447
FXUS61 KLWX 051839
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
239 PM EDT Wed Jun 5 2024

.SYNOPSIS...
Unsettled weather today through Thursday as a series of fronts
cross the region. Mostly dry conditions on Friday in the wake of
the cold front. A slow moving upper trough approaches the area
from the Great Lakes this weekend leading to more unsettled
conditions.

&&

.NEAR TERM /THROUGH TONIGHT/...
This afternoon is shaping up to be pretty active across the
region. The air mass across the region is characterized by
temperatures in the upper 70s to low 80s with dew points into
the low 70s. Expect multiple rounds of thunderstorms this
evening, with severe weather and flash flooding both possible.

- Severe weather threat - This has resulted in around 1000-1500
  J/kg of MLCAPE. The shear across the region isn`t overly
  impressive at this time, especially in the lower levels.
  However, there is enough mid- level shear out there that
  pretty much any individual cell along the warm front is
  spinning at this point. Nothing seems to be reaching the
  surface at this point, but certainly a volatile environment
  this afternoon right along the warm front. Storms seems to be
  taking on a very low-topped supercellular structure, so will
  be watching very subtle rotation signatures very closely.

- Flash flooding threat - not much has changed from the earlier
  forecast honestly. With the ongoing convection, there have
  been recent reports of almost an inch of rain in 20-30 minutes
  or so with some of the stronger storms. Should that make it to
  the metros, that could be an issue. PWATs are closing in on 2"
  across the area, so would expect torrential rainfall with
  pretty much anything that develops today. The warm front will
  provide a focal point for convection, with multiple rounds
  possible. Widespread rainfall amounts of 1-2 inches seems
  likely, with isolated amounts up to 3-4 inches is possible
  where stronger thunderstorms develop.

Showers are likely going to linger into tonight given the
continued southerly flow bringing in very moist air. This will
also bring in some lower clouds and potentially some patchy
dense fog. Low temperatures will be very warm, staying in the
70s for most.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The leading mid-level shortwave moves east of the area Thursday
morning, as a weak cold front continues its slow trek through the
area. This boundary is likely to produce a broken line of showers
and thunderstorms during the late morning to afternoon, mostly along
and east of the Blue Ridge. Additional showers could develop in the
Alleghenies. Very warm afternoon temperatures in the low to mid 80s,
with some spots possibly reaching the upper 80s.

Not much cooling in wake of the front for Thursday night as lows
settle in the upper 50s to mid 60s. High pressure starts to build in
from the west Friday as westerly winds around 5-10 mph continue.
Aside from a few showers in the Alleghenies, mostly dry conditions
are forecast Friday. Afternoon highs will be closer to normal, in
the upper 70s to low 80s. Seasonal lows Friday night in the 50s,
with low 60s along the immediate Western Shore and Potomac River.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Upper level troughing will remain over the Mid-Atlantic throughout
the long term period. There still remains a good bit of model
discrepancies with regards to when and where a cutoff low develops
within the upper level troughing. Guidance also varies on how far
south the low will go, but general consensus is having the low track
towards SE Canada and the northeast US throughout the weekend and
into early next week. With upper level troughing overhead, diurnal
precipitation chances, albeit low (<40% PoPs) are possible each day.
Saturday looks to be the driest with precipitation chances being
confined to the northwestern portions of the forecast area. The best
chances for precipitation will be Sunday into Monday as a cold front
and associated low pressure system move through the area.

Temperatures each day will be in the 70s to low 80s with higher
elevations staying in the 60s. Overnight lows will be in the 50s for
most locations. However, those along and east of I-95 and in metro
areas may stay in the low 60s.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
The first round of thunderstorms is moving through all TAF sites
at this time and should last anywhere from 2 to 3 hours.
Generally expecting showers during this time with a few embedded
thunderstorms here and there. This was depicted in the TAFs with
the tempo group, as the majority will likely just be showers for
this round.

Another round of thunderstorms is possible this evening. Had a
bit less confidence in this round, but decided to still have
some depiction of it within all TAFs, except MRB.

Showers and storms decrease late this evening after the second
round, though given the moist air mass in place, would expect
some lingering showers into the overnight. Low clouds are
likely to build in again at BWI and MTN tonight, and could reach
as far west as MRB, IAD, and DCA though confidence is low at
this time. Best confidence in IFR CIGs tonight is at BWI and
MTN.

A cold front will push through on Thursday, bringing yet another
round of showers and thunderstorms to the TAF sites. MRB should
be just showers during the morning hours before instability is
able to build. However, the rest of the TAF sites could see
thunderstorms during the early-mid afternoon.

High pressure builds into the region Thursday night into Friday,
bringing dry conditions and continued west winds.

Westerly winds blowing 5 to 10 knots on Saturday become light and
variable overnight. Winds pick up slightly on Sunday, gusting 15-20
knots while blowing out of the northwest. Prevailing VFR conditions
are expected this weekend with sub-VFR conditions possible during
afternoon showers and thunderstorms on Sunday.

&&

.MARINE...
The first of what could be two rounds of convection this evening
is approaching the waters at this time. Pretty much any decent
cell that has developed has at least some rotation, so
waterspouts are possible this afternoon in addition to the
threat for some 34+ knot wind gusts.

Increasing southerly winds tonight into Thursday morning will likely
result in SCA conditions in the open waters of the central and
southern Chesapeake Bay, along with the Lower Tidal Potomac.

Winds turn out of the southwest Thursday morning ahead of the
approaching cold front. As the cold front pushes through late
morning into the afternoon, thunderstorms may develop once
again, with some SMWs potentially needed.

Winds will then turn out of the west Thursday afternoon in the
wake of this cold front. At this time, winds are forecast to
remain below SCA level.

Westerly winds around 5-10 knots Friday, with dry conditions.

Westerly winds on Saturday may briefly gust 15-20 knots in the
afternoon, especially in the northern portions of the Chesapeake
Bay. Winds diminish overnight before shifting to northwesterly on
Sunday, gusting 15-20 knots during the afternoon. SCAs are possible
Sunday afternoon in the northern portions of the Tidal Potomac and
Chesapeake Bay.

&&

.TIDES/COASTAL FLOODING...
With a steady southerly flow in place across the region, tidal
anomalies have been on the increase today. This paired with the
approaching new moon have brought several sites to minor flood
stage in the past couple of high tide cycles. This will continue
through the Thursday morning high tide cycle, where Annapolis
could even approach Moderate flood stage. A cold front crosses
the area early Thursday, with the resulting west winds causing
tidal anomalies to drop by Thursday evening/night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch until 10 PM EDT this evening for DCZ001.
MD...Flood Watch until 10 PM EDT this evening for MDZ011-013-014-
     503>506.
     Coastal Flood Advisory until 5 PM EDT this afternoon for
     MDZ017.
VA...Flood Watch until 10 PM EDT this evening for VAZ053-054-506-
     526-527.
WV...None.
MARINE...Small Craft Advisory from 2 AM to noon EDT Thursday for ANZ532-
     533-537-540-541.
     Small Craft Advisory from 10 PM this evening to 2 PM EDT
     Thursday for ANZ534-543.

&&

$$

SYNOPSIS...KRR
NEAR TERM...CJL/KRR
SHORT TERM...KRR
LONG TERM...AVS/CJL
AVIATION...AVS/CJL
MARINE...AVS/CJL
TIDES/COASTAL FLOODING...CJL