406
FXUS61 KRNK 051439
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
939 AM EST Wed Feb 5 2025

.SYNOPSIS...
Rain returns today, with some freezing rain likely across the
Greenbrier Valley and Alleghany Highlands which will cause minor
to moderate impacts through Thursday morning. Rain continues
for Thursday before high pressure will briefly build in for the
end of the week. Another potential system could impact the
region over the weekend and again for the beginning of next week.

&&

.UPDATED NEAR TERM /THROUGH TONIGHT/...
As of 930 AM EST Wednesday...

Small changes made to the forecast for the rest of the day to take
into consideration latest temperature observations. Rainfall
and freezing rain chances have been adjusted accordingly. Most
of the freezing rain will be concentrated in northern elevated
areas and in West Virginia counties. Precipitation chances start
low this morning and pick up by this evening and overnight into
Thursday.

.NEAR TERM /THROUGH TONIGHT/...
As of 140 AM EST Wednesday...

Key Messages:

1) Precipitation arrives today and areas of freezing rain will
occur across the Alleghany Highlands and southern Shenandoah
Valley.

2) Colder temperatures with little to no warming today.

Surface high pressure to the north continues to wedge southward
along the Appalachians. Current observations indicate northeast
winds now along and east of the Blue Ridge. Dew points and
temperatures will continue to decrease as this cooler air works
into the region. A subtle wave within zonal upper flow will
approach the area today and weak isentropic lift associated with
this wave will result in light precipitation to develop later
this morning. Precipitation will increase in coverage through
tonight.

Temperature/dew point suppression will allow for some
evaporative cooling as precipitation begins. This will cool
locations further, along with locking in cold air damming
resulting in a chilly and dreary Wednesday. Coldest temperatures
will be confined to the higher elevations north of Roanoke,
particularly in the Alleghany Highlands and southern Shenandoah
Valley. Temperatures in the aforementioned locations will hover
around 28F to 32F most of today. Model soundings indicate a +4C
to +6C warm layer aloft, with a shallow cold layer in the lowest
levels. This will support areas of freezing rain today, with
the highest confidence of ice along and north of the Interstate
64 corridor in West Virginia and Virginia. A warm layer of that
magnitude with a very shallow cold layer will only support
freezing rain if below 32F or just cold rain above 32F,
therefore have removed any mentions of snow/sleet.

Cold air wedge will be very slow to erode with not much change
in temperatures through late this evening. Wedging becomes more
in- situ late tonight and the introduction of a strong
southwest low- level jet will begin to gradually scour the cold
air damming from southwest to northeast.

No changes with the current headlines and ice amounts overall
have remained unchanged.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
As of 115 AM EST Wednesday...

Key Points:

1. Cold Air Damming erodes on Thursday with well above normal
temperatures expected by the afternoon.
2. Locally heavy rain possible Thursday into Thursday night,
especially far western portion of the area.
3. Dry but still mild on Friday.
4. A warm front and then a cold front look to bring precipitation
back to the forecast Friday night through Saturday night.

On Thursday, models are in good agreement that warm air advection in
advance of an approaching cold front, and south of a passing warm
front, will help to scour out the lee side cold air damming (CAD).
Areas across the far western/southwestern sections of the forecast
area will already be on the mild side -- outside the influence of
the CAD. However, as the day progresses, all areas progressing from
southwest to northeast will be greeted by very mild air. High
temperatures on Thursday are expected to be about 25 to 30 degrees
milder across northern and eastern parts of the area as compared to
those expected today. Precipitation chances will be greatest
coincident to the northward moving warm front during the early to
mid portions of the day. By the mid/late afternoon, the focus for
the best coverage shifts to western parts of the area immediately in
advance of the approaching a slowly moving cold front. A rumble or
two of thunder cannot be ruled out over far western sections.
Additionally, we may need to pay close attention to the potential
for flooding concerns over western parts of the area. Soils in this
area are saturated from recent rains and snowmelt. Precipitation is
expected to be over this portion of the area Thursday into Thursday
evening/night, along with potentially heavier bursts rain thanks to
a the deeper convection possibility.

High pressure is expected to move into the area by Friday afternoon,
but not linger over the region before shifting northeast of the
region by Saturday morning. While our weather will turn dry for
Friday, it also will be on the gusty side given the quick approach
of the high pressure system.

