200
FXUS61 KLWX 130800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Mon May 13 2024

.SYNOPSIS...
High pressure will briefly settle over the region today bringing dry
conditions and seasonable temperatures. High pressure will push off
the Mid-Atlantic coast tonight allowing a slow moving low pressure
system to move in from the mid-Mississippi and Ohio River Valleys.
Increased shower and thunderstorm chances will accompany this low
pressure system along with below normal temperatures. Drier weather
returns Thursday before another storm system brings the threat for
showers and storms Friday into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
An area of stratus has been slowly expanding westward from the
Chesapeake Bay. There is some uncertainty how far west it will
reach before sunrise, but likely not much past the DC metro
area. Along the periphery of the stratus, as well as some of the
mountain valleys, fog is developing. All should dissipate a few
hours after sunrise.

Today will be a brief respite from the unsettled pattern as
upper ridging moves overhead and surface high pressure moves
offshore. A few high clouds will pass but plenty of sun is
expected. High temperatures will be seasonable in the 70s to
near 80.

The next low pressure system will be in the mid Mississippi
Valley tonight, with a lead shortwave and arm of isentropic lift
approaching the mid Atlantic. Clouds will gradually increase,
and showers will become possible in southwestern portions of the
area toward dawn. Temperatures will be milder in the mid 50s to
near 60.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Rain returns Tuesday into Wednesday as the broad upper trough
and surface low slowly plod eastward across the area. Showers
will be more occasional in nature, although there could be a few
periods of steadier rain. Instability appears to be rather
limited Tuesday, with the best chance of any thunderstorms west
of the Blue Ridge. If anything, there may be a better
opportunityfor some elevated rumbles of thunder Tuesday night.
On Wednesday, the greatest instability will be across the
southwestern half of the area, where there may be a better
chance for some breaks of sun. The chance of rain will decrease
Wednesday night as the low pulls offshore, although there is
some uncertainty in how quickly that revolves around a potential
closed low aloft.

There may be a few opportunities for locally heavier rain: (1)
with southeasterly upslope flow into the central Virginia Blue
Ridge on Tuesday, (2) north of the surface low track Tuesday
night, and (3) within the higher instability airmass Wednesday
when flow will be light under the upper trough. Any risk of
flooding appears to be marginal and dependent on multiple or
prolonged periods of heavier rain. Forecast totals range from
0.50-1 inch for much of the area, with 1-2 inches possible
toward central Virginia. The threat for severe thunderstorms
appears to be low through the period.

The clouds and rain will mute the diurnal temperature ranges,
with highs in the mid 60s to mid 70s and lows in the mid 50s to
mid 60s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Low pressure and the resultant upper level trough will pivot off the
Mid-Atlantic coast Thursday while brief mid-level ridging settles in
from the central Appalachians region. This will allow for a brief
reprieve in shower and thunderstorm activity before things ramp up
again later in the workweek.

Unfortunately the calmer weather conditions will be short-lived with
the next upper level trough and low pressure system set to approach
from the Ohio River Valley/Great Lakes region Friday into Saturday.
With that said, model guidance continues to show subtle
discrepancies in regards to to the timing of this system and
placement of it`s associated surface fronts across the region. Most
of the recent 00z guidance suggests an uptick in shower and
thunderstorm activity Friday afternoon and night as a warm front
lifts through the area. A slow moving cold front will immediately
follow this boundary Saturday into Saturday night bringing with it
additional showers and thunderstorms. Severe weather does not appear
to be a concern at this point although one or two strong
thunderstorms cannot be ruled out if CAPE and shear are maximized.
Localized flooding could be the bigger concern given repetitive
rounds of rain throughout the week and rich moisture flooding in
along the slow moving warm front Friday into Friday night.

