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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 171428 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1028 AM EDT Tue May 17 2022

.SYNOPSIS...
-- Changed Discussion --
A cold front will drop through the area this afternoon. High
pressure will follow tonight into early Wednesday. A warm front
will develop over the south-central Appalachian Mountains
tonight, then lift northeastward through early Friday. A cold
front is expected to approach from the Midwest over the weekend.
High pressure will likely follow early next week.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH WEDNESDAY/...

-- Changed Discussion --
A mainly dry cold front will cross the area this afternoon.
Guidance show lots of mid-level clouds (bases around 8kft)
accompanying this front as it crosses the area and even a few
CAMs show a few sprinkles or a spotty shower or two across
northwestern areas. 12Z IAD sounding shows wind gust potential
up to 25 kt likely through the day after nocturnal inversion
erodes. Anything that happens should dissipate by 00Z tonight
with clear skies expected tonight.

Previous afd...

A secondary cold front will drop southeastward out of
Pennsylvania. There is very little moisture in the atmosphere,
so no rain is expected. However, a some cumulus clouds will
likely develop along the front during the afternoon. The front
will also act to kick up winds a bit, with gusts of 25 to 30 mph
possible at times. Humidity should drop markedly through the
day, as well.

Mainly clear and calm conditions are expected tonight into
Wednesday morning, though some high clouds may begin to filter
in late tonight.

A warm front is then expected to develop over the south-central
Appalachian Mountains Wednesday. As it lifts northward, a subtle
wave aloft will crest around a building ridge. Low-level warm
advection coupled with this wave and the nearby warm front may
lead to the development of showers and a few thunderstorms
by late Wednesday.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
With the warm front nearby and a disturbance aloft, at least
scattered showers and a few thunderstorms may linger much of
Wednesday night. Shear profiles are rather impressive, but
instability (especially in the low levels) is currently expected
to be lacking. Should more instability be realized, a hail or
gusty wind threat could evolve, especially if upstream
convection that may develop over the Ohio/Tennessee River
Valleys manages to hold together as it approaches. Overnight
guidance has trended somewhat stronger with a surface low
lifting through western Pennsylvania, which raises the threat of
showers and storms at least a bit.

The warm front will continue a slow northward jog Thursday.
Instability likely increases. Shear becomes a bit more modest,
but would still be enough to support some organized convection
if it were to develop. The question is whether or not anything
develops, as there appears to be a lack of a trigger much of the
day. Perhaps warm advection or daytime heating will do the
trick. For now, the threat for any strong to severe storms looks
low and conditional, but is worth keeping an eye on.

The warm front will continue to lift slowly northward Thursday
night. The GFS has been showing a stronger potential for some
showers and thunderstorms Thursday night beyond what most other
guidance currently shows, but again given the warm front nearby,
it`s worth keeping an eye on.

Otherwise, temperatures and humidity will increase during this
time.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By Friday and Saturday, the region will be firmly in the warm sector
with a large ridge of high pressure situated off the southeast
coast. Most areas will see the hottest days so far this year, with
temperatures pushing into the upper 80s to mid 90s and heat indices
potentially in the upper 90s. High temperatures could approach
records. There will likely be a cap in place preventing much in
the way of thunderstorm development. Subtle height falls and/or
convective propagation from the Ohio Valley will provide a
little higher chance for showers and thunderstorms Saturday
afternoon and evening, especially western areas. The greatest
shear will remain to the northwest, with storm strength
dependent on instability and forcing.

On Sunday, a cold front to our northwest will finally receive a push
to the southeast, resulting in the highest rain chances for the
weekend. Timing is still uncertain, which will be important for how
much instability can build (as well as high temperatures). At
this time, thunderstorm potential is highest across the eastern
part of the area.

The front will likely be south of the area on Monday, although there
is some risk of it stalling, which could cause clouds to hang around
along with a low chance of showers. Temperatures will return closer
to normal, if not a little below.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
VFR conditions are expected through the TAF period. Few to
scattered cumulus around FL060-FL120 are possible this afternoon
as a dry cold front crosses. W/NW flow around 15 knots with
frequent gusts to around 25 knots are most likely 13z-22z,
though a few peak wind gusts of 28-33 knots are possible.

MVFR or IFR ceilings are possible ahead of an approaching warm
front Wednesday night into Thursday, along with the potential
for a few showers, thunderstorms, and low-level wind shear.
There is a lower/more conditional risk of showers or storms
Thursday into Thursday night. Otherwise, mainly VFR is expected
Wednesday into Thursday as flow becomes SE then S.

Mainly VFR conditions expected Friday and Saturday with light south
winds. The chance for thunderstorms will increase Saturday afternoon
and evening, though coverage remains very uncertain at this
time.

&&

.MARINE...
Westerly to northwesterly winds associated with a secondary/dry
cold front will likely gust to around 25 knots, with perhaps a
few gusts around 30 knots today into this evening. Gusty winds
may persist much of the night, especially over the wider waters.
Flow will become southeasterly then southerly Wednesday into
Thursday as a warm front lifts north; gusts of 20-25 knots are
possible due to channeling and a strong gradient despite warmer
air over cooler water. In addition, a few showers and
thunderstorms are possible late Wednesday through Thursday as
the warm front lifts by.

South to southwest winds are expected Friday into Saturday due to
high pressure offshore. Small Craft Advisories are possible Friday
into Friday night. With hot daytime air temperatures, stronger gusts
may be over inland areas during the day, and over the main channel
of the bay at night. Thunderstorm risk is low but not zero.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides are high currently due to the recent full moon.
Stagnant water levels will mean that DC SW Waterfront will be very
close to minor flooding this morning. Northwest winds may bring a
bit of a reprieve through Wednesday, but a return to southerly
winds could mean sensitive sites once again approach minor flood
stage Wednesday night into Thursday morning.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until noon EDT Wednesday for DCZ001.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for ANZ530>533-
     535-536-538>542.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Wednesday for ANZ534-537-543.
-- End Changed Discussion --

&&

$$
SYNOPSIS...DHOF
NEAR TERM...LFR
SHORT TERM...DHOF
LONG TERM...ADS
AVIATION...ADS/LFR
MARINE...ADS/LFR
TIDES/COASTAL FLOODING...