Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/14/20

Area Forecast Discussion

National Weather Service Blacksburg VA

 1043 PM EDT Mon Apr 13 2020

.SYNOPSIS...
A cold front will move east and off the coast tonight. Colder
air will arrive tonight as high pressure builds into the area
from the northwest. A secondary front will cross the area
Tuesday night reinforcing the cold air and providing an
opportunity for rain and higher elevation snow.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 1040 PM EDT Monday...

Only minor adjustments made to overnight temperatures. Scattered
to isolated showers had all dissipated.

As such, winds have shifted around to the west and northwest.
Drier air is now filtering into the forecast area with dewpoints
trending lower. Overall expectation is for skies to clear east
of the Blue Ridge this evening with lingering moisture causing
clouds to persist across the mountains. Temperatures tonight
will cool into the 30s across the mountains and mountain valleys
with 40s anticipated for the piedmont.

For Tuesday, a broad upper trough will encompass much of the
CONUS with a significant amount of cold air enveloping the
nations mid-section. We are now watching a disturbance that will
exit the southern Rockies tonight and get caught up within the
broad trough Tuesday, zipping east in rapid fashion across
Oklahoma and the Mid West early Tuesday, then across the OH/TN
valleys and into the central Appalachians Tuesday afternoon and
evening. Mid/upper level moisture will likely stream into our
mountain counties by mid-day Tuesday with onset of some form of
precipitation by late afternoon. The key word phrase is "some
form" because temperatures aloft will be cold enough to support
snow in the higher elevations with mainly rain in the lower
elevations. At the present time will entertain increasing POPs
tomorrow afternoon with likely to categorical chances (60-80
percent) for measurable precipitation north and west of the
Roanoke valley and into the state of West Virginia by Tuesday
evening. Through 6PM, the elevations below 3000 feet should
remain warm enough for mainly rain. Snow is favored for
elevations above 3000 feet. As we transition into Tuesday
night...after 6PM the freezing level will begin to lower and
p-type transition should take place down to about 2000 feet.

Temperatures Tuesday will be noticeably cooler, with highs
ranging from the 40s mountains to the 50s east of the Blue
Ridge. The Piedmont may tease 60, but even this will be 15
degrees cooler than Monday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 215 PM EDT Monday...

A cold front will cross over the Mid Atlantic on Tuesday night. With
temperatures expected to dip toward freezing west of the Blue Ridge,
any rain showers should transition to snow showers due to cold air
advection from northwest flow. The mix of rain and snow showers
could spread eastward all the way to the Blue Ridge, but moisture
will begin to pull away by Wednesday morning. Snowfall accumulations
appear to reach about two to three inches in western Greenbrier
County with amounts up to an inch in the highest peaks along and
west of the Blue Ridge. However, the snow could struggle to stick to
the warm and moist ground in valley locations. Elsewhere, cold rain
should reside across the Piedmont until the cold front pushes the
moisture offshore on Wednesday afternoon.

Weak high pressure should nose over North Carolina by Wednesday
night, while a weak warm front will traverse eastward across the
Ohio River Valley. This warm front could get close enough in
proximity to southeast West Virginia and allow a slight chance of
more snow showers in the highest elevations of Greenbrier County
before daybreak on Thursday. Once the warm front departs further
northward, the Mid Atlantic should finally have a chance to become
drier and milder by Thursday afternoon as high pressure gains more
control overhead. By Thursday night, the upper air pattern should
become zonal as high pressure heads off the Atlantic shoreline.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 215 PM EDT Monday...

Friday should turn increasingly milder as a surface southwest breeze
picks up from high pressure well offshore. The models diverge on the
timing of the next low pressure system to arrive from the central
Plains. The GFS drives the cold front from this system across the
Mid Atlantic by Friday night, while the ECWMF delays the frontal
passage until Saturday. Given the consistently fast bias of the GFS
in the extended range, this forecast will follow more closely with
the more reliable ECMWF solution. Thus, rain chances will slowly
increase Friday night and become more prominent by Saturday.

Weak high pressure will follow for Saturday night and Sunday, and
temperatures should continue to climb a little more during the day
as some upper level ridging occurs. Meanwhile, both the GFS and the
ECMWF show a new low pressure system developing along the lower
Mississippi River Valley. This system may provide the next chance of
rain during late Sunday night into Monday. Most of the heaviest rain
appears to stay further south based on these latest model solutions.
Temperatures could begin to cool a little as an upper level trough
swings overhead behind this low pressure system on Monday afternoon.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 745 PM EDT Monday...

MVFR/IFR conditions will linger west of the Blue Ridge as
upslope clouds persist at KBLF and KLWB. The upslope clouds will
diminish overnight with VFR conditions expected Monday morning.
Outside of upslope areas expect VFR conditions through most of
the forecast period. However, conditions will start to trend
down late in the day on Tuesday as clouds and some showers
spread in from the northwest.

Gusty winds will subside through early tonight, though some
gusts may linger at the higher elevations overnight. Winds are
not expected to significantly impact aircraft operations from
early Monday morning through the end of the valid period.

Extended Aviation Discussion...

Expect sub-VFR by Tuesday night as an area of low pressure
forms along the southeast coast and combines with an upper air
disturbance which is forecast to cross the TN valley and through
the central Appalachians. A swath of light rain and higher
elevation snow is expected to continue into early Wednesday
morning.

Expecting VFR Thursday followed by potential for sub-VFR within
the Friday/Saturday time...High Pressure passing overhead
Thursday followed by a frontal passage either Friday or
Saturday.

&&

.HYDROLOGY...
As of 1000 AM EDT Monday...

Impressive rainfall amounts occurred last night with a general
1.00 to 3.00 inches. Some isolated 6 and 7 inch amounts
occurred along the spine of the Blue Ridge southwest of Roanoke
from Floyd/Franklin into the NC mountains.

This rainfall has resulted in significant rises along area
rivers with the biggest impacts on the New River, Holston,
Clinch, Greenbrier, and Roanoke Rivers. Something to keep in
mind, our headwater rivers are flashy, in the sense that they
crest sooner than the RFC models can simulate. So if you are
looking at the AHPS forecasts on the internet, be careful of the
timing, as these crests may occur sooner rather than later.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$
SYNOPSIS...PM
NEAR TERM...AMS/PM
SHORT TERM...PW
LONG TERM...PW
AVIATION...MBS/PM
HYDROLOGY...PM