534
FXUS61 KLWX 131932
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
332 PM EDT Mon Jul 13 2026
.WHAT HAS CHANGED...
Probability of heat headlines continues to increase for
Wednesday. Probability of thunderstorms increases for the end of
week, particularly Saturday.
&&
.KEY MESSAGES...
- Increasing heat for mid week with heat headlines becoming
increasingly likely, especially Wednesday.
- Forecast confidence decreases substantially late this week
into the upcoming weekend, but the potential is there for both
extreme heat and severe thunderstorms.
&&
.DISCUSSION...
KEY MESSAGE 1...Increasing heat for mid week with heat headlines becoming
increasingly likely, especially Wednesday.
KEY MESSAGE 1 DESCRIPTION...
Upper high centered over Minnesota this afternoon will extend a
ridge southeastward into the Mid Atlantic states through mid
week bringing a very hot air mass into the area Wed with 850 mb
temps possibly reaching and/or exceeding 25C. As opposed to the
heat dome that impacted the local area in early Jul, this time
the heat dome will be centered over the Upper Midwest instead of
overhead, meaning this will be a hotter/more continental air
mass, but also less humid with more of a westerly sfc component
rather a southerly component. Even with the known ECMWF warm
bias, substracting 3-5F degs still yields highs around 100-101F
with heat indices of around 105F Wed. Potential for lower
dewpoints on Thu may result in slightly lower heat indices and
lower confidence in meeting heat advisory criteria, but still
hot nonetheless. There is also a slim chance of isolated
thunderstorms Thu, while Wed the chance of t-storms looks to be
zero.
KEY MESSAGE 2...Forecast confidence decreases substantially late this
week into the upcoming weekend, but the potential is there for both
extreme heat and severe thunderstorms.
KEY MESSAGE 2 DESCRIPTION...
Model guidance is in reasonably good agreement that the longwave
pattern across the CONUS late this week into the upcoming weekend
will feature troughing across the Pacific Northwest, ridging over
the center of the country, and then troughing downstream across New
England. Such a pattern will place us in northwesterly flow aloft.
However, there`s considerable disagreement regarding the timing and
placement of individual shortwaves and their associated surface
fronts throughout that period. As a result, there`s a highly
atypical amount of forecast spread for this time of year during that
time window. Ensemble guidance has members showing highs anywhere
from the upper 70s to the mid 100s each day Friday through Sunday,
with above average spread on Thursday as well (mid 80s to mid 100s).
So depending on which solution verifies, we could have anywhere from
well below normal temperatures to record highs each day. That, in
turn, will have impacts on severe thunderstorm potential each day.
The first of the aforementioned shortwaves will pass by to our
northeast across New England on Thursday, but mid-upper level height
falls locally are expected to be negligible, if they occur at all.
As a result, odds favor conditions remaining hot and humid here.
Model soundings show some weak capping, but there are hints of a
surface trough developing in some of the guidance. The presence of
capping and ample dry air in the mid-upper levels should act to
limit the development of showers and thunderstorms, but there are a
few solutions that show a storm or two popping up within the surface
trough during the afternoon or evening hours. If a storm were to
form, it could potentially turn severe, with a high CAPE, high DCAPE
environment in place, and somewhere between 20-40 knots of mid-
level flow present.
There`s uncertainty regarding how far south a frontal boundary
associated with the system passing to our north on Thursday will
eventually make it. Some solutions show both temperatures and
dewpoints crashing behind the front for Friday, while others
maintain the warm and humid airmass locally. While there`s still
considerable spread with respect to both temperatures and dewpoints
on Friday, recent trends favor lower dewpoint air making it into the
Mid-Atlantic. If this were to occur, we`d have reduced chances for
shower and thunderstorms activity. If the hot and humid air remains
in place, we`d have better chances for showers and storms.
The best chance for showers and thunderstorms looks to occur this
weekend as another shortwave descends down through the Great Lakes
in northwesterly flow aloft. As mentioned before, there`s still
considerable spread with respect to where this system will track,
and where it will move surface boundaries/associated air masses.
However, more solutions than not have higher temperature, higher
dewpoint air surging back in within south to southwesterly low-level
flow. That, along with most solutions showing more substantial
height falls, should lead to higher coverage of showers and
thunderstorms on Saturday, and potentially Sunday as well, depending
on positioning of the system`s surface cold front. Much like
preceding days, there will be a conditional threat for severe
thunderstorms, but forecast uncertainty remains very high this far
out.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Fair weather is expected through mid week, but with increasingly
hotter temperatures as we head into Wednesday.
Prevailing VFR conditions and light northwesterly winds are expected
on both Thursday and Friday. An afternoon thunderstorm may be
possible either day.
&&
.MARINE...
Possible SCA conditions at night beginning Tue night in
southerly channeling.
Sub-SCA level northwesterly winds are expected on both Thursday and
Friday. SMWs may potentially be needed on Thursday or Friday if
thunderstorms move over the waters.
&&
.TIDES/COASTAL FLOODING...
Onshore to s`ly flow continues through midweek, keeping tidal
levels elevated. The upcoming new moon is also accentuating the
tide cycle. Minor coastal flooding seems likely along low lying
areas of Anne Arundel County including City of Annapolis
tonight. A Coastal Flood Advisory has been issued.
Guidance does indicate gradually declining anomalies through
mid week, but Annapolis in particular may require another day
of advisories on the astronomically higher tide.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory from 3 AM to 8 AM EDT Tuesday for
MDZ014.
VA...None.
WV...None.
MARINE...None.
&&
$$
DISCUSSION...LFR/KJP/CPB
AVIATION...LFR/KJP/CPB
MARINE...LFR/KJP/CPB
NWS LWX Office Area Forecast Discussion