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669
FXUS61 KLWX 050800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Sun May 5 2024

.SYNOPSIS...
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An active pattern will continue through mid-week as multiple
disturbances pass through the area. A cold front will move through
toward the end of the week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Current water vapor imagery shows a well defined mid-level
shortwave tracking eastward across Ontario, with upper level
ridging retreating eastward across New England. At lower levels,
high pressure remains in place across northern New England and
the Canadian Maritimes. Easterly flow around the high is
maintaining a cold-air damming wedge to the east of the
Appalachians. Warm/moist advection atop the CAD wedge is
producing a large precipitation shield that extends from the
Carolinas northward to Upstate NY. Much of the forecast area is
experiencing a steady light rainfall at the moment, and this is
expected to continue through the remainder of the overnight
hours.

As we move through the day, the area of high pressure over New
England will start to shift eastward as the upper trough builds
eastward across Ontario and Quebec. In response to the high shifting
further east, winds will start to turn southeasterly and then
eventually southerly, which should allow the CAD wedge to start to
erode, and steadier precipitation to wind down. A steady rain should
continue to the east of the Blue Ridge through the morning hours.
The steadier rain could potentially linger a bit into the afternoon
to the east of I-95. While steadier rain will move out, the
afternoon hours should remain mostly cloudy to cloudy to the east of
the Blue Ridge. To the west of the Blue Ridge, some breaks in the
cloud cover may be able to develop. As a result, some instability
may develop to the west of the Blue Ridge, which may potentially
allow a few thunderstorms to develop within a lee trough later
this afternoon. The greatest chance for a storm during the mid-
late afternoon hours looks to be between the Allegheny Front and
I- 81. High temperatures today should generally be in the 60s
to near 70 to the east of the Blue Ridge, with lower to middle
70s to the west of the Blue Ridge.

Conditions should dry out overnight, but skies should remain mostly
cloudy. If any breaks in the cloud cover are able to develop, fog
may develop overnight, given weak low-level flow and ample moisture
in place at low-levels following ongoing rainfall. Temperatures will
remain mild overnight, with lows in the upper 50s to mid 60s.
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&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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A largely convectively generated disturbance (by ongoing storms
across the Southern Plains) will drift through the
Tennessee/Ohio Valleys toward the area on Monday. The day should
start out dry, but mostly cloudy for most. As the disturbance
drifts toward the area, low-level moisture will be drawn
northward into the area in southerly flow as greater mid-upper
level moisture simultaneously advects into the area aloft.
Daytime heating will allow temperatures to climb into the upper
70s and lower 80s, which when coupled with the increasing
moisture will lead to the development of some surface based
instability. Showers and thunderstorms appear possible Monday
afternoon, with the greatest coverage expected to be across the
Central Shenandoah Valley into Central Virginia, where low-
level convergence is expected to be maximized. Model soundings
show around 1000 J/kg of MLCAPE, along with relatively moist
profiles and weak flow through the lower half of the
troposphere. Such an environment could lead to slow moving,
heavy rainfall producing storms, especially from the Shenandoah
Valley into Central Virginia. 00z CAMs show isolated areas of
2-5 inches of rainfall across those locations Monday afternoon,
which potentially raises concerns for flash flooding. With the
disturbance forcing the precipitation being largely convectively
generated, that makes predictability a bit lower than normal at
this time range, so things could potentially change. However,
we`ll continue to keep an eye on the potential for heavy
rainfall Monday afternoon.

