Area Forecast Discussion Issued by NWS Blacksburg, VA
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000
FXUS61 KRNK 182347
AFDRNK
Area Forecast Discussion
National Weather Service Blacksburg VA
747 PM EDT Mon Mar 18 2024
.SYNOPSIS...
Gusty northwest winds and low relative humidity levels will
persist into late Wednesday as the Mid-Atlantic remains situated
between deep low pressure over eastern Canada, and a large area
of high pressure approaching from the northern Plains. Passage
of an upper level disturbance will trigger spotty upslope snow
showers tonight across southeast West Virginia. The next chance
for rainfall remains most probable for Friday when low pressure
develops over the Gulf Coast region.
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.NEAR TERM /THROUGH TUESDAY/...
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As of 735 PM EDT Monday...
Upslope clouds continue this evening, along with the occasional
snow shower across the mountains. Snow showers will taper off
overnight, but winds and cloud cover will remain.
No significant changes were made to the forecast. Adjustments to
the temperatures and dew points were made to account for current
trends.
As of 230 PM EDT Monday...
Key Messages:
1. Gusty west-northwest winds and drier air continue.
2. Fire Danger Statement is in effect for through this evening
for Alleghany, Surry and Wilkes Counties in northwest NC, as
well as VA Counties along and east of the Blue Ridge, and parts
of the southern Shenandoah Valley.
3. Another Fire Danger Statement likely tomorrow for much of
VA.
Surface observations indicate gusts between 20 to 30 mph across
the mountains this afternoon, consistent with a tight pressure
gradient between low pressure to our east and high pressure
sinking from the Central Plains into the ArkLaTex. Cirrus was
moving NE across the Piedmont this afternoon. Dense altocumulus
and stratocumulus covered much of the Midwest and the OH Valley
and was pushing into SE WV and parts of west VA. This last
intrusion was due to moisture streaming off the Great Lakes and
interacting with a band of upper level vorticity. This cloud
cover will bank along the Blue Ridge through tomorrow morning,
while downsloping winds will clear out skies east and south of
there. A few light snow showers are still possible for the
Greenbrier Valley through the overnight, where an inch of
accumulation is possible.
Temperatures tonight will be quite chilly with lows along and
west of the Blue Ridge dipping into the 20s, while areas further
east will bottom out around 30 degrees. High tomorrow will be in
the 40s and 50s.
At the surface, dry air prevails with dew points in the teens
and single digits. PWATs range from about 0.20 to 0.30 inches in
our region, and will continue to tumble to a tenth or two
overnight. The NAEFS forecast during this time is in the bottom
10% of all forecasts for this day and time, meaning we are
much, much lower than climatology. TOmorrow we do not improve
much.
Despite the cooler temperatures, the dry air and winds are
still having a significant negative impact as far as fire
weather concerns, and a fire danger statement remains in effect
for parts of NW NC, as well as parts of VA east of the Blue
Ridge through 8 PM. Another fire danger statement will likely be
issued for tomorrow once the current one expires.
Confidence in the near term is high.-- End Changed Discussion --
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.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 1100 AM EDT Monday...
Key Messages:
1. Windy to very windy conditions Tuesday night through
Wednesday night.
2. Potential fire weather concerns with the gusty winds and
expected low humidity
3. Weaker winds but still dry for Thursday.
Tuesday night through Wednesday night, the axis of a longwave
trough will be positioned northeast of the region. This will
place our area within a prolonged period of northwest flow.
Within this flow, a shortwave trough is expected to cross our
region on Wednesday afternoon/evening. Very limited moisture
will be associated with this feature. At best, some isolated to
scattered light rain/snow showers may occur over parts of
Western Greenbrier County, WV.
The main impact from the system will be a resurgence in wind
speed/gusts across the area in two possible surges. Forecast
850mb winds increase to 40 to 50 kts across the area Tuesday
night, and then after a small decline Wednesday morning,
increase again to 40 to 45 kts by the late afternoon, and
continue at similar values through the overnight hours. This
type of pattern with strong northwest winds - yielding a
subsidence factor east of the Blue Ridge - adds an element of
compressional warming that counters a bit of the strong cold air
advection, and also typically yields dew point values, and thus
relative humidity values, lower than those offered by numerical
guidance. Will adjust the forecast accordingly to match this
known bias. Surface wind gusts will be strongest Tuesday night,
and then again Wednesday afternoon/evening. Will need to monitor
for the potential for any wind headlines. Additionally, with
the combination of the dry conditions, very gusty winds, and
fuel moistures trending lower, we are considering a Fire Weather
Watch for Wednesday.
