Aldie, Virginia Weather Forecast Discussion

179
FXUS61 KLWX 221932
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
332 PM EDT Mon Sep 22 2025
.SYNOPSIS...
High pressure will weaken into the night while a warm front
remains north of the region. An area of low pressure and its
associated cold front will eject out of the Central Plains and
Upper Midwest toward the Ohio Valley Tuesday into Wednesday.
The front will be slow to cross the area with a series of low
pressure systems traversing the boundary through at least
Friday. High pressure gradually builds in from the west by later
in the weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
High pressure currently extends from the Carolinas up along the
Eastern Seaboard into the Canadian Maritimes. The resultant east
to southeasterly flow has supported the extended nature of a cold
air damming (CAD) wedge in the lee of the Blue Ridge. This
regime has maintained a low stratus deck across areas east of
the Blue Ridge to just west of I-95. However, GOES-19 visible
satellite imagery trends over the past hour do show multiple
breaks in this stagnant cloud shield. As winds continue to shift
to southerly, expect this stratus deck to fully erode within the
next hour, if not sooner.
It is truly the tale of two forecast regimes as cumulus towers
continue to bubble up west of the Shenandoah Valley. Some of
these have matured into locally heavy showers, but with no
lightning activity detected at this time. Based on the poor
mid-level lapse rates (4.5 to 5.5 C/km) noted in the 17Z RAP
objective analysis, this is likely contributing to weakening
ascent for these updrafts. This seems to support the 12Z high-
resolution models which indicate the I-81 corridor acting as the
eastern terminus to this activity. The most mature of these
showers could prove to be gusty wind producers, but heavy rain
is likely the biggest threat given precipitable water values
approaching 1.50 inches. All activity gradually winds down
heading into the evening hours. This results in a dry period for
the overnight hours.
Regarding temperatures, it has been a much warmer day between
the Alleghenies and Blue Ridge given ample daytime heating. Many
observations have pushed into the low/mid 80s, particularly
across the Allegheny mountain valleys to just west of I-81. This
is accompanied by seasonably humid conditions as dew points have
risen into the low/mid 60s. To the east of the Blue Ridge, the
presence of extensive cloud cover and bay/river influences have
kept temperatures in the 70s. Given renewed clearing, expect
readings to jump another few degrees before cooling off into the
evening. Tonight`s forecast calls for lows in the upper 50s to
low 60s. With ample low-level moisture and light winds, some
patchy fog is possible from I-81 and points westward.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
The coverage of showers and thunderstorms will increase within
this summer-like pattern. A complex upper pattern sets up with
multiple players involved in this evolution. The key features to
note are an evolving closed low across the Great Lakes and a
positively-tilted trough over the central U.S. As the latter
system slides eastward, ample perturbations in the low-amplitude
flow approach the eastern U.S. By mid-week, this pair of systems
gradually becomes adjoined while treking through the Upper
Midwest into the Missouri Valley.
At the surface, any associated frontal features will remain west
of the local area through at least mid-week. However, it does
appear a lee trough forms each day which should act as an
impetus toward convective development. On Tuesday, with high
temperatures warming into the mid 80s and dew points hitting the
mid/upper 60s, surface-based instability (CAPE) values rise to
around 1,500 to 2,000 J/kg. Given deep-layer shear vectors of 20
to 30 knots, some storms could become fairly organized and
capable of damaging wind gusts. The 12Z high-resolution model
suite is supportive of this as shown by the cluster of 40 dBZ
paintballs. As such, the Storm Prediction Center has upgraded
to a Marginal risk from I-81 eastward. The potential for any
severe storms should wane with the loss of daytime heating.
Overnight lows fall back into the upper 50s to mid 60s which may
come with some patchy fog across areas hit by earlier rainfall.
Similar to Tuesday`s forecast, expect a decent coverage of
showers and thunderstorms on Wednesday. The eastward extent of
the approaching longwave trough nears the region which should
yield ample forcing for ascent. A lee trough also appears
present while the parent frontal waves sit back over the Ohio
Valley. Forecast temperatures are slightly cooler than the
preceding day, but it will remain plenty humid. While the NAM
nest can often produce robust solutions, its 60-hour forecast
(Wednesday early evening) certainly supports another active day.
Nights become milder in time with lows rising into the
mid/upper 60s along and east of I-95.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
A surface low pressure system tracking from the Great Lakes Region
towards New England Thursday and Friday will push the associated
cold front towards and across the forecast area at the end of the
week. Daily shower and thunderstorms chances are expected with
recent dry conditions yielding primarily beneficial rainfall. The
greatest chances for rainfall will be Thursday and Friday as the
front approaches and moves through the region, but precipitation
chances linger on Saturday as the front remains nearby offshore.
In the wake of the cold front, surface high pressure builds over the
Mid-Atlantic from the central CONUS. Conditions generally dry out
overnight Saturday into Sunday. The exception will be a slight
chance of showers Sunday afternoon due to lingering moisture.
Coverage is expected to be isolated in nature with most areas
remaining dry. Conditions continue drying into next week as high
pressure builds to the north.
High temperatures will be in the 70s to low 80s for most each day
with higher elevations staying in the 60s. Overnight lows will be in
the 50s to 60s each night.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Expect VFR conditions through tonight across all terminals. Any
convective activity is likely to weaken before reaching KMRB.
Radar trends support that but a stray decaying shower could
near the terminal through dusk. Some patchy fog is possible
overnight, but this should stay west of I-81.
Winds remain southerly into Tuesday, but with better
thunderstorm chances. Have introduced a PROB30 group for KDCA,
KIAD, and KBWI, which may include other terminals as they move
into this time range. Some restrictions are possible as this
convection rolls through during the late afternoon into
portions of the evening. Additional rounds of convection may
affect the area again on Wednesday, but details of coverage and
timing are more uncertain.
Shower and thunderstorm chances across the terminals Thursday and
Friday may lead to sub-VFR conditions. Southwest winds on Thursday
shift to northwest on Friday, blowing 5 to 10 knots each
afternoon.
&&
.MARINE...
High pressure gradually weakens into the night with southerly
flow prevailing. Some channeling effects are possible which may
bring gusts to near 20 knots. However, confidence is low in the
duration of any such advisory caliber winds.
Convective chances increase on Tuesday and Wednesday as an upper
trough slowly approaches from the central U.S. to Great Lakes
region. Those with marine interests can expect the potential for
gusty showers and frequent lightning, particularly during the
late afternoon to evening hours. Special Marine Warnings may
accompany any of the stronger thunderstorms. Outside of
convection, background southerly winds should top out below
advisory criteria through mid-week.
Southwest winds on Thursday shift to northwest on Friday, with Small
Craft Advisory criteria winds possible Thursday evening. Otherwise,
winds remain below SCA criteria. Showers and thunderstorms are
possible both days over the waters.
&&
.TIDES/COASTAL FLOODING...
Tidal anomalies have increased amidst easterly flow today.
Coastal Flood Advisories are in effect for Annapolis for the
upcoming tide cycle. Anomalies are forecast to hold relatively
steady today, so additional Advisories may be needed for
sensitive locations late tonight into Tuesday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory until 9 PM EDT this evening for MDZ014.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...BRO
NEAR TERM...BRO
SHORT TERM...BRO
LONG TERM...AVS
AVIATION...AVS/BRO
MARINE...AVS/BRO
TIDES/COASTAL FLOODING...LWX

NWS LWX Office Area Forecast Discussion