Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 250555

Area Forecast Discussion
National Weather Service Blacksburg VA
155 AM EDT Fri Sep 25 2020

The remnants of Beta will spread rain into the region
overnight tonight, then push east of the area by Friday night.
Weak high pressure builds in late Saturday with milder
conditions Sunday. Our next cold front arrives early next week.


As of 100 AM EDT Friday...

Light to moderate rain continue to spread northeast across the
region in advance of the approach of the remnants of Beta. Have
made little change to the ongoing forecast for the remainder of
the overnight hours. The biggest adjustment was the broaden the
gradient of the probability of precipitation to include some
binary zero POPs and some 100 POPs where confidence is high over
the next few hours were precipitation will not be occurring
versus where precipitation will be occurring. Have also tweaked
hourly temperature, dew point, winds/gusts, and sky cover over
the next few hours to be better reflect the latest observations
and expected trends.

As of 800 PM EDT Thursday

Rain is staying mostly below Highway 460, a few stray drizzles here
and there further north. Amounts have been light, with the greatest
amount coming from a site in Blowing Rock, NC reporting a little
over three tenths of an inch. Expect this to be the status quo until
closer to Friday morning, when an upper trough begins to lift a
little further north, bringing the moisture of Beta`s remnants with
it. Light to moderate rain will persist for most of the CWA through
Friday night. North of 460, totals through Friday will be 0.5-1" for
the most part. South of that, totals will be more in the 1-2" range,
with the most in the NC High Country. Hydro and flooding issues
remain minimal, with flooding in poor drainage or small creeks and
streams possible.

Diurnal temperature swings will be held in check by the continuous
cloud cover and rainfall. Lows in the 50s/low 60s tonight and highs
on Friday in the 60s.


As of 200 PM EDT Thursday...

The remnants of Beta will be east of the region by Friday
evening as it is absorbed within an upper short wave tracking
east-northeast across the region. This will take the system out
to sea Friday night and early Saturday. However, there is no
clear change of air mass evident at this point, leaving the
region in a warm and humid air mass with dewpoints still largely
in the 60s, rather high for late September. Overall, the pattern
following Beta evolves to a pattern more like summer than fall
with upper ridging across the east central U.S. leading to
warmer than normal temperatures and humidity into the weekend.
While there does not appear to be any clear triggering mechanism
for precipitation, differential and diurnal heating will likely
lead to isolated to scattered pop up showers perhaps a
thunderstorms in the western mountains. This has been indicated
with 20-30 percent pops focused for the afternoon/evening hours.
Otherwise, the period will be more like early September than
late September with high temperatures in the 70s west and 80s
east with lows mainly in the 50s west and 60s east.

Confidence in this portion of the forecast is moderate to high.


As of 200 PM EDT Thursday...

The main focus through this period will be on a strong cold
front slated to develop by early next week as a deep trough
forms across the Great Lakes and dives into the eastern U.S.
Models continue to have differences in timing and intensity,
with the GFS on the fast and weaker end of the spectrum while
the ECMWF is slower, yet more intense, and also showing a double
barreled strong negatively tilted short wave tracking up the
eastern U.S. midweek opposed to the single less negatively
tilted trough shown by the ECMWF. At this point Monday looks
like a similar repeat of Sunday with a slight uptick in showers
across the western mountains. By Tuesday, the strengthening and
deepening trough to our west will lead to deepening south to
southwesterly flow aloft and thus an increase in shower
activity, especially in the western part of the CWA. The front
finally comes through in some form/fashion by Wed into Thu. Too
early to tell, but if the ECMWF is correct with the strong
negatively tilted trough, this system could bring some
thunderstorms and possibly even a chance for a few strong/severe
spring-like thunderstorms with a sharp contrast to colder
weather later on in the week.

With deep southerly flow persisting longer into the week than
previously expected, warm temperatures, higher humidity levels
will linger well into the first half of the week. Considerably
colder temperatures appear in the offing for late week as lows
drop into the 40s and highs into the 50s and 60s. However, the
depth and degree of the cold air appears less with each model
run as it becomes hung up in the Midwest and northern plains
instead of tracking as far east and south as indicated earlier
in the week.

Confidence remains low to moderate in the long term with respect
to timing and intensity, but rain appears likely during the
midweek period.


As of 130 AM EDT Friday...

Sub-VFR ceilings and visibilities are slowly working their way
into the region within the leading area of precipitation in
advance of the expected track of the remnants of Beta. By
daybreak Friday, most of the region is expected to be IFR/MVFR
regarding ceilings and MVFR with regard to visibilities. This
scenario will continue through the day with more ceilings
trending to IFR or lower. Later tonight, western sections of the
region will see improvement to VFR with only pockets of MVFR.
Winds will generally be light from the east or southeast through
the period. Some of the higher elevations this afternoon may see
sustained winds near 10kts.

Confidence in all parameters is moderate to high.

.Extended Aviation Discussion...

Showers continue through Friday afternoon before tapering off by Fri
night, though some sub-VFR conditions will likely carry into the day
Saturday before high pressure builds in. Another front arrives
Monday with a threat of showers, but could be VFR. Confidence is low
for this weekend into Monday.




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