206
FXUS61 KLWX 090608
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
Issued by National Weather Service Mount Holly NJ
208 AM EDT Tue Jul 9 2024

.SYNOPSIS...
A warm front will drift northward across the area before
stalling north of the Mason-Dixon Line this afternoon. 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 /UNTIL 6 AM THIS MORNING/...
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 generally starting to form
around 5am. However, this will be dependent on scouring out any
leftover low/mid level clouds which could linger into the
night.

&&

.SHORT TERM /6 AM THIS MORNING 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 /06Z TUESDAY THROUGH SATURDAY/...
Restrictions in the forecast for later tonight for mist at MRB
and CHO. Otherwise, light southerlies will prevail through the
morning night with VFR conditions expected.

Heading into this afternoon 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...
Southerly winds speeds start to funnel this afternoon and Small
Craft Advisory conditions are anticipated this afternoon. Timing
based on the HREF shows the chances of 20kt winds substantially
increasing after 5pm as the flow becomes funneled especially
along the western shores. Isolated thunderstorms will be
possible this afternoon due to the head and humidity but will
need some boundary interactions to trigger.

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.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from noon today to 8 PM EDT this evening for
     DCZ001.
MD...Heat Advisory from noon today to 8 PM EDT this evening for
     MDZ003>006-008-011-013-014-016>018-503>508.
VA...Heat Advisory from noon today to 8 PM EDT this evening for
     VAZ026>031-036>040-050-051-053>057-501-502-505-506-526-
     527.
WV...Heat Advisory from noon today to 8 PM EDT this evening for
     WVZ051>053.
MARINE...Heat Advisory from noon today to 8 PM EDT this evening for
     ANZ530.
     Small Craft Advisory from 4 PM this afternoon to 2 AM EDT
     Wednesday for ANZ531>533-537-539>542.
     Small Craft Advisory from 4 PM this afternoon to 6 AM EDT
     Wednesday for ANZ534-543.

&&

$$

SYNOPSIS...BRO
NEAR TERM...BRO/99
SHORT TERM...BRO
LONG TERM...CAS
AVIATION...BRO/CAS/99
MARINE...BRO/CAS/99