Area Forecast Discussion
Issued by NWS Blacksburg, VA

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326
FXUS61 KRNK 142321 CCA
AFDRNK

Area Forecast Discussion...CORRECTED
National Weather Service Blacksburg VA
621 PM EST Fri Feb 14 2025

.SYNOPSIS...
A large storm system in the central United States Saturday will
spread rain and freezing rain into the area on Saturday. Rain and
possibly thunderstorms will continue into Saturday night and Sunday
increasing the threat of flooding. Blustery and much colder
conditions arrive Sunday night and Monday as the low tracks across
New England.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 610 PM EST Friday

Key message:

     - Winter Weather Advisories Issued
     - Flood Watch Expanded

Forecast on track with high clouds increasing. Models still
showing any precip holding off til around 6-8am Saturday.

Previous discussion...

High clouds were already spreading into Virginia and North Carolina
ahead of the next storm system. At the surface winds will be light
this evening and dew points were in the teens. There is the
potential for temperatures to drop sharply in locations that do not
have cloud cover this evening.

The arrival time of precipitation has been slowed down until after
6AM Saturday morning. An in-situ wedge will develop as the
precipitation saturates and cools near surface layers along the
Blue Ridge. Have gone with the cooler MAV guidance for
temperatures on Saturday, which keeps the New River Valley, the
Roanoke Valley and the southern Shenandoah Valley in the 30s for
much of the day.

Warm air advection increases throughout the day and will scour out
the wedge from southwest to northeast. This is aided by a 40 to 60
knot 850 jet. These stronger winds over the wedge will create a
layer of warm air that will be enough to melt any frozen
hydrometeors. Freezing rain remains in the forecast for Saturday
morning but will gradually end as temperatures rise above
freezing.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 1245 PM EST Friday...

Key Points:

1. Flood Watch Continues for parts of the area into Sunday.
2. Very gusty and colder Sunday night into Monday.
3. Cold weather concerns late Monday night for western Greenbrier
County for wind chills at or below -5F.

A look at the 14 Feb 00Z NCEP Ensemble Mean 500mb Geopotential
Heights show a closed low centered over the western sections of
Hudson Bay. A longwave trough is expected to extend south of the low
over central CONUS. Flow over our region will be southwest. On
Sunday, the axis of the trough shifts east over our region by the
evening hours and trends negatively tilted. The center of the parent
low heads south to near western Ontario. On Monday into Monday
night, the center of the low and its associated trough will be over
the Canadian Maritimes. Nearly zonal flow is expected for our
region.

At the surface, low pressure early Saturday night is expected to
located over the Mid-Mississippi and Lower Ohio Valleys. An
associated warm front is expected to be extending eastward into the
Tennessee Valley. A cold front will extend southwest of the low into
South Texas. By Sunday evening, the low is expected to have moved
northeast, and be situated over New England with its associated cold
front trailing southwest along the East Coast. Concurrently, high
pressure will be building south into central CONUS. By Monday
evening, an associated ridge axis of the high building into the
central US will be nosing into our region.

A look at the 14 Feb 00Z NAEFS Ensemble Situational Awareness data
shows 850mb temperatures within the +8C to +10C range, n-s, across
the area Saturday night. These values for the overnight hours fall
within the 90 to 99 percentile of the 30-year CFSR climatology. On
Sunday, values will fall rapid in the wake of a cold front. By the
evening hours, anticipate values of -6C to 0C, nw-se. Values
continue to fall Sunday night, reaching -13C to -10C, nw-se, by
daybreak Monday. On Monday, values only moderate slightly with
values of -10C to -5C, n-s, by the evening hours. Monday night
expect only a minor upward change to -9C to -3C, n-s, by daybreak
Tuesday.

The above weather patterns offers a generous coverage of rainfall
Saturday night, especially in the area along and immediately north
of the warm front which will cross our region. A secondary maximum
is expected to be along and immediately east of the crest of the
Blue Ridge. Strong southerly very moist flow advecting into the
higher terrain will allow for enhanced upslope flow precipitation
within this corridor. As we progress into Sunday, the warm front
will continue its trek north of the region, with the best potential
for precipitation during the early morning hours again along and
immediately east of the crest of the Blue Ridge. By the late morning
into the afternoon hours, a cold front is expected to progress into,
across, and exit our region. This feature will help yield a strong
convective line of heavy rain showers which will cross our region.
Some of the best dynamics and convection are expected to develop
along this line south of our region. This activity will have the
potential to mitigate, but not completely remove the heavy rain
impact for this line of showers across our region. While chances are
low, but not non-zero, parts of the area on Sunday could also
experience a few thunderstorms. The greatest potential looks to be
the far southeastern sections during the early afternoon.

