Severn, Maryland 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

628
FXUS61 KLWX 241910
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
310 PM EDT Tue Jun 24 2025

.SYNOPSIS...
A ridge of high pressure overhead will bring continued hot
conditions over the next several days. As the upper-level ridge
slowly retreats in the coming days, daily chances for showers
and thunderstorms will increase through the end of the week. A
weak frontal boundary slowly drift southward by the end of the
week into the weekend, before slowly lifting north into early
next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A strong 598dm ridge overhead is leading to continued very hot
temperatures across the region. Highs so far are generally in
the mid to upper 90s, with some spotty 100 degree readings in
the climo-favored urban hot spots. Extreme Heat Warnings remain
in effect through this evening as a result of this heat combined
with high levels of humidity. However, as the afternoon has
progressed, we have actually mixed down some lower dew points
compared to yesterday, with values in the upper 60s to low 70s.
Do still think we achieve the highs near 100 for most, but the
humidity levels may come up a bit lower than initially
anticipated. At any rate, it will still be dangerously hot, so
whether the heat index is 107 or 112 makes very little
difference at this point. Continue to practice proper heat
safety procedures if you are exposed to the heat this afternoon.
Take plenty of breaks and drink plenty of fluids as well.

Overall storm chances appear limited given the degree of
subsidence underneath the strong anticyclone aloft. Additionally,
a number of solutions keep the 700-300 mb layer rather dry
which would limit any vertical cloud development. While
subsidence could easily win out today, there are a few high-
resolution models that continue to fire off some convection
over the Shenandoah Valley and central Virginia Blue Ridge later
this evening. If such thunderstorms developed, inverted-V
signatures within the surface to 850-mb layer would be conducive
to fairly strong downbursts (DCAPE values of 1,000 to 1,300
J/kg). Storms will need to be able to grow pretty tall to
tap into this however, which again I think will be a struggle
given the abundance of dry air aloft. This could be one of those
days where we get a few storms that grow to around 15-20kft,
produce some quick 30 to 40 mph, and die out. Such storms would
quickly propagate toward the southeast into central Virginia.


Otherwise, hot and humid conditions will largely rule the day
with some flat fair weather cumulus percolating up during
diurnal heating.

Do not expect much change in the pattern into tonight with
continued dangerous heat and humidity. Perhaps a degree or two
is shaved off overnight lows relative to last night. However,
these readings are still above average and coupled with dew
points staying in the low/mid 70s. Depending on if storms
develop, some cirrus debris could linger overhead across central
VA.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The upper ridge does remain centered over the region through at
least Thursday. However, we will start to see mid-level height
falls on Wednesday into Thursday. While they will be subtle
(around 3 to 5 dm or so), it will be enough to put our region on
the northern periphery of the ridge. This is due to a very weak
frontal boundary dropping southward towards the region on
Wednesday, which likely remains stalled near the MD/PA border
through at least Thursday. Not only will forcing improve as
mesoscale shortwaves traverse the region during this time, but
also there should be an added focus from the boundary sagging
southward in time. Given the degree of cloud cover and possible
convective contamination, high temperatures are expected to be
lower on Wednesday, so Heat Advisories were issued for most
areas, rather than Extreme Heat Warnings. That being said, it
will be quite hot either way, so continue to practice good heat
safety precautions.

As mentioned, thunderstorms return to the forecast for Wednesday.
The Storm Prediction Center has placed the entire region in a
Marginal risk for severe weather. Locally stronger downbursts
may pose a threat for damaging wind gusts. Given the degree of
heat and humidity in the atmosphere, some storms linger into the
first half of the night. Low temperatures remain fairly close
to preceding nights.

Thursday marks the first real drop in temperatures with a
forecast of upper 80s to mid 90s. Given elevated humidity
levels, heat indices should still push into the 100 to 105
degree range, with highest values south of I-66. Shower and
thunderstorms chances further increase as the boundary meanders
about the area, some of which may be severe in nature. A
stronger shortwave also looks to traverse the region, which will
lead to a higher chance for storms Thursday. With anomalous
moisture in place, a non-zero threat for flash flooding also
exists, particularly for training elements along this front.
Conditions remain unsettled into subsequent days.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By Friday, the front to the north will have likely slipped into the
area in backdoor fashion, potentially resulting in a cold air
damming-like wedge of cloudier and cooler conditions. The
uncertainty in the position of this front results in a large range
of potential temperatures, with upper 70s to the north and lower 90s
to the south. The greatest convective coverage will also likely be
near and southwest of the boundary.

