221
FXUS61 KLWX 091428 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1028 AM EDT Wed Jul 9 2025

.SYNOPSIS...
A weak front will remain stalled near the area through tonight
before lifting back to the north on Thursday. It may settle back
into the area over the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...

Sfc obs indicate that moisture discontinuity/front is located
well north of the area, generally along I-80 in northern
Pennsylvania. Air mass looks significantly moister today with
PWATs at 1.93" compared to 1.66" yesterday. Forcing today looks
stronger with a sharper trough in place which will likely result
in more widespread and longer lasting convection. Flood Watch
remains in place and it looks good in areal coverage.

Previous afd...

At least scattered cloud cover may be more likely to start the
day compared to yesterday. A more notable shortwave trough
currently over the lower Ohio Valley will spread eastward by
this afternoon. This will enhance mid/upper level wind fields
while adding lift for shower and thunderstorm development. A
hot and humid airmass will again support moderate to strong
instability, especially east of the mountains. As storms spread
into this environment, severe potential will increase, with a
primary threat of damaging winds. A Slight Risk (Level 2 of 5)
of severe storms has been outlooked by SPC. Precipitable water
values will remain near 2 inches with deep warm cloud layers.
There is a greater model QPF signal this afternoon compared to
Tuesday, as there may be a better opportunity for multiple
rounds and/or backbuilding. There is some uncertainty where that
corridor is most likely to set up, with the strongest signal
from the Virginia piedmont toward southern Maryland. However,
some models show the convergence lifting toward the metro areas
as well toward evening. A Flood Watch for flash flooding is in
effect and has been expanded to include a portion of the
Shenandoah Valley where there is overlap of greater QPF and
lower flash flood guidance. A Moderate (level 3 of 4) excessive
rainfall outlook clips our southern border, and WPC will be
monitoring if this needs to be expanded northward. It won`t be
quite as hot as Tuesday, but upper 80s and lower 90s will be
common. Heat indices will reach the upper 90s and perhaps lower
100s in spots.

While the severe and flood threat should decrease with time,
showers and thunderstorms may linger into the night as the
trough remains overhead and moisture and convergence look to
linger. With abundant low level moisture, some low clouds may
develop, or fog where skies can clear.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The surface boundary becomes even more diffuse by Thursday, with
WPC analyzing it north of the area. However, the broad trough
remains overhead, and deep moist southwest flow will promote
more cloud cover. Therefore it will be a bit cooler, and showers
and thunderstorms may more readily develop. With lower
instability, storms should be less intense overall, with only a
marginal severe risk. The QPF signal is likewise lower. However,
slow storm motions in the very moist environment could still
lead to isolated flooding, especially since soils will likely be
increasingly saturated.

The trough moves off to the east Friday, carrying the deeper
moisture plume with it. Weak flow will be in place at the
surface and aloft. Therefore, there may be less of a trigger for
showers and storms other than mesoscale forcing in the warm and
humid airmass. An isolated flood risk will continue given
expected slow storm motions.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A typical summertime pattern will persist across the area this
coming weekend through early next week, with seasonable heat and
humidity, as well as chances for thunderstorms each afternoon and
evening.

On the synoptic scale, the pattern is expected to change very little
over the course of the long term period, with the stronger belt of
westerlies staying well to our north, and no strong frontal passages
to speak of. A shortwave trough and associated surface low are
expected to track through the Western Great Lakes and then
northeastward toward Hudson Bay this weekend. Weak height falls on
the periphery of this upper trough may lead to a slightly higher
coverage of afternoon showers and storms on Saturday and Sunday
compared to Monday and Tuesday, but at least a chance will be there
each day. Ample sunshine is expected through the morning hours each
day. High temperatures are expected to rise into the upper 80s to
around 90 each day, with overnight low temperatures in the mid-upper
60s to the west of the Blue Ridge, and then lower to middle 70s
further east.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
Clouds still linger neat most of the terminals, which may limit
the fog threat. Some IFR stratus has develop just east of CHO,
so this may spread westward through daybreak.

Another round of showers and strong thunderstorms are expected
to develop this afternoon and evening. Compared to Tuesday,
there is greater potential for multiple rounds and/or lingering
storms this afternoon and evening. For now have portrayed this
with a longer period of prevailing showers with a TEMPO for
storms during the most likely period. MRB appears to have
slightly lower potential for a direct storm impact. Storms will
be capable of strong downbursts, heavy rain, and frequent
lightning. Some showers may linger into the night. Statistical
guidance suggest IFR ceilings will develop tonight, although
there isn`t much support for this in the HREF and SREF
ensembles, so have limited to MVFR for now. Fog is possible if
skies clear.

Any ceilings likely lift Thursday, but numerous showers and
thunderstorms will again develop through the day into the
evening. Intense storms may be less common, but will continue to
monitor. Low clouds/and or fog may develop again Thursday night.
Friday may offer some slight drying and lower coverage of
showers and storms, but the threat will still be present.

Prevailing VFR conditions are expected on both Saturday and Sunday,
but showers and thunderstorms may lead to brief restrictions either
afternoon or evening. Winds will be light out of the south on
Saturday, before turning light out of the west to northwest on
Sunday.

&&

.MARINE...
A few gusts may approach 18 kt on the middle bay early this
morning, but otherwise light winds will prevail. Another round
of strong to severe thunderstorms is expected this afternoon and
evening, with some storms possibly lingering into the night.
Marginal Small Craft conditions may develop on the middle bay
this evening into tonight if storm outflows are not too
disruptive or dissipate early.

Overall light winds should prevail Thursday and Friday. Strong
thunderstorms will be the main threat each afternoon and evening,
although the coverage of intense storms may decrease compared
to Tuesday and Wednesday.

Sub-SCA conditions are expected over the waters this coming weekend,
with light southerly winds on Saturday, and light west to
northwesterly winds on Sunday. Thunderstorms may be possible during
the afternoon and evening hours, potentially leading to the issuance
of SMWs.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from 2 PM EDT this afternoon through this evening
     for DCZ001.
MD...Flood Watch from 2 PM EDT this afternoon through this evening
     for MDZ004>006-008-011-013-014-016>018-503>508.
VA...Flood Watch from 2 PM EDT this afternoon through this evening
     for VAZ025>027-029-030-036>040-050-051-053>057-501-502-
     505>508-526-527.
WV...None.
MARINE...Flood Watch from 2 PM EDT this afternoon through this evening
     for ANZ530.

&&

$$

SYNOPSIS...ADS
NEAR TERM...LFR
SHORT TERM...ADS
LONG TERM...KJP
AVIATION...LFR/KJP
MARINE...LFR/KJP