Scientific Forecaster Discussion
fxus61 krnk 180447
Area forecast discussion
National Weather Service Blacksburg Virginia
1147 PM EST sun Nov 17 2019
high pressure at the surface will remain overhead through
Monday. An upper disturbance passes across Monday, followed by
another Tuesday. High pressure should return by Wednesday, but
a cold front will arrive later in the week.
Near term /through Monday/...
as of 1120 PM EST Sunday...
Clouds continue to push westward in the low levels while mid and
high clouds work in from the southwest. Will mainly have a
cloudy night and this will steady out temperatures, and possibly
send some a couple degrees warmer. Will be watching our Blue
Ridge counties across Virginia/North Carolina for fog/drizzle.
Further north into the Shenandoah Valley/Amherst area some temps
could skirt 32f, so patchy freezing drizzle not out of the
question, though appears coverage so isolated that no headlines
Monday, overall, models showing more agreement into producing
some light rainfall into our southern coverage area from NC into
the Piedmont of Virginia and possibly as far west as the New River
valley. Have nudged pops up to 30/40 in the southeast to slight
chance in the west, except dry in southeast WV and the alleghanys.
Confidence is increasing that light amounts of rain will occur
in the southeast, so forecast pops may need to be bumped up
This will also impact highs Monday, with clouds lingering, so
made some adjustments down in the east.
Previous discussion from early this evening...
Clouds will continue to increase overnight with many of the
higher elevations up into the clouds with fog and drizzle. The
latest guidance indicates the approaching short wave tomorrow
will have a bit more dynamic support and moisture to generate a
chance of showers mainly east of the Blue Ridge.
The coastal low should head northward overnight into Monday.
Meanwhile, the lingering cool wedge of high pressure and an
approaching upper level trough from the west will bring back the
cloudiness. Some of the clouds could get rather low tonight,
and it is not totally out of the question that spotty fog or
sprinkles could develop after midnight. The upper level trough
should cross overhead on Monday.
Short term /Monday night through Wednesday night/...
as of 1240 PM EST Sunday...
Closed 500mb low over the Ohio Valley tracks east Monday night and
will be off the New Jersey coast Tuesday morning. A second wave
closes off within the eastern long wave trough by Wednesday morning
but by this time the mean trough axis will be well east of the mid
Atlantic region. Heights rise with a brief period of upper ridging
into Thursday. Not much to reflect these waves at the surface but
some bands of mid to low level isentropic lift and moisture will
bring periods of clouds Monday night through Tuesday night. Light
precipitation cannot be ruled out, especially in the mountains and
north of Route 460 but nothing organized or prolonged.
Wednesday evening surface high pressure will be centered over the
mid Atlantic states. But air mass is moderating and expecting some
mid level warm air advection clouds overnight. Timing of the cloud
cover will greatly impact temperatures. If the surface wind
decouples after sunset, but before the clouds move in, low
temperatures will be early in the night with steady or slightly
rising temperatures late.
Long term /Thursday through Sunday/...
as of 1230 PM EST Sunday...
The next strong short wave through comes through the northern stream
on Friday, mainly across the northeast United States as the closed
low southwest of California begins to lift across the southwest.
Timing and location differences between models are large by
High pressure moves offshore on Thursday with deep broad southwest
flow Thursday night through early Friday. Have the potential for a
mild day on Thursday with good warm air advection, but heating will
depend on the amount of cloud cover and how fast clouds pull out to
the northeast in the morning. Will be increasing wind speeds
Thursday and probability of precipitation across the mountains late
Thursday night into Friday morning.
The cold front with the northern stream feature will come through on
Friday, before stalling well south of the Carolinas on Friday night.
Cooler Post-frontal air mass, clouds and precipitation with result
in little to no rise in temperatures Friday.
The surface high that follows the front shows some signs of becoming
wedged down the central and southern Appalachians, possibly as in-
situ cold air damming Saturday night and Sunday. The southern stream
surface low suggest overrunning precipitation into the region from
southwest to northeast over the weekend. For now will follow wpc
guidance that has a low pressure system crossing the region Saturday
night and Sunday.
Aviation /06z Monday through Friday/...
as of 1140 PM EST Sunday...
Confidence increasing on sub-VFR with IFR in the mountains
overnight into early Monday with southeast/east flow and wedge
hanging tough. Will see mid/high clouds overrun this layer of
low level moisture keeping them from mixing out til later
Monday. At the moment think fog will mainly impact elevations
along the Blue Ridge/alleghanys overnight.
Should see improvements to MVFR/VFR by late in the afternoon as
flow turns more southwest to west while upper disturbance moves
across. Rain may impact Dan Monday, though confidence is not
high enough to have any vsby restrictions.
Winds will generally be light through the period.
Extended aviation discussion...
More upper level waves will follow behind the upper level
trough, which may provide more cloudiness for Monday night into
Tuesday and the potential for MVFR ceilings. High pressure
should build over the mid Atlantic by Wednesday to bring a
return of good flying weather through Thursday. A cold front
will arrive on Friday to bring showers and potential
restrictions to ceilings and visibilities.