In the wake of the cold front, winds shift northwest and become
gusty. Gusts of 25 to 40 mph will be common across the mountains
with 20 to 30 mph across the Piedmont. Locally higher values are
possible for both geographical area. The northwest flow across the
mountains will help generate upslope snow showers, especially over
the preferred locations of southeast West Virginia, south into the
Northern Mountains of North Carolina. Coverage will gradually
decrease through the night, ending last over parts of Southeast West
Virginia perhaps as late as Monday morning.

High pressure will gradually work its way into the region on Monday.
This feature will provide for colder temperatures and drier
conditions. Our pressure gradient will be relaxing, but enough will
remain so that winds will still be gusting to around 15 to 25 mph
across the mountains in the late afternoon. Dry and colder and less
gusty conditions are expected Monday night. Western parts of
Greenbrier County could be a candidate for Cold Weather Advisory
conditions with wind chills dipping to under -5F for parts of this
region.

Confidence in the above weather scenario is moderate to high.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 100 PM EST Friday...

Key Point:

1. Potential winter storm Wednesday into Thursday, confidence on the
details are still not high, but confidence is trending upward.

A look at the 14 Feb 00Z NCEP Ensemble Mean 500mb Geopotential
Heights shows the axis of a longwave trough developing over central
CONUS on Tuesday. In response, flow over our region backs southwest.
On Wednesday, the trough axis is expected to make progress eastward,
reaching the Mississippi Valley by the evening hours. There are
hints that a closed low may try to form on the northern end of the
trough over the Great Lakes. Flow over our region remains southwest
but likely increases in speed. Heights drop slightly. For Thursday,
the through axis crosses our region, reaching the area of Maine
southwest to the VA/NC coast. A secondary shortwave trough may trail
over the Great Lakes. Concurrently, a shortwave trough is expected
to develop over the Rockies. By Friday, the shortwave trough in the
west ejects into central CONUS. The east coast trough is expected to
be centered over Newfoundland-Labrador by the evening hours.

At the surface, by Tuesday evening, a ridge axis is expected to
remain over our region. Low pressure in the form of an inverted
trough is expected to develop over the Lower Mississippi Valley. By
Wednesday evening, the ridge over central CONUS holds fast. The
inverted trough to the south is expected to head eastward, reaching
the area of northern Florida to just off the Southeast US coast. By
Thursday evening, the central US high pressure expands even further
in scope. The trough off the US East Coast heads northeast over the
Canadian Maritimes. On Friday, the center of the surface high shifts
east to over the Lower Ohio Valley.

A look at the 14 Feb 00Z NAEFS Ensemble Situational Awareness data
shows 850mb temperatures on Tuesday inching upward during the day
reaching a range of -7C to -2C, n-s, by the evening hours. Values
change little Tuesday night. On Wednesday, values by the early
evening are expected to range from -8C to -3C, nw-se. Values trend
lower Wednesday night, reaching -13C to -7C, nw-se, by daybreak
Thursday. These values correspond to the 2.5 to 10 percentile of the
30-year CFSR climatology. On Thursday, values continue their
downward trend, reaching -16C to -11C, nw-se, by the early evening.
These values correspond to the 1 to 10 percentile of the 30-year
climatology. For far southwestern sections of the region, the range
would be the 0.5 to 2.5 percentile. For Thursday night, expect
values of -14C to -10C, nw-se, or within the 2.5 to 10 percentile of
climatology. For Friday, values moderate slightly, reaching -10C to
-6C, nw-se, by the early evening.

The above weather patterns offer dry and below normal temperatures
on Tuesday thanks to the influence of high pressure over the region.
Tuesday night into Wednesday, moisture will begin to stream into the
region on the east side of the eastward moving inverted trough. The
bulk of the energy and associated moisture is expected to remain
south of the region. However, the moisture that does arrive will be
intersecting the cold high will be situated over or just north of
the region. There are still uncertainties regarding the values of
the low level thermal profile across the region during this
precipitation event. However, the latest trends point toward
northern and western sections of the area more like to experience
snow with this evening. The farther southeast within the forecast
area a person is located, the better the chance of other wintry
weather types such as freezing rain or sleet. However, for the sake
of simplicity and recognition of the uncertainties, our forecast
will continue to reflect a rain versus snow forecast with surface
temperature being the determining factor.

