Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281446 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1046 AM EDT Sun May 28 2017 .SYNOPSIS...
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A frontal boundary stretching across Indiana, southeast to NC will shift northward today. as a low tracks into New York. A stronger cold front will move through the region on Wednesday morning.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 1030 AM EDT Saturday... Getting very concentrated area of moderate to heavier showers along the Blue Ridge north of Peaks of Otter, with isolated lighter coverage elsewhere. The 13z HRRR and RAP13 showed this fairly well, can hang onto a higher pop regime from Southeast WV to the Blue Ridge north of Roanoke, east to Buckingham through early afternoon. At the surface there is an area of convergence in the wind field over northern NC. Vis satellite indicated strong insolation taking place in the south, with heavier cloud cover north of Danville. This looks to be a place where differential heating and some upper vorticity advection takes place through early afternoon. However, 12z RNK sounding even modified is not too aggressive with severe threat today, in terms of an organized threat. Airmass is highly moist so will have to watch for downpours as low level flow is weaker and storms may get anchored. Severe mode today will be pulse to multicellular with isolated large hail or damaging winds. The front should act to focus these storms. SPC still has slight risk out. No flood watches at this time, see hydro section below for details. Forecast update to lower pops based on radar in most of the forecast area, and adjust sky cover to have more sun in the south per latest satellite trends and 12z NAM. Previous discussion from early morning... Large upper low will deepen over southeast Canada today and tonight and gradually back the mean flow over the Mid Atlantic region from the west to the southwest. Models showing a series of small short waves tracking through the southern stream around the base of this trof. Any of these features may aide in occurrence of precipitation. At the surface low pressure will be just off the southeast Virginia coast this morning along a warm front trailing into central Ohio. This boundary will provide some low level surface convergence in the Virginia piedmont this afternoon. By late today the low and front move northeast, with the models showing the front east of Farmville by 03Z/11PM. A weak cold front approaching from the northwest will reach the mountains by Monday morning. Amount of high clouds left over from the line of showers and thunderstorms across Tennessee and North Carolina will impact amount of heating this morning. Expecting enough sunshine to support MUCAPES in the 500-1000J/kg range this afternoon. No good consensus between models today on where most likely areas and times where there will be thunderstorms. Will have the highest probability when the instability will be largest, between 18Z/2PM and 03Z/11PM.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY/... As of 250 AM EDT Sunday... A lee trough will reside east of the Blue Ridge while a west wind limits convection activity in the morning. By Memorial Day afternoon, this lee trough and a convergence boundary across northern North Carolina will generate showers along and south of the VA-NC border. The better dynamics and moisture will be across central-south North Carolina where the stronger storms will develop. With afternoon heating and modest instabilities, scattered thunderstorms are possible across Southside, and should clear the area by sunset. Under a fair amount of sun Monday, temperatures will warm above normal with high in the mid to upper 70s west and mid to upper 80s east. Skies will become mostly clear overnight with temperatures dropping into the 50s across the mountains and lower 60s east. A closed low over the Great Lakes will push a surface trough over the region Tuesday. Instabilities and moistures will remain limited with scattered showers and thunderstroms tracking eastward late Tuesday afternoon and into the evening. A weak cold front will cross the region Wednesday with another round of scattered showers and thunderstorms. Temperatures Tuesday will be cooler than Monday but remain warmer than normal by 5F or so. Wednesday`s temperatures are expected to be near normal. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 310 AM EDT Sunday... Fans of cooler drier weather will appreciate the second half of the work week as high pressure tracks across the region. Temperatures will be near normal with dew points in the 50s. High pressure will move off the coast by Saturday, bringing a return of heat and humidity back into the region. Scattered afternoon and evening thunderstorms are likely Saturday ahead of the next front. More widespread showers and thunderstorms will accompany a slow moving front Sunday. This front may stall over the area on Monday. && .AVIATION /15Z SUNDAY THROUGH THURSDAY/... As of 755 AM EDT Sunday... Expecting isolated showers this morning for southwest Virginia, northwest North Carolina and southeast West Virginia. Expect the IFR clouds and fog to dissipate around 14Z. High confidence that scattered thunderstorms will develop this afternoon, but low confidence as to where. Some storms will be along the front from central West Virginia to southeast Virginia. Models also suggested that a ling of storms may cross the region out of the Tennessee Valley from west to east, possible between 20Z/4PM and 03Z/11PM. There is a slight risk for severe storms...containing large hail and potential for downburst winds. Have added fog in again for tonight once a majority of the thunderstorms dissipate. High confidence of MVFR visibilities. Extended Aviation Discussion... Deep convection becomes less organized Monday into Tuesday with only hit and miss sub-VFR conditions. Perhaps late night and early morning sub-VFR river and mountain valley fog. Better organization of convection Wednesday with the passage of a cold front. Thursday is expected to be VFR and dry. && .HYDROLOGY...
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As of 1040 AM EDT Sunday... No flood/flash flood watches at the moment for us. Will have to watch the Blue Ridge north of Roanoke, as well as the Alleghanys, as high-res models favor this area to get showers/storms locked in over the terrain per weaker low level winds this morning. WPC already highlighting this area for possible hydro issues where the low level flow along the front works to keep showers slower moving and meandering along the boundary. Given isolated threat will not put a flash flood watch out at this point.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/WP NEAR TERM...AMS/PM/WP SHORT TERM...RCS LONG TERM...AL/RCS AVIATION...AMS/PM HYDROLOGY...WP

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