Arlington, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

148
FXUS61 KLWX 021929
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
329 PM EDT Sun Aug 2 2026

.WHAT HAS CHANGED...
With convection forming earlier than expected, have made
multiple updates to the forecast package to include this earlier
timing. This has especially impacted the aviation forecasts for
the 6 terminals across the region. Flood Watches remain in
effect from the Blue Ridge westward.

&&

.KEY MESSAGES...
- 1) Repetitive rounds of locally heavy showers and
  thunderstorms could lead to instances of flash flooding
  through Monday.

- 2) Additional shower and thunderstorm chances Tuesday into the
  upcoming weekend ahead.

&&

.DISCUSSION...
KEY MESSAGE 1...Repetitive rounds of locally heavy showers and
thunderstorms could lead to instances of flash flooding through
Monday.

Relative to high-resolution model guidance, convection has
filled out the region much earlier than anticipated. As of the
mid-afternoon hours, a swath of heavier showers and
thunderstorms are currently working their way across southern
Maryland up toward the Baltimore metro area. A number of
mesoscale circulations continue to form along this wavy line;
however, none have warranted any convective-based warnings at
this time. This activity should reach the Chesapeake Bay and
north of the Mason-Dixon Line within the next hour.

As this complex of showers and thunderstorms exit off to the
east, the upstream environment will need to continue to be
monitored. The 17Z RAP objective analysis indicates instability
has not been fully exhausted as 1,000 to 2,000 J/kg of surface-
based CAPE (uncapped) remains. In fact, the KLWX radar shows
additional cells percolating just north of I-64 in central
Virginia. These are largely forming within breaks in the low
clouds where instability has been maximized. Expect these to
follow a similar north to north-northeastward path over the next
couple of hours. For the Blue Ridge westward, overall
conditions have been quieter for the most part. Flood Watches
remain in effect for the threat of flash flooding through much
of this evening. While high-resolution models have struggled
with this event, there is a signal for convection to fill in
where the Flood Watch exists.

Today`s thunderstorms will all carry a risk for heavy rainfall
given precipitable water (PWAT) values ranging from 2 to 2.25
inches. Sitting near record numbers certainly supports the
torrential downpour potential. Earlier activity which moved
across I-95 in Virginia produced 2 to 2.50 inches in about 90
minutes. This may warrant an expansion of the current Flood
Watch depending on whether locations experience additional
rounds of storms. Besides the convective threats, it will be a
warm and humid day with highs topping out in the low/mid 80s.
Did bring temperatures down a tad given the dense low clouds
over much of the region. Off and on again showers continue into
the night with forecast lows in the mid 60s to low 70s. Despite
thick cloud cover overnight, some patchy fog may develop in
areas that see winds go calm or feature plenty of ground water
from earlier rainfall.

The upper low/trough responsible to the shift to active weather
will track from the Ohio Valley toward the northeastern U.S.
through Monday. Relative to previous days of model runs, there
has been a shift to a more progressive regime. The accompanying
cold front works its way to near the I-95 corridor on Monday
afternoon. This system will continue to have access to highly
anomalous tropical moisture with similar PWATs to today. A flash
flood risk exists along/east of I-95, particularly for areas
impacted by recent heavy rainfall. Forecast highs on Monday
should again reach the low/mid 80s, with mainly 70s across
mountain locales. While post-frontal winds become northwesterly,
humidity levels remain elevated into the night with lows in the
60s to low 70s (mid/upper 50s across the higher terrain).


KEY MESSAGE 2...Additional shower and thunderstorm chances
Tuesday into the upcoming weekend ahead.

It`s a typical summertime regime for remainder of the workweek into
the upcoming weekend as we sit within the warm sector. Synoptically,
we are still monitoring the progression of an upper level low
pressure system over the Ohio River Valley/central Appalachians.
This system will be slow to push eastward heading into the upcoming
weekend. At the surface, is a stalled boundary that will act as a
catalyst for several pieces of shortwave energy to move along
yielding increased chances for showers and thunderstorms during the
diurnal periods each day.