Uncertainties continue Wednesday night into Thursday. Guidance
varies regarding how much influence the trough/low moving over the
Great Lakes region will have on our area. Some solutions offer a
better pairing of this northern stream system with the exiting
southern stream system. Other solutions allow enough time to pass so
that there is not a pairing of systems. If there is a pairing,
precipitation on Wednesday would like continue into Wednesday night
and Thursday. As colder air arrives with the northern system, the
greater the probability the precipitation would fall as snow.  If
the pairing does not occur, then we would more like see a clear
ending of precipitation from the southern stream system. This would
be followed by primarily northwest flow upslope snow showers across
the mountains, with limited to no precipitation for eastern sections
Thursday into Thursday night. For consistency, our forecast will
continue to favor a solution that has a least some pairing of the
two system. All guidance is pretty good agreement of high pressure
arriving for Friday.

Confidence in the above weather scenario is moderate for Tuesday
and Friday, but still low, but inching upward for Wed/Thurs.

&&

.AVIATION /23Z FRIDAY THROUGH WEDNESDAY/...
As of 610 PM EST Friday...

High clouds will increase this evening, then lower through the
night to a mid deck.

The arrival time of precipitation has been slowed down until after
6AM Saturday morning. An in-situ wedge will develop as the
precipitation saturates and cools near surface layers along the
Blue Ridge. Ceilings drop to MVFR as the rain begins, mainly
after 14Z/9AM at local TAF sites. KLWB, KBCB, and KROA may begin
as freezing rain, lasting only 1-3 hours.

Warm air increases throughout the day and will scour out the
colder low levels changing freezing rain to liquid rain.

Poor flying weather expected though from about 13z-end of this
taf period with cigs/vsbys lowering areawide to IFR, possibly
some LIFR vsbys at times.

A strong low level jet may bring some low level wind shear
Saturday afternoon into the mountains.

Above average confidence for ceiling, wind, and visibility.
Average confidence in type of precipitation on Saturday.

.EXTENDED AVIATION OUTLOOK...

Ceilings will continue to stay in the IFR range into Sunday,
maybe rising to MVFR with the front Sunday afternoon. Rain
showers could be heavy at times Sunday.

Isolated thunderstorms are also possible across southern
Virginia and northern North Carolina late Saturday night through
Sunday.

Behind the front ceilings/vsbys improve east of the mountains
but upslope may keep sub-VFR with snow showers across BLF/LWB
into early Monday. Also west to northwest winds behind the front
Sunday could gust over 40 mph along/west of the Blue Ridge.

Should be VFR into late Tuesday maybe even Tuesday night but
another winter storm could bring poor aviation conditions across
the mid-Atlantic/NC midweek.

&&

.HYDROLOGY...
As of 330 PM EST Friday...

Key Message:

     -Flood Watch in effect until Sunday evening along and west of
      the Blue Ridge

A prolonged period of rain will move into the area Saturday. The
precipitation will start as freezing rain, mainly at the higher
elevations, but then change to rain from southwest to northeast
Saturday as temperatures rise above freezing. Rain continues through
Sunday. Rainfall amounts will be from 1 to 2 inches.

Snow remains on the ground north of US 460. Rain that falls in this
area will melt the snow adding to the efficient runoff due to frozen
ground. Rapid rises are possible along streams and creeks.

Saturday night and Sunday rainfall rates higher than 1 inch/hour are
possible. This would produce excessive runoff on the saturated
ground. Thunderstorms are possible south of US 460 late Saturday
night and Sunday morning.

As these smaller streams and tributaries drain into the main stem
rivers, flooding is also possible. The Greenbrier, Upper James, and
upper Clinch river valleys are especially susceptible to river
flooding.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flood Watch from Saturday morning through Sunday evening for
     VAZ007-009>020-022>024-035.
     Winter Weather Advisory from 7 AM to 7 PM EST Saturday for
     VAZ011-013>020-022>024-032>035.
NC...Flood Watch from Saturday morning through Sunday evening for
     NCZ001-002-018.
     Winter Weather Advisory from 7 AM to 7 PM EST Saturday for
     NCZ001>003-018-019.
WV...Flood Watch from Saturday morning through Sunday evening for
     WVZ042>044-507-508.
     Winter Weather Advisory from 7 AM to 7 PM EST Saturday for
     WVZ043-044-507-508.

&&

$$

SYNOPSIS...AMS
NEAR TERM...AMS/WP
SHORT TERM...DS
LONG TERM...DS
AVIATION...AMS/PM/WP
HYDROLOGY...AMS