418
FXUS61 KLWX 041956
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
356 PM EDT Thu Jul 4 2024

.SYNOPSIS...
High pressure will remain in place offshore through early next
week. A weak cold front will move through on Saturday, before
stalling out in the vicinity through early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Current radar imagery shows two large clusters of shower/thunderstorm
activity. One stretches from south-central PA to just east of
the Blue Ridge in Central Virginia. This activity is slowly
progressing off toward the east, and should track through the
remainder of the forecast area between now and roughly 7 PM.
Behind that activity, there`s around a 100 mile gap where there
isn`t much thunderstorm activity through western portions of our
forecast area. Then another area of thunderstorms extends
southward from Ohio through central West Virginia and into far
southwestern Virginia. This activity is also tracking eastward,
and will move into our area this evening. Most CAMs attempt to
have these storms fall apart as they cross the mountains, but if
they do hold together, they could have implications for
fireworks shows in the evening. Extrapolating out the forward
motion of this system puts it in the middle of our forecast area
around 9 PM, with the ongoing storms in our area located off to
the east.

Thus far, storms have been rather unimpressive despite around
1000-2000 J/kg of MLCAPE present. Deep, saturated profiles (PWAT
values around 2.2-2.3 inches according to SPC Mesoanalysis) have
limited outflow accelerations, but have led to heavy rainfall
producing storms. With around 20-25 knots of mid-level flow
present, storms have remained progressive thus far. With storms
moving along and background drought conditions in place,
flooding isn`t expected in rural areas (where nearly 3 inches of
rain in an hour is needed to cause issues). Some isolated
instances of flooding can`t be ruled out in urban areas, but
even that doesn`t look overly likely at the moment. A wet
microburst or two can`t be ruled out as well, but it largely
appears to be an environment that isn`t favorable for severe
thunderstorms.

Thunderstorm activity will wind down with loss of daytime
heating through the first half of the overnight. Drier
conditions are expected during the second half of the night.
Some patchy fog may be possible later tonight, especially in
locations to the west of the Blue Ridge that received rainfall
today. Temperatures will remain mild overnight, with lows
generally in the low-mid 70s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Hot and humid conditions will persist into Friday and Saturday.
Highs both days are expected to make it into the low-mid 90s.
When coupled with dewpoints in the mid 70s, this will lead to
peak heat index values in excess of 100-105 degrees. Heat
Advisories are in effect for portions of the area tomorrow, and
additional Heat Advisories may be needed on Saturday.

Afternoon/evening thunderstorms will also be possible both days.
There won`t be much large scale forcing for ascent present
tomorrow, so overall coverage of storms may be a bit lower. By
Saturday, a shortwave trough will track to our northwest,
driving a cold front into our area. This boundary may help to
focus thunderstorm activity to the east of the Blue Ridge
Saturday afternoon.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
A cold front is expected to push through the area by Sunday morning,
stalling as a weak boundary just to our east. 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.

Heading into the work week, continuing moisture advection on
southerly flow behind high pressure offshore will allow for
scattered afternoon showers and thunderstorms on Monday. The focus
of showers will be dependent on where the stalled boundary is
(currently still expected to be to our east) and where there are any
minor perturbations aloft.

For Tuesday, as a low pressure system moves into the Great Lakes, a
leading trough could act as the focus for convection in the
afternoon and evening over our area. Showers and thunderstorms
appear more likely Tuesday than Monday thanks to the added lift,
with PoPs 50-70%. Precip chances on Wednesday will be dependent on
how the cold front associated with the Great Lakes system evolves.
With only weak boundaries moving through and southerly flow for most
of the extended, high temperatures are expected to remain in the 80s
to low 90s for much of the area.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Prevailing VFR conditions are expected at the terminals through
Saturday. Afternoon/evening thunderstorms will be possible each
day, potentially leading to temporary restrictions. Winds will
be light out of the south.

Storms are currently ongoing from near HGR southward to CHO.
Those storms will progress eastward through the late afternoon
and evening, eventually impacting the metro area terminals.
Additional thunderstorms are present across central WV, and will
move into the area during the late evening, after a few hour
lull in-between.

Sunday appears dry with high pressure building in behind a boundary
stalled to our east. For Monday, scattered showers and thunderstorms
are possible in the afternoon which could bring brief periods of sub-
VFR conditions to the terminals.

&&

.MARINE...
SCAs remain in effect this afternoon in southerly flow in
central portions of the Bay, as well as the lower tidal Potomac.
Elsewhere, sub-SCA southerly flow is expected today. SMWs may be
needed over the waters late this afternoon into this evening in
association with any thunderstorms that move over the waters.

Sub-SCA level southerly flow is expected on both Friday and
Saturday. SMWs may be needed once again either afternoon as
storms move over the waters.

Light winds are expected on Sunday with high pressure over the
waters and a boundary stalled to the east. Winds increase out of the
south/southeast on Monday and could approach SCA criteria with
southerly channeling.

&&

.TIDES/COASTAL FLOODING...
Steady southerly winds through Saturday night are likely to result
in minor coastal flooding at the more sensitive locations each day.
This is going to be during the highest diurnal tide, which is
currently in the morning. Annapolis is most likely to hit minor
flooding each day, with DC SW Waterfront, Havre de Grace, and
Baltimore needing a close watch.

A weak front pushes south of the area Sunday, bringing light
northwest/north winds and a brief reprieve from coastal flooding.
However, stronger southerly flow is expected again next week, likely
leading to additional periods of coastal flooding.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from noon to 8 PM EDT Friday for DCZ001.
     Heat Advisory until 8 PM EDT this evening for DCZ001.
MD...Heat Advisory from noon to 8 PM EDT Friday for MDZ008-011-013-
     014-016>018-504-506-508.
     Heat Advisory until 8 PM EDT this evening for MDZ011-013-014-
     016-504-506.
VA...Heat Advisory from noon to 8 PM EDT Friday for VAZ050-051-
     053>057-502-527.
     Heat Advisory until 8 PM EDT this evening for VAZ053>056-527.
WV...None.
MARINE...Heat Advisory from noon to 8 PM EDT Friday for ANZ530.
     Small Craft Advisory until 8 PM EDT this evening for ANZ533-
     537-541.
     Small Craft Advisory until 1 AM EDT Friday for ANZ534-543.

&&

$$

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