Tuesday appears to be the driest day of the next 7 days as the front
stalls down across central and southeast Virginia with weak high
pressure building over north-central PA. Storm chances look to
increase Wednesday through late week as pieces of shortwave energy
pivot across the trough with mid level flow increasing to 30-40 kts
between the stalled front over the Great Lakes and stalled front to
our south. The warm and moist airmass combined with these passing
waves of energy will yield greater thunderstorm coverage especially
during the afternoon and evening periods Wednesday through Sunday.
Right now, confidence remains low for severe weather based on
coverage, magnitude, and timing during the period. SPC does have a
mention for severe weather during the Thursday through Sunday period
due to increased instability and mid level flow (30-40kts). This
aligns with 15-30 percent probabilities from medium range machine
learning outputs during the same timeframe. Based on current 6z/12z
outputs, any focus for severe weather would be on Thursday west of
the Blue Ridge and again Friday into Saturday as a weak front slides
through. Main threats with storms would be damaging winds and
locally heavy rainfall leading to instances of flash flooding given
PWATs around 2 inches. Current drought conditions should help us
avoid widespread flooding woes although poor drainage and urban
areas will be the most susceptible over the coming days ahead.

Expect oppressive humidity with seasonable temperatures in the mid
80s and low 90s. The increased humidity combined with some sunshine
Wednesday through Saturday will yield heat indices in the mid 90s
to low 100s each afternoon east of the mountains.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
With convection migrating further east than expected, convection
has impacted the D.C. and Baltimore terminals much earlier in
the day. Aside from KBWI and KMTN, any nearby lightning has
waned. While convection has weakened across northeastern
Maryland, will keep the convective TEMPO groups through 20Z.
Otherwise, have shifted from TEMPO back to PROB30 groups for
later this afternoon given a more questionable setup in the
wake. Low clouds also remain a fixture in the forecast with TAF
sites teetering between VFR and MVFR. Some showers linger into
the night with IFR ceilings possible as the boundary layer
stabilizes.

For Monday, low ceilings continue in the morning before another
round of storms look likely during the afternoon/evening hours.
This is especially the case for areas along/east of U.S. 15.
Have placed PROB30 groups for the threat of restrictions due to
thunderstorms. Winds shift from southerly over to northwesterly
on Monday evening behind the associated cold front.

Expect periods of sub-VFR conditions to continue at times
Tuesday through the upcoming weekend given increased chances for
showers and thunderstorms. The greatest coverage storms will be
during the afternoon and evening hours each day. North to
northeast winds Tuesday switching to the south and southeast for
the remainder of the workweek.

&&

.MARINE...
Given southerly channeling effects, Small Craft Advisories
remain in effect across all waters. Aside from the upper/middle
tidal Potomac, these remain in place through the overnight
hours. Aside from gradient wind gusts, convection has become
rather widespread this afternoon. Stronger storms will require
Special Marine Warnings through this evening, some of which
could include the threat for waterspouts given some low-level
wind shear. A stabilizing boundary layer should limit convective
gusts into the overnight hours.

Southerly gusts decrease to around 10 to 15 knots for much of
Monday, although some upticks could approach advisory levels at
times. Otherwise, another round of stronger storms are possible
during the afternoon/evening hours. Further Special Marine
Warnings may be necessary which would lend itself to hazardous
boating/swimming conditions.

Sub-SCA level winds are expected out of the north and northeast
Tuesday. SCA level southerly channeling is expected Wednesday
through Friday for portions of the waters. A few showers &
thunderstorms are possible over the waters during this period due to
a stalled front nearby. SMWs may be needed to encompass this threat
during the afternoon and evening hours.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies will continue to remain elevated through much
of the Monday before dropping Tuesday due to a wind shift.
Additional coastal flooding is possible at times of high tide as
sensitive locations as a result. Anomalies climb again mid to
late week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 8 AM EDT Monday for MDZ008.
     Flood Watch through late tonight for MDZ501-502-509-510.
VA...Flood Watch through late tonight for VAZ503-504.
     Flood Watch from 2 PM EDT this afternoon through late tonight
     for VAZ025>027-029-036>040-507-508.
WV...Flood Watch through late tonight for WVZ050-055-501>506.
MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ530>534-
     537>543.
     Small Craft Advisory until 11 PM EDT this evening for ANZ535-
     536.

&&

$$

DISCUSSION...BRO/EST
AVIATION...BRO/EST
MARINE...BRO/EST