Ashburn, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

328
FXUS61 KLWX 041853
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
253 PM EDT Sat Jul 4 2026

.WHAT HAS CHANGED...
A Severe Thunderstorm Watch is in effect for the entire region
until this evening. Strong instability will lead to numerous
thunderstorms capable of 60-75 mph wind gusts.

&&

.KEY MESSAGES...
- 1) A highly impactful Independence Day lies ahead today with
  extreme heat and an Enhanced Risk for severe thunderstorms.

- 2) Severe thunderstorm chances continue Sunday and Monday
  along with an increased risk for flash flooding.

- 3) More seasonable conditions return by mid/late next week.

&&

.DISCUSSION...
KEY MESSAGE 1...A highly impactful Independence Day lies ahead
today with extreme heat and an Enhanced Risk for severe
thunderstorms.

Numerous strong to severe thunderstorms are expected through
this evening, and the most intense storms may be capable of
producing wind gusts to 75 mph. It is extremely important to
have a plan to get to sturdy shelter quickly when storms
threaten. In addition to high winds, frequent lightning is
occurring with many of the storms today due to the heat.

As of 18Z/2PM EDT, convective initiation has commenced across
WV into western VA and western MD. A subtle mid/upper-level wave
emanating out of the KY/WV/VA intersection coupled with a
lingering surface trough/outflow as well as strong heating and
terrain circulations will continue to lead to thunderstorm
development through late afternoon.

The axis of the surface trough across north-central VA into
central MD may prove to be a favored corridor for storms, though
they will be rather numerous areawide.

Subtle mid-level cooling and 25-30 kt mid-level flow associated
with the aforementioned wave should be just enough when coupled
with 2500-3500 J/kg MLCAPE and steep lapse rates through the
troposphere to result in numerous to widespread strong storms.

Storms over the Shenandoah Valley will propagate across the
Blue Ridge into the Piedmont through 4pm, with storms crossing
the I-95 corridor between 4-8pm. Additional activity may develop
with a trailing wave until about 10pm, but after that time
increasing low-level stability should result in a quickly waning
severe threat.

Additional showers and a few thunderstorms are possible until a
bit past midnight (1-2am) with lingering instability aloft.


KEY MESSAGE 2...Severe thunderstorm chances continue Sunday and
Monday along with an increased risk for flash flooding.

To finish out the holiday weekend, an active weather pattern
likely continues into the start of the new work week. Behind the
earlier shortwave trough, residual lower heights will approach
from the Ohio Valley on Sunday into Monday. This carries a
parent frontal system into the Mid-Atlantic region which may be
slow moving or even quasi-stationary at times. Until this system
exits the area to the south, unsettled conditions will remain in
the picture.

While a bit cooler than recent days, it will be another
seasonably hot and humid day across the area. High temperatures
should fall short of the century mark, but heat indices are
likely to range from 100 to 105 degrees, locally a bit higher
south of I-66. Additional Heat Advisories might be needed if
these elevated heat indices persist in subsequent forecast
packages. Ample cloud cover and shower/thunderstorm activity may
hinder surface heating in spots. Otherwise, convection looks
widespread again with a Slight Risk for severe weather east of
the Alleghenies (Marginal Risk over these mountains). If similar
thermodynamic profiles continue into Sunday, damaging winds
would be the primary threat with the stronger cells.

An additional aspect to the Sunday into Monday forecast is the
flash flooding threat. With multiple rounds of showers and
thunderstorms expected from today/Saturday into early next week,
excessive rainfall may occur across portions of the area.
Precipitable water (PWAT) values remain quite anomalous in
nature, generally averaging between 1.75 and 2.25 inches. Adding
this tropical laden moisture with a near stalled frontal system
will aid in a discernible flood threat. Due to the flashy
nature of the metro areas, these would be the most  to
any rapid hydrologic response. Although the area remains in a
longstanding drought, rapid run-off can still occur in these
high PWAT environments. Consequently, the Weather Prediction
Center is maintaining a Slight Risk for excessive rainfall on
Sunday into Monday night.


KEY MESSAGE 3...More seasonable conditions return by mid/late
next week.

