972
FXUS61 KLWX 040159
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
959 PM EDT Fri Jul 3 2026
.WHAT HAS CHANGED...
Severe Thunderstorm Watch for northeast and north-central MD has
been allowed to expire early as thunderstorm activity remains north.
Went ahead and fine tuned heat headlines and storm timing for the
Independence Day holiday.
&&
.KEY MESSAGES...
- 1) A highly impactful Independence Day ahead with extreme heat and
an increased risk for widespread severe weather.
- 2) Severe thunderstorm chances continue Sunday and MOnday along
with and increased risk for flash flooding.
&&
.DISCUSSION...
KEY MESSAGE 1...A highly impactful Independence Day ahead with
extreme heat and an increased risk for widespread severe weather.
Overall the forecast remains on track. Went ahead and dropped the
Severe T-Storm Watch early for northeast and north-central MD as
storms remained confined up across eastern PA/central NJ. There was
enough of a stable layer in our 00z IAD sounding which suppressed
any convective chances across the region. Will continue to monitor
overnight as an additional complex of storms ejects from northern
Indiana/Ohio into western PA. This complex of storms looks to
congeal together and push east across PA and perhaps down along the
PA/MD border heading into early Saturday morning. The track of this
complex of storms will help dictate the severe threat going into
Saturday given the boundaries it may put off and ingredients of high
heat/humidity (=high instability) to feed off of. Outside of the
Severe T-Storm Watch, went ahead and let the Excessive Heat Warnings
and Heat Advisories expire this. Heat indices will remain around or
above 100 degrees through at least 10pm before falling into the 90s
and eventually 80s overnight.
It`s rinse and repeat for Independence Day another day of extreme
heat and more widespread thunderstorm coverage. The complex of
storms to the north overnight may inhibit some of the heating during
the day due to some extra cloud cover, especially north of I-66/US-
50. This same complex will aid in subtle height falls as the ridge
slowly buckles leading to a complex afternoon/evening convection
forecast during the peak heating period.
The Storm Prediction Center continues Slight Risk for severe
thunderstorms (Level 2 out of 5) for the entire area Saturday. The
likely triggers for diurnal convection will be around mesoscale
boundaries like the lee-side trough, as well as bay and river
breezes. Multiple days of intense heat and humidity yields somewhat
extreme levels of instability (i.e., mixed layer CAPEs around 3,000
to 4,000 J/kg in some models). With downdraft CAPE values nearing
1,500 J/kg, significant wind damage (due to 70-80 mph winds) is not
out of the question with more potent updrafts. While difficult to
hone in on timing, multiple rounds cannot be ruled given the degree
of instability in the atmosphere. Most reasonable guess on
timing per the latest CAMS seems to focus on 2-9pm for
thunderstorm activity. This include the 3-7pm window in the
immediate Baltimore/DC metro area.
Extreme Heat Warnings are in place from 10 AM until 9 PM for areas
east of the Blue Ridge. Heat indices again reach the 110 degree
mark, slightly higher toward the urban areas and along the
Chesapeake Bay. For the Shenandoah Valley, it will be another day of
Heat Advisories as heat indices rise to around 100 to 103 degrees.
Overall, additional daily temperature records could be broken
through Saturday (see the Climate section near the bottom of this
discussion).
KEY MESSAGE 2.. Severe thunderstorm chances continue Sunday and
Monday along with and increased risk for flash flooding.
Sunday brings another Slight Risk severe weather day to the local
area. A series of weak to modest perturbations in the flow will
work in tandem with an approaching nearby frontal system. The
position of remnant outflows, degree of convective debris, and
additional development are all questions looming for Sunday`s
forecast. Despite the uncertainty, the parameters remain favorable
for further thunderstorm activity. Damaging winds and instances
of flash flooding especially over urban/poor drainage areas
cannot be ruled out.
Things start to get a little more concerning for flooding Monday. As
the upper-level ridge continues to buckle, a trough over the Great
Lakes will form with a cold front tracking through the region by
Monday. Storms on Sunday are likely to trigger ahead of this front
and along existing outflow boundaries from Saturday, terrain
circulations, and Bay/River breezes. Storms should generally be
progressive, but the threat for training increases if any of these
existing boundaries line up parallel to the mean flow. A lot of
uncertainty with this, as we have to see how Saturday`s event
unfolds first and see what boundaries are left behind in its wake.
By Monday though, the slow-moving frontal boundary drops into our
region. This front will be very wavy in nature, but some portion
seems likely to line up with the mean low-mid level flow, which is
out of the WSW. Training convection is much more likely Monday
afternoon. Additionally, several days of convection before Monday
could reduce the flash-flood guidance, with some areas becoming more
susceptible. Either way, the urban areas are the greatest area of
concern, as model guidance wants to hang this front up somewhere
nearby. With PWATs in excess of 2", skinny CAPE profiles, a deep
warm cloud layer, and boundary-parallel low-mid level flow, a lot of
ingredients are there for a more widespread flash flooding threat.
