763
FXUS61 KLWX 301945
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
345 PM EDT Tue Jun 30 2026
.WHAT HAS CHANGED...
The Heat Advisory for Wednesday has been expanded to include
Calvert and St. Mary`s Counties. The Extreme Heat Watches for
Thursday and Friday have been expanded to include Green,
Albemarle, Nelson, Augusta, and Rockingham Counties. Have
included brief low precipitation chances focused around subtle
boundaries over the next few days.
&&
.KEY MESSAGES...
- (1) Extreme heat builds over the region through at least the
end of the week.
- (2) Thunderstorm chance increase through this weekend, with
an increased risk for severe thunderstorms Friday into the
Independence Day weekend.
&&
.DISCUSSION...
KEY MESSAGE 1...Extreme heat builds over the region through at
least the end of the week.
What may turn out to be the most intense heat wave since 2012 is
on our doorstep. It is important to plan ahead on how to best
keep safe from the heat.
Have a plan on how to stay cool (and hydrated).
Tips for the heat...
-Keep Cool: If there is not access to air conditioning, you can
look up nearby cooling centers through local county websites.
Buildings that do not have air conditioning may remain hot for
several days after the worst of the heat wave.
-Stay Hydrated: Remember that drinks containing alcohol or
caffeine actually dehydrate, so balance that with water or
sports drinks.
-Take It Easy: Try to limit strenuous outdoor activity (work,
exercise, etc.) to early morning or late evening when it`s not
as hot.
-Dress For Heat: Wear lightweight, light-colored, loose fitting
clothing; this helps reflect the sun and allows for airflow to
keep cooler.
-Look Before You Lock: Never leave anyone unattended in a
vehicle as temperatures can reach lethal levels in a matter of
minutes.
-Check In With Each Other: Check in on family, friends, and
neighbors. The elderly, very young, and those with compromised
immunity or mental health are at an increased risk from heat.
-Be Aware: Stay tuned to the latest heat alerts and forecast
from NWS, and be mindful that prolonged extreme heat could
impact power, water, and transportation systems.
The meteorology...
Low-level moisture has increased substantially with dew points
well into the 70s in the valleys west of I-81. Combined with
widespread air temperatures to around 90, this is resulting in
heat index values of 100 to 105 in the lower elevations of
western MD and eastern WV in the lee of the Appalachian crest.
The heat will continue to build Wednesday as ridging continues
to strengthen just to the south and west. Temperatures soaring
well into the 90s with dew points in the upper 60s (west of the
Blue Ridge) to lower 70s (east of the Blue Ridge) will lead to
heat index values around or a little over 100 (west) and 105
(east) during the afternoon hours. This is covered with a Heat
Advisory for all except the higher elevation zones, although
there is growing concern that prolonged abnormal heat even at
higher elevations could be impactful where there is limited AC
available. Will evaluate as the event draws near to see if those
zones need to be added. In the meantime, have expanded the
advisory into Calvert and St. Mary`s Counties. It looks like the
low-level moisture gets there a bit quicker than in previous
cycles of guidance, possibly aided by slightly higher surface
dew points in the vicinity of the tidal Potomac River and the
Chesapeake Bay.
Extreme Heat Watches remain in effect for Thursday through
Friday when the heat peaks, and have been expanded to include
all but the higher elevation zones (though again concern is
growing for impactful heat even at higher elevations). Air
temperatures are likely to near record values Thursday and
Friday. Dew points will remain elevated especially east of the
Blue Ridge resulting in widespread heat index values well over
100, with increasing potential to exceed 110 east of the Blue
Ridge toward the metros. Areas near larger bodies of water
(tidal Potomac River, Chesapeake Bay) could see spotty heat
indices near 115 at times.
The heat is likely to continue into Saturday, though the exact
magnitude becomes increasingly uncertain several days out. This
uncertainty is also raised due to potential for showers and
thunderstorms that could put a lid on temperatures. Heat
headlines are likely at some point, but confidence in reaching
widespread warning criteria is low for now. Either way, it will
likely be very impactful given it will be several days in a row
of high heat and humidity.
Sunday looks relatively "cooler" though temperatures likely
still reach the 90s with elevated humidity. This could push us
close to Heat Advisory criteria once again.