Persistent troughing to start the week will gradually see these
lower heights pull away from the Atlantic coast. The resultant
reflection at the surface would carry the surface cold front
down into the Carolinas by mid-week. As this boundary settles
to the south, a more seasonable air mass takes over the Mid-
Atlantic states. Daily high temperatures will be in the mid 80s
to low 90s, with overnight lows in the mid 60s to low 70s. For
mountain locales, expect these readings to be around 5 to 10
degrees cooler. However, this comes with some temperature spread
as evident in ensemble box-and-whisker plots. Additionally, there
should be some diurnal convection at times during this mid/late
week period, but details are more difficult to discern this far
out in time.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Numerous showers and thunderstorms are breaking out this
afternoon, many of which will be strong to severe in nature.
The most likely timeframe for impacts has been narrowed down to
a 2-hour TEMPO at the TAF sites. Additional restrictions are
certainly possible outside this window given the continued
threat for showers. Otherwise, for today, winds stay on the
lighter side while shifting from northwesterly over to west-
southwesterly. Some low-level wind shear is possible in the
03-09Z window tonight as a southwesterly jet tracks through.

Looking ahead to Sunday and Monday, a nearby frontal system will
make for more widespread convection. This supports more periods
of restrictions, particularly for the afternoon to evening
hours. Given the amount of rainfall expected through Monday,
some nighttime patchy fog cannot be ruled out. Winds on Sunday
into Monday begin out of the southeast before turning more
easterly into the new work week.

On Tuesday into Wednesday, mainly VFR conditions are expected in
the wake of the exiting cold front. Winds will be out of the
north to northeast behind this boundary. Some diurnal convection
may occur, but restrictions are looking less likely at this
time.

&&

.MARINE...
Overall synoptic gradients are on the weaker side given the time
of year. There could be a few surges up the Chesapeake Bay at
times, but confidence is low if these will be strong enough to
cause any Small Craft Advisories. The bigger issue for the
waterways will be a multi-day period of strong to severe
thunderstorms. For today, there is an Enhanced Risk for severe
weather which will likely necessitate a number of Special Marine
Warnings. For those with outdoor plans on Independence Day, make
sure you have multiple ways to receive hazardous weather alerts.
A brunt of the activity is expected in the late afternoon to
evening hours, but this could fester into the overnight hours as
well. Additional storms are possible on Sunday into Monday which
will make for hazardous conditions at times over the waters.

&&

.CLIMATE...
There is a Significant Heat Risk today (Independence Day). The
numbers below aren`t a forecast, but rather a reference for
historical context for comparison. Latest forecast:
weather.gov/lwx. A number of daily records have been broken at
the local airports the past couple of days (July 1-3).

==================================================================
                    *** ALL-TIME RECORD HIGHS ***
==================================================================
Baltimore                 107 (set on Jul 10, 1936)
Washington                106 (set on Jul 20, 1930 + Aug 06, 1918)
Sterling-Dulles Airport   105 (set on Jul 22, 2011)
Baltimore Downtown        108 (set on Jul 07, 2012 + Jul 22, 2011)
Annapolis                 106 (set on Aug 06, 1918)
Hagerstown                105 (set on Jul 14, 1954)
Martinsburg               112 (set on Jul 11, 1936)
Charlottesville           107 (set on Sep 07, 1954 + 3 other times)

==================================================================
                  *** ALL-TIME RECORD WARM LOWS ***
==================================================================
Baltimore                  83 (set on Aug 05, 1930 + 2 other times)
Washington                 84 (set on Jul 24, 2011 + 2 other times)
Sterling-Dulles Airport    79 (set on Aug 08, 2007)
Baltimore Downtown         88 (set on Jul 22, 2011 and Jul 10, 1993)
Annapolis                  92 (set on Jul 07, 1994)
Hagerstown                 86 (set on Jun 15, 1899)
Martinsburg                86 (set on Jul 21, 1930)
Charlottesville            85 (set on Aug 07, 1918)