The front will lift back to the north over the weekend, allowing
upper 80s and lower 90s temperatures to return. While it will also
be humid, it looks like the heat index will remain below advisory
thresholds. Terrain circulations and perturbations in the zonal flow
aloft will be responsible for daily shower and thunderstorm
development...most numerous in the mountains, with at least
scattered storms potentially moving into the eastern half of the
area. A cold front may move toward the area on Tuesday, resulting in
greater coverage of convection.

In terms of severe weather potential, it`s difficult to pinpoint any
one day for a greater risk given weaker shear and largely mesoscale
processes. However, strong instability could result in localized
gusty downbursts. Precipitable water values will also range from
1.5 to 2 inches, which will result in heavy rain rates.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
Conditions should remain VFR today underneath the strong upper
ridge. Although the area is expected to stay dry, an isolated
thunderstorm may fire off over the central Virginia Blue Ridge.
This could near the KCHO terminal area during the 23-02Z
timeframe (PROB30 accounts for this). Otherwise, gradients
remain weak with northwesterly winds under 10 knots.

A slow moving frontal zone approaches the MD/PA border Line from
the north on Wednesday. This will increase opportunities for
showers and thunderstorms on both Wednesday and Thursday. Some
restrictions are possible as the pattern shifts toward more
active weather, but should be brief during time of thunderstorms.
Weak pressure gradients will keep winds generally under 10
knots outside of any convection.

Sub-VFR ceilings are possible at times Friday into Saturday as a
backdoor front settles into the area before lifting back north over
the weekend. Scattered afternoon thunderstorms will also be possible
each afternoon and evening from Friday through Sunday.

&&

.MARINE...
Weak summertime gradients will maintain sub-advisory level
winds over the waters through Thursday. Conditions will be dry
today, but with hot and humid weather expected.

A slow-moving frontal zone nears southern Pennsylvania from the
north, shower and thunderstorm chances will increase during
subsequent days. Hazardous marine conditions are possible on
Wednesday and Thursday, particularly during the afternoon/evening
hours. A few Special Marine Warnings are possible for the
stronger storms.

There aren`t any obvious opportunities for strong gradient winds on
the waters from Friday through Sunday. A backdoor front will result
in east winds Friday, becoming southerly over the weekend as the
front lifts back north. In additional, there will be daily scattered
thunderstorm potential 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
24-27, 2025 timeframe:

A `+` sign indicates multiple years currently hold that record.

                 ***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)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Extreme Heat Warning until 9 PM EDT this evening for DCZ001.
     Heat Advisory from 11 AM to 9 PM EDT Wednesday for DCZ001.
MD...Air Quality Alert until midnight EDT tonight for MDZ008-508.
     Extreme Heat Warning until 9 PM EDT this evening for
     MDZ003>006-008-011-013-014-016>018-503>508.
     Heat Advisory from 11 AM to 9 PM EDT Wednesday for MDZ003>006-
     008-011-013-014-016>018-502>508.
     Heat Advisory until 9 PM EDT this evening for MDZ502.
VA...Extreme Heat Warning until 9 PM EDT this 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 Wednesday for VAZ026>031-
     036>040-050-051-053>057-501-502-505-506-526-527.
     Heat Advisory until 9 PM EDT this evening for VAZ025-026.
WV...Extreme Heat Warning until 9 PM EDT this evening for WVZ052-
     053.
     Heat Advisory from 11 AM to 9 PM EDT Wednesday for WVZ050>053-
     055-502-504-506.
     Heat Advisory until 9 PM EDT this evening for WVZ050-051-055-
     502-504-506.
MARINE...Air Quality Alert until midnight EDT tonight for ANZ530.
     Extreme Heat Warning until 9 PM EDT this evening for ANZ530.
     Heat Advisory from 11 AM to 9 PM EDT Wednesday for ANZ530.

&&

$$

SYNOPSIS...CJL
NEAR TERM...CJL
SHORT TERM...BRO/CJL
LONG TERM...ADS
AVIATION...ADS/BRO/CJL
MARINE...BRO/ADS
TIDES/COASTAL FLOODING...LWX
CLIMATE...LWX