890
FXUS61 KLWX 160004
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
804 PM EDT Thu Aug 15 2024

.SYNOPSIS...
Dry weather is expected through tonight as the result of broad high
pressure nearby. Shower and thunderstorm chances return late Friday
into Friday night as a warm frontal boundary lifts in from the Ohio
River Valley. Additional showers and thunderstorms are likely this
weekend with a cold front slowly crossing the region. Shower chances
will linger into Monday before cool Canadian high pressure builds in
by the middle of next week.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 00Z/8 PM EDT, the Mid-Atlantic was dry with high cirrus
streaming overhead. These high clouds will likely continue to
move across through much of the night as surface high pressure
slowly moves further east offshore. This will allow a southerly
flow to build in overnight into Friday morning. Overnight lows
will drop down into the upper 50s across the Allegheny Front,
with 60s further east. A few weakening showers may approach the
Alleghenies around daybreak as a warm front approaches.

Shower and thunderstorm chances return from the west late Friday
as longwave troughing over the Great Lakes advances east and a
surface warm front lifts in from the Ohio River Valley. Ahead of
this system, expect increasing clouds with broad ascent and
height falls slowly spreading across the Mid-Atlantic region.
Meanwhile, high pressure will continue to kick off the New
England coast allowing for increasing moisture from southerly
low-level flow. The added moisture combined with the associated
warm front will lead to increased chances for scattered shower
and thunderstorm activity starting west of the Alleghenies
Friday afternoon before spreading east toward the Blue Ridge
Friday evening. Current 12Z/18Z deterministic and ensemble
guidance continues to hold this activity mainly west of I-95
through Friday evening with the bulk of widespread precipitation
chances coming through during the late evening and overnight
hours. As for severe weather, the threat remains low, but will
need to be watched given a warm front lifting into the region.
The flooding threat remains very low given several days of dry
weather leading up to this event combined with current drought
concerns. High temperatures Friday will remain near normal in
the mid to upper 80s east of the mountains with 70s over the
mountains. Low temperatures Friday night will drop into the 60s
to lower 70s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
By Saturday, activity should become more widespread as the warm
front will have lifted further north and ushered in a warmer,
moist airmass to work with. Showers and thunderstorms will be
most common for the afternoon and evening hours. Some storms may
be strong to severe but it is really going to be dependent on
the timing of a cold front expected to slowly approach the area
later in the day on Saturday. Should the timing not match up
with peak heating, severe chances diminish. As of now, there
should be enough instability around to spawn a few strong storms
later in the day. Highs will climb into the mid to upper 80s
for the afternoon and evening hours. Precipitation chances will
likely continue into Saturday night as the front slowly moves
through the Mid-Atlantic going into Sunday. Overnight lows will
drop down into the 60s west of the Blue Ridge, with low 70s more
common further east.

With the front slow to cross the region Sunday, expect
continued chances for showers and thunderstorms. No washouts are
expected with a focus during the afternoon and evening hours. A few
storms could be strong depending how warm and unstable it gets,
though modest shear and poor mid-level lapse rates lend
uncertainty to a more widespread severe weather episode.

Outside of the precipitation chances, mostly cloudy skies are
expected leaving high temperatures east of the Alleghenies in
the upper 70s and low to mid 80s. Shower activity will likely
linger along and east of US-15 toward the I-95 metros through
Sunday night as the front is slow to progress toward the coast.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
1) Continued precipitation chances through Monday as a slow
moving cold front and trailing shortwave trough slide east.

2) Near to slightly below normal temperatures expected through the
extended period.

Synoptically, not too much of a change as we continue to monitor a
slow moving occluded frontal system cross the region. Meanwhile,
eyes will turn toward the Atlantic as Hurricane Ernesto works its
way northward from Bermuda. The upper-level trough overhead and slow
moving front will help steer Ernesto away from our region and off
the East Coast heading into early next week. One indirect effect
will be for those traveling to the beaches where waves and rip
currents will likely increase into the middle part of next week.

