179
FXUS61 KLWX 081908
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
308 PM EDT Mon Jul 8 2024

.SYNOPSIS...
A warm front will drift northward across the area before
stalling north of the Mason-Dixon Line on Tuesday. This boundary
continues pushing to the north through mid-week. The air mass
over the region will allow for excessive heat and humidity, as
well as increasing chances for daily showers and thunderstorms.
By Thursday, a cold front will approach from the Ohio River
Valley. The front will try to cross the area Friday before
washing out along the coast as broad high pressure builds for
the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A frontal zone mainly comprised of a dew point gradient remains
just east of I-95. Temperatures are actually a bit warmer on the
"cool" side of the boundary owing to great amounts of solar
insolation. Current observations are characterized by
temperatures in the low/mid 90s, but with lower dew points.
South of the boundary, conditions are much more humid with dew
points in low/mid 70s. With all that said, Heat Advisories
remain borderline in a number of locations as criteria east of
the Blue Ridge requires heat indices of 105 degrees. This will
likely fall short for those farther away from the tidal Potomac
River and Chesapeake Bay. Thus, Heat Advisories remain in effect
for locations along/near I-95 and points eastward until 8 PM
this evening.

The latest RAP objective analysis shows ample buoyancy in place
with surface-based CAPE values of around 1,000-2,000 J/kg. No
capping is evident which is fairly consistent with the fact a
vast Cu field exists over the area. However, away from the
terrain and near the frontal zone (southern Maryland), any
cumulus have been fairly suppressed in nature. Given poor mid-
level lapse rates, the latter area will likely struggle to see
any convective development. Any activity that does go up this
afternoon and early evening should diminish by dusk given the
loss of heating.

A warm and humid air mass persists into the overnight hours with
above average temperatures expected. The current forecast calls
for widespread 70s along I-81 and east of the Blue Ridge, while
mid/upper 60s are more commonplace over the higher terrain.
Given light winds overnight, some patchy fog may develop across
areas west of U.S. 15. However, this will be dependent on
scouring out any leftover low/mid level clouds which could
linger into the night.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Certainly a wash, rinse, and repeat setup in place as a
summertime pattern persists. The warm front will continue its
slow northwestward drift across the Mid-Atlantic region. By
Tuesday evening, the position of this boundary should be near
the Mason-Dixon Line which pushes the entire region into the
warm/moist sector. Another hot day is in store with forecast
high temperatures in the mid/upper 90s, locally in the upper 70s
to 80s across the mountains. Humidity levels come up with the
passage of the warm front as dew points rise into the 70 to 75
degree range east of the Blue Ridge. The combination of
excessive heat and humidity has led to the issuance of another
Heat Advisory from noon until 8 PM on Tuesday. This generally
covers all spots east of the Blue Ridge, as well as a good chunk
of the Shenandoah Valley up to the Mason-Dixon Line. As always,
continue to follow typical heat safety practices like wearing
light and loose clothing, staying hydrated, and seeking breaks
in the shade and/or inside air conditioned locations.

In terms of thunderstorm chances, there should be a bit better
spatial coverage relative to today/Monday. Some isolated showers
and thunderstorms could encroach on the metro areas. However,
the high-resolution model signal still favors locations to the
south as well as mountain locales. For Tuesday night, expect
another warm and muggy night with lows staying near to a couple
degrees above the previous night.

Wednesday is expected to offer another day of Heat Advisory
caliber heat indices. While temperatures may cap out in the mid
90s, dew points creep up a bit further with mid 70s becoming a
bit more widespread. This combination yields heat indices to
around 105 degrees again which would warrant additional Heat
Advisories over the area. Will assess this need on Tuesday.
Expect a better shot for showers and thunderstorms with
probabilities around 40 to 60 percent. Where these storms do
occur would offer beneficial rains to drought-stricken areas as
well as provide some relief from the heat. Low temperatures stay
fairly close to preceding nights. The exception would be the
Alleghenies where clouds and showers should keep lows in the
60s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
On Thursday, the remnant energy of Beryl is expected to be passing
to our north with a broader trough behind it, moving into the Great
Lakes and Ohio Valley. Meanwhile at the surface, a cold front
associated with a surface low over the Northeast will be pressing
into the area. With the high pressure over the Atlantic remaining
strong, the front likely stalls across the area into Friday. PoPs
are persistently elevated to 50-60% or higher from Thursday
afternoon through Friday evening as a result. Additionally, while
Thursday will be a bit cooler than Wednesday, dewpoints in the mid
to upper 70s and highs in the low 90s still spells out heat indices
near and above 100 degrees. Friday does look cooler however, with
highs in the low to mid 80s for much of the area.

