169
FXUS61 KRNK 151457
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
1057 AM EDT Thu Aug 15 2024

.SYNOPSIS...
High pressure will keep our weather mainly dry through
tonight. A front will bring a better opportunity for showers
and storms Friday into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1045 AM EDT Thursday...

No change to near term forecast. Regional soundings remain dry
above 700 mb, so cu development will be hard pressed to get any
depth. Exception will be along the Appalachian Divide, TNB-
BLF, where increasing moisture from the southwest will begin to
infiltrate aloft promoting weak CAPE, cloud build-ups and
isolated showers.

Key Message: Mainly dry/quiet weather through tonight.

High pressure centered to our north will provide another dry day
today, though a warm front lifts across the TN/OH Valleys this
afternoon. Cannot rule out a few showers across the mountains,
but most stay dry with mostly sunny skies. Temperatures
through the near term will be close to normal. Patchy fog
possible again early this morning favoring the rivers valleys.

Tonight, a 500mb ridge will be over the area, while  trough
approaches from the upper Midwest. The ridge aloft and high
pressure at the surface will keep conditions dry through early
Friday morning, though looking at increasing clouds with warm
front an potential for a few showers making it to our far
southwest VA into southern WV counties around dawn.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 115 AM EDT Thursday...

Key Points:

1. Showers/Storms expected each day.
2. Locally heavy rain possible Friday into Friday night, especially
western sections.
3. Temperatures trending milder to slightly above normal values.


A look at the 14 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a shortwave trough over the Upper Mississippi Valley
that progresses slowly eastward. As it moves east, it gradually
become more amplified with its axis over our region by late Sunday
night. At the surface, on Friday, a ridge of high pressure will be
situated along the US East Coast. Low pressure will be over the
Upper Mississippi Valley. As we progress through the weekend, the
low pressure is expected to progress eastward, reaching the area of
PA/NY/NJ by late Sunday night. An associated cold front is expected
to cross our region late Saturday night into early Sunday morning.

Output from the 14 Aug 12Z Ensemble Situational Awareness Table
shows 850mb temperatures ranging from +16C to +18C on Friday, +17C
to +19C on Saturday, and +16C to +17C on Sunday. Precipitable Water
values are expected to range from 1.25 to 1.50 inch on Friday, 1.50
to 1.75 inch on Saturday, and 1.25 to 1.50 inch on Sunday. The
values on Friday into Friday night that reach or top 1.75 inch falls
within the 90 to 97.5 percentile of the 30-year climatology. Mean
Integrated Water Vapor Transport is expected to reach a maximum of
400 to 500 units Friday night into Saturday across the region. This
range of values corresponds to the 90 to 97.5 percentile of the 30-
year climatology for this parameter.

The above weather scenario offers a forecast with good chances of
showers and storms in advance of and coincident to the passage of a
cold front. Precipitable Water values over 1.75 inch on Friday and
well above normal moisture transport Friday night through Saturday
point at this time period for the best opportunities for locally
heavy rain, especially across western sections.

While the cold front is expected to cross the region late Saturday
night into early Sunday, the parent upper trough is not expected to
reach our area until late Sunday night. With this feature still
approaching, we will continue to have showers/storms in the forecast
Sunday/Sunday night, just not the level of coverage prior to the
frontal passage.

Temperatures during this portion of the forecast will trend milder
into the weekend.

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

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 115 AM EDT Thursday...

Key Points:

1. Precipitation chances trending lower each day, with the best
chances on Monday.
2. Temperatures trending cooler to near or slightly below normal
values.

A look at the 14 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows an upper trough over our area Monday morning. Through
Wednesday, this feature is expected to make little to no headway
eastward. Rather, it loses its amplification as it experiences
overall height rises and broadening of the trough. As the surface, a
cold front will become stalled along the Southeast US Coast Monday
into Tuesday as the center of high pressure moves from the Upper
Mississippi Valley into the Ohio Valley. By Wednesday, the front
still remains stalled along the Southeast US Coast while the high
shifts east toward the mid-Atlantic region.

Output from the 14 Aug 12z Ensemble Situational Awareness Table
shows 850mb temperatures ranging from +15C to +17C on Monday through
Wednesday. Precipitable Water values are expected to be around 1.25
inch on Monday, a little less than 1.00 to a little less than 1.25
inch on Tuesday, and 1.00 to 1.25 inch on Wednesday.

An upper level trough parked over the region through Thursday.
However, this feature will be weakening each day. Additionally, each
day, surface high pressure makes more progress into at least western
parts of the region. This combination offers a trend of decreasing
potential of showers/storms each day, although with no day have a
zero chance over at least some portion of the area. Coverage will be
greatest on Monday.

Temperatures will trend cooler during this portion of the forecast.

Confidence in the above weather scenario is moderate.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
As of 1100 AM EDT Thursday...

VFR conditions are expected at all terminals through most of
the TAF period.

SCT-BKN cumulus field expected this afternoon with cloud build-
ups and isolated showers along the Appalachian Divide...BLF-TNB.
Winds stay light and shift to the south. Thinking increasing
clouds early Friday will limit fog so not adding it to LWB at
this point.


.EXTENDED AVIATION OUTLOOK...

Clouds will increase from the west due to an approaching cold
front Friday. This front should bring a good chance of showers
and thunderstorms along with potential MVFR/IFR ceilings during
Friday-Sunday, with less coverage by Monday.

&&

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

&&

$$

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