Scientific Forecaster Discussion
fxus61 krnk 220053
Area forecast discussion
National Weather Service Blacksburg Virginia
853 PM EDT Thu Sep 21 2017
high pressure will cover the region into the weekend. A cold
front will approach the mid Atlantic region the middle of next
Near term /through Friday/...
as of 845 PM EDT Thursday...
Showers have all but faded across the region with loss of heating
despite lingering decent instability over the far west. Thus
cant totally rule out added isolated showers popping up through
midnight given moisture around but not enough to continue pops
into the overnight. However will continue to see some passing
rounds of leftover strato-cu within the rather deep northeast
flow well to the southwest of Jose. This supports more of a
partly cloudy flavor north and west to mostly clear elsewhere
before all likely clear late. Again appears fog an issue across
the valleys and where earlier showers occurred provided can get
enough clearing. Therefore left in fog coverage espcly early on
in locations that saw spotty showers over the west, with more
widespread fog espcly mountain valleys overnight. Lows similar
to the past couple of nights, although a bit warmer in the
low/mid 60s espcly east per moist dewpoints, and elsewhere
where fog develops.
Previous discussion as of 325 PM EDT Thursday...
An upper level ridge will remain stationary over the Midwest
but will expand in areal coverage to include the south-central
appalachains tonight into Friday. As this ridge expands, it will
nudge an upper level trough south into North Carolina tonight.
While this trough remains in our vicinity, scattered afternoon
showers are possible, mainly across the mountains south of Hwy
460 and along western slopes of southeastern West Virginia.
These showers will fade with loss of heating this evening.
Surface high pressure will build in overnight and remain
through the day Friday, decreasing chances and areal coverage of
showers Friday afternoon to the North Carolina high country.
Any afternoon showers today and Friday will remain light with
less than a tenth of an inch of rainfall. Patchy dense fog is
highly likely in mountain valleys for friday's morning commute.
Area remains under high pressure with very little change in air
mass. Temperatures will stay above normal tonight and Friday.
Highs Friday will range from the upper 70s to lower 80s west of
the Blue Ridge to the mid 80s east.
Short term /Friday night through Sunday night/...
as of 142 PM EDT Thursday...
Upper ridge will remain just to our northwest through the
weekend. The center of the ridge will build northeast and be
located over Pennsylvania.
At 17z, Hurricane Maria was located near 20.4 N, and 69.4 west.
Maria was moving toward the northwest near 9 mph. Data from an
Air Force Reserve reconnaissance aircraft indicate that maximum
sustained winds remain near 120 mph with higher gusts. Maria is
expected to turn toward the north-northwest Friday, then
northward into the weekend.
Summerlike conditions will continue into the weekend with 850mb
temperatures around plus 16 to plus 18. It will be a real nice
weekend for outdoor activities with mild temperatures and
comfortable humidity levels.
Any isolated shallow convection Friday afternoon will diminish
quickly Friday evening with the loss of solar heating. Clear to
partly cloudy conditions will result in good radiational
cooling. Added some patchy valley fog to isc grids. Low
temperatures Friday night will range from the lower 50s in the
mountains to the lower 60s in the Piedmont.
Under plenty of sunshine, high temperatures Saturday will vary
from the mid 70s in the west to the mid 80s in the east. Mostly
clear conditions will continue Saturday night with lows from the
the lower 50s in the mountains to the lower 60s in the
Piedmont. Sunday will feature bright sunshine with high readings
from the mid 70s in the mountains to the mid 80s in the
Piedmont. A good night to keep the window open Sunday night with
low values from the lower 50s in the west to the lower 60s in
Long term /Monday through Thursday/...
as of 142 PM EDT Wednesday...
Models showed good large-scale agreement across Continental U.S. Through
medium range. The amplified weather pattern continues across the
country with an active tropics in the western Atlantic Ocean.
Model ensembles and consensus from NHC keep Maria east of the
Mainland. See latest NHC advisory for position and track.
The trough across the central U.S. And associated cold front
will slowly travel eastward. The strong upper level ridge should
hold across our area. Operational models showed the potential
for some clouds and possible showers to flirt with our Piedmont
counties Tuesday afternoon with Maria interacting with coastal
front and trough. Hard to tell how far west any moisture really
pushes. 12z run looked less impressive with moisture and qpf.
Interesting to note the weak shortwave rotating around the upper
ridge across southeast portions of forecast area. A cold front
will weaken as it moves east and travel through the eastern U.S.
Thursday into Friday.
Temperatures remain above normal during extended period with
lows generally in the upper 50s to around 60 in the west, to
lower to mid 60s in the east. High temperatures will range from
the mid 70s to around 80 in the west, to lower to mid 80s in the
east. The strength of the subsidence with Maria and amounts of
cloud cover will greatly impact the temperatures.
Aviation /00z Friday through Tuesday/...
as of 645 PM EDT Thursday...
Isolated convection lingers across the southwest sections,
mainly southwest of kbcb/klwb attm. Expect coverage to linger a
while longer before dissipating shortly after sunset with loss
of heating. May still need to include a vcsh mention at a few
western locations pending release trends, otherwise maintaining
overall VFR into the evening. Weak upper level trough should
push farther south overnight allowing clearing to take place.
Just like the last several mornings, patchy dense fog is highly
likely in mountain river valleys as supported by fog stability
and latest href output. Expect this mainly to affect klwb/kbcb
with a period of IFR/LIFR late, although kblf may drop into sub-
VFR after earlier rainfall, as well as kdan where low level
moisture is greater. Any fog/stratus should lift by 14z/10a
making for mainly VFR under light east to northeast winds as
high pressure aloft starts to build in.
Extended aviation discussion...
Overall persistence forecast to prevail this weekend into early
next week as strong high pressure aloft builds in from the
northwest keeping tropical moisture offshore. This should also
maintain good flying conditions along with mostly dry weather,
outside of any late night/early morning fog from Saturday