Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KRNK 200404
Area Forecast Discussion
National Weather Service Blacksburg VA
1104 PM EST Thu Jan 19 2017
High pressure centered over our region this afternoon will shift
east to the coast tonight as a warm front lifts north from the Gulf
Coast states into the southern Appalachians. The warm front will
swing north across Virginia and into the mid-Atlantic Friday, before
stalling. Another storm system moving across the southern U.S. will
impact our region Sunday into Monday.
.NEAR TERM /THROUGH FRIDAY/...
As of 1100 PM EST Thursday...
Adjustment to the forecast address to main features, overnight
low temperatures and timing of arrival of precipitation. Several
locations over parts of Southside Virginia and neighboring
portions of north central North Carolina are already
experiencing temperatures in the upper 30s. Forecast lows were
in the lower 40s. Have adjusted forecast lows to reflect
readings not too much lower than the ongoing readings, allowing
for additional slow cooling into the early morning hours before
a slight rise in temperatures before sunrise as weak warm air
Have slowed the arrival of rain into the region from west to
east. This amounted to not a whole lot of changes across the
western portions of the area, but for eastern areas, the arrival
of the main area of rain looks delayed until a little after
As of 700 PM EST Thursday...
Incoming moisture is hitting a wall of dry air this evening,
therefore slowed the arrival of rain entering the forecast area
until after midnight. Otherwise no major changes to previous
As of 200 PM EST Thursday...
Upper Ridge over our region this afternoon will slide east tonight
into Friday. Warm advection high clouds this afternoon will be
followed by increasing mid clouds starting to roll into the
southwest by dusk.
Low pressure over western Tennessee this afternoon will lift
northeast into the Ohio Valley tonight and reach Lake Erie by Friday
afternoon. A warm front trailing from the low will lift northward
tonight into Friday. Isentropic lift increases this evening across
the mountains of North Carolina and shift to the rest of the
forecast area overnight. With a dry airmass in place, slowed down
the onset of the rain this evening. Used a blend of HRRR and
HiResW-arw-east for pops this evening, then utilized a mix of NAM
and Continuity with pops tonight into Friday. The best chance for
rain is in the mountains with lower threat in the Piedmont. Lower
dewpoints in the evening combined with increasing moisture may
allow for temperature drop once the rain starts to fall tonight.
However, it should remain mild with low temperatures ranging from
the upper 30s in the Alleghanys and portions of the Greenbrier
Valley to upper 40s to about 50 degrees in Mountain Empire.
On Friday, the best lift will push quickly northeast through the
region. An upper level shortwave ridge will build over the Mid-
Atlantic region. The bulk of the rain will have moved northeast of
the area by the early to mid afternoon. Added the mention of fog to
isc grids. Lowered high temperatures a few degrees especially in the
north Friday with clouds and rain. High temperatures Friday will
vary from the upper 40s in the mountains to the lower 60s in the
south. Rainfall amounts overall will average around a quarter inch
with locally higher in the western mountains of Southwest Virginia
and North Carolina.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 300 PM EDT Thursday
Even with limited sunshine on Saturday the air mass will be
unseasonably warm, 15 to 25 degrees above normal. Deep moisture
begins to arrive back into the area from the southwest on Saturday
afternoon. But Bufkit not showing a saturated sounding until closer
to Sunday morning.
Models forecasting good lift Sunday with a strong vorticity maximum
crossing the central and southern Appalachians along with upper
diffluence. Winds at 850MB back to the southeast by 12Z/7AM Sunday
with good upslope and increasing inflow off the Atlantic first
along the Appalachians in northern North Carolina on the Sunday
morning gradually shifting north of Roanoke by the end of the
More significant differences in the guidance in the amount of
instability across southern Virginia and northern North Carolina on
Sunday all related to the location of the warm front. 12Z NAM/GFS
and latest RAP indicating enough of a secondary low developing
over eastern North Carolina that with the precipitation there
should be strong in-situ wedging. Large spread in location of
heaviest rain also so will lean toward WPC guidance. Wedge and
precipitation will keep temperatures on the cool side/or below
guidance for Sunday. Have added slight chance of thunder from
extreme southern Virginia into northern North Carolina but
confidence is low.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Thursday
Precipitation will remain in the area through Monday with the
highest rain amounts on Sunday night and Monday, mainly along and
east of the Blue Ridge. Experimental hydrologic ensembles
showed at least a small potential for 1 to 3 inches of rain.
