-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KLWX 071413
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1013 AM EDT Tue Sep 7 2021

.SYNOPSIS...
High pressure will remain over the area today. A cold front
will progress through the area during the middle of the week
with high pressure building in by late in the work week and into
the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Satellite imagery indicates a few patches of clouds, but many
areas are clear, and few clouds are expected through the day.
Forecast remains on track for a quiet and warm high pressure
day.

Previous discussion follows...

Latest analysis depicts high pressure sprawled across the
region. A cold front is crossing the northern Plains a general
east-southeast trajectory. Aloft, a weak broad trough sits over
the eastern US with a weak ridge over the Corn Belt and a
stronger shortwave diving southeast across the northern Plains.

For today, dry weather and sunshine will dominate under the high
pressure. Temperatures will nudge a little warmer than yesterday
as the flow turns back to a bit more southwest, but overall, not
much difference from the bulk of yesterday. Highs mostly in the
80s.

Clouds will start to increase as the system over the northern
plains starts to approach tonight, and combined with a stronger
southerly flow, temperatures will stay a bit milder, with most
places remaining in the 60s. Otherwise, it should remain dry.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Warm advection will continue on Wednesday as the strengthening
southerly flow brings warmer, more moist air northward across
the region. A weak disturbance embedded within the broad
southwest flow aloft may make use of this increasing warmth and
moisture to cause spotty showers or even t-storms across mainly
eastern parts of the forecast area by midday into the afternoon,
but the bulk of Wednesday looks very warm, more humid, breezy
but otherwise dry with some sun.

Cold front plowing into this air mass late in the day into the
night Wednesday will bring two threats. First, enough
instability will be present late in the day into the evening to
bring at least an isolated severe weather risk, with damaging
winds being the main threat. As the night wears on and the front
slows a little while the storms potentially congeal into a more
focused band of heavy rain, an isolated flood threat may emerge.
For these reasons, a marginal risk of severe weather and flash
flooding exists later Wednesday into Wednesday night.

Front is slow to clear the region as the large trough aloft
slowly swings through on Thursday. This will cause clouds to
linger, and in fact, a few isolated showers or storms could
develop along the Allegheny Front later in the day thanks to
instability from the upper trough`s passage. Further east, the
bulk of the day looks dry, but showers may linger early,
especially east of I-95. The cooler air mass and lingering
clouds likely keep temps below normal, with highs struggling to
reach 80.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
High pressure will dominate much of the long term forecast
period, with mostly clear skies and dry weather on tap. Below
normal temperatures ranging from the 60s in the mountains to
near 80 degrees elsewhere will exist on Friday as the high over
the central U.S. nudges into the Mid-Atlantic region. The high
will transit the region Friday night and begin to shift offshore
Saturday with continued mostly clear skies and dry conditions.
Seasonable temperatures Saturday will moderate to slightly above
normal by Sunday as a return flow sets up with the core of the
high situated offshore. Low pressure tracking well north of the
Great Lakes late Sunday into Monday may drop a frontal boundary
into Pennsylvania. Coupled with a weak shortwave aloft, can`t
rule out a shower or two across our far northern and northwest
zones in Maryland and adjacent eastern West Virginia counties.
That being said, slight chance POPs at best will exist in the
forecast database for now Sunday afternoon and evening. Dry and
seasonable conditions will exist Monday as we remain on the
western flank of the high over the Atlantic and overall zonal
flow aloft, while temperatures trend near to slightly above
normal for the middle of September.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Mainly VFR thru tonight all terminals. Intervals of sub-VFR
possible later Wednesday with scattered showers and t-storms,
with this becoming more likely Wednesday night when a more
widespread band of showers and thunderstorms may move through
with the passing cold front. The risk of sub-VFR should dwindle
quickly after dawn Thursday as drier air slowly builds back in.

High pressure over the central U.S. will build into the region
Friday, beginning to shift offshore Saturday. Resultant weather
will be VFR with mostly clear skies and dry conditions. Light
northwesterly winds Friday will turn southerly on Saturday,
remaining at less than 10 knots.

&&

.MARINE...
-- Changed Discussion --
Light and variable winds will become south/southwest this
afternoon but should stay below advisory criteria through the
day. As high pressure slides off the coast and a cold front
approaches from the northwest, southerly channeling should
result in fairly widespread SCA conditions tonight into
Wednesday, although winds may subside somewhat during the middle
of the day. Isolated strong storms may required special marine
warnings later Wednesday into Wednesday night. Winds relax with
a rapidly dwindling threat of further strong storms late
Wednesday night into Thursday as the front passes.

SCA gusts will be possible early Friday as high pressure over
the central U.S. builds into the region. Thereafter, the high
will transit the area Friday night, shifting offshore on
Saturday. Light northwest winds Friday afternoon and night will
turn light and southerly Saturday, with sub SCA conditions
likely.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
Southerly breezes will return today through Wednesday, allowing
for tidal anomalies to creep upward and bring a threat for
minor tidal flooding. Current forecast brings minor flooding to
Annapolis with the high tide cycles late tonight and during the
day on Wednesday. Many other sites will achieve action stage,
with DC Southwest Waterfront flirting close to minor during this
time period as well. A cold front will push through the area
Wednesday and early Thursday, allowing winds to turn offshore,
producing lowering anomalies, and lessening the threat for tidal
flooding through the end of the work week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 PM EDT
     Wednesday for ANZ531>534-537-539>543.
     Small Craft Advisory from 6 AM to 6 PM EDT Wednesday for
     ANZ530-538.

&&

$$
SYNOPSIS...BKF/RCM
NEAR TERM...ADS/RCM
SHORT TERM...RCM
LONG TERM...BKF
AVIATION...BKF/RCM
MARINE...BKF/RCM/ADS
TIDES/COASTAL FLOODING...BKF