Additional showers and thunderstorms appear possible again on
Tuesday as a disturbance tracks into the Great Lakes. Much like
Monday, high temperatures are expected to reach into the upper
70s and lower 80s. Soundings again show relatively saturated
profiles along with some surface based instability, so storms
may once again be heavy rainfall producers.
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&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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Rain and thunderstorm chances will continue by Wednesday, with
an approaching cold front from the west. The precip chances will
increase from west to east later in the day on Wednesday with
highs in the mid to upper 80s for the lower elevations and 70s
for the mountains. Winds out of the west will be gusting to 15
to 20 knots throughout the afternoon. Precipitation chances
increase overnight Wednesday and through the day on Thursday as
the front continues to approach the area. Given the increasing
instability ahead of the front, a few isolated strong to severe
thunderstorms may be possible with the frontal passage on
Thursday. Additionally, some isolated instances of flooding will
be possible with the continuous prolonged batches of
precipitation over just a few days. Still a lot of uncertainty
pertaining to timing, intensity and antecedent conditions. Highs
on Thursday will climb into the upper 70s to low 80s for most
areas.

Behind the front on Friday, precipitation will likely linger around
with highs in the 70s for the lower elevations and 60s in the
mountains. Northwest winds will remain elevated with gusts getting
into the 15 to 25 knots range, with the higher amounts along the
higher elevations. Lingering light showers may persist into the
weekend with highs in the mid to upper 60s for most areas with 50s
in the mountains.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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IFR and rainy conditions remain in place at all terminals early this
morning. The steady rain should wind down during the late
morning/early afternoon hours, with a few showers potentially
lingering through the afternoon. Additional thunderstorms may
potentially develop across western MD and the eastern WV Panhandle
this afternoon, potentially impacting MRB. IFR ceiling are expected
to persist through much if not all of the day, although some
locations could go MVFR for a few hours this afternoon. Winds today
will be easterly to start, and then trend southeasterly and
eventually southerly as the day wears on. IFR ceilings and fog look
to build back in tonight.

Gradual improvement back to VFR conditions is expected on Monday. An
afternoon or evening shower or thunderstorm may be possible at any
of the terminals, with CHO standing the greatest chance to see
impacts. Winds will be light and somewhat variable Monday.
Prevailing VFR conditions continue into Tuesday, with afternoon
showers and thunderstorms possible once again. Winds will turn
southerly on Tuesday, but remain relatively light.

Mainly VFR conditions for the terminals on Wednesday with increasing
chances of sub-VFR ceilings by Wednesday night into Thursday as
precipitation begins to track across the area. Winds out of the west
will continue to gust out of the west.
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&&

.MARINE...
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Winds will start out easterly today, before gradually turning
southeasterly and then southerly by later this afternoon. SCAs
remain in effect for the wider waters through the day today. SCAs
may potentially need to be extended a bit into the overnight
hours in channeled southerly flow. Thereafter, sub-SCA magnitude
is expected on both Monday and Tuesday. Thunderstorms will be
possible both Monday and Tuesday. Any storms that move over the
waters could lead to the issuance of SMWs.

SCA conditions are possible Wednesday and Thursday with increasing
pressure gradient over the waters. Additionally, an SMW may be
needed for any stronger thunderstorms that cross the waters Thursday
afternoon and evening.
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&&

.TIDES/COASTAL FLOODING...
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Onshore flow will continue to usher in minor to moderate tidal
flooding at the more sensitive locations along the Chesapeake Bay
through Monday morning. Winds will begin to turn more out of the
southwest on Monday with slow improvements in coastal flooding
through midweek. Additional periods of coastal flooding are possible
into Wednesday.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until 9 AM EDT this morning for DCZ001.
MD...Coastal Flood Warning until 8 AM EDT this morning for MDZ014.
VA...Coastal Flood Advisory until 9 AM EDT this morning for VAZ054.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
     ANZ530-536-541.
     Small Craft Advisory until 3 PM EDT this afternoon for ANZ531-
     532-538>540-542.
     Small Craft Advisory until 6 PM EDT this evening for ANZ533-
     534-537-543.
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&&

$$

SYNOPSIS...KJP
NEAR TERM...KJP
SHORT TERM...KJP
LONG TERM...ADM
AVIATION...KJP/ADM
MARINE...KJP/ADM
TIDES/COASTAL FLOODING...ADM