148
FXUS61 KLWX 060132
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
932 PM EDT Fri Jul 5 2024

.SYNOPSIS...
A cold front will approach the area from the Ohio River Valley late
tonight into Saturday. The front will bring shower and thunderstorm
chances to areas west of the Blue Ridge tonight and to areas further
east Saturday. Humidity decreases Sunday in the wake of the front
with high pressure briefly building overhead. Heat, humidity, and
daily thunderstorm chances return early next week as high
pressure pushes offshore and several weak fronts push through the
region.

&&

.NEAR TERM /THROUGH SATURDAY/...
Current radar imagery shows two areas of decaying showers
leftover from earlier thunderstorms. One is located in the
Shenandoah Valley, while another is located over north-central
West Virginia into far western Maryland. The current thinking is
that both of these areas of showers should continue to decay
through the remainder of the evening, with a passing light
shower possible in some places through midnight. Some
redevelopment of storms can`t totally be ruled out as the
remnant MCV associated with the showers in the Shenandoah Valley
tracks northeastward into a higher instability environment in
the metro areas, but that looks to be a low probability
occurrence at the moment. The 00z IAD sounding shows a small
layer of capping around 700 hPa, which may be preventing the
development of storms.

Dry conditions are expected through the second half of the
night. Little relief from today`s heat will be felt overnight,
with dewpoints holding in the 70s, and overnight lows in the mid
70s to low 80s for most (upper 60s to low 70s in the mountains).

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
On Saturday, an upper shortwave and associated surface low pressure
system are expected over the Great Lakes. By Saturday morning an
associated weak cold front is expected to approach from our
west and then slowly move through the area through Sunday
morning. Guidance continues to quickly fill in the upper trough
and takes it northeast, resulting in a continuing drier trend
for Saturday west of the Blue Ridge as the best forcing leaves
with it. Scattered showers and thunderstorms remain possible
Saturday afternoon and evening with PoPs focused east of the
Blue Ridge. This based on the current progged location of the
boundary, due to westerly flow behind the boundary drying from
downsloping, and along and east of the boundary having the
better forcing and moisture from southerly flow. We`re continuing
to monitor the potential for severe thunderstorms and isolated
flooding. Currently the I-95 corridor east is under a Marginal
ERO, but only a general thunder from SPC.

Additionally, Temperatures on Saturday are expected in the low
to mid 90s for most of the non-mountainous areas and heat
indices near 100-105 east of the Blue Ridge. We`re monitoring
the heat threat which could necessitate Heat Advisories, but
appears thresholdy at this time, and only for an hour or so.
Regardless, one can expect hot and humid conditions, with the
highest heat indices in the Virginia Piedmont and along the
waters due to the higher dewpoints.

The weak boundary stalls just to our east on Sunday morning.
Brief ridging looks to keep us mostly dry on Sunday, with highs
a little cooler than Saturday, but not as humid with dewpoints
in the 60s. Any showers and thunderstorms that do develop will
be restricted to near the stalled boundary, so far southern
Maryland in our area.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Synoptically, not too much of a change in the extended as we enter
the true crux of Summer. Upper level ridging/broad high pressure
will continue it`s influence over the north-central Atlantic while
broad upper level trough/low pressure over the central CONUS slowly
progresses east mid to late next week. Meanwhile, upper level low
pressure will continue to meander off the Carolina coast Monday
before washing out toward the middle of the workweek.

This will result in an uptick of moisture across the region along
with the threat of daily diurnally/terrain driven showers and
thunderstorms. Chances will be relatively low (25-50 percent each
day) with no large scale features to point to for widespread drought
busting rain.

A cold front looks to potentially cross the area Tuesday into early
Wednesday bringing with it the highest potential for widespread
rainfall. Even here precipitation chances have been capped to 50
percent or less given some uncertainty amongst the models. Severe
weather and even the potential for flooding could be an issue on
this day given the unstable airmass ahead of the boundary. Learning
machine probabilities also highlight this concern, so we`ll continue
to monitor.

High pressure builds back in behind the front Wednesday into the
weekend. Most of the area will remain dry during this time although
a few diurnally/terrain driven thunderstorms cannot be ruled out.
Temperatures will drop back close to seasonal norms during this
period.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Two earlier areas of convection are in the process of decaying,
with just some leftover light showers left in the Shenandoah
Valley, and across central WV. While there`s still a slight
chance that new storms form, just some passing light showers
are expected at the terminals this evening, with dry conditions
overnight. Prevailing VFR conditions are expected through
Sunday.

Terminals can expect scattered diurnal showers and
thunderstorms once again on Saturday, but primarily along and
east of the Blue Ridge, so MRB might miss out on the action.

Prevailing VFR conditions are expected through Wednesday as the
influence of upper level ridging remains nearby. Shower and
thunderstorm chances are expected each afternoon and evening as a
series of weak fronts push through. Sub-VFR conditions are possible
for a brief period of time in and around these storms with a focus
on terminals west of the Blue Ridge Monday and further east Tuesday
as a cold front pushes through. High pressure briefly returns
Wednesday and into the weekend ahead. W/SW flow is generally
expected at 5-10 kts with occasional gusts to around 15 kts possible
in the afternoon (both Monday and Tuesday).

&&

.MARINE...
Southerly winds prevail through tonight. Southerly channeling
is expected to produce SCA winds in the middle portion of the
Chesapeake Bay between Smith Point and Drum Point this evening.
A Small Craft Advisory has been issued for those waters through
tonight. Otherwise, sub-SCA winds gusting to around 10-15
knots. Winds diminish heading into the weekend, but stronger
gusts remain possible during any scattered showers and
thunderstorms over the waters on Saturday. Sunday should be
mostly dry, but will be dependent on where the stalled cold
front sets up in relation to the waters.

Southerly channeling looks to become a concern for portions of the
waters Monday into Tuesday as the gradient tightens between upper
level low pressure off the Carolina coast and the incoming cold
front from the Ohio River Valley. SCA level winds return Tuesday
into Wednesday in the wake of the cold frontal boundary. High
pressure builds over the waters later next week.

&&

.TIDES/COASTAL FLOODING...
Generally light southerly to southwesterly flow will result in
elevated tide levels through the weekend. Vulnerable shoreline may
come close to minor flooding during the early morning high tides.

&&


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

&&

$$

SYNOPSIS...EST
NEAR TERM...KJP
SHORT TERM...CAS
LONG TERM...EST
AVIATION...KJP/CAS/EST
MARINE...KJP/CAS/EST
TIDES/COASTAL FLOODING...EST