520
FXUS61 KLWX 240127
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
927 PM EDT Mon Jun 23 2025
.SYNOPSIS...
A prolonged period of very hot weather is expected through the
middle of the week as a large ridge of high pressure builds
over the eastern United States. A risk of showers and
thunderstorms returns during the middle to latter portions of
the week as a frontal system approaches from the north. This
system meanders nearby late in the week and into the weekend.
&&
.NEAR TERM /THROUGH TUESDAY/...
Dangerously hot through this evening. 5980m height of 500m at
IAD from morning sounding appearing to break daily record and is
tied for third highest 12Z value on record for all dates.
Earlier heat headlines were allowed to expire at 9 PM with loss
of daytime heating.
Little to no relief is expected into tonight as winds become
nearly calm. A warm and humid air mass will hold low
temperatures well into the 70s, with low 80s across D.C. and
Baltimore. Elevated humidity levels keep heat indices in the 80s
to near 90 degrees in the warm spots. The potential for heat
illnesses will continue in this environment.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Evening update: One small change made to the forecast for
tomorrow was to add in mentionable thunderstorm chances in
Central Virginia and the Central Shenandoah Valley. Some of the
12z CAMs have storms firing in that area during the late
afternoon and evening hours. Model soundings show around
2500-4000 J/kg of MLCAPE, 1400-1800 J/kg of DCAPE, dry adiabatic
low-level lapse rates, and ample dry air in the mid-levels.
Those MLCAPE and DCAPE values are pushing the upper limit of
what can be observed locally. If storms were to form in this
environment (which isn`t a guarantee given the lack of large
scale forcing and the amount of dry air present in the mid-
levels), they would be capable of producing very strong
localized downbursts. Previous discussion follows...
Not much of a change in terms of weather or associated impacts
on Tuesday. Hot. The upper level ridge of high pressure will
remain overhead with well anomalous H5 heights around 597dm.
Another day of widespread upper 90s are likely with some spotty
100 to 102 degree readings possible. Even for mountain
locations, highs will still be well into the 80s to near 90
degrees. This may prove challenging for some areas that
traditionally do not have air conditioning. Extreme Heat
Warnings have been issued for Tuesday across the northern
Shenandoah Valley and all locations east of the Blue Ridge
Mountains. Heat Advisories are currently in place over the
central Shenandoah Valley northward into portions of the eastern
West Virginia panhandle into western Maryland. Heat indices
again push into the 100 to 110 degree range.
With the center of the upper ridge positioned over the area,
large-scale subsidence will largely limit any storm threats.
However, some global guidance continues to attempt to fire off
some isolated convection over the higher terrain. Given the
consistent signal in some models, have added this to the
forecast during the late afternoon to early evening hours.
Outside of this possible development, skies should be mostly
sunny amidst ample summertime humidity. Dew points could be a
smidge lower given forecast soundings show a bit more boundary
layer mixing. Overall conditions remain warm and muggy into
Tuesday night with another round of mid/upper 70s (low 80s
inside D.C. and Baltimore) expected.
Although the upper ridge continues its presence into Wednesday,
forecast models do show heights decreasing by around 2 to 4 dm.
This slight weakening of the ridge may help shave off a couple
of degrees off daytime temperatures. However, despite this
subtle shift, highs are forecast to still punch well into the
90s. Contemplated an Extreme Heat Watch for Wednesday, but
decided to let today`s heat products run course before issuing
for Wednesday. A light northwesterly wind continues through the
period, but conditions remain humid over the region. The
heat/humidity combination will yield heat indices into the 100
to 107 degree range.
Given some subtle weakening of the ridge, shower and
thunderstorm chances return to the forecast on Wednesday
afternoon/evening. Depending on where a west-east oriented
frontal zone sets up to the north, an additional focus for
convective development may emerge. For now, will maintain a 20
to 30 percent chance for thunderstorms before the threat wanes
into the night given the loss of diabatic heating. Wednesday
night`s temperatures could be a couple degrees cooler, but this
still supports widespread 70s (mid/upper 60s in the mountains).
