Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 301420
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1020 AM EDT Fri Jul 30 2021

.SYNOPSIS...
A cold front will move through the area later this afternoon.
High pressure will build over the area tonight. A weak area of
low pressure will pass south of the area Sunday night.
Additional systems may impact the region next week as troughing
becomes established over the eastern half of the country.

&&

.NEAR TERM /THROUGH TONIGHT/...
Isolated showers will develop ahead of a cold front and move
southeast across the central and southern areas as a persistent
northwest flow at the surface and the mid-levels continues into
the weekend. Once the front passes through the region, drier and
slightly cooler conditions will unfold through tonight.
High pressure will settle in over the area tonight. High
temperatures this afternoon will be around 90 or low 90s. Low
temperatures tonight will drop into the upper 50s to lower 60s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Dry conditions will persist through the day Saturday under weak
high pressure. Widespread clouds and showers are expected to
develop Saturday night and Sunday north of a sfc front across
North Carolina and along the base of longwave trough over the
eastern US. Scattered to locally nmrs showers are expected with
a 700 mb wave well depicted in model guidance late Saturday
night into Sunday morning before this wave moves offshore Sun
evening. Rainfall amounts of a quarter to half inch are expected
east of the Blue Ridge Mountains.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The H5 ridge in the western US and trough in the east will continue
through most of the long term. Behind the frontal passage, high
pressure will build Monday keeping conditions dry.

Tuesday through the rest of the long term becomes unsettled with
numerous opportunities for precipitation. The aforementioned front
will stall over the Carolinas as the upper level flow becomes nearly
parallel to the front. Low pressure may form along this boundary and
track northeast, bringing showers and thunderstorms to the southeast
portions of the FA Tuesday into Tuesday night. The strength of the
upper-level trough will influence the northern extent of the
precipitation associated with the low pressure Tuesday.

Some guidance forms a closed upper-level low in the trough by
midweek. Regardless, the base of the trough/low looks to be situated
over the Ohio Valley. This allows a moisture plume of Gulf origin to
be advected into the region by Wednesday and continue Thursday. The
same front looks to move back north/northeast Wednesday into
Thursday as several areas of low pressure track along the front
which could produce locally heavy rainfall. Cannot rule out isolated
hydro issues, especially in the urban and hydrophobic areas.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Quiet weather is expected through Saturday. Showers return late
Sat night into Sun. NW winds this afternoon becoming light and
variable late tonight.

VFR conditions Monday as high pressure builds in with the winds
becoming northwest. MVFR conditions possible late Tuesday as low
pressure tracks nearby bringing showers/Thunderstorms.

&&

.MARINE...
Winds will shift to NW this afternoon behind a frontal passage
and gust around 20 kt through tonight before diminishing
Saturday.

Winds remain below SCA levels at 5-10 knots out of the northwest
Monday. Winds increase Tuesday afternoon and could approach SCA
criteria if the region of low pressure tracks close enough to the
southern Chesapeake Bay.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT Saturday for ANZ530>543.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR/KLW
SHORT TERM...LFR
LONG TERM...CPB
AVIATION...KLW/CPB
MARINE...KLW/CPB


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