On Saturday, low pressure is expected to be developing across the
Central Plains states. Its associated developing warm front is
expected to lift north towards and across our region during the day.
Currently low level thermal profiles support a rain forecast for
much of the region. However, we may have the potential wintry p-type
options across northern parts of the area. A lot will depend upon
the arrival time of the precipitation in relation to how much
remaining sub-freezing air exists at the surface and boundary layer
as potential warm nose aloft crosses the area.

For Saturday night, the warm front is expected to continue on its
progression north while the Central Plains low progression into and
across the Great Lakes region. This associated cold front is
expected to be reaching western portions of the area by daybreak
Sunday.

Output from the 4 Feb 12Z Ensemble Situational Awareness Table shows
850mb temperatures on Thursday increasing to roughly +10C to +13C, n-
s, across the region. These value exceed the 90 percentile of the 30-
year CFSR climatology, with the top end of this range exceeding the
99.5 percentile. Thursday night, values begin to fall, reaching 0C
to +9C, nw-se, by daybreak Friday. Values continue falling on
Friday, reaching 0C to +6C, n-s, by the early evening. On Saturday,
values are expected to gradually increase during the day, reaching
+6C to +10C, ne-sw, by the early evening. Values hover around +8C to
+10C into the overnight hours, before starting to fall in the west
as daybreak Sunday approaches.

Confidence in the above weather scenario is moderate/high on
Thursday and Friday, but trends to low/moderate for the start of the
weekend.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 1215 AM EST Wednesday...

Key Points:

1. Active weather pattern with precipitation possible each day.
2. Wintry weather possible for parts of the area, but low confidence
on p-type/timing/location.
3. Above normal temperatures Sunday, with near normal values Monday
and Tuesday.

The general synoptic trend during this portion of the forecast is
for a broad longwave trough to be located across the central to
southwestern portions of CONUS. Within this broad trough, both a
southern stream and northern stream jet are expected to be in place.
The former allowing for periodic shortwave troughs to traverse the
Gulf Coast states and the southeast US. The latter is expected to be
less impressive in terms of precipitation makers, but is expected
more to be a source of colder air working its way into the region.
The result could be an active period of precipitation across the
area with the potential for wintry weather for parts of the area.

Output from the 4 Feb 12Z Ensemble Situational Awareness Table shows
850mb temperatures on Sunday decreasing behind an exiting cold
front. By the early evening, values are expected to range from -4C
to +5C, n-s. From Sunday night through Tuesday, little variation is
expected with only minor deviations of roughly -4C to +4C, n-s,
across the area. With the 850mb 0C isotherm centered over the
region, this gives greater credence to the potential for some type
of wintry weather with systems expected Monday into Tuesday. Given
the uncertainty in the low level thermal profile, our forecast for
simplicity will offer a rain versus snow forecast based solely on
expected surface temperatures.

Confidence in the above weather scenario is moderate in terms of an
active weather pattern and temperature expectations, but low on
other elements.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
As of 145 AM EST Wednesday...

Overall VFR conditions ongoing across the region this morning,
but expecting impacts to aviation and sub-VFR conditions to
arrive later today. High clouds have continued to increase ahead
of an approaching system. Will continue to see clouds increase
and lower through the morning. Sub-VFR cigs arrive late this
morning and into early afternoon, along with increasing rain.
Easterly flow and rain will create a combinations of low cigs
and the potential for fog for most terminals through the end of
the valid 24hr TAF period. Pockets of freezing rain will be
possible for LWB late this morning and into the evening,
eventually transitioning back to rain. Elsewhere, expecting all
precipitation to be rain.

EXTENDED AVIATION OUTLOOK...

Rain showers with MVFR conditions will continue on Thursday
before the rain slowly clears out on Friday. Friday is expected
to be dry with flight conditions returning to VFR.

More precipitation and restrictions on flight conditions are
forecast for Saturday ahead of another low pressure system which
will linger into Sunday before a front moves through and clears
the area back out Sunday evening.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Winter Weather Advisory until 7 AM EST Thursday for VAZ019-020-
     024.
NC...None.
WV...Ice Storm Warning until 7 AM EST Thursday for WVZ507-508.

&&

$$

SYNOPSIS...BMG
NEAR TERM...BMG/CG
SHORT TERM...DS
LONG TERM...DS
AVIATION...BMG