344
FXUS61 KLWX 251447
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1047 AM EDT Tue Jun 25 2024

.SYNOPSIS...
Dry conditions look to continue through tonight as high pressure
slowly pushes offshore. Excessive heat and humidity return Wednesday
ahead of a strong cold front approaching from the Ohio River
Valley. The cold front will cross the region late Wednesday
afternoon into early Thursday morning bringing the next risk for
strong to severe thunderstorms. High pressure briefly returns
from the north and west late Thursday into Friday. Unsettled
conditions are possible this weekend which comes with increasing
heat and humidity.

&&

.NEAR TERM /THROUGH TONIGHT/...
Another hot and not too terribly humid day ahead with high pressure
nearby. The surface high over the region will gradually weaken while
shifting south and east toward the VA/NC coast later this afternoon
and evening. This will allow the winds to shift toward more of west
to southwest flow. The downslope component to the wind will lead to
compression off the mountains boosting temperatures 3 to 5
degrees above climatology for late June standards. Highs today
will push into the upper 80s and low 90s for areas east of the
Allegheny Front. Mountain locations will be a touch cooler in
the upper 70s and low to mid 80s.

Skies will remain mostly sunny with just a few instances of high
cirrus passing through from time to time. Some additional high and
perhaps mid-level cloud cover will sink into areas west of the
Alleghenies and Blue Ridge Mountains later this evening and
into the overnight hours. This is attributed to a complex of
thunderstorms dropping south from the eastern Great Lakes and
central Ohio River Valley. For our region, dry conditions will
prevail through the evening and overnight period. With south to
southwesterly flow in place expected a milder night ahead with
lows in the upper 60s and low to mid 70s. Mountain locations
will stay in the low to mid 60s. Some river valley fog is
possible west of the Blue Ridge overnight. This will be fairly
localized and dependent upon how much convective cloud debris is
realized heading into early Wednesday morning.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A progressive array of shortwaves are forecast to track from
southern Alberta toward the north-central tier of the U.S.
today. These height falls will provide the next chance for any
organized convective activity. Based on the latest Storm
Prediction Center update, areas north of the Potomac Highlands
and central Virginia are in a Slight risk for severe
thunderstorms. The primary threats will be damaging wind gusts
and isolated large hailstones. Some of the guidance does show
some higher Supercell Composite indices along the Mason-Dixon
Line given the backed flow. With that in mind, a brief tornado
cannot be ruled out along this area of the Mid-Atlantic.

The thermodynamic environment should become increasingly
unstable as the boundary layer moistens through the day. This is
in the presence of afternoon temperatures which should rise into
the mid/upper 90s. The degree of low-level moistening is
somewhat uncertain, but the consensus does raise dew points into
the mid/upper 60s. This would support heat indices into the 100
to 104 degree range which does near Heat Advisory criteria. Will
continue to monitor the need for any such heat-related products.

Depending on how upstream activity survives the Appalachian
chain, some early morning showers could push into areas west of
I-81. However, the main show likely initiates along a lee-side
trough during the afternoon hours. This occurs in the presence
of rising buoyancy levels on the order of 2,000 to 2,500 J/kg.
High-resolution guidance favors propagating this activity
downstream toward the metro areas by the late afternoon to early
evening. Model soundings indicate there is plenty of vertical
shear to work with (35-40 knots), so expect storms to be
reasonably well organized. Depending on how everything else
plays out during peak heating, the cold front tracking through
late Wednesday could bring additional thunder chances if any
instability remains. Low temperatures on Wednesday night will
mainly be in the 60s, locally in the low 70s along and east of
I-95.

