051
FXUS61 KRNK 130533
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
133 AM EDT Tue Aug 13 2024

.SYNOPSIS...
An upper level disturbance will cross the area Tuesday resulting
in clouds and isolated showers/storms, otherwise a large area
of high pressure centered over the northern Mid-Atlantic will
keep the weather mainly dry. The next widespread chance for rain
arrives toward the end of the week as a low pressure system
approaches from the Ohio Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 100 AM EDT Tuesday...

Key Message: Mainly dry weather but more clouds and a few
showers Tuesday along and south of the VA/NC border.

Just minor changes from previous forecast and still looks like a
disturbance moves across overhead today and with some moisture
convergence along/south of the VA/NC border, could see a few
showers, possibly some thunderstorms. Otherwise high pressure
will keep things dry but expect more mid and high clouds today
mixed in with intervals of sunshine, along with scattered
cumulus.

Any showers should fade with dusk and clearing out tonight for
most. Amount of fog Tue night will depend on how much coverage
of rain occurs. Models hinting at some fog/lower vsbys
along/south of the VA/NC border Wed morning.

Highs today will run about 5 degrees below normal with lower 80s
east to 70s west. Lows tonight closer to normal int the lower to
mid 60s Piedmont to mid to upper 50s mountains.

Forecast confidence above average except sky cover/storm
coverage today.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
As of 130 AM EDT Tuesday...

Key Points:

1. Mainly dry on Wednesday.
2. Increasing chance of showers/storms on Thursday, but especially
on Friday.
3. Near normal temperatures.

A look at the 12 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows a nearly stationary upper trough across the western
Atlantic, extending from Greenland to the Canadian Maritimes.
Additionally, a shortwave ridge shifts east from the Great Lakes to
New England. Also, an upper trough progresses from the Northern
Plains to the Great Lakes/Ohio Valley region. At the surface, high
pressure will be centered over the Ohio Valley on Wednesday. This
high progress eastward and be near the Canadian Maritimes by Friday.
Additionally, a trough of low pressure over the Dakotas will head
east deepen as a closed low over the western Great Lakes region by
Friday.

Output from the 12 Aug 12Z Ensemble Situational Awareness Table
shows 850mb temperatures trending slightly higher through this
portion of the forecast. On Wednesday, values are expected to
average +14C to +16C over the region. By Friday, values of +16C to
+18C are forecast. Precipitable Water values on Wednesday and
Thursday are expected to range from a little under 1.00 inch to
1.25 inch. On Friday, expect values closer to 1.50 inch.

The above weather scenario offers decreasing influence of dry high
pressure Wednesday into Thursday. Thursday into Friday, the approach
of a trough and exit of high pressure will help provide for a better
southerly fetch of moisture into the region. With the better
moisture, and daytime heating in advance of the approaching system,
look for much better coverage of showers/storms on Friday as
compared to the previous two days. Temperatures will be near normal
through the period.

Confidence in the above weather pattern is moderate to high.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
As of 130 AM EDT Tuesday...

Key Points:

1. Good coverage of showers/storms this weekend.
2. Less, but still scattered coverage, on Monday.
3. Near normal temperatures.

A look at the 12 Aug 12Z NCEP Ensemble Mean 500 mb Geopotential
heights shows slowly eastward moving upper rough which amplifies each
day. On Saturday the feature is expected to be over the Great
Lakes/Lower Ohio Valley region. By Monday, the axis will be near the
spine of the central to southern Appalachians. At the surface, low
pressure over the Great Lakes will progress eastward and be over the
mid-Atlantic region by Monday.

Output from the 12 Aug 12z Ensemble Situational Awareness Table
shows 850mb temperatures around +18C on Saturday and Sunday, but
closer to +16C to +17C for Monday. Precipitable Water values on
Saturday are expected to be around 1.50 to 1.75 inch, 1.25 to 1.50
inch on Sunday and Monday.

With the approach and arrival of upper trough and surface
trough/cold front, look for increasing chances of showers/storms
over the weekend. By Monday, while the surface front is expected to
be to our east, the parent upper trough will still be over the
region with its associated upper level cold pool, yielding steep
lapse rates aloft. Showers/Storms will continue to be a possibility
on Monday, but with less coverage than what is expected
Saturday/Sunday.

Temperatures will be near normal for this time of year.

Confidence in the above weather pattern is moderate with timing of
the surface cold front and upper trough axis the biggest question
mark.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 110 AM EDT Tuesday...

Mainly VFR expected through the 24 hour valid TAF. Increasing
mid/upper level moisture tonight should prevent river fog
formation, except LWB. Weak instability may lead to widely
scattered showers/thunderstorms across the piedmont of NC
Tuesday afternoon possibly approaching DAN but too low of pops
to have in the forecast tafs.

Winds generally 5kt or less from the northeast to east.


AVIATION OUTLOOK...

Could be some fog Wed morning in typical mountain valleys and
along/south of the VA/NC border. Mainly dry weather expected
Wednesday and Thursday.

An organized area of low pressure will approach the area by
Friday bringing the potential for precipitation and widespread
sub-VFR flight conditions which could last through Saturday.

&&

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

&&

$$

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