It`s not until Monday when the front pushes offshore. Some
additional shower and thunderstorm chances may linger into Monday as
the upper-level trough swings through. Once again the focus will be
during the afternoon and evening hours starting in the west and
progressing eastward throughout the day. Skies will remain mostly
cloudy with clearing skies late as the trough exits east of the
area. High temperatures Monday will push back into the mid to upper
80s east of the Alleghenies with lows in the 50s and 60s. Winds will
switch to the west and northwest in the wake of the departing trough
Monday afternoon and evening.

A broad area of Canadian high pressure looks to settle over the
region Tuesday through Thursday leading to dry conditions and lower
humidity. Most locations will see high temperatures in the upper 70s
to low 80s which comes with dew points in the mid 50s to low 60s.
Overnight lows should fall into the upper 50s to mid 60s. For those
along the I-81 corridor and points westward, widespread low/mid 50s
are possible (upper 40s along the Allegheny ridges). Next chance for
rain comes late next week into next weekend as another front
approaches the region.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VFR conditions are expected through Friday. Winds will gradually
shift to southerly later tonight into Friday as surface high
pressure slides east. Rain chances increase west to east on
Friday, but precip likely doesn`t reach any of the main
terminals until Friday evening or later. Winds could gust 15-20
kts Friday afternoon.

Showers and thunderstorms are expected Saturday behind a warm
front and ahead of an approaching cold front, particularly in
the afternoon and evening. Similar to Friday, these could bring
restrictions to terminals, and gusts to 15-20 kts are possible
outside of thunderstorms before winds diminish overnight.

Shower and thunderstorm chances look to continue Sunday and Monday
as a slow moving cold front pushes through. This will lead to
additional sub-VFR restrictions at times especially during the
afternoon and evening hours when convection looks to peak. Outside
of the precipitation/thunderstorm threat, VFR conditions will
persist. Southerly winds with gusts up to 15 kts are possible Sunday
switching to the west and northwest Monday and Tuesday as the
front/upper-level trough exits offshore.

&&

.MARINE...
Winds will gradually turn southerly tonight into Friday as
surface high pressure slides east. Winds increase out of the
south on Friday and could reach SCA criteria as early as the
afternoon hours. Confidence in SCA level winds is highest over
the wider waters Friday night, which is when a SCA has been
issued; this may need to be expanded/extended. Winds could
still hover around SCA criteria especially over the southern
waters through Saturday afternoon and evening. Additionally,
showers and thunderstorms possible Friday night and Saturday
could bring stronger gusts to the waters. Stronger storms could
require Special Marine Warnings on Saturday.

Additional SCAs may be needed into Sunday as southerly channeling
looks to linger. The highest confidence for this will be over the
central and southern waters. Winds will decrease Monday while
switching to the west and northwest. SCAs may be needed Monday night
into Tuesday as the gradient tightens between the exiting trough and
incoming high pressure system.

Shower and thunderstorm chances loom through early next week, with
the greater coverage of storms likely on Sunday with the cold front
just off to the east. Thus, some hazardous conditions are expected
over the waters at times through Monday.

&&

.TIDES/COASTAL FLOODING...
With light winds becoming southerly tonight, sensitive tidal
sites (i.e., Havre de Grace, Annapolis, and D.C. Southwest
Waterfront) near Action stage during high tides (especially the
early morning higher astronomical tide) through Friday morning.
Expect an additional boost of the tidal anomalies as southerly
winds increase Friday into the weekend. At this point, the
forecast carries locations like Havre de Grace and Annapolis
into Minor coastal flooding by Saturday morning. This threat
likely persists further into the weekend with continued
southerly winds along and ahead of the approaching cold front.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory from 6 PM Friday to 6 AM EDT Saturday for
     MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM Friday to 6 AM EDT Saturday for
     ANZ530>534-537>543.

&&

$$

SYNOPSIS...DHOF/EST
NEAR TERM...DHOF/ADM
SHORT TERM...DHOF/ADM
LONG TERM...EST
AVIATION...DHOF/ADM/EST
MARINE...DHOF/ADM/EST
TIDES/COASTAL FLOODING...LWX