405
FXUS61 KLWX 150749
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
349 AM EDT Tue Sep 15 2026
.WHAT HAS CHANGED...
The forecast remains on track with temperatures cooling rather
quickly early this morning given Canadian high pressure in
place. The biggest uncertainty in the period is late this
weekend into early next week. A number of complex features will
hopefully become better resolved in the next couple of days.
&&
.KEY MESSAGES...
- 1) Remaining cool today, with shower and thunderstorm chances
returning late in the week and into the weekend.
&&
.DISCUSSION...
KEY MESSAGE 1...Remaining cool today, with shower and
thunderstorm chances returning late in the week and into the
weekend.
The influence of Canadian high pressure is well underway with a
marked fall in temperatures and dew points over the region.
Relative to 24 hours ago, most locations have seen such readings
fall by around 10 to 15 degrees. This translates to early
morning temperatures that will start off in the upper 40s to
50s, locally into the mid 40s along the Allegheny Front. With
low-level moisture being trapped within nocturnal radiation
inversions, some patchy fog may materialize before daybreak.
This would occur around the usual vulnerable locations like
river valleys and other low-lying areas.
With a broad 1026-mb surface anticyclone anchored over the
northeastern U.S., expect conditions to be fairly similar to
yesterday/Monday. The one major difference will be the marked
reduction in winds given weak gradients within the influence of
this dome of high pressure. Today`s high temperatures are
forecast to reach the mid 70s to low 80s (upper 60s to low 70s
in the mountains). This comes with continued low humidity with
dew points mainly in the upper 40s to low 50s. Aside from some
passing high cirrus, abundant sunshine is expected throughout
the day. Light southeasterly gradients will favor an uptick in
overnight temperatures. While still cooler than recent days,
most can anticipate lows in the mid 50s to low 60s (mildest
along the I-95 urban areas as well as near the Potomac River and
Chesapeake Bay shorelines).
Behind an exiting longwave trough that pushes into the Canadian
Maritimes, mid/upper heights begin to build in earnest. An
expansive 594-dm mid-level ridge initially over the southern
U.S. will flex northward in time. These above average heights
remain a fixture in the forecast through Thursday. This supports
a return of warmer temperatures along with building humidity
levels. Daily highs push back into the mid/upper 80s, locally
reaching the low 90s in the warm spots. The return of the
humidity also favors milder nights with widespread lows in the
60s. Any shower and thunderstorm chances should hold off until
Thursday given the stout ridge aloft quelling most precipitation
chances. Most models keep such a threat mainly west of the
Shenandoah Valley, especially closer to the Alleghenies.
A high latitude trough digging across southeastern Canada should
be enough to nudge the upper ridge back toward the south-central
U.S. This allows a cold front to push through early Friday
which again brings a gradual cool down with decreasing humidity
into Saturday. However, this reprieve is somewhat brief as
additional disturbances in the atmosphere track toward the area
late in the weekend. The overall jet pattern turns a bit more
complex as an array of features enter the picture. A broad
upper low retrogrades across the Gulf of America. At the same
time, a myriad of shortwaves will eject across the central U.S.
toward the Mississippi Valley. How these impulses behave along
with where surface features reside will dictate any local
weather impacts. However, all signs point toward a more active
pattern on Sunday into early next week.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Canadian high pressure will support VFR conditions through mid-
week. Weak gradients keep lighter winds than yesterday/Monday,
with winds gradually shifting from east to southeasterly today.
This ridge eventually edges toward the Atlantic coastline which
will support mainly southerly winds on Wednesday into Thursday.
Some storm chances emerge by Thursday, but these are currently
expected to stay west of the area terminals.
A cold front moves through early Friday which results in some
uptick in shower chances. This may come with a few restrictions
if convection becomes more pronounced. In the wake of this
frontal passage, winds turn more northerly with afternoon gusts
to around 15 knots or so. High pressure building to the north
results in a east to southeasterly wind for Saturday. This comes
with likely VFR conditions.
&&
.MARINE...
While most land observations have seen winds turn light, the
cooler air overriding the warm waters have maintained a breezy
northeasterly wind early this morning. Small Craft Advisories
continue over the southern waters through 7 AM with gusts to
around 20 to 25 knots. Across the middle Chesapeake Bay, gusts
occasionally approach 20 knots, but these are more sporadic and
infrequent in nature. However, gradients weaken through the day
with gusts around 5 to 10 knots.
Thereafter, high pressure slowly pushes away toward the coast
which results in a south to southeasterly wind for Wednesday and
Thursday. Some southerly channeling effects may necessitate
Small Craft Advisories for parts of Thursday, especially across
southern sections of the Chesapeake Bay. A cold front tracks
across the waters on Friday morning which favors a shift to
north to northeasterly winds. These could near advisory
criteria, but confidence is low. High pressure passing by to the
north will result in a shift to east-southeasterlies for
Saturday. Gusts up to 15 to perhaps 20 knots are possible.
&&
.TIDES/COASTAL FLOODING...
Current tidal anomalies remain around zero feet. However, expect
a gradual rise in water levels later today as high pressure
pulls away from the Eastern Seaboard. This again pushes a number
of sites into Action stage during the higher of the two
astronomical high tides, particularly tonight and again late
Wednesday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 7 AM EDT this morning for ANZ534-
537-543.
&&
$$
DISCUSSION...BRO
AVIATION...BRO
MARINE...BRO
TIDES/COASTAL FLOODING...BRO
NWS LWX Office Area Forecast Discussion