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
The subtropical ridge will remain across the southeastern US through
the end of the week, but will flatten due to several troughs moving
across Canada. A front will approach from the north but will likely
stall out. There`s some opportunity for it to act as a backdoor
toward the weekend, but it might just remain to the north. Overall,
this will result in gradually lowering temperatures, though likely
remaining above normal, along with continued high humidity. Thursday
will present another opportunity for heat index values in the 100-
109 range. Beyond that, temperatures will likely be low enough that
additional Heat Advisories are unlikely, although daily values could
still top 100 in some spots. Overnight temperatures likely stay in
the 70s east of the higher elevations as well, providing little
relief for those without air conditioning.
With less capping and potential for perturbations in the zonal flow,
daily thunderstorms chances will increase. Current guidance suggests
scattered to numerous storms almost every afternoon and evening.
While low shear will minimize organized threats, high CAPE could
result in strong storms with localized downbursts. Light flow and
precipitable water values near 2 inches will also support heavy rain
with these storms.
&&
.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
A strong upper ridge remains parked over the region through at
least the first half of the week. VFR conditions are likely
through Tuesday night in this setup. An isolated shower or
thunderstorm could fire off Tuesday afternoon/evening, but these
should be tied to the terrain. A better chance for a few storms
is possible on Wednesday as the ridge weakens a tad. This could
lead to a few restrictions if occurring around one of the TAF
sites. Otherwise, winds remain on the lighter side (10 knots or
less), with prevailing winds out of the northwest.
Scattered afternoon thunderstorms will be possible each afternoon
and evening from Thursday through Saturday.
&&
.MARINE...
Gradients remain on the weaker side with a strong ridge aloft
through Wednesday. Overall wind fields should yield gusts to
around 5 to 10 knots. Although wind directions will be variable
at times, the prevailing direction should be out of the
northwest. Some storm chances emerge by Wednesday
afternoon/evening which could impact portions of the waterways.
There aren`t any obvious opportunities for strong gradient winds on
the waters from Thursday through Saturday. However, there will be
daily scattered thunderstorm chances which could pose a threat of
lightning and gusty winds.
&&
.TIDES/COASTAL FLOODING...
Tidal anomalies will remain slightly elevated through the next
several high tide cycles. This will keep water levels slightly
elevated for the more sensitive tidal sites. At this point, only
Fort McHenry and Annapolis are slated to reach Action stage
during the next couple of astronomical high tides. Expect the
shift to northwesterly winds to lower anomalies over the next
day or two.
&&
.CLIMATE...
Here are some daily high temperature records during the June
23-27, 2025 timeframe:
A `+` sign indicates multiple years currently hold that record.
***MONDAY, JUNE 23RD, 2025***
LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR)
Washington-National (DCA) 99F (2024) 81F (2024)
Washington-Dulles (IAD) 98F (2024) 78F (2024)
Baltimore (BWI) 98F (2024) 81F (2024)
