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203
FXUS61 KLWX 221429
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1029 AM EDT Sat Jun 22 2024

.SYNOPSIS...
High pressure remains offshore today while a stationary front
will stretch across the Great Lakes. This front will push south
through the area late Sunday into Monday. High pressure briefly
builds back over the area Tuesday before an another cold front
sweeps through the region Wednesday and Thursday next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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High pressure remains offshore today, with southwesterly low
level flow advecting hotter and more humid air into the area.
Near record highs in the mid 90s to near 100 are expected, with
heat index values between 100 and 108 for the lower elevations.
Based on current temperatures vs. this time yesterday, the area
is generally about 3 to 6 degrees ahead of yesterday`s pace.
Given the nearly cloudless skies and quick start to the
heating, have opted to raise temperatures by another degree or
two. Consequently, Heat Advisories remain in effect for much of
the area until 8 PM.

Thunderstorm chances may be slightly higher this afternoon than
preceding days, although large scale forcing is lacking.
Initiation will likely occur over the terrain and/or along a
weak SW to NE oriented lee trough. Computer models suggest
sparse coverage overall, likely owing to the lack of strong
forcing and dry air aloft. A brief strong to severe thunderstorm
with a damaging downburst could occur due to the building
instability, but overall flow is weak and storms may be too
widely spaced to produce colliding outflows that often trigger
this scenario.

Any storms quickly dissipate this evening. There won`t be much
relief to the heat tonight as lows only drop into the 70s, with
urban centers perhaps remaining in the 80s.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Hot conditions with near record highs will continue Sunday,
although there is increasing uncertainty due to quickly
advancing clouds ahead of the next trough. The highest chance
for upper 90s will be along the I-95 corridor, with gradually
declining values to the west where clouds will be thicker and
heights falling. Additional Heat Advisories will likely be
needed, but probably less widespread than today.

A few showers may advance across the mountains during the
morning with a lead perturbation. The surface trough appears to
set up near or just east of the Blue Ridge. This is where the
greatest moisture and instability will pool and where at least
scattered convection may intensify heading into the afternoon.
Flow will be a bit stronger, so a severe risk could evolve, with
primarily a damaging wind threat. Convection will also develop
ahead of the cold front and shortwave aloft across the Ohio
Valley, approaching the Appalachians during the late afternoon
or evening. It`s still not clear at this point whether this
convection survives across the mountains, or if a different
threat materializes as forcing overspread what will likely still
be a moderately unstable atmosphere despite the time of day.
Some risk for severe storms and perhaps even localized flash
flooding could continue into the late evening/overnight hours,
although activity should eventually progress to the east.

Most guidance now has the cold front most of the way through the
area Monday. This puts temperatures and thunderstorm chances in
question, although the primary trough axis could still provide
some forcing. The highest rain chances will be across southern
Maryland. Temperatures do look cooler north and west of
Washington, while areas to the south and east may still climb
into the 90s. Lower humidity is ushered in Monday night, with
lows falling into the 60s to near 70, with 50s possible in the
mountains.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Upper troughing will depart off to the east on Tuesday, allowing
high pressure to build overhead at the surface. Sunny skies are
expected along with hot, but much less humid conditions. High
temperatures should reach into the upper 80s and lower 90s for most,
with low-mid 80s in the mountains. Dewpoints are expected to fall
into the 50s to near 60.

A shortwave trough will track through the Great Lakes on Wednesday.
Low-level flow will turn southwesterly in response out ahead of this
system, which will allow very hot and humid conditions to work back
into the area. Temperatures will soar back into the mid-upper 90s,
with dewpoints also climbing into the upper 60s. After a sunny start
to the day, clouds will be on the increase through the afternoon,
and thunderstorms may be possible during the afternoon into the
overnight hours. The system`s cold front will progress through
during the day Thursday. Additional showers and thunderstorms may be
on Thursday depending on the ultimate positioning of the front.
Temperatures will also be dependent on the positioning of the front,
which has some uncertainty associated with it this far out. As for
now, highs are forecast to reach into the mid 80s to low 90s.

