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000
FXUS61 KLWX 060131 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
931 PM EDT Sun Sep 5 2021

.SYNOPSIS...
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A cold front will cross the region from the northwest tonight.
High pressure will return later Monday into Tuesday. Another
cold front will progress through the area during the middle of
the week with high pressure building in by late in the work
week.
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&&

.NEAR TERM /THROUGH MONDAY/...

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Scattered showers are seen on radar mainly over southern MD
ahead of a frontal zone moving through central PA. Model
guidance show these showers exiting the forecast after 09Z with
cold front clearing the area around 12Z. However, clouds are
expected to persist a bit longer into the mid-late morning
hours. Only a Trace to a couple of hundredths of an inch of rain
are expected overnight.

Previous afd...

High-resolution models continue to show some local enhancement
in the activity overnight, generally from I-95 eastward. Most
notably, the 12Z NAM nest/HREF mean are showing such solutions
so have maintained higher chances for showers in this corridor.
All of this activity will be falling ahead of a eastward
propagating cold front. This frontal zone is forecast to exit
toward the Eastern Shore by Monday morning with winds shifting
to west-northwesterly through the day. Before this occurs, some
patchy fog may form in areas west of I-95, particularly along
the lower lying areas. Any fog should quickly burn off an hour
or so beyond sunrise. In the wake of the frontal passage, model
soundings general unidirectional west to northwesterly flow
which will raise temperatures a bit given downsloping effects.
This flow regime will combine with ample sunshine to bring highs
into the low to mid 80s. The usual cool spot is across the
mountains with mid 60s to low 70s being more likely.
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&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
High pressure will continue to build off to the west leading to
some cooler overnight temperatures. Expect lows in the low/mid
60s inside the I-95 corridor, with 50s in most other spots.
Numerical models show progressive flow aloft which allows a
shortwave ridge to sweep through on Tuesday ahead of a strong
system spinning over the Upper Great Lakes. Warm advection in
the open warm sector will maintain mild weather with another day
in the mid 80s and abundant sunshine. The dry forecast continues
into the night with southerly winds keeping temperatures on the
warm side. Compared to early September norms, lows will be
around 4 to 8 degrees above average.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Models are in agreement with an upper level trough moving over the
Great Lakes on Wednesday. At the surface, a region of low pressure
will form over Canada, with a cold front extending south through the
local region. Showers and thunderstorms are possible along the
front, however the spatial coverage remains in question. Guidance
has trended slower with the frontal passage, meaning temperatures on
Wednesday may be a few degrees higher than previously forecast.
Wednesday could be the only day over the next week with a chance of
high temperatures near 90 degrees, mainly along and east of I-95.
Given the slower frontal passage, CAPE will increase to 500-1000
J/kg. The modest CAPE and ample shear (40-45 knots), could support
organized storms along the front. The biggest uncertainty remains if
storms will actually form this far south due to the better dynamics
being offset towards New England. There is the potential for at
least an isolated strong to severe wind gust. Given the progressive
nature of the already moisture lacking front, do think the flash
flood threat is low/minimal.

The winds will turn northwesterly behind the front and a region of
Canadian high pressure will move in through the end of the week.
This will bring high temperaturesback to the upper 70s to near 80
for most (60s in the mountains). Temperatures moderate a few degrees
Saturday as heights rise.

Attention will need to be paid to two features in the tropics this
week and how they evolve (Hurricane Larry off in the Atlantic and an
area being monitored for potential development in the Gulf of
Mexico). Both of these feature are currently not anticipated to
cause direct impacts to our region through the long term.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
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Showers linger into the overnight, particularly across
terminals along and east of I-95. Some patchy nighttime fog may
develop around KCHO and KMRB.

Southerly winds will shift to west-northwesterly on Monday with
VFR conditions anticipated through Tuesday.

The winds will be southerly ahead of the cold front Wednesday. There
could be a period of sub VFR conditions Wednesday in any showers or
thunderstorms.VFR conditions return Thursday with light northwest
winds behind the front.
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&&

.MARINE...
Expect southerly channeling of the winds across lower sections
of the Chesapeake Bay and tidal Potomac. Small Craft Advisories
are in effect through tonight for this pattern. Conditions
should remain below SCA levels in the west-northwesterly flow
behind the front on Monday. The resurgence of southerly warm
advection on Tuesday will raise marine winds to near SCA levels
again by the evening into the overnight.

There could be a period of SCA winds Wednesday into early Thursday
along and behind the cold front. SCA conditions are not likely to
end the week as high pressure builds.

&&

.TIDES/COASTAL FLOODING...
Southerly flow will allow anomalies to remain high today, with
highest ones near heavy fresh water inflows such as the tidal
Potomac as well as the middle Chesapeake Bay. As winds turn
westerly behind a weak cold front later tomorrow, anomalies
likely drop a bit, and this will also be assisted by a slow
diminishment of freshwater inflow.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ534-543.
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&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...BRO
LONG TERM...CPB
AVIATION...LFR/CPB
MARINE...LFR/CPB
TIDES/COASTAL FLOODING...LWX