Flooding and Heavy Rain in Virginia, February 16 to 18, 2023

Area Forecast Discussion
National Weather Service Blacksburg VA
700 AM EST Thu Feb 16 2023

.SYNOPSIS...
A strong low pressure system over the central U.S. will move
northeast through the Upper Midwest and Ohio Valley today, then
across the Great Lakes and into New England Friday. A cold
front trailing south from the low will sweep east across the
Mid-Mississippi and Tennessee Valleys today, then across the
Appalachians tonight. Moderate to heavy rain showers will
accompany the front in addition to a few thunderstorms. Winds
will increase ahead of the front today, then become gusty with
the passaged of the front late tonight and Friday. After a very
warm day today, much colder temperatures will arrive with the
passage of the front Friday. The weekend is looking dry with
temperatures cooling to near normal. Warm weather returns again
for next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EST Thursday...

     Above Normal Temperatures Today...
     Potential For Heavy Rain Tonight...

Low pressure developing over the central U.S. will move
northeast today spreading showers and thunderstorms across the
Ohio and Tennessee Valleys. Showers are expected to tease our
western CWA today with best chance for measurable rainfall
across WV and into far western VA. Thunderstorms may also bring
a some heavier downpours...introducing a marginal risk for
excessive rainfall.

For most of our central and eastern CWA, today will be
mainly dry, featuring another day of unseasonably warm
temperatures. Afternoon temperatures east of the Blue Ridge are
once again expected to climb into the lower to mid 70s. It will
also become breezy, the pressure gradient increasing ahead of
the approaching frontal boundary.

For tonight, the front is expected to cross the mountains, models
suggesting a late night or early Friday morning frontal passage.
It will remain very mild and breezy ahead of the front with an
opportunity for a half inch to an inch of rain. Moderate to
heavy showers will spread from west to east across the area,
favoring the late night hours for the heaviest of the rainfall.
A rumble of thunder is not out of the question...elevated CAPE
running at about 300 j/kg. There is a marginal risk for
excessive rainfall, but think residence time of the heaviest
rain will be limited due to the transient nature of the front.
Never the less, expect downpours to produce localized poor
drainage issues.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 315 AM EST Thursday...

     Windy and Sharply Colder Friday into Saturday with Mountain
Snow Showers...

Winter returns this period, albeit only briefly. Sharply colder
temperatures on the heels of gusty northwest winds and strong
cold advection will sweep through the area Friday behind a
strong cold front. The cold front will move into the western
part of the CWA around daybreak moving eastward through the CWA
during the morning. A non-diurnal temperature trend can be
expected as a result with morning high temperatures in the west
and late morning or midday high temperatures across the
Piedmont. Temperatures will fall below freezing in the western
mountains by mid-afternoon as a trough of 850mb temperatures on
the order of -10C to -12C sweeps through the region late Friday
into early Saturday. This represents a good 20C drop in 850mb
temperatures from those that will be seen today/Thursday.

Surface temperatures will plunge from mild early morning
readings Friday in the 40s/50s to even near 60 across the
Piedmont down into the 20s/30s along/west of the Blue Ridge by
afternoon then bottom out in the upper teens to lower 20s across
the region by daybreak Saturday. Wind chill readings will fall
into the single digits Saturday morning in the west to the teens
across the Piedmont. Please prepare accordingly for this rapid
drop in temperatures and bitter cold expected Friday night and
Saturday. Given the very mild and well above normal
temperatures of the past several days, the wind and cold will be
a real shock if you are not properly prepared for it.

Widespread rain will be ongoing at daybreak Friday in advance of
the strong cold front with categorical near 100% pops expected
in the 12Z-15Z time frame from west to east. Temperatures will
still be above freezing in the west at this time. The main area
of precipitation/rain will move east of the area by early
afternoon. As temperatures plummet at 850mb and upslope flow
becomes more favorable across the western mountains, any rain
showers will change to snow showers. Limiting factors for
significant post frontal snow shower activity will be a limited
period of favorable upslope snow, rapidly decreasing low-level
moisture, and limited duration of strong cold advection as the
associated upper trough quickly lifts out of the region Saturday
in response to rapidly evolving zonal upper flow. Snowfall
accumulations are expected to average less than 1 inch with 1/4
to 1/2 inch northwest NC/southwest VA mountains and up to 3/4
inch across western Greenbrier. Although a few flurries may make
it as far east as the Blue Ridge no accumulation of snow is
expected outside of the western mountains.

In addition to the sharply colder temperatures, another concern
for late Friday into early Saturday will be the gusty northwest
winds. Sustained northwest winds of 15-20 mph are expected late
Friday into early Saturday with 20-25 mph sustained winds at the
higher elevations. Gusts of 40 mph will be possible, especially
along and near the Blue Ridge. A Wind Advisory may be needed for
late Friday/Friday Night with later forecasts.

Temperatures will begin to moderate fairly quickly Saturday
afternoon as the cold trough aloft lifts northeast out of the
region. Afternoon temperatures are expected to rebound fairly
nicely into the 40s west and 50s east with abundant sunshine.

/Confidence Levels in Forecast Parameters/
- Moderate to High Confidence in Temperatures,
- Moderate to High Confidence in Precipitation Probabilities,
- Moderate to High Confidence in Wind Direction and Speed,
- Moderate Confidence in Snow Shower Prospects West Friday
  night.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 330 AM EST Thursday...