Baltimore Inner Harbor (DMH) 99F (2024)+ 83F (2024)
Martinsburg (MRB) 100F (1934) 72F (2024)+
Charlottesville (CHO) 100F (1894) 76F (1996)
Annapolis (NAK) 98F (1988) 77F (2011)
Hagerstown (HGR) 98F (2010) 78F (2024)
***TUESDAY, JUNE 24TH, 2025***
LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR)
Washington-National (DCA) 100F (2010) 78F (2010)
Washington-Dulles (IAD) 97F (2010) 73F (2010)
Baltimore (BWI) 100F (2010) 76F (2010)+
Baltimore Inner Harbor (DMH) 101F (2010)+ 82F (2010)
Martinsburg (MRB) 97F (1943) 70F (2024)+
Charlottesville (CHO) 101F (1930) 74F (1914)
Annapolis (NAK) 97F (2000)+ 81F (1896)
Hagerstown (HGR) 96F (2010)+ 75F (2010)
***WEDNESDAY, JUNE 25TH, 2025***
LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR)
Washington-National (DCA) 100F (1977) 76F (2010)+
Washington-Dulles (IAD) 97F (1966) 71F (1981)
Baltimore (BWI) 99F (1997) 77F (1949)+
Baltimore Inner Harbor (DMH) 104F (1997) 79F (1998)+
Martinsburg (MRB) 99F (1997) 72F (1949)
Charlottesville (CHO) 99F (1997) 77F (1951)
Annapolis (NAK) 98F (2000)+ 78F (1997)+
Hagerstown (HGR) 98F (1952) 75F (1949)
***THURSDAY, JUNE 26TH, 2025***
LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR)
Washington-National (DCA) 101F (1952) 77F (1952)+
Washington-Dulles (IAD) 99F (2024) 72F (2023)+
Baltimore (BWI) 99F (2024)+ 80F (1952)
Baltimore Inner Harbor (DMH) 104F (1998) 83F (1952)
Martinsburg (MRB) 102F (1943) 75F (1949)
Charlottesville (CHO) 99F (1998) 78F (1952)
Annapolis (NAK) 98F (1998)+ 81F (1952)
Hagerstown (HGR) 98F (1954)+ 75F (1952)
***FRIDAY, JUNE 27TH, 2025***
LOCATION RECORD HIGH (YEAR) RECORD WARM LOW (YEAR)
Washington-National (DCA) 99F (2010) 80F (1952)
Washington-Dulles (IAD) 100F (1964) 72F (2021)+
Baltimore (BWI) 100F (2010) 78F (1949)+
Baltimore Inner Harbor (DMH) 101F (2010) 83F (1998)
Martinsburg (MRB) 101F (1943) 75F (1952)
Charlottesville (CHO) 100F (1952) 79F (1952)
Annapolis (NAK) 98F (1911) 79F (1943)
Hagerstown (HGR) 99F (2010) 77F (1952)
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Extreme Heat Warning from 11 AM to 9 PM EDT Tuesday for DCZ001.
Extreme Heat Watch from Wednesday morning through Wednesday
evening for DCZ001.
MD...Air Quality Alert until midnight EDT Tuesday night for MDZ008-
508.
Extreme Heat Warning from 11 AM to 9 PM EDT Tuesday for
MDZ003>006-008-011-013-014-016>018-503>508.
Extreme Heat Watch from Wednesday morning through Wednesday
evening for MDZ003>006-008-011-013-014-016>018-503>508.
Heat Advisory from 11 AM to 9 PM EDT Tuesday for MDZ502.
VA...Extreme Heat Warning from 11 AM to 9 PM EDT Tuesday for
VAZ027>031-036>040-050-051-053>057-501-502-505-506-526-
527.
Extreme Heat Watch from Wednesday morning through Wednesday
evening for VAZ027>031-036>040-050-051-053>057-501-502-
505-506-526-527.
Heat Advisory from 11 AM to 9 PM EDT Tuesday for VAZ025-026.
WV...Extreme Heat Warning from 11 AM to 9 PM EDT Tuesday for WVZ052-
053.
Extreme Heat Watch from Wednesday morning through Wednesday
evening for WVZ052-053.
Heat Advisory from 11 AM to 9 PM EDT Tuesday for WVZ050-051-
055-502-504-506.
MARINE...Air Quality Alert until midnight EDT Tuesday night for ANZ530.
Extreme Heat Warning from 11 AM to 9 PM EDT Tuesday for ANZ530.
Extreme Heat Watch from Wednesday morning through Wednesday
evening for ANZ530.
&&
$$
SYNOPSIS...BRO
NEAR TERM...BRO/KJP/CPB
SHORT TERM...BRO/KJP/CPB
LONG TERM...ADS
AVIATION...ADS/CPB
MARINE...ADS/CPB
TIDES/COASTAL FLOODING...LWX
CLIMATE...LWX