810
FXUS61 KLWX 181830
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
230 PM EDT Thu Jul 18 2024

.SYNOPSIS...
A cold front will continue to push through central and southern
Virginia this evening as high pressure returns from the north
Friday. The front will stall to the south this weekend before
returning as a warm front during the early and middle part of next
week. As a result, expect temperatures to remain at or slightly
below normal with daily chances for showers and thunderstorms due to
the front nearby.

&&

.NEAR TERM /THROUGH TONIGHT/...
The surface cold front has dropped into southern VA and the
lower eastern shore of MD as of mid afternoon. A couple of vort
maxes trailing the front along with residual instability beneath
gently falling heights aloft are resulting in scattered showers
and a few thunderstorms, mainly south of I-66/US-50.

As we head into the evening, a secondary (dew point) boundary
and subtle wave aloft look to pivot across. Latest high-res
guidance pops a few showers or even a thunderstorm this evening
over central MD/northern VA. Have a 20-30 pct area to account
for this, but it may need to be raised if trends favor more
widespread or persistent activity.

Overnight, clouds will begin to clear. Falling humidity on
northerly winds should allow for below normal lows.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
High pressure will build over the Great Lakes Friday while the
front stalls across the Carolinas due to the strength of the
Bermuda high offshore. Some models continue to try to spit out
a few showers mainly across southern areas, but have maintained
a dry forecast given low PWs and a lack of better forcing. It
will definitely have the lowest chance of rain in the next
seven days regardless. A mix of cumulus and cirrus will prevent
a fully sunny sky, though. High temperatures will remain
seasonable in the mid 80s to near 90.

The front will gradually lift back to the north Friday night
into the weekend in response to an approaching trough from the
middle part of the country and the weakening high to the north.
A chance of showers will start spreading north late Friday
night. A more notable shortwave will approach Saturday though,
and be effective at drawing moisture northward along with
providing ascent. Most areas will have a chance of rain
Saturday, although chances start decreasing northeast of the
Potomac River with increased distance from the surface boundary
which will likely remain over central or southern Virginia.
While a few thunderstorms are possible, instability looks to be
meager and will limit their coverage and strength. Rainfall
should largely be beneficial. Rain chances will decrease
Saturday night as the shortwave departs.

The added cloud cover will likely hold high temperatures below
normal Saturday, especially across central Virginia. Increasing
dew points will lead to warmer overnights in the mid 60s to
around 70.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Key Messages:

1) Potential drought relief for some as the confidence remains high
for daily shower and thunderstorm chances throughout much of next
week.

2) Near normal temperatures expected in the extended period.

Synoptically, not much has changed as we sit under an upper-level
trough sandwiched between a ridge over the western U.S. as well
as Bermuda. At the surface, we continue to monitor the
progression of a stalled frontal boundary draped over Virginia
and North Carolina. This boundary will slowly progress northward
Monday as the western ridge slides east before stalling
overhead Tuesday and Wednesday next week. As a result, expect
increasing chances for showers and thunderstorms each day with
the greatest coverage falling during the Tuesday and Wednesday
timeframe. Some of these storms could be strong to severe given
the convective parameters at play along with a warm 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. The warm front
continues north of the area Thursday, although shower and
thunderstorm chances will remain. It`s not until later in the
week or perhaps next weekend when a cold front tries to clear
the area.

As for temperatures, expect values closer to normal Sunday into the
early and middle part of next week. Highs will range from the upper
70s and low 80s over the mountains to mid and upper 80s east of the
Alleghenies each afternoon. This aligns with the 6 to 10 day and 8
to 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 with light winds.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
There is a chance of a thunderstorm near CHO through about
22-23Z, and confidence has increased enough based on obs and
high-res model trends to include a VCTS. Some guidance develops
a few showers or even a thunderstorm along a moisture boundary
this evening near the metros; confidence was too low for even
VCSH, but will monitor closely. Otherwise, there will just be a
slight uptick in northerly winds.

VFR conditions are expected tonight into Friday as high pressure
builds to the north. The front will stall to the south and
return north this weekend. Some sub-VFR ceilings could reach CHO
tonight and could affect all terminals by Saturday night.
Showers and isolated thunderstorms are possible Saturday as a
disturbance passes.

VFR conditions continue Sunday into early 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 on Tuesday and Wednesday. Winds will be out of the
southeast on Sunday and will turn more southwesterly by Monday
and Tuesday with gusts up to 10 knots expected.

&&

.MARINE...
A few thunderstorms are possible near central/southern Maryland
into this evening, but seem unlikely to be strong. A surge of
northerly winds will work down the bay tonight as high pressure
builds to the north and cooler/drier air arrives. An advisory
remains in effect for late tonight through Friday morning for
the bay and wider tributaries with gusts to around 20 kt
expected. Lighter winds are expected Friday and Friday night as
high pressure to the north remains in place.

The front will gradually move back north into this weekend. A
few thunderstorms will be possible Saturday. However, gradient
winds look to remain at sub-SCA levels.

Sub-SCA level winds out of the southeast are expected Sunday before
turning to the southwest Monday and Tuesday as a 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. The
greatest potential for a thunderstorm looks to come Tuesday and
Wednesday as a warm front sits over the region.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory from midnight tonight to 10 AM EDT Friday
     for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory from midnight tonight to 10 AM EDT Friday
     for ANZ530>534-537-539>541-543.

&&

$$

SYNOPSIS...EST
NEAR TERM...DHOF
SHORT TERM...ADS/DHOF
LONG TERM...EST
AVIATION...ADS/DHOF/EST
MARINE...ADS/DHOF/EST