     Mild Temperatures Return as Clouds and Rain Chances
Increase...

The bitter cold of early Saturday will all be a memory by Sunday
afternoon as zonal/progressive flow aloft quickly replaces the
sharp/cold trough from the early weekend. 850mb temperatures
rebound to well above normal levels for late February once
again. While perhaps, at least initially, not reaching the +12C
levels of the past few days, the -10C air of early Saturday will
be replaced rapidly by 850mb temperatures on the order of +8C
as quickly as Sunday morning. Thus, after a frosty/cold Sunday
morning mostly in the 20s under remnant Canadian high pressure,
afternoon temperatures should rebound nicely well into the 50s.
The cold mornings will also become a thing of the past as the
week progresses with minimum temperatures trending toward the
40s and maximum temperatures primarily in the 50s and 60s.

On the other hand, weather conditions will become increasingly
unsettled as the week progresses. Sunday is expected to be dry
and most of Monday should be as well. However, a baroclinic
zone will become established across the TN/OH valley Monday-
Tuesday and gradually sag southward into the Mid-Atlantic and
central/southern Appalachians by mid week and remain or meander
about this region for several days. Waves of low pressure will
ride along the boundary resulting into abundant cloud cover and
an increasing threat for rain. Consistency among the long range
models with respect to timing and impact of these waves is very
low at this point. Therefore, have kept precipitation chances in
the 30-50% range for most of the extended period beginning
Tuesday and continuing through the end of the extended period.
Clearly, with later forecasts, there will be periods of likely
precipitation, but model agreement at this juncture is too poor
to highlight those periods this far out in the forecast.

The good news for all of next week is that temperatures will
remain mild and well above normal thus precluding any concerns
for winter precipitation. In fact, the probability of closing
out February without any additional significant winter weather
events appears to be much greater than 50% at this point in
time.

/Confidence Levels in Forecast Parameters/
- Moderate to High Confidence in Temperatures,
- Low to Moderate Confidence in Precipitation Probabilities,
- Moderate Confidence in Wind Direction and Speed.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
As of 700 AM EST Thursday...

Mainly VFR conditions are expected east of the mountains today
with MVFR conditions along and west of the mountains due to
lowering cloud bases...showers and thunderstorms. A strong low
pressure system over the central U.S. will move into the Ohio
Valley by tonight, a cold front trailing south from the low.
Showers and thunderstorms will be prolific along the frontal
boundary and just ahead of the Low pressure area. This shower
activity is expected to remain generally confined to areas west
of KROA/KBCB today...with opportunity for showers and
thunderstorms at KBLF/KLWB. Shower activity will spread east of
the mountains tonight...impacting KBCB/KROA toward
midnight...then east across KLYH/KDAN after midnight. Rain may
be heavy at times tonight with elevated instability supporting
potential for mainly in- cloud lightning. Look for deteriorating
conditions areawide tonight with period of IFR associated with
the showers and frontal passage. Winds will be on the increase
ahead of the front today, from the south to southwest at 15 to
25 kts. A direction change is expected with the frontal passage
Friday morning...winds becoming northwest and speeds increasing
into the 20 to 30 kt range.

Forecast confidence = good.

Extended Aviation Outlook...

Expect precipitation to come to an end from west to east Friday
morning...winds increasing from the northwest in the wake of a
frontal passage. Sustained winds of 20 kts and gusts of 30 to 35
kts are expected during the day Friday. Skies are expected to
clear east of the mountains by afternoon with conditions
generally becoming VFR. MVFR cloud bases are expected to linger
across the mountains with cooling temperatures resulting in
lowering freezing levels and the opportunity for flurries.

Clearing skies across the mountains Friday night should begin a
period of VFR that should last through the weekend. Winds will
also diminish. Next system to impact the region may arrive as
early as Monday...rain as the precipitation type.

&&

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

&&

SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...RAB
LONG TERM...RAB
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Blacksburg VA
417 AM EST Thu Feb 16 2023

NCZ001-002-018-VAZ007-009>020-022>024-WVZ042>044-507-508-170930-
Ashe-Alleghany NC-Watauga-Tazewell-Smyth-Bland-Giles-Wythe-Pulaski-
Montgomery-Grayson-Carroll-Floyd-Craig-Alleghany VA-Bath-Roanoke-
Botetourt-Rockbridge-Mercer-Summers-Monroe-Eastern Greenbrier-
Western Greenbrier-
417 AM EST Thu Feb 16 2023

This Hazardous Weather Outlook is for northwest North Carolina,
southwest Virginia, west central Virginia and southeast West
Virginia.

.DAY ONE...Today and tonight.

There is a marginal risk of excessive rainfall tonight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Strong wind gusts expected Friday...gusts up to 45 mph.
From Saturday through Wednesday, the probability for
widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

NCZ003>006-019-020-VAZ032>035-043>047-058-059-170930-
Surry-Stokes-Rockingham-Caswell-Wilkes-Yadkin-Patrick-Franklin-
Bedford-Amherst-Henry-Pittsylvania-Campbell-Appomattox-Buckingham-
Halifax-Charlotte-
417 AM EST Thu Feb 16 2023

This Hazardous Weather Outlook is for north central North Carolina,
northwest North Carolina, central Virginia, south central Virginia,
southwest Virginia and west central Virginia.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.