Thursday into Thursday night will be a period of transition as
the low to our northeast exits, and a low near the Four
Corners region intensifies and shifts eastward. This transition
will allow for our low level winds to back and decrease in
speed. This process will keep us dry, but start a trend towards
milder temperatures.
Confidence in the above weather scenario is moderate to high.
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.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 1100 AM EDT Monday...
Key Messages:
1. Continued low confidence in the details of the forecast.
2. Rain chances Friday into Friday night.
3. Mainly dry Saturday into Monday with a warming trend.
For the past few days, our weather forecast for Friday has been
a bit of a question mark. There has been pretty decent
consistency that rain will occur, the challenge has been the
potential impact, or lack thereof, both a southern stream system
and a northern stream system interacting over the area. Greater
inaction would mean more rainfall, whereas less interaction
would mean less. The latest guidance does not help in solving
this question as there still are notable differences. What has
remained consistent for a while now is the track of the southern
stream trough/low remains south and southeast of our region.
Given no firm evidence to deviate significantly from the ongoing
forecast, our forecast for Friday into Friday night will remain
roughly the same - rain arriving Friday southwest to northeast,
continuing Friday night with the best coverage in the south,
and moving out Saturday morning.
In the wake of the system we trend dry again through Sunday, and
most likely Monday as well. Much will depend upon the evolution
of the southern stream low. Guidance ranges from having a system
progress east, so that by Monday it is northeast of the
Bahamas. Other solutions suggest a slower exit such that the low
may ride north along the East Coast of the US with westward
advecting moisture returning to the area by Monday. Our forecast
will place more weight on the drier solution, which will also
be a solution with a warming trend as a trough develops across
central CONUS, allowing for southerly advection into the area.
Confidence in the above weather scenario is on the low side of
moderate.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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As of 745 PM EDT Monday...
Key Messages:
1. Gusty northwest winds will persist through tomorrow night.
2. Possible -SHSN at LWB/BLF through tonight.
VFR conditions this evening with the occasional MVFR category in
the mountains overnight. Some light snow showers are possible
for BLF/LWB, but not expecting any vsby reductions.
The main concern continues to be gusty west-northwest winds
that may reach 25kts through Tuesday night. There may be a lull
early Tuesday morning, but deep mixing ensures winds will kick
back up once the sun comes up.
EXTENDED AVIATION OUTLOOK...
Mainly VFR conditions will prevail through Thursday. Gusty
northwest winds continue through Wednesday, a little lighter on
Thursday. Speeds will be strongest in the mountains, potentially
reaching 40 kts or higher locally at times, especially on
Wednesday.
Chances for rain and MVFR conditions or lower ceilings increase
beginning Friday and continue through Saturday as low pressure
moves up the east coast.-- End Changed Discussion --
&&
.FIRE WEATHER...
As of 230 PM EDT Monday...
Key Messages:
1. Gusty west-northwest winds and drier air expected through
Thursday.
2. Fire Danger Statement in effect for through this evening for
Alleghany, Surry and Wilkes Counties in northwest NC, as well
as VA Counties along and east of the Blue Ridge, and parts of
the southern Shenandoah Valley.
3. Fire Danger Statement likely tomorrow for much of VA.
4. Fire Weather Watch issued for Wednesday for VA Counties
along and east of the Blue Ridge.
Cool dry air will continue to filter across the central
Appalachians through Wednesday. Despite the cooler temperatures,
strong mixing associated with the gusty winds will maintain low
afternoon RH values each day through Thursday. The combination
of low humidity and gusty winds increases the possibility of any
fires burning out of control. The next chance for widespread
wetting rain may come Friday.
A fire danger statement remains in effect for parts of NW NC,
as well as parts of VA east of the Blue Ridge through 8 PM.
Another fire danger statement will likely be issued for tomorrow
once the current one expires.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Fire Weather Watch from Wednesday morning through Wednesday
evening for VAZ019-020-022>024-032>035-043>047-058-059.
NC...None.
WV...None.
&&
$$
SYNOPSIS...NF/SH
NEAR TERM...BMG/SH
SHORT TERM...DS
LONG TERM...DS
AVIATION...BMG/SH
FIRE WEATHER...NF/SH