Even at night, temperatures will stay in the 70s for most
(perhaps not falling below 80 in the major urban centers). This
keeps heat indices in the 90s most of the night, offering
little to no relief from the heat.
Lastly, the intense heat and humidity will likely result in poor
air quality at times. Visit your state`s air quality information
website for more information.
KEY MESSAGE 2...Thunderstorm chance increase through this weekend,
with an increased risk for severe thunderstorms Friday into the
Independence Day weekend.
With excessive heat and humidity comes the potential for severe
weather as abundant instability and moisture pool over the region.
Any showers and thunderstorms through mid week should be very
spotty. A few spots to look out for: near the intersection of a
bay breeze and lee pressure trough Wednesday afternoon, and near
the higher terrain Thursday afternoon. Most of the area/time
will be dry, but any storms that do manage to form could produce
very gusty winds, frequent lightning, and torrential downpours
or even some hail given large amounts of potential energy (CAPE).
Upper-level ridging will gradually buckle Friday before flattening
over the weekend into early next week as the broad subtropical
high pressure shifts further offshore and a series of shortwave
disturbances pivot through. Timing and coverage of storms have
yet to be determined given the placement of synoptic/mesoscale
features. With that said, looking at scattered strong to severe
thunderstorms mainly during the afternoon and evening period
with damaging wind gusts, large hail, heavy rainfall, and
frequent lightning as the main threats. Storms may be of the
pulse variety likely forming along the lee side trough east of
the Alleghenies or residual outflows (i.e the bay/river breeze)
due to the lack shear aloft Friday into Saturday. Of course
this is subject to change based on any ripples of energy that
move between over top of the ridge shunted to the south and the jet
stream to the north (Great Lakes/Ohio River Valley). If this were
to occur, we could be looking at more organized and widespread
storm clusters, but confidence in this is low at this time.
Multiple instances of deterministic/ensemble guidance illustrate
this on both Saturday into Sunday as the ridge flattens further.
Google AI WxNet along with CIPS/CSU AI probs illustrate this
with rather high probabilities of severe weather this weekend.
As we approach the Independence Day weekend, have a weather
preparedness plan ready to go, especially if you are outdoors (i.e
at a picnic with family or a fireworks show). Plan ahead for any
outdoor activities this weekend, as they are likely to be
interrupted by storms at some point. Have a way to get trusted
warnings, download a radar/lightning app to keep aware of changing
weather conditions, and know when to act. When thunder roars, go
indoors. Lightning can strike up to 15 miles outside of the core
of thunderstorms, so wait 30 minutes after that last rumble of
thunder before resuming outdoor activities. Given the heat in
place, some storms could be quite intense (if they form). From a
historical perspective, prolonged near record heat in summer
often ends in a period of strong storms. Intense storms can
produce hail and high winds in addition to rain and lightning,
so having access to sturdy shelter is important.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Prevailing VFR conditions are expected through Thursday. Winds
are expected to remain out of the south tonight before becoming
southwesterly on Wednesday. Afternoon bay breezes may cause
more E/SE flow at MTN and possibly BWI. Dry weather is expected
through mid week, though a pop up t-storm can`t be ruled out
near any bay breezes (especially Wednesday).
VFR conditions are generally expected on both Friday and Saturday.
Intermittent sub-VFR conditions return Friday afternoon and evening
and again during the afternoon/evening periods this weekend as
thunderstorm chances increase. Should thunderstorms materialize,
some could become severe resulting in erratic changes in wind
speed and directions, potentially exceeding 50 knots. Additionally,
storms would come with the likelihood of frequent lightning and
the chance for some hail. Timing will generally be during the
mid-late afternoon through evening hours each day, with further
west areas earlier and the metros later.
&&
.MARINE...
Southerly winds are forecast over the waters through Thursday,
with SCAs in effect this afternoon into tonight. Additional SCAs
have been issued Wednesday afternoon and evening, when strong
southerly channeling could result in some gusts near 30 knots
over the main channel of the Chesapeake Bay. Additional
channeling is possible each afternoon and evening through the
weekend, though with gradually lessening intensity.