Some residual shower chances persist into the first half of
Thursday. During the morning hours, this frontal system should
be located near the Delmarva Peninsula. Expect a drying trend
through the day as post-frontal northwesterlies ensue. Forecast
highs drop back down into the mid/upper 80s along with lower
humidity levels. This eventually leads into a cooler night as
most stay in the 60s, with mid/upper 50s over the mountains.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A quick-moving area of high pressure passes to our north on Friday.
Mostly dry conditions are expected during the day, but some showers
could develop in the evening/overnight around the Shenandoah Valley
and Virginia Piedmont as the center of high pressure swiftly moves
offshore by the evening and a shortwaves passes to the northwest.
Temperatures look relatively cooler, topping out in the upper 80s.
Lows hover in the 60s to low 70s.

Confidence has increased for the potential of warm frontal precip on
Saturday, focused in the afternoon and evening. With the warm front,
temperatures get back into the 90s. The cold front associated with
the approaching system looks to arrive Sunday, bringing another
round of showers and thunderstorms. These could linger into early
Monday as well, but surface high pressure looks to build in quickly
behind the cold front on Monday.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
High pressure in charge of the forecast will maintain VFR
conditions across the area through Wednesday morning. Initial
northwesterly winds should gradually shift over to west to
southwesterly today.

The main action holds off until Wednesday afternoon through the
evening and night. The potential for multiple rounds of showers
and thunderstorms would favor restrictions at times.
Additionally, some of these storms could become severe in nature
which would bring stronger wind gusts and perhaps some hail.
Winds shift to west-northwesterly late Wednesday into Thursday
morning behind a well defined cold front. Sub-VFR conditions
could linger into Thursday morning depending on how quickly the
system exits. Expect an eventual return to VFR conditions on
Thursday with northwesterly winds gusting up to 15 knots.

Prevailing VFR conditions are expected Friday and Saturday. Mostly
dry conditions are expected Friday as high pressure passes to the
north, but some showers and thunderstorms could develop as early as
Friday night with an approaching warm front. As the front moves
through Saturday, shower and thunderstorm chances increase. Any that
move over the terminals could bring brief restrictions.

&&

.MARINE...
Winds across the marine waters have diminished in strength as a
ridge of high pressure has moved over the region. As the
anticylone settles to the south and east, southerly channeling
ensues by early this evening into the night. Small Craft
Advisories will likely be issued for the Chesapeake Bay and
lower tidal Potomac. Gusts up to 25 knots are possible for the
more southern waters.

Ahead of the slow moving cold front, southerly winds again pick
up by Wednesday afternoon/evening which likely yields more Small
Craft Advisories. Additionally, strong to severe thunderstorm
activity may necessitate a number of Special Marine Warnings
over the region. Initial activity likely nears the waters by the
late afternoon on Wednesday. The convective threat persists
through the evening and into parts of the night. This frontal
system exits by Thursday morning with sub-advisory level winds
expected for the day.

Sub-SCA conditions are expected Friday as high pressure passes to
our north. Winds increase out of the south on Saturday as a warm
front approaches the waters, and could approach SCA criteria by the
afternoon.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies decrease through this morning with NW flow. A
return of southwest winds later this afternoon into Wednesday
will bring another increase in water levels, although no
flooding is forecast at this time.

&&

.CLIMATE...
Very hot temperatures are expected on Wednesday. Several
records could be in jeopardy. Below is a list of record high
temperatures for June 26th, the year the record was set, and
the current forecast high temperatures for that day. A plus sign
after the date signifies the record was set multiple times,
with the most recent year indicated below. RERs are only issued
for DCA, IAD, BWI, and MRB, but other sites are shown for
reference.

                                    Wednesday Jun 26th
Washington-National (DCA)    101F (1952)          98F
Washington-Dulles (IAD)       95F (1998)          98F
Baltimore (BWI)               99F (1954+)         99F
Martinsburg (MRB)            102F (1943)          93F
Charlottesville (CHO)         99F (1998)          97F
Annapolis (NAK)               98F (1952)          94F
Hagerstown (HGR)              98F (1954+)         93F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT
     Wednesday for ANZ530-537>543.
     Small Craft Advisory from 4 PM this afternoon to 6 AM EDT
     Wednesday for ANZ531>534.

&&

$$

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