336
FXUS61 KLWX 170126
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
926 PM EDT Tue Jul 16 2024

.SYNOPSIS...
High pressure will persist offshore through Wednesday while a
surface trough will reside east of the Blue Ridge Mountains.
The surface trough will be overtaken by a cold front late
Wednesday into Thursday. This front will then stall to the south
through the end of the week and into the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
High pressure remains situated offshore with a surface trough
east of the Blue Ridge Mountains. A couple of clusters of strong
to severe thunderstorms are noted over Northeast Maryland, parts
of central Maryland and near Washington DC, and in parts of the
Virginia Piedmont. This activity has the potential to produce
damaging wind gusts and some hail. The organization should
remain present with this activity as additional isolated showers
or storms develop in between the multiple clusters and all of it
moves to the Chesapeake Bay between 930pm (northern Bay) and
11pm (southern Bay).

Isolated showers or a rumble of thunder could develop farther
northwest and southwest, but much of the more intense convection
should fade during the overnight hours. Temperatures will be
somewhat cooler by a few degrees overnight too with lows getting
down to between 70 and 80 degrees.

Wednesday will consist of more heat and humidity, but may not be
as extreme as this afternoon with heat indice values being a few
degrees lower. Make no mistake about it, the heat and humidity
that we do encounter Wednesday could be dangerous as heat
indices poke back up into the lower 100s widespread. A Heat
Advisory remains in effect mainly east of the Blue Ridge with
another area of concern being the northern and central
Shenandoah Valley.

As for strong to severe thunderstorms, these should become more
widespread as we look at a cold front sagging across the region
during Wednesday and Wednesday evening. Damaging winds will be
the main threat with the strong to severe thunderstorms.

In terms of timing of an active thunderstorm day and evening, we
could see storms developing around Noon or up to about 2pm along
the trough over the central zones mainly east of the Blue Ridge.
Precipitable water values over 2 inches and intense storms could
result in possibility of the flooding aspect.

The potential for Flash Flooding exists as well with multiple
rounds or one solid line of intense thunderstorms moving across
the region, especially in the DC and Baltimore metro areas.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Once we get closer to the midnight hour Wednesday night into
early Thursday morning, strong and more severe thunderstorms
should wane as they move east and southeast with the front. Some
scattered showers could still linger or develop behind the
heaviest activity overnight Wednesday/early Thursday, but the
intensity should be much less and some slightly cooler and drier
air fills in behind each passing shower.

As we get more into the daytime heating aspect of things during
the day Thursday into early Thursday evening, a re-emerging of
showers and a few isolated thunderstorms could be present and
mainly across the southeastern half of our region. Highs will be
cooler and reaching the middle 80s for most of the area. More
comfortable air will be working in by Thursday night, with lows
generally in the 60s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Shortwave troughing will depart off to our east on Friday as high
pressure builds into the Ohio/Mississippi Valleys at the surface.
Northerly flow ahead of the high will advect a somewhat drier
airmass (precipitable water values below one inch) into the region.
The combination of drier air and weak subsidence behind the
departing shortwave should lead to dry conditions locally.
Temperatures should be seasonable, with highs in the mid to upper
80s.

Flow at the surface turns southerly by next weekend, which will
allow moisture to work back into the area from the south. As deeper
moisture works in from the south, daily chances for showers and
thunderstorms will return, although overall coverage shouldn`t be
overly high in the absence of any well-defined upper level features.
Seasonable temperatures will continue through the weekend into early
next week, with highs generally in the mid 80s to low 90s. Dewpoints
will climb into the 60s and lower 70s, making it feel a bit more
humid compared to Friday.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
The CHO terminal will encounter showers and a passing strong
thunderstorm for another hour or so, while much bigger
thunderstorms producing gusty winds move across the MTN and BWI
terminals through 11pm. A thunderstorm could brush the DCA
terminal through 10pm this evening; elsewhere at MRB and IAD
should be quiet for the overnight.

A higher likelihood of thunderstorms is expected Wednesday
afternoon and evening as a cold front approaches. Multiple
rounds of showers and thunderstorms are possible. Some showers
and storms, along with localized sub- VFR ceilings/visibilities
may linger into Wednesday night as the front pushes to the
south. Some uncertainty with how quickly the front pushes south
of the area Thursday. The highest convective chances will be
near CHO and to the south.

Prevailing VFR conditions are expected on both Friday and
Saturday, although a passing thunderstorm can`t be ruled out
Saturday afternoon. Winds will be light out of the north on
Friday, and then light out of the south on Saturday.

&&

.MARINE...
Small Craft Advisories remain in effect into tonight. Scattered
thunderstorms with gusty winds have resulted in Special Marine
Warnings from the far northern Chesapeake Bay and south to the
Chesapeake Bay Bridge to the east of Annapolis.

Thunderstorms with strong winds will become more likely
Wednesday afternoon and evening as a cold front approaches with
Special Marine Warnings likely. Marginal advisory conditions
are possible in southwesterly flow ahead of the front.

Sub-SCA winds are expected on both Friday and Saturday. Winds will
be out of the north to northeast on Friday, and out of the south to
southeast on Saturday.

&&

.CLIMATE...
Here are some daily high temperature records during the July 16-17
timeframe this week.

Records (RERs) are only issued for DCA, IAD, BWI, and MRB, but
other sites are shown for reference. A `+` sign indicates multiple years
currently hold that record.

                  ***TUESDAY, JULY 16TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        104F (1988)          102F
Washington-Dulles (IAD)          104F (1988)          102F
Baltimore (BWI)                  104F (1988)          102F
Martinsburg (MRB)                107F (1988)           99F
Charlottesville (CHO)            102F (1988)          100F
Annapolis (NAK)                   98F (1997)+          98F
Hagerstown (HGR)                 104F (1988)          100F

                 ***WEDNESDAY, JULY 17TH, 2024***
LOCATION                       RECORD (YEAR)        FORECAST
Washington-National (DCA)        102F (1980)           97F
Washington-Dulles (IAD)          100F (1997)+          96F
Baltimore (BWI)                  101F (1988)           97F
Martinsburg (MRB)                102F (1988)+          93F
Charlottesville (CHO)            100F (1988)+          96F
Annapolis (NAK)                  100F (1900)           94F
Hagerstown (HGR)                 100F (1953)+          93F

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from 11 AM to 8 PM EDT Wednesday for DCZ001.
MD...Small Craft Advisory until 2 AM EDT Wednesday for MDZ008.
     Heat Advisory from 11 AM to 8 PM EDT Wednesday for MDZ003>006-
     008-011-013-014-016>018-503>508.
VA...Heat Advisory from 11 AM to 8 PM EDT Wednesday for VAZ026>031-
     037>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.
MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ530>533-
     537-539>541.
     Heat Advisory from 11 AM to 8 PM EDT Wednesday for ANZ530.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ534-543.

&&

$$

SYNOPSIS...CPB
NEAR TERM...KLW/CPB
SHORT TERM...CPB
LONG TERM...KJP
AVIATION...KLW/KJP
MARINE...KLW/KJP
CLIMATE...