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348
FXUS61 KLWX 031349
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
949 AM EDT Fri May 3 2024

.SYNOPSIS...
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A backdoor cold front will cross the area today before sinking
south Saturday. The boundary will return north as a warm front
Sunday into Monday before secondary cold front approaches and
stalls near the area for the middle portion of next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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High pressure remains centered over the New England coast this
morning while an upper-level ridge axis is slowly moving off to
our east. An upper-level trough is building over the central
CONUS. A backdoor cold front is currently located near the
I-81 corridor into central Virginia this morning.

The backdoor boundary will most likely stall out near the area
through this afternoon before eventually pushing off to our
south and west tonight as high pressure strengthens along the
New England Coast.

As convergence strengthens along the backdoor boundary this
afternoon/evening, this will combine with peak heating and
moisture advection (southerly flow aloft around periphery of the
high), triggering some showers and a few thunderstorms over the
Allegheny and Potomac Highlands into the Shenandoah Valley. This
activity will likely advect eastward into the metro areas late
this evening and overnight. Low clouds and noticeably cooler
conditions are expected overnight as the onshore flow continues
behind the backdoor cold front. Lows will be in the 50s for most
areas, with upper 40s in portions of northern Maryland.
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&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
A series of weak upper level perturbations will move across the
region over the weekend gradually eroding the ridge pattern and
allowing moisture to deepen, particularly during the Saturday
night and Sunday time frame. Expect a gloomy and soggy weekend
with off and on showers through Sunday evening. Rainfall amounts
are likely to exceed one inch over the entire weekend. The lack
of instability suggests that rainfall rates will be manageable.
Also, the long duration of the event should allow for the
ground to absorb much of the rain without causing much in the
way of flooding problems.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
A cold front draped across the region Monday and Tuesday will bring
unsettled weather to the forecast area. Diurnally driven showers and
thunderstorms are possible both days with atmospheric conditions
peaking each afternoon and into the evening. Ample moisture aloft
(PWATS 1.5in-2 in) will allow for heavy rainfall rates at times.
Beginning Tuesday, the focus will be on the parent low pressure
system as it begins to lift northward through the Great Lakes
region. The cold front draped over the forecast area will begin
lifting northward as a warm front while the associated cold front
approaches from the Plains. From Tuesday through the remainder of
the long term period, the forecast area will be in the warm sector
allowing for an increasing threat for strong to severe
thunderstorms. In addition to the severe weather threat, isolated
instances of flooding are possible due to recent weekend rainfall
possibly saturating soils. We will continue to monitor this system
as is approaches.

Temperatures will be in the 70s to low 80s Monday and Tuesday with
overnight low temperatures expected to be in the mid 50s to mid 60s.
In the wake of the warm front, temperatures rise into the 80s for
most Wednesday and Thursday. Those at higher elevations will stay in
the upper 70s each day.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
VFR through 06Z Sat, then rapidly lowering cigs overnight to
IFR/LIFR as onshore flow develops. Off and on rain/showers
develop Saturday and persist through Sunday with prevailing IFR
conditions persisting through early next week.

Reduced CIGs and VSBYs are possible during showers and thunderstorms
Monday and Tuesday. Outside of showers and thunderstorms, VFR
conditions are expected along with light winds 5-10 knots and
gusting up to 15 knots. Winds will be out of the south each day.

&&

.MARINE...
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SCA conditions will continue to develop into this afternoon,
likely persisting through Monday as onshore flow strengthens.
However, there may be a lull in the SCA winds later tonight into
Saturday as the gradient briefly subsides behind a backdoor
boundary. Rain/showers will be widespread both Saturday and
Sunday, but the threat of thunder will remain low.

Showers and thunderstorms will impact the waters both Monday and
Tuesday as southerly winds stay below SCA criteria. As a warm front
moves over the waters, winds increase to just below SCA criteria
Tuesday night.
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&&

.TIDES/COASTAL FLOODING...
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Onshore flow will strengthen today and persist through early
next week. This will raise water levels and keep them elevated
through early next week causing minor tidal flooding for many
locations. Moderate tidal flooding is possible around Annapolis
and St. Marys County with the high tide cycle late Saturday
night, and again late Sunday night into Monday morning.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...Coastal Flood Advisory from midnight tonight to 5 PM EDT
     Saturday for MDZ014.
     Coastal Flood Watch from late Saturday night through Sunday
     morning for MDZ014.
     Coastal Flood Advisory from 9 PM this evening to 2 PM EDT
     Saturday for MDZ017.
     Coastal Flood Watch from Saturday evening through Sunday
     morning for MDZ017.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ530>534-
     537>543.
     Small Craft Advisory until midnight EDT tonight for ANZ535-536.
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&&

$$

SYNOPSIS...LFR
NEAR TERM...BJL/LFR
SHORT TERM...LFR
LONG TERM...AVS
AVIATION...BJL/AVS/LFR
MARINE...BJL/AVS/LFR
TIDES/COASTAL FLOODING...BJL