Shenandoah, Virginia Weather Forecast Discussion

454
FXUS61 KLWX 200615
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
215 AM EDT Sat Sep 20 2025
.SYNOPSIS...
Surface high pressure wedges south from eastern Canada and northern
New England today while a backdoor cold front stalls across the
western Alleghenies and southwest Virginia. Scattered slow moving
showers and thunderstorms will accompany the boundary over the
drought stricken mountain areas with dry conditions further east.
Wedging high pressure remains overhead Sunday with a warm front set
to lift through the area Monday. Widespread precipitation chances
arrive with a slow moving cold front by the middle of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
Broad high pressure wedges in from northern New England and eastern
Canada today shunting a backdoor cold front south and west of the
region. The associated front eventually stalls in the vicinity of
southwest and south-central Virginia bending back across the
Alleghenies later this afternoon. With the boundary nearby expect
increased chances for shower and thunderstorm activity mainly over
the Alleghenies and south/central Shenandoah Valley. This is in
association with a piece of shortwave energy that looks to traverse
the boundary from west to east later this afternoon and evening.
Continuing to run 30-50 percent PoPS over the aforementioned
areas above with hi-res CAMS focusing over the Allegheny
Highlands (Highland, Pendleton, western Grant, and western
Augusta counties) as the area of greatest concern for scattered
shower and thunderstorm development. Storms look to be slow
moving and perhaps tied to the terrain given weak/veering
upslope flow and shear at less than 25 kts. Any rain will be
welcomed especially over the Alleghenies and Shenandaoh Valley
where moderate to severe drought conditions persists. Elsewhere,
dry conditions prevail with partly cloudy skies expected.
Clouds will likely increase late in the day and during the
evening hours as the shortwave disturbance passes to the south.
Once again the bulk of any shower and thunderstorm activity will
remain west of the Blue Ridge with a few showers making it as
far east as southern MD given the current trends amongst 00Z hi-
res guidance. Some western mountain locations mentioned above
could pick up a quick 1-2 inches of rain with locally heavier
amounts possible if convection locks onto the terrain.
Highs today will be back around normal for this time of year in the
upper 70s and low 80s (low to mid 70s mountains). Lows tonight will
fall back into the upper 50s and low 60s as a maritime airmass takes
hold especially east of the Blue Ridge. With wedging high pressure
and a front nearby expect a subtle pressure gradient over the
region. This will result in wind gusts of 10 to 20 mph mainly over
the ridges and near the waters this afternoon into early evening.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
1030mb high pressure will remain anchored over the Gulf of Maine
while wedging south along the eastern face of the Appalachians
Sunday. Meanwhile, the associated stalled boundary to the south will
wash out over central and southern portions of Virginia before
retreating back to the north as a warm front Sunday night into
Monday. Onshore flow will ensue prior to the warm frontal passage
yielding cooler temperatures and increased low level cloudiness
across the region. Some patchy drizzle and light shower activity
also cannot be ruled out, especially east of the Blue Ridge although
confidence in this has lowered given the proximity of the
dissipating front and an area of low pressure further offshore.
Highs Sunday will range from the low to mid 70s across the
mountains and northeast/central MD to upper 70s across central
VA. The stratus looks to hold tough across most of the area
throughout the day likely eroding across central/eastern VA and
the western Alleghenies Sunday afternoon and evening as a warm
front lifts northward into the region.
The warm front continues to lift north Sunday night into Monday
while surface high pressure shifts off the northern New England
coast. As a result, expect the wedge to continue to erode as
southerly return flow takes over yielding warmer temperatures and
increased moisture across the region. Lows Sunday night will fall
back into the upper 50s and low to mid 60s. Some fog cannot be ruled
out especially in areas where the stratus clears outs. Highs Monday
will climb back into the upper 70s and low to mid 80s (low 70s
mountains). A shower or thunderstorm cannot be ruled out west of I-
81 given the proximity of the warm front and piece of shortwave
energy riding to the north. Coverage will be spotty to scattered
given the residual dry air leftover from high pressure
departing offshore. Any mountain shower and thunderstorm
activity will come to an end by Monday evening with lows Monday
night falling back into the upper 50s and low to mid 60s.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
An upper-level trough will eject into the central plains early next
week before becoming cut-off through the middle to later portions of
the week over the Ohio Valley. How this feature evolves as it moves
eastward is uncertain in models/ensembles. A cold front will drop
through the area on Wednesday. What is certain is daily rain chances
in the form of showers and thunderstorms. Greatest coverage is
likely later in the week as the upper level system and associated
sfc features move through the Mid-Atlantic. At this time, rainfall
looks in large beneficial, but it will be worth keeping an eye on
the higher-end ensemble solutions that could result in isolated
hydro issues. Still plenty of time to figure out.