Localized minor flooding is possible if this amount of
precipitation is realized.
Once the surface low is off the coast on Monday night and Tuesday,
precipitation will be confined to favored western upslope areas.
Enough colder air comes in Monday night that we will have snow
in the forecast from southeast West Virginia into northwest
North Carolina. Winds will also increase Monday night and
Tuesday. There may be enough of a low level jet along with cold
air advection and pressure rises for wind gusts in the 40 to 50
By Wednesday and Thursday a long wave positively tilted upper trof
will extend from the Great Lakes across the central United States.
Prevailing deep southwest flow over the Mid Atlantic region
during this time frame results in differences among the models
in how fast any front will progress east. For now WPC has
surface front crossing the region Wednesday and Wednesday
night. Behind this system is a much colder air mass. More
upslope snow showers in the mountains are possible. At this time
the models are showing snow showers for Thursday night.
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 650 PM EST Thursday...
Fast moving negatively tilted short wave will rotate through the
region late tonight/early Friday, followed by an extended period
of southwest flow preceding another short wave during the
weekend and a deep low pressure area slated to move through the
southeast U.S. early next week. This system will be in/out
fairly quickly, but will leave low clouds, drizzle, fog in its
wake given the persistence of southwest flow aloft remaining in
place. It appears that the timing of this system is a little
slower than previously thought, with the main wave of rain
coming through in the 12Z-16Z time frame as opposed to 08Z-14Z
time frame. Current VFR ceilings will quickly deteriorate to
MVFR/IFR after the rain spreads into the region, then settle
into an IFR/LIFR condition during the afternoon in fog, drizzle,
low clouds. Visibility will drop into the MVFR category,
occasionally IFR during the rainfall, then settle mainly into
MVFR during the afternoon in fog and drizzle. Winds will be
mostly east-southeast 3-5kts this evening, becoming southeast
4-8kts as the rain moves into the region. Some low end gusts are
possible at KBLF with the southeast flow. Winds will become
light and variable or calm east of the Blue Ridge after the rain
moves out of the region, but become SSW-SW 4-8kts with again
some low end gusts at KBLF during the afternoon Friday.
Medium confidence in ceilings and visibilities through the TAF
Medium confidence in wind speed/direction through the TAF valid
Extended Aviation Discussion...
As noted above southwest flow aloft will persist ahead of a deep
upper low that will develop across the southeast states over the
weekend, then move off the southeast U.S. coast Monday. Low
clouds, drizzle, and fog are likely to persist Friday night with
additional waves of rain moving into the area late Saturday and
persisting into Monday. At this point it appears that the only
period of potential VFR cigs would be Saturday afternoon.
Otherwise, much of the period will be characterized by MVFR or
worse ceilings and visibilities. Winds will become strong and
gusty from the northwest Monday night into Tuesday as the major
weather system moves up the east coast. Ceilings and
visibilities should finally improve east of the Blue Ridge after
Tuesday, but likely persist with MVFR and upslope flow west of
the Blue Ridge.
As of 305 PM EST Thursday...
Record warm Mins for January 21
Blacksburg....42 in 1954
Bluefield.....47 in 1999
Danville......56 in 1954
Lynchburg.....51 in 1927
Roanoke.......51 in 1959
Record highs for January 21
Blacksburg....59 in 1954
Bluefield.....60 in 1999
Danville......68 in 1959
Lynchburg.....72 in 1932
Roanoke.......74 in 1932