Area Forecast Discussion
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FXUS61 KRNK 270512
Area Forecast Discussion
National Weather Service Blacksburg VA
112 AM EDT Thu Oct 27 2016
A weak cold front in the midwest will approach the region from the
west later tonight before passing across the area Thursday into
Thursday night. High pressure follows the front Friday bringing a
return to drier and milder weather into Saturday. Another weak
cold front will dip south through the mid-Atlantic region later
Sunday into Sunday night followed by high pressure for early next
.NEAR TERM /THROUGH TODAY/...
As of 930 PM Wednesday...
Forecast on track. High thin clouds currently overspreading
forecast area will continue to increase overnight as surface front
approaches from the west. Do not anticipate any shower activity
tonight, and not overly confident that a lot will fall across our
CWA on Thursday. Regional radars indicate scattered showers along
the front (IND-PAH corridor as of 9PM) but think most of this
precip will wane as it crosses the mountains Thursday...per dry
antecedent airmass east of the Blue Ridge and fading upper
dynamic support. Best chance for a wetting shower Thursday will be
along and west of the Blue Ridge.
Actual surface low and strongest part of the upper trough will
track well north of the Mid- Atlantic region, across the Great
Lakes tonight and into New England Thursday. The tail end of this
short wave will result in slightly lower heights on Thursday, but
dynamic lift will be pretty anemic this far south latitude per
vorticity getting strung out yeilding only weak PVA. There may be
some pre-frontal showers in the morning which will help saturate
the air mass but the surface cold front will just be into the
mountains of West Virginia by late Thursday afternoon. NAM/GFS
were similar with this timing. Like the NAM depiction of the
eastern extent of the light precipitation by 00Z Friday/8PM
Thursday. Precipitable water values rise to near 1.0 inch with the
front. Rainfall amount around 0.25 inches in the mountains were
still reasonable, but anticipating a tenth of an inch or less east
of the Blue Ridge, and a tenth might be too generous.
A warmer air mass with 850 mb temperatures just above +10 surges
north through the Ohio Valley overnight. This warmer air stays
just west of the Appalachians tonight but spread over the region
on Thursday ahead of the cold front.
Southwest low level jet gradually increases tonight. Overnight
temperatures will be dependent on the winds, with the higher
elevations staying mixed, especially later tonight and locations
east of the Blue Ridge decoupling and cooling quickly in the
.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM EDT Wednesday...
Low pressure located over New York Thursday evening with a trailing
cold front will lift northeast into New England on Friday and push
out into the Atlantic ocean Saturday. Behind this system, High
pressure in the Ohio Valley will build eastward.
A cold front with scattered convection will sweep east across the
Appalachians Thursday night and reach the coast by Friday morning.
The best dynamics with the frontal boundary remains well off to our
west and north. The swody2 has portions of forecast area in general
thunderstorms primarily because of the mid level lapse rates.
Low temperatures Thursday night will range from around 40 degrees in
the northwest mountains to the lower 50s in the Piedmont.
Surface winds will be gusty Friday morning behind the front, then
relax Friday afternoon. High pressure to our northwest will build
southeast across our area Friday into Friday night. High
temperatures Friday will range from the mid 50s in the northwest
mountains to around 70 degrees in the Piedmont. Under Mostly clear
skies, low temperatures Friday night will generally be in the lower
and mid 40s.
High pressure will remain centered over the Southeast Saturday into
Saturday night. It will be a great autumn day to check out our Open
House. Highs on Saturday will warm into the upper 60s in the
mountains to the Mid 70s in the Piedmont. Aloft a weak shortwave
will pass to our north in the zonal upper flow Saturday night. Low
temperatures will drop to the upper 40s in the mountains to the
lower 50s along the southern Blue Ridge Mountains.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 300 PM EDT Wednesday...
Above normal temperatures will continue into the medium range
with Southeast ridging. Several shortwaves will rotate across
the northern Tier of the CONUS in the fast upper flow.
Low pressure over the Ohio Valley will travel eastward Sunday and
push off into the Atlantic Sunday night. A cold front with limited
moisture associated with low center will move south across our area.
The richest moisture along with most of the convections remains
north of our area. GFS has a stronger further south with shortwave
compared to ECMWF. The placement of this feature affects the timing
of the frontal passage. High pressure will build south into our
region for Monday into Wednesday.
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 105 AM EDT Thursday...
Upper trough and its associated surface low will move east across
the Great Lakes overnight and into New England Thursday. A weak
cold front trails the surface low and will cross the mid-Atlantic
region Thursday afternoon and evening. There may be some pre-
frontal showers Thursday morning which will help saturate the air
mass but the surface cold front will not cross the mountains until
the afternoon and into the VA/NC piedmont during the evening.
Increasing mid and high clouds will continue overnight with some
strato-cu likely across the western locations before daybreak
Thursday. However still appears these cigs will remain just above
VFR levels given low level dry air in place. Bases will gradually
lower Thursday, but even with the showers, should remain VFR
outside of possibly KBLF/KLWB where cigs may lower into MVFR at
times if showers are a bit more widespread later in the day. Sub-
VFR cigs are also likely along the western slopes of the
Appalachians into Thursday night, but these low clouds are not
expected to make it east of the Blue Ridge.
A southwest low level jet gradually increases overnight. Expect
winds to decouple in the valleys this evening, so have kept in LLWS
in for KLWB late tonight where models show the jet aloft a bit
Extended aviation discussion...
High pressure builds in from the northwest Friday, lingering MVFR
cigs are possible at KBLF/KLWB through daybreak Friday before
clearing. Another cold front will approach from the north on
Saturday and pass through the region Sunday with possible showers
and MVFR ceilings mainly in the mountains. However, models were
still showing differences in the timing of the weekend system with
potential for showers to stay mainly north of the region. High
pressure and dry weather with VFR conditions are expected on