Upper level ridging tries to build back into the area Sunday
bringing slightly drier conditions. Another front will follow with
renewed chances for showers and thunderstorms Monday and Tuesday
next week. Temperatures throughout the extended forecast period will
remain at or slightly below normal for the middle of May.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Stratus is in place across the Baltimore terminals and inching
toward DCA. IFR to LIFR ceilings will be possible at BWI/MTN,
while DCA could range from IFR to VFR depending on the western
extent of the stratus (split the difference in the TAF for now).
Visibility may also be slightly reduced in this area as well
toward sunrise. Stratus is unlikely to reach the remainder of
the TAF sites, although some ground fog could form at MRB.

Fog/stratus will break up between 12-15Z. VFR conditions are
expected the remainder of the day, with southerly winds
increasing during the afternoon. Ceilings increase tonight ahead
of the next system but likely remain VFR. Showers may reach CHO
by dawn Tuesday.

Occasional showers return Tuesday and Wednesday as a slow
moving area of low pressure crosses the region. MVFR to IFR
ceilings are expected, with LIFR possible Tuesday night. Cloud
bases may attempt to lift for a time Wednesday. Thunderstorm
coverage will be isolated for most of the period, with a higher
chance Wednesday afternoon near CHO.

Sub-MVFR cigs and vsbys remain possible with any spotty shower or
thunderstorm activity that looks to linger Thursday. Mid-level
ridging should promote drier conditions during the late afternoon
and evening as low pressure pushes further offshore. Sub-VFR
conditions return Friday into Saturday as another upper level trough
and series of fronts traverse the region. Shower and thunderstorm
activity will increase across the terminals especially Friday and
Saturday afternoons. Slightly drier conditions and VFR return Sunday
into Monday next week.

&&

.MARINE...
Light winds this morning will become south-southeast and
increase through the day as high pressure moves offshore.
Small Craft Advisories have been issued during the late
afternoon into tonight as stronger winds spread north and
channel. Winds are forecast to gradually scale back toward dawn
Tuesday and there may be a relative lull in the winds through
the morning

Unsettled weather returns to the area as a slow moving area of low
pressure crosses the region. Winds will increase again Tuesday
into Tuesday night as the low pressure passes to the south and
east, with additional advisories likely. Strongest winds may
occur Tuesday evening, although there is some uncertainty on the
strength of the low and how much wind will mix to the surface.
Isolated to scattered thunderstorms are possible late Tuesday
through Wednesday, but they may not become too strong. Wind
forecast for Wednesday into Wednesday night has trended
downward, but additional advisories could be needed depending on
the offshore low.

SCA conditions are likely Thursday into Friday as low pressure
pushes offshore and weak high pressure builds in. SCA conditions
will linger into the weekend as a series of fronts traverse the
region. This will be the case Friday with a warm front and Saturday
with a cold front set to cross the waters. Shower and thunderstorm
activity will also increase especially during the afternoon and
evening hours.

&&

.TIDES/COASTAL FLOODING...
Southerly flow returns to the region today and continues into
midweek as an area of low pressure pushes in from the Ohio and mid-
Mississippi River Valleys. This will allow for increasing anamolies
and additional periods of coastal flooding at sensitive locations
today and Tuesday. These locations include, but are not limited to
Otter Point. Annapolis, DC Waterfront. Straits Point, and Baltimore.
The highest confidence for minor flooding today into Tuesday appears
to be at Annapolis, Straits Point, and DC Waterfront. Coastal Flood
Advisories may be needed for these locations in the upcoming
forecast issuance.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM this evening to midnight EDT
     tonight for ANZ530-538.
     Small Craft Advisory from 6 PM this evening to 6 AM EDT
     Tuesday for ANZ531-539>541.
     Small Craft Advisory from 4 PM this afternoon to 6 AM EDT
     Tuesday for ANZ532>534-537-543.
     Small Craft Advisory from 4 PM this afternoon to midnight EDT
     tonight for ANZ542.

&&

$$

SYNOPSIS...EST
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...EST
AVIATION...ADS/EST
MARINE...ADS/EST
TIDES/COASTAL FLOODING...EST