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140
FXUS61 KLWX 301357
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
957 AM EDT Tue Apr 30 2024

.SYNOPSIS...
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A cold front will slowly push through the region this afternoon and
evening bringing scattered showers and thunderstorms. A few showers
linger Wednesday morning with dry high pressure settling back in for
the afternoon. Warm and dry conditions continue Thursday before
shower and thunderstorm chances return with another front Friday
into the start of the weekend.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Subtle relief from the heat in the form of a cold front/lee trough
is expected to pass through the region later this afternoon and
evening. The front is evident on radar with a band of precipitation
extending from Lake Erie south along the Ohio River into eastern
Kentucky. This area of precipitation will continue to slowly move
east this morning allowing for an uptick in cloud cover across our
region heading into early to mid-afternoon. As for precipitation
chances, 6z/12z hi-res CAM guidance continues to show varying
differences in regards to timing and coverage. Most of the
guidance shows the leading edge of the precipitation entering
our western most counties (i.e Garrett Co. MD and
Pendleton/Hardy Co. WV ) around 2- 4pm with isolated showers
along the higher ridgetops of the Blue Ridge/Alleghenies during
this same timing window. The main band of shower and
thunderstorm activity will work into the I-81/Blue Ridge
corridor between 5-8pm before shifting toward the metros and
dissipating after sunset. As for the threat of severe weather,
it remains low, but not zero. Instability will remain fairly low
on the order of 500-1200 j/kg with 0-6km bulk effective shear
values running 20-30 kts. Both SPC, CSU Machine Learning, and
CIPS analogue products continue to point to a very low
probability of severe weather. Even with that said, one or two
storms could become strong given the antecedent conditions
especially west of the Blue Ridge. Biggest threats with any
storms this afternoon and evenings looks to be wind gusts 40-50
mph, frequent lightning, and locally heavy rainfall (PWATS
running 0.75-1.25 inches).

High temperatures today will push back into the mid to upper 80s
with 70s over the mountains/near the bay. Metro areas could flirt
with 90 degrees. Heat index values will remain below 95 degrees
given the fact that dewpoints will remain in the mid to upper 50s
and low 60s.

Storms move out of the area before midnight, with a slight chance of
showers lingering through early Wednesday morning as the front moves
to our south and east. Lows tonight will fall back into the upper
50s and low 60s with areas of patchy fog that due see the rain.
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&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
By Wednesday morning, the aforementioned cold front will be lifting
northward as an upper level trough pivots over the area. This will
allow for precipitation chances to linger throughout the morning.
Recent model guidance has trended drier for Wednesday, with
conditions expected to dry out areawide in the afternoon. Surface
low pressure near the Carolinas make so an isolated rain shower
cannot be ruled out in the southernmost portions of the area.
However, chances for this remain low as dry air aloft filters into
the area.

Dry conditions continue on Thursday as high pressure builds in over
the area. A moisture starved cold front will linger over the
forecast area, but no precipitation is expected with this. High
temperatures each day will be in the 70s to mid 80s with overnight
lows dipping into the 50s to low 60s each night.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
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Large scale ridge will start breaking down Saturday as
successive mid-level perturbations move across the Mid-Atlantic
region during the second half of the weekend. Moisture will pool
along a decaying/weakening frontal zone Saturday to bring the
threat of showers. This frontal zone will be slow to exit the
area with the risk of showers persisting through Sunday. Given
the slow progression of this front, isolated heavy rain totals
exceeding an inch are possible which may cause isolated
flooding in the more vulnerable urban areas. The lack of
instability suggest any rainfall should be manageable. By
Monday, enough dry air appears to make it into the area and the
frontal zone dissipates to lower PoP chances allowing sunshine
to bring temperatures back up.
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&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
VFR conditions are expected this morning through the early
afternoon, ahead of any precipitation expected later today. A cold
front moving over the area will bring scattered showers and
thunderstorms to all terminals this evening and into the late
evening. Some storms may be strong, possibly producing winds gusts
of 35 knots or greater, frequent lightning strikes, and heavy
rainfall leading to reduced visibilities. Shower and thunderstorms
chances move out of all terminals between 03-04 UTC with the
exceptions being CHO where conditions dry out earlier around 01 UTC.

Outside of showers and thunderstorms, VFR conditions are expected.
Southwesterly winds today will shift to northwesterly winds on
Wednesday. Winds gust between 10-15 knots this afternoon with winds
gusting up to 20 knots at DCA. Winds diminish overnight before
remaining light on Wednesday, blowing between 5-10 knots. VFR
conditions continue on Thursday as high pressure builds in over the
area.

Showers are likely on Saturday. Cig restrictions are possible
Saturday.

&&

.MARINE...
A cold front will cross the waters this afternoon and into the
overnight, leading to increased chances of showers and
thunderstorms. A SCA is in effect for this afternoon and into this
evening for southwest winds 10 to 15 knots with gusts up to 20 knots
expected. During thunderstorms, higher wind gusts of 35 knots or
greater are possible along with lightning. Special Marine Warnings
may be required as showers and thunderstorms cross the waters.

By  Wednesday morning, showers and thunderstorms will have moved
away from the waters. Winds shift to the northwest an are expected
to stay below SCA criteria. Winds shift to the south on Thursday,
but continue to remain below SCA criteria.

Small Craft Advisory conditions likely Friday through the
weekend. Showers appear likely over the weekend, but the threat
of thunderstorms remains low.

&&

.CLIMATE...
Below is a list of record high temperatures for today, April
30th.

                                       Apr 30th
Climate Site                  Record High     Forecast High
Washington-National (DCA)     92F (1942+)     87F
Washington-Dulles (IAD)       86F (2017+)     85F
Baltimore (BWI)               92F (1910)      87F
Martinsburg (MRB)             91F (1974+)     84F

+ denotes that multiple years reached this value, but the depicted
  year is the most recent

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ530>543.
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&&

$$

SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...AVS/EST
LONG TERM...LFR
AVIATION...AVS/LFR
MARINE...AVS/LFR
CLIMATE...LWX