High pressure will build to our north on Friday. Mostly sunny skies,
light onshore flow, and seasonable temperatures (highs in the mid
80s to near 90, upper 70s to lower 80s in the mountains) are
expected.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions with light south winds continue through tonight.
Isolated to scattered thunderstorms may develop this afternoon
into the early evening across the mountains and perhaps toward
northern Maryland. Consensus keeps most of the activity
northwest of the metros, so no TAF mention for now, but it could
be close. VCTS is included for MRB, where the chance is the
highest.

A greater thunderstorm threat is expected Sunday and could come
in two rounds. The first with scattered storms developing across
the metro terminals during the afternoon, then an additional
opportunity during the evening or overnight hours. Strong to
severe storms are possible. With a quicker frontal progression,
most thunderstorms may be southeast of the terminals on Monday.

Prevailing VFR conditions are expected at the terminals on both
Tuesday and Wednesday. A passing thunderstorm may be possible
Wednesday afternoon or Wednesday night. Winds will be out of the
west to northwest on Tuesday, and then out of the south on
Wednesday.

&&

.MARINE...
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Southerly winds will strengthen again from mid afternoon into
tonight, and another Small Craft Advisory is being issued. While
an isolated gusty thunderstorm could reach the waters later
this afternoon or early evening, most of the activity should
stay inland.

Advisories will likely be needed for all waters Sunday as
south-southwest winds increase. There will also be potentially
two opportunities for strong to severe thunderstorms during the
afternoon and evening to overnight hours.

Small Craft Advisories may be needed for portions of the waters
Monday into Monday night as a cold front passes through and
winds shift to the west and northwest. Thunderstorms may develop
again Monday, although this chance is trending downward.

Sub-SCA west to northwesterly flow is expected on Tuesday. Winds
turn southerly on Wednesday, and may near low-end SCA levels in
channeled southerly flow.
-- End Changed Discussion --

&&

.CLIMATE...
Very hot temperatures are expected through Sunday. Several
records could be in jeopardy, as seen below. Below is a list of
record high temperatures for Jun 22nd and the 23rd, and
the year the record was set, and the current forecast high
temperatures for those days. RERs are only issued for DCA, IAD,
BWI, and MRB, but other sites are shown for reference.

                                    Saturday Jun 22nd
Climate Site                  Record High     Forecast High
Washington-National (DCA)    101F (1988)          100F
Washington-Dulles (IAD)       99F (1988)          99F
Baltimore (BWI)              100F (1988)          99F
Martinsburg (MRB)            102F (1933)          97F
Charlottesville (CHO)        101F (1933)          98F
Annapolis (NAK)              101F (1988)          95F
Hagerstown (HGR)             100F (1988)          98F

                                    Sunday Jun 23nd
Climate Site                  Record High     Forecast High
Washington-National (DCA)     98F (1988)          98F
Washington-Dulles (IAD)       96F (1988)          97F
Baltimore (BWI)               97F (2010)          98F
Martinsburg (MRB)            100F (1934)          94F
Charlottesville (CHO)        100F (1894)          96F
Annapolis (NAK)               98F (1988)          95F
Hagerstown (HGR)              98F (1988)          94F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Heat Advisory until 8 PM EDT this evening for DCZ001.
MD...Heat Advisory until 8 PM EDT this evening for MDZ003>006-008-
     011-013-014-016>018-501>508.
VA...Heat Advisory until 8 PM EDT this evening for VAZ025>031-
     036>040-050-051-053>057-501-502-504>506-526-527.
WV...Heat Advisory until 8 PM EDT this evening for WVZ050>053-055-
     502>504-506.
MARINE...Small Craft Advisory from 2 PM this afternoon to 2 AM EDT
     Sunday for ANZ531-532-538>542.
     Small Craft Advisory from 2 PM this afternoon to 6 AM EDT
     Sunday for ANZ533-534-537-543.
-- End Changed Discussion --

&&

$$

SYNOPSIS...ADS
NEAR TERM...ADS/BRO
SHORT TERM...ADS
LONG TERM...KJP
AVIATION...ADS/KJP
MARINE...ADS/BRO/KJP
CLIMATE...