Thunderstorm chances increase Friday afternoon and especially
by Saturday afternoon. With any storms will come the chance for
erratic and strong wind gusts, potentially in excess of 50
knots, as well as frequent lightning and hail. Timing of storms
is still a bit uncertain, but should generally be during the
mid-late afternoon through the evening hours, as is typical
with summer convection.
&&
.TIDES/COASTAL FLOODING...
Increasing southerly flow could cause near minor flooding
particularly at Annapolis and possibly Havre de Grace, Bowley`s
Quarters and Alexandria early Wednesday morning.
&&
.CLIMATE...
There is a significant heat risk this week. The numbers below
aren`t a forecast, but rather a reference for historical context
for comparison. Latest forecast: weather.gov/lwx.
==================================================================
*** 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 01
==================================================================
Baltimore 103 (1901) | 80 (1933 + 1901)
Washington 102 (1901) | 79 (1977)
Sterling-Dulles Airport 96 (2012) | 72 (2017 + 3)
Baltimore Downtown 101 (2012) | 82 (2012)
Annapolis 103 (1901) | 79 (1945 + 1901)
Hagerstown 100 (1901) | 74 (2017 + 1977)
Martinsburg 102 (1933) | 74 (1933)
Charlottesville 101 (2012 + 1945) | 78 (1901)
==================================================================
*** DAILY RECORD HIGHS | WARM LOWS ***
VALID: Jul 02
==================================================================
Baltimore 103 (1901) | 80 (1901)
Washington 101 (1898) | 79 (2012 + 1872)
Sterling-Dulles Airport 98 (1966) | 75 (2022)
Baltimore Downtown 102 (1966) | 84 (2002)
Annapolis 105 (1901) | 80 (1901)
Hagerstown 100 (1966) | 74 (2018 + 1901)
Martinsburg 102 (1933 + 1931) | 75 (1933 + 1901)
Charlottesville 100 (1954) | 76 (1910)
==================================================================
*** DAILY RECORD HIGHS | WARM LOWS ***
VALID: Jul 04
==================================================================
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)
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...Heat Advisory from 11 AM to 8 PM EDT Wednesday for DCZ001.
Extreme Heat Watch from Thursday morning through Friday
evening for DCZ001.
MD...Heat Advisory from 11 AM to 8 PM EDT Wednesday for MDZ003>006-
008-011-013-014-016>018-503>508.
Extreme Heat Watch from Thursday morning through Friday
evening for MDZ003>006-008-011-013-014-016>018-502>508.
Heat Advisory until 8 PM EDT Wednesday for MDZ502.
VA...Heat Advisory from 11 AM to 8 PM EDT Wednesday for VAZ025>031-
036>040-050-051-053>057-501-502-504>506-526-527.
Extreme Heat Watch from Thursday morning through Friday
evening for VAZ025>031-036>040-050-051-053>057-501-502-
505-506-526-527.
WV...Heat Advisory from 11 AM to 8 PM EDT Wednesday for WVZ051>053.
Extreme Heat Watch from Thursday morning through Friday
evening for WVZ050>053-055-502-504.
Heat Advisory until 8 PM EDT Wednesday for WVZ050-055-502-504-
506.
MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ530-534-
539>541-543.
Small Craft Advisory from 2 PM to 11 PM EDT Wednesday for
ANZ530-535-536.
Heat Advisory from 11 AM to 8 PM EDT Wednesday for ANZ530.
Extreme Heat Watch from Thursday morning through Friday
evening for ANZ530.
Small Craft Advisory until 6 AM EDT Wednesday for ANZ531>533.
Small Craft Advisory from 11 AM Wednesday to 2 AM EDT Thursday
for ANZ531>534-537>541-543.
Small Craft Advisory until 1 AM EDT Wednesday for ANZ535>538-
542.
Small Craft Advisory from 11 AM to 11 PM EDT Wednesday for
ANZ542.
&&
$$
DISCUSSION...BRO/DHOF/CJL/KJP/EST
AVIATION...DHOF/CJL/KJP/EST
MARINE...DHOF/CJL/KJP/EST
TIDES/COASTAL FLOODING...DHOF/BRO/KJP
CLIMATE...DHOF
NWS LWX Office Area Forecast Discussion