-- Discussion containing changed information from previous version are highlighted. --
891
FXUS61 KRNK 201737
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
137 PM EDT Fri Sep 20 2024

.SYNOPSIS...
Weak high pressure will remain nestled over the Appalachian
chain through the weekend, maintaining a mix of clouds and
sunshine, in addition to a low probability for rainfall. A cold
front will gradually approach up the Ohio River Valley during
the early half of the next workweek, resulting in a higher
chance of showers and thunderstorms that will persist into next
weekend.

&&

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
As of 130 PM EDT Friday...

Key Messages:

1) Isolated showers and a few thunderstorms will develop this
afternoon into the evening.

2) Fog and low stratus redevelop overnight into Saturday
morning.

3) Confidence is moderate on more widespread convection
tomorrow, but only expecting a few strong to severe cells.

The Mid-Atlantic region remains between low pressure off the
western Atlantic Ocean and high pressure centered over the
southern Plains. This keeps our area in progressive NW flow
through the weekend. Isolated showers and thunderstorms have
begun to develop over the piedmont where more some mid level
energy was streaming by. Otherwise, we may see a few small
cells develop over the mountains and drift south before
dissipating. Lack of significant forcing and moisture will keep
coverage to a minimum this afternoon and evening. These cells
may produce moderate, brief rainfall at times.

Areas of very low stratus/dense fog from overnight dissipated
finally around noon today. Expect this to redevelop tonight and
take until midday Saturday before burning off. Overnight
temperatures will be in the 50s to low 60s.

A little more widespread convection is expected Saturday with
most of the stronger storms to our north and northeast, closer
to the better forcing. However, gusty winds and heavy downpours
will be possible, especially for the mountains beginning in the
early afternoon, and then spreading south into the piedmont of
VA and NC. A few things could keep these storms from being
stronger and/or more widespread here, and this includes
low and mid level capping. This was evident even on this
morning`s RNK sounding and is partly why cumulus fields and
convection are having a hard time developing today. Expect it
to be evident once again on tomorrow morning`s sounding.

Other reasons convection may struggle include the amount of dry
air in the atmosphere and relatively weak shear and instability.
That said, brief heavy rainfall could lead to urban and small
stream flooding, and inverted-V sounding profiles support
isolated damaging downbursts. This activity should weaken after
dark.

Highs Saturday will warm into the mid 70s to the low 80s...with
a few mid 80s possible in urban areas.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 200 AM EDT Friday...

Key Messages:

1) Confidence is moderate for a chance of showers and
thunderstorms on Saturday.

2) Drier weather may be possible on Sunday, but more showers
and thunderstorms may return in the mountains by Monday.

Although an upper level ridge will try to nose eastward from
the southern Plains on Saturday, it will be blocked from
advancing further as a shortwave trough dips southeastward from
the Great Lakes. This shortwave trough should spark a chance of
showers and thunderstorms with the highest chances north of
Route 460. Some weak ridging may arrive by Sunday to bring drier
weather. However, the flow should turn towards the east as high
pressure from the New England states wedges against the eastern
slopes of the Blue Ridge. A cold front is forecast to move
eastward from the central Plains by Monday to bring increasing
chances of showers and thunderstorms west of this high pressure
wedge. After a milder weekend, temperatures may dip a little
lower on Monday due to the rise in cloud cover.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 200 AM EDT Friday...

Key Messages:

1) Confidence is moderate for a daily chance of afternoon
showers and thunderstorms as a cold front approaches.

2) The timing of the eventual frontal passage still remains in
doubt due to large uncertainty in the models.

There are still notable timing discrepancies among the models
regarding an eventual frontal passage later this week.
Nevertheless, with a cold front approaching the Appalachian
Mountains during Tuesday and Wednesday, the chance of showers
and thunderstorms will continue and become more widespread. The
flow should eventually turn towards the south and erode a
lingering wedge of high pressure east of the Blue Ridge, but it
is likely that this erosion process will not happen quickly.
Despite the aforementioned timing discrepancies, the best model
consensus seems to suggest a frontal passage perhaps by
Thursday. Lingering chances of showers were kept through
Thursday in case this model consensus is still too fast.
Temperatures will remain near or slightly below seasonable
values.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
As of 130 PM EDT Friday...

Areas of IFR to LIFR stratus/fog were still dissipating as of
noon. Enough heating has taken place to lift and scatter out
most of it, and trigger cumulus clouds to develop. Isolated
SHRA/TSRA had developed as well. Forcing is quite lacking
today, so not expected much impact at all, even compared to
yesterday. Coverage is low but convection may briefly impact
area terminals. Areas of IFR fog and stratus are likely to
redevelop tonight across the lower Mid-Atlantic and may take
until midday Saturday before burning off.

More widespread SHRA/TSRA is expected Saturday with most of the
stronger storms to our north and northeast, however gusty winds
and heavy downpours will be possible, especially for the
mountains (BLF/LWB followed by KBCB and KROA) beginning around
21/17Z, and moving into the piedmont of VA (KLYH and KDAN) later
in the afternoon.


EXTENDED AVIATION OUTLOOK...

Isolated to widely scattered showers and thunderstorms are
expected again Sunday afternoon/evening. Otherwise, VFR during
the day then areas of MVFR/IFR fog and stratus at night.

Daily chance of showers, thunderstorms, and lingering sub-VFR
conditions continue Monday through at least midweek as a slow-
moving cold front approaches from the west.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...NF
NEAR TERM...SH
SHORT TERM...PW
LONG TERM...PW
AVIATION...SH