003
FXUS61 KLWX 200040
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
840 PM EDT Fri Jul 19 2024

.SYNOPSIS...
Dry conditions and lower humidity are expected today as high
pressure builds into the region. Shower and thunderstorm chances
return Saturday as a weak piece of energy traverses a stalled front
draped along the Virginia and North Carolina border. High pressure
briefly returns Sunday before a warm front lifts into the region
Monday and Tuesday. This will result in daily shower and
thunderstorm chances along with increased humidity throughout much
of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A few showers are currently tracking northeast across the
eastern panhandle of WV and the I-81 corridor in western VA.
These showers will linger for a few hours, but are expected to
dissipate due to dry air and loss of forcing due to the loss of
daytime heating. Any shower activity is expected to remain west
of the Blue Ridge. Increased PoPs to account for these showers
tracking east, but no further changes were made to the previous
forecast. Previous discussion follows:

Northeast to southeast flow and a mix of cumulus and cirrus are
resulting in slightly below normal temperatures and lower
humidity across the Mid-Atlantic. A front remains stalled over
the Carolinas while high pressure builds from the Ohio River
Valley toward New England. Any shower activity looks to be very
brief, isolated, and limited to near the higher terrain given
weak forcing and dry air.

Clouds (especially cirrus) look to linger tonight as a jet
streak pivots across and weak low pressure develops to the
south. Humidity ticks up slightly with low temperatures near to
slightly below normal for mid July.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
On Saturday, the stalled boundary to our south is expected to
meander northward as a shortwave passes overhead. Precip chances
will increase from southwest to northeast through the day,
bringing some much needed rainfall to the area. 12Z guidance
continues to trend down with overall QPF amounts. Cloud cover
will keep high temperatures below normal, topping out in the low
to mid 80s for most of the area. Rain chances drop off
overnight as the shortwave exits and forcing is lost. Low
temperatures will be a few degrees cooler than Friday, in the
low to mid 60s for most.

The front likely remains stalled to our south into Sunday,
limiting PoPs to our southern zones. Expect coverage to be
reduced compared to Saturday with subsidence on the back end of
the exiting shortwave. Reduced cloud cover and southerly flow
brings highs back to the upper 80s to low 90s. Clouds build in
overnight resulting in milder lows, hovering in the 70s along
and east of the I-95 corridor, with mid-upper 60s expected
elsewhere.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Key Messages:

1) Confidence is high for daily shower and thunderstorm chances
throughout the workweek. Localized flood issues are possible
especially in areas that see repetitive rounds of rain.

2) Seasonable temperatures and increasing humidity during the
extended period.

No big changes in the synoptic pattern remain amongst the latest
deterministic and ensemble model runs. Still looking at a blocked
pattern with upper-level ridging in the western U.S and a
slight retrograde westward with the ridge over the
Bermuda/central Atlantic. In between lies the upper-level
trough and associated stalled frontal boundary which will slowly
lift north as warm front Monday before oscillating near the
region for the middle part of the workweek. As a result, showers
and thunderstorms look to become a mainstay of the forecast, in
particular during the afternoon and evening hours. Humidity
values will also increase as a result of steady south to
southwesterly flow off the Gulf of Mexico aiding in the
potential for locally heavy rainfall and drought relief for some
mid next week. Any rainfall that we do see is likely to be
mostly beneficial, especially along and west of US-15 where
severe/extreme drought conditions are being observed. Locally
heavy rainfall in the I-95 urban corridor could result in some
flooding issues if storms persist over an area. As for severe
weather, the threat remains low given the abundant cloud cover
from the stalled front nearby. This is highlighted by both the
CSU and NSSL machine learning probabilities which suggest a non-
zero chance of severe weather during the middle and latter half
of next week.

By Thursday, the upper-level trough and associated cold front
approach the area from the Ohio River Valley and Great Lakes
region. Some uncertainty remains in the exact timing and
strength of this system. For now, will leave chance PoPs in the
forecast through Thursday and perhaps even Friday as models
still hold the front up from clearing the area.

As for temperatures, expect values closer to seasonable norms
for late July. Highs will range from the upper 70s and low 80s
over the mountains to mid and upper 80s and low 90s east of the
Alleghenies each afternoon. This aligns with the 6-10 Day and 8-
14 Day Temperature Outlooks from the Climate Prediction Center.
Overnight lows through the period will fall into the mid to
upper 60s and low 70s.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are forecast to prevail through the weekend,
though some patches of MVFR CIGs are possible mainly near CHO
during the early morning hours as they are closer to a front
meandering to the south. Weak low pressure along this front may
deliver occasional shower activity to the terminals along with
brief restrictions Saturday (especially near CHO). Generally
weak instability lowers confidence in thunder potential for most.
Winds will become SE to S through Saturday, then NW Saturday
night through Sunday at 5-10 kts.

VFR conditions continue into next week, although the
opportunity for sub-VFR remains during the afternoon and evening
hours as a warm front lifts into the region. This will lead to
increased chances for showers and thunderstorms at the terminals,
although confidence remains low on which terminals will be
impacted. The highest coverage for thunderstorms appears to be
Monday through Wednesday. Winds will will turn southwesterly
Monday and Tuesday generally AOB 10 knots.

&&

.MARINE...
SE to S winds are forecast through Saturday. Showers and a few
thunderstorms are possible Saturday as weak low pressure moves
along a front moving up from the south. Winds become NW Sunday,
and look to remain below SCA levels through the weekend.

Southerly winds kick back into gear over the waters Monday and
Tuesday. Sub-SCA level conditions are expected although some
channeling could occur especially over the open waters. Stronger
southerly channeling is expected Tuesday night into Wednesday,
especially over the open and middle waters of the Chesapeake
Bay/lower tidal Potomac River. SCAs may be needed during this
time. Outside of channeling, expect daily shower and
thunderstorm chances each afternoon and evening next week as a
stalled front sits nearby. An SMW cannot be ruled out for any
potential strong thunderstorms that look to pop up during the
afternoon and evening hours.

&&

.TIDES/COASTAL FLOODING...
Light easterly to southerly flow through Saturday will lead to
an uptick in water levels. Although minor flooding is unlikely,
vulnerable shoreline (such as Annapolis) could come close early
Saturday morning.

&&

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

&&

$$

SYNOPSIS...EST
NEAR TERM...AVS/DHOF
SHORT TERM...DHOF/CAS
LONG TERM...EST
AVIATION...DHOF/EST
MARINE...DHOF/EST
TIDES/COASTAL FLOODING...