Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 212000 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 400 PM EDT Sun May 21 2017 .SYNOPSIS...
-- Changed Discussion --
Abundant moisture will lift over a stalled front tonight, then a cold front will cross through the region from the west of Monday. Several periods of precipitation are expected through the rest of the week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --
As of 345 PM EDT Sunday... Flash Flood Watch in effect along the southern Blue Ridge this afternoon and tonight. Regional radar showed elongated axis of showers from western Pennsylvania to South Carolina. Along the southern end of this band of precipitation the air mass was unstable enough to support scattered thunderstorms. Soundings showed the wedge of colder stable air below 850 mb with the boundary at the surface well west of Boone and well south into northern North Carolina. Satellite and radar loops showed a compact vorticity maximum tracking into extreme southwest North Carolina. Models showed good consistency in the timing and location of this feature through Monday, bringing it into southern Virginia after midnight tonight and into Maryland Monday afternoon. As this wave crosses the area southeast upslope winds will be enhanced and that will result in a period of moderate to heavy rainfall. The surface cold front approaching from the west will cross southwest Virginia, northwest North Carolina and southeast West Virginia Monday morning. At 850MB the front may not make much progress southeast as the region will be between the large 500MB low moving east through the Great Lakes and the upper ridge moving east off the coast. Used a non-diurnal trend for both tonight and Monday. Temperatures may have a slight rise as the wedge erodes tonight and with any clearing behind the front on Monday afternoon.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
As of 330 PM EDT Sunday... Southwesterly flow aloft ahead of a developing closed low moving out of the midwest will keep us in a wet and unsettled pattern through midweek. A cold front will be pushing off to our east early Monday night, but any break in precipitation will be short lived as the front stalls out just to our east and waves of energy slide northward along the front and push a good chance of precipitation back into the region during the predawn hours of Tuesday morning. With the wave expected to pass by to our southeast, the best isentropic lift and deformation look to bring the greatest precipitation totals to locations east of the Blue Ridge. There is considerable spread in guidance QPF but there is an upward trend and the latest runs indicate a good probability for amounts over one inch, especially across Southside. This will be enough to cause hydro problems with the possibility of river flooding so later model runs will be watched closely to see if the upward trend continues. The wave will move off to our northeast Tuesday night with some high pressure wedging developing behind, but Wednesday looks to be wet once again as another wavy front moves in from the southwest. Deep moisture transport and strengthening low level flow will once again bring widespread precipitation with potentially another good amount of rainfall. If the expected antecedent wet conditions materialize as currently indicated by guidance, the hydro threat will remain elevated Just lingering showers overnight Wednesday night as we get into the dry slot of the large stacked low spinning over the Great Lakes. Given expected clouds, precipitation, and being on the cool side of the boundaries, temperatures will be trending well below normal through Wednesday.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
-- Changed Discussion --
As of 330 PM EDT Sunday... On Thursday, short wave energy and the cold pool associated with the upper low moving through the region will generate showers and thunderstorms with moderately steep mid/upper lapse rates aiding convective instability. Relatively low freezing levels and increasing low level flow make graupel/small hail and gusty winds possible with any showers/storms especially west of the Blue Ridge, but severe storms are not likely. The upper pattern will then be progressive into the weekend as the upper low moves off to the northeast Friday allowing for a brief period of ridging, followed by a transition to a zonal regime by Sunday. This will give us a mostly dry Friday after any lingering upslope showers west of the Blue Ridge dissipate, but another frontal system will push in from the north and stall over the region on Saturday and bring an increasing chance of showers/storms to the forecast for the weekend. Temperatures will be trending from below normal on Thursday to at or slightly above normal levels for the weekend with lower 80s east of the Ridge and mid/upper 70s to the west.
-- End Changed Discussion --
&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/... As of 120 PM EDT Sunday... High confidence of MVFR or lower ceilings east of KTNB to KBLF today and tonight. Medium confidence of locations that will have LIFR ceilings Stalled front over the southern Appalachians will result in abundant cloud cover into Monday. A compact short wave along the North Carolina/South Carolina border will track east this afternoon and tonight. This will enhance southeast winds and upslope along the Blue Ridge and into the eastern foothills. Medium confidence on the timing of the models which has the precipitation and best lift crossing the area from west to east from 21Z/5PM through 06Z/2AM. A surface cold front crosses through the area on Monday. Precipitation will end and ceilings will lift to VFR behind the front. Confidence on the timing of this improvement is low. Extended Aviation Discussion... Expecting several periods of precipitation with sub-VFR conditions Monday night through Friday. Any breaks between rainfall events with better flying conditions will likely be less than 12 hours. && .HYDROLOGY...
-- Changed Discussion --
As of 345 PM EDT Sunday... Flash Flood guidance remained low in spots, less than 1.8 inches in 3 hours along parts of the Blue Ridge in Floyd and Patrick Counties. 24 hour expected rainfall amounts along the Blue Ridge and into the foothills will be as much as 1.5 inches. Rates may be enhanced late this afternoon into this evening so the Flash Flood Watch has been expended.
-- End Changed Discussion --
&& .RNK WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
VA...Flash Flood Watch until 2 AM EDT Monday for VAZ015>017-032-033. NC...Flash Flood Watch until 2 AM EDT Monday for NCZ001>003-018-019. WV...None.
-- End Changed Discussion --
&& $$ SYNOPSIS...AMS/PM NEAR TERM...AMS/PM SHORT TERM...MBS LONG TERM...MBS AVIATION...AMS/PM HYDROLOGY...AMS

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.