Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 161635 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1235 PM EDT Tue May 16 2017 .SYNOPSIS...
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High pressure will continue to shift offshore through this evening and remain into Thursday. This will bring a gradual increase in southwest flow including an uptick in heat and humidity through late in the week. A weak cold front approaches from the northwest Friday bringing better chances of showers and storms by the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 940 AM EDT Tuesday... Not a lot of change to the going forecast this afternoon with strong upper ridging overhead while surface high pressure slides to the east. This will result in more of a south to southwest trajectory leading to a gradual weakening of capping aloft. However forcing outside of orographics remains weak with analysis showing the residual boundary a bit farther south, and overall lower dewpoints outside of the far southwest to start. Most short term guidance also on the dry side with only the RAP and GFS able to pop isolated convection southern Blue Ridge through 00z with the new 12Z Nam now basically dry as well. Since moisture remains limited aloft per morning raobs and the blended TPW will only keep an isolated mention NC mountains for now. Otherwise mainly sunny and quite warm with highs mostly 80s given 850 mb temps near +17 to +19C late. However humidity should still be rather low as will take until tonight for moist dewpoints to return farther north. Previous discussion as of 111 AM EDT Tuesday... Looking at mainly sunny and warmer weather today. Not much change in the models, with the 00z GFS still highlighting more shower/storm threat along the higher ridges than other models. At this time, moisture per model forecast soundings seem scant. Cannot rule out a lone shower/storm to fire up along the High Country this afternoon but overall most places will stay sunny, with few cu and thin cirrus possible. 8h temps warm to +16 to +18C which with full sun translates 80s most areas, with mid 80s most common. Record highs for most sites look out of reach, but Bluefield could break it. See Climate section below for records over the next couple of days. Tonight will be mainly clear and mild with dewpoints increasing keeping lows in the mid to upper 50s mountain valleys, with around 60 elsewhere. River valley fog should form late given increased humidity. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 320 AM EDT Monday... An upper level ridge over the eastern US will continue support a surface high off the mid Atlantic coast through midweek. Southwesterly flow across the region in this summerlike pattern will keep conditions very warm and humid, though there is enough convective inhibition present in model soundings to suppress shower/storm formation through Wednesday to maintain a generally dry forecast. However, energy rotating around the expansive trof dominating much of the western US will be trying to beat down the eastern ridge over time, eventually allowing a lazy cold front to sag into the region from the northwest by early Friday before stalling over the area. The net result will be scattered showers/storms for Thursday afternoon. then much better chances for showers/storms on Friday. The overall lack of good dynamics in the convective environment appears to favor a pulse mode of convection with a relatively low threat for severe weather. Temperatures will continue to run 10 to 15 degrees above normal with high temperatures in the upper 80s/near 90 degrees east of the Blue Ridge, middle 80s to the west. && .LONG TERM /SATURDAY THROUGH MONDAY/... As of 230 PM EDT Monday... The upper ridge will flatten across the eastern CONUS, while a trough will transition into the central part of the country by the weekend. There remains some differences between the GFS/ECMWF regarding the evolution of the synoptic pattern for this weekend into early next week. The GFS suggests that a persistent upper level trough over the Rockies will become progressive over the weekend, with strengthening Southwest flow aloft and a cold front approaching from the west early Monday. GFS supports cooler temperatures and increased chances for convection. The 00z ECMWF maintains troughing over the west through the weekend, re-amplifying the upper level ridge along/east of the Appalachians through Sunday, then gradually transitions to a more zonal pattern early next week. The ECMWF has a slower cold front passage from west-east Monday and Tuesday. The 12z run of the ECMWF continued the slower timing of the frontal boundary. Used the Superblend for pops Saturday through Monday which was a nice compromise. In general, temperatures will remain warm headed into the weekend with increasing dewpoints preventing temperatures from falling below 60 degrees in most areas. High temperatures will cool early next week with increased convective chances and additional cloud cover. The details will become more clearer as we head closer in time. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/...
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As of 1225 PM EDT Tuesday... VFR conditions look to prevail through the period with any isolated convection later this afternoon remaining to the southwest of the terminals. Some potential for the valley locations espcly KLWB/KBCB to see a brief period of sub-VFR vsby in fog near daybreak on Wednesday but iffy. Latest HREF and fog stability values off forecast soundings also indicate a late night window for fog as winds go light and higher dewpoints return. Thus added in an hour or two in spots late. Appears skies will stay clear on Wednesday with some thin cirrus along with areas of scattered cumulus setting up along the higher terrain during the afternoon. However expect combination of dry air aloft and ridging to keep convection to a minimum Wednesday afternoon at this point. Extended Aviation Discussion... Mainly VFR conditions continue Thursday with isolated storms in the afternoon along the Blue Ridge. Could be some late night valley fog espcly where any afternoon/evening rainfall occurs. Better threat for afternoon sub-VFR by Friday afternoon as a frontal boundary slips southeast toward the Central Appalachians. Front stalled across the region likely to lead to more convection by Saturday afternoon espcly Blue Ridge and points westward with periodic MVFR possible.
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&& .CLIMATE... As of 110 AM EDT Tuesday.... List of record highs today 5/16 and Wednesday 5/17 for our 5 climate sites. Tuesday 05/16/2017 Site MaxT Year Bluefield 83 2015 Danville 89 1991 Lynchburg 92 1941 Roanoke 93 1941 Blacksburg 86 1982 Wednesday 05/17/2017 Site MaxT Year Bluefield 84 1977 Danville 92 1990 Lynchburg 93 1911 Roanoke 92 1977 Blacksburg 85 1962 && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...MBS LONG TERM...KK AVIATION...JH/WP CLIMATE...WP

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