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000
FXUS61 KLWX 170759
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
359 AM EDT Wed Apr 17 2024

.SYNOPSIS...
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A stationary front will slowly lift northward as a warm front
today, eventually pulling north of the region by early Thursday.
A weak cold front will track through on Thursday before a
stronger cold front arrives on Saturday. High pressure returns
on Sunday and into early next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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A stationary front remains draped across central Virginia
extending back into far western Maryland. Based on the latest
observations, moisture content appears to be the biggest
difference as temperatures and wind direction are fairly
similar. The prevailing southerly flow has maintained a very
mild air mass early this morning. Most spots remain in the mid
50s to low 60s, accompanied by some mid to high clouds tracking
overhead.

Expect clouds to continue to increase through the morning and
afternoon as an upstream moisture plume migrates toward the
Eastern Seaboard. Despite the uptick in cloud cover, it should
prove to be another warm mid-April day owing to persistent
southerly winds. There will likely be a north/south disparity in
today`s temperatures which is dependent on the position of the
wavy warm front. Most solutions stall this boundary somewhere
between U.S. 50 and I-70. Thus, the cool spots today may be
over northeastern Maryland and mountain tops with highs confined
to the mid/upper 60s. Elsewhere, low to mid 70s are more
likely.

Recent guidance has continued the downward trend in forecast
rainfall amounts. Although an upstream shortwave pushes toward
the area, the main forcing/lift likely moves up into the Lower
Great Lakes. Weak height falls coupled with several subtle
perturbations in the flow aloft will bring a few rounds of rain
shower chances to the area. Instability levels are not terribly
impressive, generally averaging around 250 to 500 J/kg,
accompanied by some areas of non-zero inhibition (CIN). Thus,
have capped the convective threat at isolated given the above
unknowns. The best chance for any severe thunderstorms would be
over far western Maryland where the Storm Prediction Center
paints a Marginal risk. The primary severe threats would be
damaging wind gusts and a spotty larger hailstone.

Overall, the threat for showers should diminish overnight with
low clouds beginning to take over. A thickening stratus deck
will favor another mild night with lows in the 50s to low 60s.
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&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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As the mentioned warm front slowly pulls north toward the
Mason-Dixon Line, an upstream cold front begins to push across
the Allegheny Front. Although somewhat diffuse in nature, it
will carry a wind shift as west-northwesterlies ensue on
Thursday. A few showers may fall over the Alleghenies on
Thursday morning, but the rest of the area likely stays dry
thanks to a downsloping component to the flow. The latter
artifact of the wind fields should help raise temperatures given
well-mixed boundary layers. The latest model soundings indicate
dry adiabatic profiles up to around 825-mb. With forecast 850-mb
temperatures around 12C in central Virginia, dry adiabatic
mixing to the surface would yield highs in the low 80s. Area
wide high temperatures should stay in that mid 70s to low 80s
range, with mid/upper 60s in the mountains and across
northeastern Maryland. The latter area may be stuck in thick
cloud cover which keeps temperatures down relative to other
locations. Overall cloud cover increases across the entire area
on Thursday night. Any nocturnal shower chances should be
relegated to western Maryland. The post-frontal air mass will be
cooler as most areas north of I-66/U.S. 50 are forecast to be in
the mid/upper 40s.

Shower chances increase across the area on Friday. A broad
longwave trough extending across the northern tier of the
country into the Great Lakes will lead to an expanding
precipitation shield. All of this activity moves eastward ahead
of a stronger cold front set to arrive late Friday into the
early weekend. Temperatures come down given the mostly cloudy
skies and showers. The forecast keeps most in the 60s although
low/mid 70s can still be found south of I-66, over portions of
the Shenandoah Valley, and Allegheny mountain valleys. The
influence of the cold front becomes noticed at night as lows
fall into the 40s across a bulk of the area. Any shower chances
ends from west to east overnight.
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&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
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The cold front will likely be south of the area by Saturday morning.
However, with gusty downsloping winds and gradual cold advection
aloft, temperatures will likely still be above normal for much of
the area (mid 60s-mid 70s). The front will be stalling out over the
southeastern states. Sunday should largely be dry, but cooler than
preceding days with high temperatures slightly below normal (upper
50s-mid 60s). An area of low pressure will ride along the front late
Sunday into early Monday as a trough approaches from the west.
Although most of the rain will remain south of the area, there
remains some potential of light rain reaching the forecast area
during this time.

High pressure will likely build in from the west Monday, although
model spread begins to increase in the height pattern aloft.
Temperatures will likely remain near to below normal. The next
shortwave may approach from the Great Lakes on Tuesday, resulting in
a chance of showers. 00Z guidance has trended toward a slower
solution however. With southerly flow developing, a warming trend
will commence.
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&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
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A warm front sprawled across the area will gradually lift north
toward the Mason-Dixon Line. Expect light southerly winds,
accompanied by a few rounds of shower opportunities. Although
isolated thunderstorms are in the forecast, confidence is fairly
low in where/when these will occur given questionable
instability. Heading into the late evening to overnight, a
thickening stratus deck will likely carry all TAF sites to
MVFR, locally IFR around the Baltimore terminals. These low
ceilings may linger into early Thursday morning before a weak
cold front tracks through.

This boundary should make for a mostly dry Thursday, accompanied
by VFR conditions after any lingering low clouds erode.
Prevailing west-northwesterly winds are expected before shifting
to east-northeasterly on Thursday night. A better chance for
showers looms on Friday which will support MVFR to IFR ceilings
at times. The best thunder chances appear to be confined to
areas west of I-81. A more defined cold front tracks through
late Friday which yields a shift from southerlies back to
northwesterlies.

Gusty WNW winds are likely on Saturday. A low pressure system will
pass south of the area Sunday, but minimal impacts are expected at
this time.
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&&

.MARINE...
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After a couple hour uptick in southerly winds, nearly all
locations have seen gusts drop to 15 knots or less. Some showers
may impact the area today, with an isolated threat for
thunderstorms. Uncertainty in the instability of the atmosphere
casts some doubts on these thunder chances. Some southerly
channeling effects may warrant Small Craft Advisories over the
lower waters late this evening into portions of the night. A
weak cold front pushes across the waters Thursday morning which
results in a shift to northwesterly flow. Very warm air
temperatures on top of the cooler waters will likely limit
vertical mixing. Any higher gusts would be restricted near the
land/bay interface.

Winds on Friday largely stay below advisory levels, but there
will be an uptick with a more formidable cold front. As this
system pushes across the waters late Friday night, 20 knot gusts
become possible. Small Craft Advisories will likely be needed by
then.

SCA conditions are likely on Saturday and Saturday night in gusty
WNW postfrontal flow. Winds will lessen Sunday, but still might be
near the advisory threshold.
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&&

.TIDES/COASTAL FLOODING...
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While some action stages may be reached through Thursday night
(anomalies 1-1.5 feet above normal), the greater water level rises
and potential for minor flooding will be toward Friday and Friday
night as onshore or southerly flow develops ahead of a low pressure
system.
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&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$

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