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000
FXUS61 KLWX 190800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Fri Apr 19 2024

.SYNOPSIS...
Low pressure will track well to our north today, causing a cold
front to move through late tonight. High pressure will gradually
build in from the west this weekend into early next week while
waves of low pressure pass well to the south. The next cold
front will reach the area Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Onshore flow between low pressure east of the Delmarva and high
pressure over New England has been advecting marine stratus
westward overnight. These clouds will be most prevalent east of
the Blue Ridge through the morning, with some spilling west into
the northern Shenandoah Valley. Although the low clouds may mix
out toward midday as winds take on a more southerly component,
additional clouds will have advected over the area ahead of the
next weather system.

That cold front will slowly approach from the Ohio Valley
through the day. Shower chances will gradually increase west of
the Blue Ridge through the morning, but it appears doubtful more
than spotty light showers will advance east of the Blue Ridge
into the afternoon. As weak instability increases, a few
thunderstorms are also possible this afternoon west of I-81. The
duration of low clouds will impact temperatures today, with
areas near/northeast of the Potomac remaining in the lower to
mid 60s. Some spots in central Virginia and the valleys west of
the Blue Ridge could top 70 with enough cloud breaks.

The cold front will continue eastward tonight accompanied by
scattered showers. With weak forcing and a downsloping wind
component aloft, it appears showers will have difficulty holding
together, and have capped PoPs at 50 percent or less east of the
Blue Ridge. A stray thunderstorm could cross southern Maryland
with some weak elevated instability, but an overall poor
convective environment should preclude thunder across much of
the area. Some patchy fog could develop with light winds
overnight, but this is less certain. Cooler air begins entering
western areas late, with lows near 40 in the higher elevations,
increasing to the mid 50s to the south and east.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
WNW winds will become gusty behind the front on Sunday, with
gusts of 20-30 mph common. Clearing skies and the downsloping
winds will result in warm temperatures ranging from the mid 60s
to mid 70s in the lower elevations. High level clouds begin to
increase Saturday night with lows from the upper 30s to mid 40s.
The higher Alleghenies will likely fall below freezing.

Low pressure will pass well south of the area Sunday along the
stalled front. High pressure extending eastward from the Plains
will likely keep the area dry, although there is still a 20
percent chance some light rain could reach Nelson to St. Marys
Counties should a northern solution verify. Even though it will
be dry, mid and high level clouds will be prevalent through the
day. These clouds will clear to the east Sunday night, and winds
should be fairly light. This will result in a chilly night with
lows ranging from the mid 30s to mid 40s. With dew points in the
upper 20s and lower 30s, some frost can`t be ruled out in rural
valleys, especially west of the Blue Ridge.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
To start off the work week, the hemispheric pattern features a split
flow regime. An expansive longwave trough extending into the high
latitudes will pull away from the northeastern U.S. At the same
time, a weak shortwave in the southern stream is expected to remain
suppressed with no direct influence on the local weather. Eventually
the height falls with this system will induce cyclogenesis off the
southeastern U.S. coast on Monday evening. Ensembles agree on
carrying this area of low pressure well out to sea as high pressure
briefly settles over the southern/central Appalachians on Tuesday
morning. Farther upstream, the next weather maker looms across the
Upper Great Lakes. The associated cold front is likely to cross the
Mid-Atlantic region early Wednesday. The progressive nature of this
system should limit total rainfall amounts. In the wake, a gusty
northwesterly wind is expected through the remainder of the day. The
current forecast package calls for gusts around 20 to 25 mph,
locally a bit higher in the terrain. High pressure returns on
Thursday into Friday which will favor a return to dry weather.

Fairly seasonable temperatures are expected through mid-week with
highs in the mid 60s to low 70s, with 50s across the mountains.
Behind the front, cold advection will help lower temperatures back
down into the upper 50s to mid 60s by Thursday. Regarding overnight
conditions, only Tuesday night appears mild given the warm advection
pattern. Otherwise, multiple nights see low temperatures falling
into the mid/upper 30s which could bring some frost concerns where
the growing season has commenced (everywhere outside the
Alleghenies). For the Allegheny mountain range, lows push near to
below freezing at times through Thursday night.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Onshore winds have advected marine stratus into the area this
morning. So far these clouds have been MVFR, although IFR is
developing toward central Virginia. It still appears a period of
IFR conditions is likely for several hours from daybreak through
late morning (with possible exception of DCA where wind off the
river may keep bases above the threshold). These clouds will
likely lift by this afternoon as winds take on a more southerly
component. However, the timing is uncertain, as well as if and
how long some locations may lift into VFR.

A cold front will progress into the area late this afternoon and
tonight. Showers ahead of the front appear scattered at best,
with a slightly better chance at MRB. The showers will be light
in nature and thunderstorms are unlikely. MVFR conditions likely
return this evening as winds will be light near the front, and
IFR can`t be ruled out. A drying NW wind will arrive late
tonight and scour out lower clouds.

WNW wind gusts of 20-25 kt are likely behind the front on
Saturday with VFR conditions. Low pressure will pass well to the
south between Saturday night and Sunday night, with any ceilings
mid/high level in nature. W to NW winds will generally be 5-10
kt through this period.

VFR conditions are expected on both Monday and Tuesday. The forecast
should be dry as high pressure largely remains in charge.
Northwesterly winds on Monday will eventually give way to southerly
flow Monday evening into Tuesday. Afternoon winds on Tuesday may
gust up to 20 knots.

&&

.MARINE...
Light onshore flow is present this morning. As winds take on a
more southeasterly component this afternoon and evening,
marginal Small Craft Advisory conditions are expected south of
the Bay Bridge and the Potomac below Dahlgren. A cold front will
cross over the waters tonight, causing winds to turn out of the
northwest. Small Craft Advisory conditions appear likely in
northwesterly Saturday and Saturday night, although there may be
three stages: an initial surge down the waters behind the front
early Saturday morning, diurnal mixing across the northern bay
and upper Potomac through the afternoon, then another surge down
the waters Saturday night.

Winds should be lighter Sunday and Sunday night with low
pressure passing well to the south and high pressure building in
from the west. However, a few 18 kt gusts can`t be ruled out
during periods of pressure rises.

Winds over the marine waters remain below advisory levels on Monday.
Winds shift from northwesterly to southerly by late Monday.
Southerly flow on Tuesday likely brings gusts up to 20 knots which
suggests Small Craft Advisories may be needed.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies have spiked in a couple of locations due to the
enhanced easterly flow. However, no locations are expected to see
any coastal flooding during this high tide cycle. Subsequent tidal
cycles will need to be monitored as southerly winds today should
further pile up water. The usual more sensitive locations like
Annapolis, Strait`s Point, and the Southwest DC Waterfront may hit
Minor during the next couple of high tides through early Saturday.
Thereafter, a gusty northwesterly wind should quickly lower water
levels through the remainder of the weekend.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 3 PM this afternoon to midnight EDT
     tonight for ANZ532>534-537-541-543.

&&

$$

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