considerable cloudiness will persist with the low level waa pattern and the cool moist ground. Deep low-level moisture across the area will result in patches of drizzle and fog especially from the Shenandoah Valley southwest into the New River Valley. Low temperatures tonight will range from around 40 degrees in the northern mountains to near 50 degrees in the far western mountains. Our region will be in the southern stream of a split flow regime on Thursday, with a large cutoff low over the southwest and flat ridging over the Southeast. This will keep us in a mild and moist pattern with cold air bottled up well to our north. With a weak baroclinic zone just off to our west, isolated to scattered rain showers are possible west of the Blue Ridge Thursday. High temperatures Thursday will vary from the mid 50s in the mountains to the lower 60s in the Piedmont.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... AS OF 334 PM EST Wednesday... Cold front enters the mountains Thursday night. Best low level convergence stays across the Central Appalachians and points west, so will stay with drier scenario per model blend east of the Blue Ridge with high chance to low likely over Southeast WV to the Clinch River Valley of Southwest Virginia. With front crossing the Blue Ridge late, should see temperatures stay relatively steady Thursday night and mild, with lows actually expected to be warmer than what are normal high temperatures are for mid-January, in the upper 40s to lower 50s. We may see some record warm low temperatures broken. Friday, the front slides southeast to NC with a wave of low pressure tracking along it from leading to an increase in chances of rain. Should be a cooler day as wind flow turns more northwest yet light, with cloudy skies. However, temperatures starting out in the upper 40s to lower 50s may surge up enough about 5 to 15 degrees before it rains, especially in the piedmont to have highs range from the lower 50s out in WV to mid 60s southside VA to the NC foothills. Could see a bust if the front is slower or faster and less or more rain occurs than forecast. Friday night-Saturday becomes tricky in terms of strength of high as cold air damming sets up lee of the Appalachians. The 1046 high over the Great Lakes Friday evening, crosses to New England by Saturday morning slightly weakening. Low pressure over the TN valley starts to lift northward bringing overrunning setup across the area with best coverage across WV and the Alleghany Highlands Friday night into early Saturday. Setup is such that cooler northeast to east flow will send temperatures to around freezing overnight Friday night into Saturday especially along the Blue Ridge north of Floyd/Roanoke/Bent Mountain, northwest to the Alleghanys in Craig County north to Bath. Warm nose aloft suggests more a freezing rain vs rain scenario though further north column may cool enough for sleet. At the moment too early for any headlines but will highlight in the HWO icing threat for the Blue Ridge and Alleghanys late Friday night into Saturday. Rest of the forecast area will see rain with best chances across the mountains. Temperatures Saturday southwest of the wedge will warm into the lower 50s, i.e. Chilhowie and Richlands, while most stay in the 40s, except cooler across the Blue Ridge north of Roanoke and the eastern slopes of the Alleghanys north of New Castle, VA. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... .AS OF 334 PM EST Wednesday... Amplified southern stream to take shape Sunday into next week with 2- 3 systems moving from the desert SW northward/northeastward to the upper MS Valley. Will start to see the cold air damming setup weaken by Sunday with frontal boundary over us weakening. Will still be on the cloudier side at times, but at the moment Monday looks like the driest day with highs in the 50s. Will see frontal boundary approach midweek with southwest flow increasing aloft keeping temperatures well above normal. Will see some showers scattered around Tuesday with better chance Wed-Wed night as the front tracks west of the Appalachians. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... As of 555 PM EST Wednesday... Overall outside of the exiting rain/drizzle near KLWB, conditions have briefly improved to VFR for early this evening. However a warm front will lift north across the region tonight resulting in another round of strong southwest winds aloft as the jet increases to around 50 kts overnight. This will again result in areas of low level wind shear espcly this evening so included a LLWS mention in most spots excluding KBLF where should see stronger surface winds. As the front moves north of the region a moist air mass will be left in place over some snow covered ground tonight into Thursday morning. Expect widespread fog and drizzle to develop as a result with attendant IFR-LIFR conditions at most TAF sites by midnight, then continuing through the remainder of the night. Latest ensemble HREF has the most widespread dense fog developing out east so expecting the lower vsbys and cigs to take shape there where more snow remains. Look for cigs and vsbys to rise Thursday morning with most locations returning to VFR during the afternoon. Winds will remain light in most areas overnight as the jet aloft skims across the top of the inversion and perhaps mixes down along the ridges from time to time. Southwest winds should increase as deeper warm air arrives Thursday with speeds at 10 to 20 kts including gusts perhaps to 30 kts Thursday afternoon. Medium to low confidence in ceilings, visibilities and winds through the valid TAF period. Extended Aviation Discussion... Little to no improvement is expected through the period. A backdoor frontal system will work its way south into the region Friday into Saturday, maintaining the threat for additional sub- VFR in low cigs along with light rain and/or drizzle. Unsettled weather will continue into Sunday with some slow improvement in conditions as high pressure wedges in from the north, but likely still MVFR cigs at best. Southerly flow will develop Monday ahead of a frontal system in the Central Plains with periods of MVFR possible mainly west where a few showers may occur. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/KK SHORT TERM...WP LONG TERM...WP AVIATION...JH/KK/RAB

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