Potomac, Maryland 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

574
FXUS61 KLWX 261357
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
957 AM EDT Sat Jul 26 2025

.SYNOPSIS...
A weak frontal boundary will drop into the region today and
linger through early next week before eventually fizzling out.
A stronger cold front will push through during the middle of the
next week, leading to a more substantial air mass change
towards the end of the week into next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A Heat Advisory is in effect from Noon to 7PM today for
portions of the I-95 corridor spanning from Spotsylvania County
to southern Fauquier Counties in VA. Hot temperatures and high
humidity will yield heat index values around 105 in areas within
the Heat Advisory. The KIAD 12Z sounding this morning already
measured plenty of moisture (PWATS 1.73 inches) and instability
(SBCAPE nearing 1000 J/kg). Scattered showers and thunderstorms
remain possible this afternoon and into the evening. No other
changes were made to the forecast with the previous forecast
discussion below.

Today will start fairly quiet and humid with temperatures a few
degrees cooler than we saw on Friday and heat indices a couple
of degrees cooler than Friday as well. Heat indices may get
close to advisory criteria in eastern parts of the Virginia
Piedmont and eastern Virginia, particularly near the
Fredericksburg area. For now, have held off on Heat Advisories
at this time, but it will be very close. Main question was how
cloudcover will impact temperatures during peak heating. As
always with this time of year, even though we may not quite hit
Advisory criteria, it will still be very hot, so take plenty of
breaks and stay cool and hydrated today.

Additionally, chances for showers and thunderstorms will
increase today as a weak frontal boundary drops south into the
region. Scattered heavy convection in the form of showers and
strong to possibly severe thunderstorms are anticipated to
develop this afternoon/evening as a result of this boundary
colliding with very warm and humid air that remain entrenched
across our area. While any given location could encounter
showers or a thunderstorm today, a few isolated spots could
receive 1 to 2 inches of rain in a short period of time,
frequent lightning, wind gusts to 50 mph or all of the above.
SPC has much of our region in a Marginal Risk for Severe
Thunderstorms on Saturday into Saturday night. High temperatures
lower 90s for most, with heat indices in the low 100s.

Going into this evening, the lingering boundary and continued
humidity will likely allow for some showers and storms to
continue well into the overnight hours. Low temperatures will
only drop down into the mid 70s overnight. As any showers do
come to an end, fog looks likely to develop, especially in areas
that get rain during the day. Current model guidance is really
hitting central VA, especially east of the Blue Ridge. There is
the potential that some patchy Dense Fog could develop into
Sunday morning in those areas.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As we get into the day Sunday into Sunday night, a more active
shower and thunderstorm day is anticipated for most as a more
potent piece of shortwave energy pushes through the region from
the northwest. The aforementioned frontal boundary remains
stalled nearby and continues to interact with a hot and humid
air mass. There is a possibility that thunderstorms could become
strong to severe once again as they generate in or around this
heat and humidity. The main threats will be torrential rainfall
rates, frequent cloud-to-ground lightning, and damaging wind
gusts.

The front may dissipate to the south by Monday, allowing weak
surface high pressure to build across the area. Forcing will be
nebulous, so thunderstorm chances appear to be relatively lower and
focused on the diurnal terrain circulations. However, we will be in
northwest flow aloft around the mid-CONUS ridge, so will have to be
mindful of any remnant MCVs that could provide an extra source of
lift.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Warm and humid conditions continue through midweek as surface high
pressure remains over the forecast area. A cold front will slowly
approach from the northwest through Wednesday, before moving through
the area on Thursday. This will yield daily afternoon shower and
thunderstorm chances Tuesday through Thursday. As the cold front
settles over the Carolinas, precipitation chances will linger in the
southern portions of the forecast area Friday. Conditions dry out in
the northern half of the forecast area Friday afternoon and through
the overnight as surface high pressure builds in from the Great
Lakes.

In addition to the daily thunderstorm chances, the main story of the
long term period will be the summertime heat. High temperatures
Tuesday and  Wednesday will be in the 90s for most with higher
elevations staying in the upper 80s. Dewpoint temperatures in the
low/mid 70s will yield heat indices of 100-105 for most of the lower
elevations. Heat indices could reach 110 east of the Blue Ridge,
mainly on Tuesday afternoon.

High temperatures cool on Thursday in the wake of a cold front, with
highs in the 80s (70s mtns) expected. Heat indices fall below
criteria level, with values in the 80s and 90s. High temperatures
continue to cool on Friday with highs in the 70s to low 80s across
the area.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
Showers and thunderstorms are expected to develop this afternoon
through this evening as a front drops through the region amidst
very warm and humid air. While the overall condition today is
expected to be VFR, could see some reductions if storms hit a
terminal directly. Torrential rainfall (1-2"/hour), frequent
lightning, and wind gusts up to 50 mph will all be threat this
afternoon. These will be scattered in nature though, so exact
impacts on any one given terminal are still somewhat uncertain,
so kept the PROB30 groups in. For MRB, certainty is higher
though, so did a prevailing group with a tempo for more intense
storms. later TAF AMDs may be able to hone in on the threat a
little better.

IFR CIGS seem likely tonight across much of the region as low-
level moisture increases and becomes trapped beneath the
inversion. Could even see some dense fog in areas, but not sure
if that will impact any of the terminals at this time.

More showers and gusty thunderstorms are expected Sunday as a
more potent piece of upper-level energy traverses the region.
Expect the same threats as we see today, but with a bit more
certainty. Expect this activity to show up with the afternoon
TAF package.

On Monday, the upper ridge begins to build back overhead, which
could lead to a decrease in thunderstorm coverage. However,
there does appear to be a disturbance moving around the eastern
edge of this ridge, which could bring storms to MRB and CHO.

Flight restrictions are possible Tuesday and Wednesday afternoon due
to shower and thunderstorm chances. Otherwise, prevailing VFR
conditions are expected across all terminals. Northwesterly winds
blow 5 to 10 knots each afternoon before becoming light and variable
overnight.

&&

.MARINE...
The only marine hazards that are anticipated will be Special
Marine Warnings that could be issued pending heavy showers and
strong to severe thunderstorms this afternoon and evening. This
will be a threat again on Sunday afternoon and evening with a
more potent upper-level disturbance traversing the region and
interacting with the stalled frontal boundary.

Monday may remain mostly dry over the waters as the upper ridge
begins to build back into the region. There is a slight chance
that a disturbance around the eastern periphery of the ridge
moves over the water, but keeping chances below 30 percent for
now, as this activity should remain over the higher elevations.

Daily shower and thunderstorm chances may lead to hazardous
conditions over the waters Tuesday and Wednesday afternoon. SMWs may
be needed if storms become strong to severe. Otherwise, winds remain
below SCA criteria both days, blowing out of the northwest both
days.

&&

.TIDES/COASTAL FLOODING...
Tides will be on the gradual rise throughout the weekend and
could reach Minor Flooding at the sensitive sites like Annapolis
by Sunday night into early Monday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...Heat Advisory until 7 PM EDT this evening for VAZ050-051-
     055>057-502.
WV...None.
MARINE...None.

&&

$$

SYNOPSIS...CJL
NEAR TERM...AVS/CJL
SHORT TERM...LFR/CJL
LONG TERM...AVS
AVIATION...AVS/CJL
MARINE...AVS/CJL
TIDES/COASTAL FLOODING...LWX