614
FXUS61 KLWX 030800
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Fri Jul 3 2026
.WHAT HAS CHANGED...
For areas east of the Blue Ridge, have extended Extreme Heat
Warnings out until 9 PM through Saturday as heat has lingered
beyond sundown. Have raised thunderstorm chances to isolated
this evening given the non-zero signal of convection arriving
from the north. Otherwise, models agree on increasing convective
threats through the holiday weekend.
&&
.KEY MESSAGES...
- 1) Extreme heat and humidity continues through the
Independence Day holiday weekend with some relief early next
week.
- 2) An increased risk for severe thunderstorms through the
Independence Day holiday weekend.
- 3) Temperatures gradually decrease early next week, with
potentially lingering shower and thunderstorm chances.
&&
.DISCUSSION...
KEY MESSAGE 1...Extreme heat and humidity continue through the
Independence Day holiday weekend with some relief early next
week.
Record temperatures will continue through much of the upcoming
Independence Day holiday weekend. An upper ridge remains parked
across a vast portion of the southeastern U.S. into the
Tennessee/Ohio Valleys and Mid-Atlantic region. Lower
tropospheric temperatures remain very anomalous and record
breaking in nature. Of note, the 00Z IAD sounding reported an
850-mb temperature of 25.0 C which is not only the 3rd highest
of all time, but breaks the daily record by over 4.0 C.
Recent 00Z models show a subtle decrease in these 850-mb
temperatures. However, based on yesterday`s observations, models
have been slightly too cool with this layer of the atmosphere.
Thus, see little reason to diverge from another hot forecast
with widespread temperatures punching into the 98 to 102 degree
range. Even during the writing of this discussion (~3 AM), a
number of the warmer spots remain entrenched in the upper 70s to
mid 80s. High dew points should also remain a fixture in the
forecast with readings holding steady in the low/mid 70s.
Although some boundary layer mixing could slightly lower such
dew points, the combination of triple digit highs and low 70s
dew points will easily crank heat indices to around 110F.
Extreme Heat Warnings continue from 10 AM until 9 PM across a
bulk of the Mid-Atlantic region. For those in the Blue Ridge,
Alleghenies, and across the central Shenandoah Valley, heat
indices around 100 to 104 degrees supports Heat Advisories
today.
Winds remain on the lighter side under this expansive dome of
high pressure. Skies should stay mostly sunny with any
convective threats likely holding off until the evening (see Key
Message for more information). Otherwise, it is a literal wash,
rinse, and repeat setup heading into Saturday/Independence Day.
This does offer a bit of transition in the overall pattern as
mid-level heights slowly decrease. These subtle height falls
will make for a slightly more challenging temperature forecast
as convection becomes more active during the core heating
hours. How much convection and cloud cover overspread the region
could hinder some of the diurnal heating. At this point, the
guidance keeps humidity levels plenty high to support additional
heat products. 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).
Temperatures drop off a bit into Sunday as convection becomes a
larger part of the equation. However, even with forecast highs
now in the low/mid 90s, elevated dew points could yield
additional heat headlines (i.e., Heat Advisories) on Sunday.
KEY MESSAGE 2...An increased risk for severe thunderstorms
through the Independence Day holiday weekend.
The Storm Prediction Center outlooks through late Sunday paint
the picture of an active convective pattern ahead. A Slight Risk
for severe thunderstorms is being advertised across portions of
the area during this period.
Starting with today, despite being earlier in the time period,
there is also a great deal of uncertainty. The strong
anticyclone aloft remains centered over the general area. To the
north, the usual summertime "ridge rollers" will form as
convective complexes traverse instability gradients. While not
all 00Z high-resolution models depict convection nearing the
Mason-Dixon Line, some do carry residual mesoscale convective
systems (MCS) approaching from the north. Have opted to add
isolated thunderstorms into the forecast, particularly along and
north of I-70. This generally follows the southern bound of the
Slight Risk area stretching up into southern New York.
As the upper ridge begins to undergo some weakening, the threat
of strong to severe thunderstorms will increase through the
holiday weekend. While the guidance shows deep-layered
westerlies on Saturday, the flow is on the weaker side which
would limit the negative influence of this flow on convective
development. 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 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. A
Slight Risk for severe convection remains across the entire
region.
The updated Day 3/Sunday outlook also brings another Slight Risk
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.
With the potential of repeat convection as well as a nearby
frontal system, an increasing flash flood risk exists. This
would particularly be the case across the more vulernable urban
corridors as well as any region with poor drainage. With the
front not clearing the Mid-Atlantic region until at least
Monday, this setup may persist another day.
KEY MESSAGE 3...Temperatures gradually decrease early next week,
with potentially lingering shower and thunderstorm chances.
As the upper-level ridge continues to buckle, a trough over the
Great Lakes will form with a stemming cold front tracking through
the region by early next week. This could cause additional chances
for showers and thunderstorms through potentially Monday and
Tuesday, 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 /06Z FRIDAY THROUGH TUESDAY/...
Have maintained VFR conditions at all terminals for the next 24
to 30 hours which runs out to early Saturday morning. Winds
remain on the light side and meander between west-northwesterly
before shifting to southwesterly. There is still a non-zero
chance an evening convective complex approaches the Mason-Dixon
Line from the north. If probabilities increase, a PROB30 group
could be introduced at the Baltimore terminals.
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. 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 in time. The bigger issue will be related to
convection impacting the waterways. While chances are low, a few
storms could approach the northern-most waters later this
evening/night. Otherwise, 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 this morning to 9 PM EDT this
evening for DCZ001.
Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
DCZ001.
MD...Extreme Heat Warning from 10 AM this morning to 9 PM EDT this
evening for MDZ004>006-008-011-013-014-016>018-503>508.
Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
MDZ004>006-008-011-013-014-016>018-503>508.
Extreme Heat Warning from 10 AM this morning to 8 PM EDT this
evening for MDZ003-502.
Heat Advisory from 10 AM to 8 PM EDT Saturday for MDZ003.
Heat Advisory from 10 AM this morning to 8 PM EDT this evening
for MDZ501-509-510.
VA...Extreme Heat Warning from 10 AM this morning to 9 PM EDT this
evening for VAZ036>040-050-051-053>057-501-502-505-506-
526-527.
Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
VAZ036>040-050-051-053>057-501-502-505-506-526-527.
Extreme Heat Warning from 10 AM this morning to 8 PM EDT this
evening for VAZ027>031.
Heat Advisory from 10 AM to 8 PM EDT Saturday for VAZ025>031.
Heat Advisory from 10 AM this morning to 8 PM EDT this evening
for VAZ025-026-503-504-507-508.
WV...Extreme Heat Warning from 10 AM this morning to 8 PM EDT this
evening for WVZ050>053-055-502-504.
Heat Advisory from 10 AM to 8 PM EDT Saturday for WVZ050>053-
055.
Heat Advisory from 10 AM this morning to 8 PM EDT this evening
for WVZ501-503-505-506.
MARINE...Extreme Heat Warning from 10 AM this morning to 9 PM EDT this
evening for ANZ530.
Extreme Heat Warning from 10 AM to 9 PM EDT Saturday for
ANZ530.
&&
$$
DISCUSSION...BRO/SRT
AVIATION...BRO/SRT
MARINE...BRO/SRT
CLIMATE...LWX
NWS LWX Office Area Forecast Discussion