==================================================================
                  *** JULY MONTHLY RECORD HIGHS ***
==================================================================
Baltimore                 107 (set on Jul 10, 1936)
Washington                106 (set on Jul 20, 1930)
Sterling-Dulles Airport   105 (set on Jul 22, 2011)
Baltimore Downtown        108 (set on Jul 07, 2012 + Jul 22, 2011)
Annapolis                 105 (set on Jul 21, 1930 + Jul 02, 1901)
Hagerstown                105 (set on Jul 14, 1954)
Martinsburg               112 (set on Jul 11, 1936)
Charlottesville           107 (set on Jul 10, 1936 + Jul 20, 1930)

==================================================================
                 *** JULY MONTHLY RECORD WARM LOWS ***
==================================================================
Baltimore                  83 (set on Jul 21, 1930)
Washington                 84 (set on Jul 24, 2011 + 2 other times)
Sterling-Dulles Airport    78 (set on Jul 24, 2010 + Jul 08, 2010)
Baltimore Downtown         88 (set on Jul 22, 2011 + Jul 10, 1993)
Annapolis                  92 (set on Jul 07, 1994)
Hagerstown                 83 (set on Jul 24, 2010)
Martinsburg                86 (set on Jul 21, 1930)
Charlottesville            84 (set on Jul 22, 1930)

==================================================================
               *** DAILY RECORD HIGHS | WARM LOWS ***
                          VALID: Jul 04
==================================================================
Baltimore                100 (2002 + 2)    |   78 (1911)
Washington               100 (1919)        |   80 (2018 + 2002)
Sterling-Dulles Airport   97 (2002 + 1999) |   75 (2018)
Baltimore Downtown       101 (2002 + 1990) |   83 (2002)
Annapolis                 98 (1999)        |   81 (2018)
Hagerstown               100 (1966 + 1919) |   76 (2018)
Martinsburg              103 (1898)        |   76 (1999)
Charlottesville          100 (2012)        |   78 (1919)

-----------------------------------------------------------------

             Number of Consecutive Days Max Temp >=100
Area (obs site)              Longest Streaks

------------------------------------------------------------------
Baltimore (BWI)          4 days  July 14-17,2024 & July 19-22,1930
Washington (DCA)         4 days  July 14-17, 2024 & July 5-8, 2012
Sterling-Dulles (IAD)    2 days  July 7-8, 2012, July 21-22, 2011
                                 July 6-7, 2010, July 16-17, 1997

Baltimore Downtown (DMH) 5 days July 3-7, 2010 & July 7-11, 1993
Annapolis (NAK)          1 day  July 21, 2019, July 7, 2012,
                                July 22, 2011, June 29, 1959

Hagerstown (HGR)         3 days July 5-7, 2010
Martinsburg (MRB)        6 days June 1-6, 1925
Charlottesville (CHO)    5 days July 4-8, 2012



     Period of Record (POR) context...
Area (obs site)              Records since
------------------------------------------------------------------
Baltimore (BWI)                     Jan 1872
Washington (DCA)                    Jul 1872
Sterling-Dulles Airport (IAD)       Jan 1960
Baltimore Downtown (DMH)            Jul 1950
Annapolis (NAK)                     Jan 1894
Hagerstown (HGR)                    Jan 1899
Martinsburg (MRB)                   Jan 1891
Charlottesville (CHO)               Jan 1893

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Extreme Heat Warning until 9 PM EDT this evening for DCZ001.
MD...Extreme Heat Warning until 9 PM EDT this evening for
     MDZ004>006-008-011-013-014-016>018-503>508.
     Extreme Heat Warning until 8 PM EDT this evening for MDZ003.
     Heat Advisory until 8 PM EDT this evening for MDZ502.
VA...Extreme Heat Warning until 9 PM EDT this evening for
     VAZ036>040-050-051-053>057-501-502-505-506-526-527.
     Extreme Heat Warning until 8 PM EDT this evening for
     VAZ027>031.
     Heat Advisory until 8 PM EDT this evening for VAZ025-026-504.
WV...Extreme Heat Warning until 8 PM EDT this evening for
     WVZ050>053-055.
     Heat Advisory until 8 PM EDT this evening for WVZ502-504-506.
MARINE...Extreme Heat Warning until 9 PM EDT this evening for ANZ530.

&&

$$

DISCUSSION...BRO/DHOF
AVIATION...BRO/DHOF
MARINE...BRO/DHOF
CLIMATE...LWX