Additional chances for showers and thunderstorms continue into
Wednesday, although the speed at which this weekend`s trough tracks
south will be critical for these continued chances to materialize.
ML guidance shows an upwards chance in thunderstorm & severe
potential for Monday, with NCAR`s Medium-Range AI NWP guidance
showing a 30%-45% probability in the 00z guidance for Monday
afternoon/evening. Synoptic setup in the days beforehand will be
critical in understanding the nature & scope of thunderstorms during
this period.
Temperatures look to potentially drop as this cold front tracks to
the south by early Tuesday, although dewpoints will remain elevated
for now resulting in continued humid conditions. Nevertheless, heat
indices look to potentially dip back into double digits by Tuesday
afternoon in the metros. High pressure moves over the region midweek.
&&
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Prevailing VFR conditions are expected at all terminals through at
least 16z/12pm Saturday. Outside of a few passing mid and high level
clouds, conditions will remain relatively quiet overnight. We`ll
continue to monitor a complex of storms up toward KPIT as it pushes
east/southeast heading into early Saturday morning.
Restrictions driven by thunderstorm activity become more likely over
the holiday weekend. While difficult to hone in on exact timing, the
afternoon/evening hours could yield fairly widespread showers and
thunderstorms. Some of these storms could become severe in nature
with damaging gusts as the primary threat. Latest 18z guidance
suggest the 19z-00z/3-8pm time window as the highest impact window
for storms for the Independence Day holiday. Storms will
initiate west of the corridor around 18-20z/2-4pm before
advancing east into the corridor between 20-00z/4-8pm. Storms
will diminish after 00- 02z/8-10pm with scattered to broken mid
and high level clouds overnight. Some LLWS may be noted in the
late evening deep westerly flow 2-3kft at 35-40 kts just off the
surface. Did make a mention of this at the corridor terminals
between 02-06z/10pm-2am. Additional severe weather threats are
expected Sunday during the afternoon/evening period. Overall
winds start off out of the west before turning more
southeasterly later in the weekend.
Periodic sub-VFR conditions remain possible through Monday and into
Tuesday as shower and thunderstorm chances remain possible Monday
afternoon & evening. Some of these storms could become severe
resulting in erratic changes in wind speed and directions,
potentially exceeding 50 knots. Frequent lightning is also possible
with any storms that form.
&&
.MARINE...
In response to expansive high pressure over the region, winds remain
light and well below any hazard thresholds. The weaker flow will
yield a series of wind shifts as this ridge reconfigures into the
weekend.
An active weather weekend lies ahead for those out and about for the
Independence Day holiday.Special Marine Warnings may be needed at
times, particularly during the afternoon/evening hours this weekend.
Before going out on the waters, ensure to check the forecast and
have multiple ways of receiving hazardous weather information.
Wind gusts stay below SCA thresholds through Monday afternoon. Winds
could potentially approach SCA thresholds Monday evening before
diminishing again Tuesday. Showers & thunderstorms remain possible
over the waters for Monday afternoon & evening, potentially causing
erratic winds, lightning, and storm-associated wind gusts.
&&
.CLIMATE...
There is a Significant Heat Risk through at least Saturday
(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 1-2).
==================================================================
*** 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 03
==================================================================
Baltimore 104 (1898) | 80 (1898)
Washington 101 (1966 + 2) | 80 (2018)
Sterling-Dulles Airport 103 (1966) | 73 (2018 + 2)
Baltimore Downtown 102 (1997) | 82 (2018 + 1983)
Annapolis 100 (1901) | 84 (1896)
Hagerstown 102 (1966) | 76 (2002)
Martinsburg 102 (1941 + 1911) | 74 (1980)
Charlottesville 100 (1966 + 1954) | 79 (1911)
==================================================================
*** 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) Records since
------------------------------------------------------------------
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 from 10 AM to 9 PM EDT Saturday for
DCZ001.
MD...Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
MDZ004>006-008-011-013-014-016>018-503>508.
Heat Advisory from 10 AM to 8 PM EDT Saturday for MDZ003-502.
VA...Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
VAZ036>040-050-051-053>057-501-502-505-506-526-527.
Heat Advisory from 10 AM to 8 PM EDT Saturday for VAZ025>031-
504.
WV...Heat Advisory from 10 AM to 8 PM EDT Saturday for WVZ050>053-
055-502-504-506.
MARINE...Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
ANZ530.
&&
$$
DISCUSSION...BRO/DHOF/CJL/SRT
AVIATION...BRO/DHOF/CJL/EST
MARINE...BRO/DHOF/CJL/EST
NWS LWX Office Area Forecast Discussion