There are still many uncertainties, however, with how the extended
will turn out, given how much is dependent on where the remnants of
Beryl end up. While the area will have plenty moisture to work with
from southerly flow Thursday and Friday, more could arrive thanks to
Beryl`s influence, depending on track. Where the front stalls is
also uncertain. It could remain stalled into the weekend until it
either dissolves or gets swept out by another system. As of now,
dissolving looks the most likely as high pressure builds into the
region late in the weekend, which would mean the return to highs in
the 90s.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
The threat for any restrictions at the local terminals will be
confined to KCHO and KMRB. However, it is looking less likely at
KMRB so the next TAF package will address any changes that are
needed. Any convective threat today is largely tied to the
terrain and near the frontal zone which stretches over southern
Maryland into portions of central Virginia. Otherwise, light
southerlies will prevail through the night with VFR conditions
expected.

Heading into Tuesday and Wednesday, southerlies persist across
the area with the warm front lifting north of the Mason-Dixon
Line. Convective opportunities increase each day which could
lead to some sub-VFR conditions at times, particularly by mid-
week. Southerly winds on Wednesday pick up ahead of a slow
moving cold front to the west. Afternoon gusts may push up to
around 15 to 20 knots before decreasing some overnight.

As a cold front moves into the region and stalls, sub-VFR
conditions are possible with any showers and thunderstorms
moving over the terminals Thursday and Friday. Energy streaming
aloft could maintain showers along the stalled boundary
overnight Thursday as well. Sub- VFR conditions are also
possible outside of thunderstorms depending on how much moisture
is available and where the front sets up.

&&

.MARINE...
Wind speeds stay below advisory criteria through Tuesday.
Southerlies persist over the waterways with isolated
thunderstorms possible over the southern waters this afternoon
and evening. The convective threat expands a bit on Tuesday, but
activity should stay somewhat isolated in nature.

For Wednesday, southerly winds pick up with channeling effects
likely requiring Small Craft Advisories from Wednesday
afternoon through the night, particularly over the wider waters
of the Chesapeake Bay. Gusts up to 20 to 25 knots are possible
during this period of enhanced flow. Additionally, ahead of a
cold front, showers and thunderstorms become more likely on
Wednesday afternoon/evening. Thus, Special Marine Warnings may
be needed for some of the more robust convective development.

Southerly flow is expected both Thursday and Friday with a front
likely stalled to the west of the waters. Winds could approach SCA
criteria by Thursday afternoon. Winds likely diminish overnight, but
could remain around the threshold in our far southern waters. SCAs
may be needed again Friday.

&&

.TIDES/COASTAL FLOODING...
Tides will gradually increase throughout the week but should still
remain below action stage everywhere at this time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory until 8 PM EDT this evening for DCZ001.
     Heat Advisory from noon to 8 PM EDT Tuesday for DCZ001.
MD...Heat Advisory until 8 PM EDT this evening for MDZ008-011-013-
     014-016>018-504-506-508.
     Heat Advisory from noon to 8 PM EDT Tuesday for MDZ003>006-008-
     011-013-014-016>018-503>508.
VA...Heat Advisory until 8 PM EDT this evening for VAZ053>055-057-
     527.
     Heat Advisory from noon to 8 PM EDT Tuesday for VAZ026>031-
     036>040-050-051-053>057-501-502-505-506-526-527.
WV...Heat Advisory from noon to 8 PM EDT Tuesday for WVZ051>053.
MARINE...Heat Advisory until 8 PM EDT this evening for ANZ530.
     Heat Advisory from noon to 8 PM EDT Tuesday for ANZ530.

&&

$$

SYNOPSIS...BRO
NEAR TERM...BRO
SHORT TERM...BRO
LONG TERM...CAS
AVIATION...BRO/CAS
MARINE...BRO/CAS
TIDES/COASTAL FLOODING...LWX