In terms of temperatures, above average Tuesday and Wednesday ahead
of the cold front, then likely below average as more clouds and rain
exist later in the week. Nighttime lows a tad above average through
the period.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected to continue through the 18z/2pm TAF
period. Wedging high pressure will build south from northern New
England while a cold front remains stalled south and west of the
area. The stalled front will lead to temporary sub-VFR reductions
over portions of the southern Shenandoah Valley and Allegheny
Highland terminals (i.e SHD, ROA, LWB, and CHO) this afternoon and
evening. Did add a PROB30 in for CHO this afternoon for spotty to
scattered shower and thunderstorm development along the stalled
front as a ripple of energy moves through (between 20-00z/4-8pm).
Elsewhere, dry conditions will prevail with mostly sunny to partly
cloudy skies to start and increasing clouds this evening as onshore
easterly flow increases. Light northeast winds this morning will
shift to the east this afternoon at 5 to 15 kts. With a subtle
pressure gradient in place between the front stalling to the south
of the area and wedging high pressure to the north expect gusts
between 10-15 kts this afternoon and evening mainly at terminals
along the ridges and close to the water. Sub-VFR conditions look to
return as early as this evening and especially tonight as onshore
flow increases.
Low level clouds (i.e stratus) will lead to sub-VFR conditions
especially at terminals east of the Blue Ridge Sunday into Sunday
night. Some light drizzle and showers cannot be ruled out although
confidence remains low. VFR conditions return Monday into Tuesday as
a warm front lifts through the region. A shower or thunderstorm
cannot be ruled out west of a line from KHGR/KMRB to KCHO as the
warm front lifts north and several pieces of energy pass to the
north and west of the region. This may lead to temporary sub-VFR
reductions on Monday afternoon. The front combined with high
pressure moving offshore will shift the winds from the east on
Sunday back to the south Monday. Expect gusts between 10 to 15 kts
mainly during the afternoon and evening hours (especially at
terminals near the waters and along the ridges).
Southwest winds on Tuesday, blowing around 5 to 10 kts. There is a
chance for showers and thunderstorms across all terminals on Tuesday
but even more so Wednesday with the cold frontal passage with sub-
VFR conditions possible. Behind the cold front, winds become
westerly than northerly but generally less than 10 kts.
&&
.MARINE...
One or two SCA level gusts have been observed across the northern
bay this morning due in part to northerly channeling behind the
departing backdoor cold frontal boundary. The front will stall south
of the waters this afternoon with winds turning back toward the
northeast and easterly direction. SCA conditions are possible over
the open waters of the bay and tidal Potomac tonight into Sunday
with increased onshore easterly flow. This is due in part to a
tightened pressure gradient between wedging high pressure to
the north and a dissipating front that will lift north as a
warm front Sunday into Monday. High pressure shifts offshore
Monday while the warm front lifts north of the waters. This will
lead to southerly channeling and an additional period of SCA
conditions Monday night into Tuesday morning.
There is a chance of showers and thunderstorms across the waters on
Tuesday and especially Wednesday with cold frontal passage. Winds
remain out of the south Tuesday, but become westerly then northerly
Wednesday. Could have marginal SCA conditions depending on gradients
midweek.
&&
.TIDES/COASTAL FLOODING...
Northeasterly winds will lead to decreasing tidal anomalies
through this morning`s high tide cycle. Sensitive locations
including Annapolis, Straits Point, and Alexandria may reach
action stage during the higher tide cycles, but are not expected
to reach minor flood stage. Tide levels may increase Sunday as
onshore easterly flow increases. Additional increases are
possible Monday as high pressure pushes offshore and southerly
winds return blocking excess water from leaving the bay.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...EST
LONG TERM...CPB
AVIATION...CPB/EST
MARINE...CPB/EST
TIDES/COASTAL FLOODING...LWX

NWS LWX Office Area Forecast Discussion