267
FXUS61 KLWX 150120
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
920 PM EDT Wed Aug 14 2024

.SYNOPSIS...
Quiet weather conditions are expected through Thursday before
precipitation chances return with a slow moving low pressure
system Friday into the weekend. A cold front will cross the
region late Saturday into Sunday bringing the highest
probability for showers and thunderstorms.This system exits off
the coast Monday into Tuesday with high pressure set to return
to the region by the middle of next week.

&&

.NEAR TERM /THROUGH TODAY/...
Smoke from Canadian wildfires continues to filter through the
forecast area with levels expected to decrease overnight.
Isolated showers are filtering south from PA so PoPs were
increased to account for an isolated shower in NE Maryland.
Otherwise, no changes were made to the forecast with mostly dry
and mild conditions expected to continue. Previous Discussion
follows:

Upper level troughing will continue to exit off
the Atlantic coast today while broad high pressure builds
eastward from the Great Lakes region. Tranquil weather
conditions are expected as a result with less cloud cover
(stratocumulus) and low humidity. Highs today will rise into the
low to mid 80s east of the Alleghenies with 70s along the
higher ridges.

One thing to note will be some Canadian wildfire smoke in
the mid to upper troposphere. This smoke is evident on the GOES
GeoColor this afternoon with a subtle band dropping south through
northern and central MD. High-resolution smoke guidance also picks
up on this with northerly flow carrying this elevated smoke plume
through the area mid to late afternoon. Consequently, have opted to
put haze in the forecast grids for areas along and east of U.S. 15
through at least sunset. While this could impact locations to the
west, confidence was not high enough to do so. Smoke is unlikely to
affect the surface, although some minor reductions in visibility (6-
8SM) are possible throughout the afternoon period.

High pressure will rule the forecast tonight with plenty of
subsidence overhead. Looking like a good radiational cooling set up
with mainly clear skies and calm winds. This will allow temperatures
to fall into the low to mid 60s east of the Blue Ridge with 50s
west. Mountain and high valley locations could fall back into the
40s. Patchy river/valley fog is possible heading into daybreak
Thursday.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
One more day of quiet weather is expected Thursday as broad longwave
ridging sits nearby. Humidity will remain low with light north to
northwesterly flow for much of the day before the low level flow
turns to the south Thursday night into Friday as surface high
pressure slides offshore. Skies will trend mostly sunny to start
with increasing clouds late in the afternoon and evening as a warm
front moves toward the region from the Upper Midwest and Ohio River
Valley. With persistent north to northwest winds expect low humidity
to remain with dewpoints in the upper 50s and low 60s. High
temperatures Thursday will push into the mid to upper 80s east of
the mountains with metro areas potentially touching 90 degrees.
Mountain locations will be a tad cooler in the mid to upper 70s and
low 80s.

Shower and thunderstorm chances return from the west 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 as early as Thursday night before
spreading east toward the Blue Ridge Friday afternoon. Current 12z
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 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.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
An upper trough will continue to drop further south into the area
Saturday as an associated warm front lifts further north. Increasing
chances for showers and thunderstorms will be apparent for at least
the early portion of the weekend. Given the warm sector, increased
instability and flow, there may be a chance for strong to severe
thunderstorms Saturday afternoon and evening. Main threats would be
damaging winds and isolated instances of flooding. Afternoon highs
will be in the upper 80s for most of the lower elevations, with mid
70s more common across the mountains.

Timing of the cold front remains uncertain with this system,
therefore there may be some areas that remain in the warm sector
through Sunday mid-morning. Showers and thunderstorm chances remain
in place for the afternoon and evening hours especially.
Precipitation chances linger into the early part of the work week
next week with highs on Monday remaining seasonable. High pressure
builds in by Tuesday into the middle part of next week.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Prevailing VFR conditions are likely at all terminals through Friday
midday. Some elevated smoke may impact terminals mainly east of the
Blue Ridge mountains this afternoon and evening as northern Canadian
wildfire smoke funnels south on light northerly flow. No large
visibility reductions are expected with vsbys running between 5-8 SM
(due to haze). Northerly winds are expected for the remainder of the
afternoon with gusts 15 to 20 kts. Winds will turn light and variable
overnight into Thursday as high pressure settles overhead.

By Thursday night, winds will switch to the south as high pressure
pushes toward the New England coast. VFR conditions will prevail
although SCT-BKN mid and high level clouds will increase across the
region. These clouds are in association with a longwave trough of
low pressure and surface warm frontal boundary that will lift into
the area Friday. Showers and thunderstorms will accompany this
boundary at terminals west of the Blue Ridge Friday afternoon before
spreading eastward into the corridor Friday evening and Friday
night. This will lead to intermittent periods of sub-VFR conditions
especially within the Friday evening and night timeframe when the
bulk of the precipitation is expected to move through. Winds Friday
will remain out of the south with gusts up to 15 kts.

Sub-VFR conditions are possible Saturday and Sunday as showers and
thunderstorms potentially impact the terminals during the afternoon
and evening hours especially. Outside of these, VFR conditions will
persist.

&&

.MARINE...
No marine hazards are expected through Friday morning as surface
high pressure slowly slides east of the area. Light north to
northwest winds are expected Thursday switching to the south Friday.
Gusts of 10-15 kts can be expected each afternoon. SCA level winds
may return as early as Friday afternoon and night due to southerly
channeling. Additionally, showers and few thunderstorms may also
impact the waters by late Friday.

SCA conditions are becoming increasingly likely Saturday as a
pressure gradient increases across the waters. Lower winds are
expected Sunday as the front moves east of the waters. Cannot rule
out an SMW for the waters with any strong to severe thunderstorms
that impact the waters.

&&

.TIDES/COASTAL FLOODING...
Light north to northwest flow under broad high pressure will lead to
sensitive tide sites (i.e Havre de Grace, Annapolis, and DC
Waterfront) remaining near action stage during the next 3 high tide
cycles (through Friday morning morning). Winds will turn to the
south late Thursday into Friday allowing water levels and anomalies
to increase later this week and into the weekend. As a result, some
sensitive locations may approach Minor flooding.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

SYNOPSIS...EST
NEAR TERM...AVS/EST
SHORT TERM...EST
LONG TERM...ADM
AVIATION...BRO/ADM/EST
MARINE...ADM/EST
TIDES/COASTAL FLOODING...