372
FXUS61 KLWX 080751
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
351 AM EDT Mon Jul 8 2024

.SYNOPSIS...
A warm front will lift north into region today before stalling out
Tuesday into Wednesday. Heat, humidity, and daily thunderstorm
chances will return as a result of the front wavering nearby. By
Thursday, a cold front will approach from the Ohio River Valley. The
front will try to cross the area Friday before washing out along the
coast as broad high pressure builds for the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Much of the same as we start out the new workweek when it comes to
the current Summertime weather pattern. Temperatures look to start
in the 70s in many locations with low 80s over the Baltimore/DC
metros. Skies will remain mostly clear to partly cloudy with a
wavering front nearby. The stalled front currently draped across the
western Delmarva, eastern VA and central/eastern NC will gradually
lift northward as a warm front later this morning and into the
afternoon hours. Current 00z deterministic CAM guidance continues to
show some uncertainty in regards to the placement of this boundary
and ultimately where convection will fire during the peak heating
period this afternoon and evening. Right now, general consensus is
for shower and thunderstorm activity to spark between 2-7pm mainly
over the Shenandoah Valley and the central Virginia Piedmont region.
Even with that said, a few spotty thunderstorms cannot be ruled out
further north given the potential placement of the boundary and over
the terrain where better orographic lift can be found.

One of the big questions today is to if we will still see a capping
inversion or not. This is what suppressed most of our convection
this past weekend along with westerly flow aloft. It was also
evident on last night`s 00z KIAD sounding with dry air at the 700-
850 mb level and an even larger pool of dry air above 500 mb. With
southwesterly flow aloft today, slightly less dry air should be able
to mix to the surface.

Even with that said, it will be another hot and humid day. Heat
Advisories remain in effect from 12pm-8pm for areas along and east
of US-15. Heat indices in these locations will reach as high as 105
degrees. Elsewhere expect heat index values in the mid to upper 90s
to around 100 degrees. High temperatures this afternoon will range
between the mid to upper 90s east of the Alleghenies. Mountain
locations will remain in the mid to upper 80s. Winds will remain
light out of the south/southeast at 5-10 mph.

Any thunderstorm activity looks to wane with the loss of daytime
heating. Residual scattered to broken mid and high level clouds will
be leftover along with patchy fog in locations that do see
rain/clearing. No relief is expected in the temperature nor humidity
department with lows in the 70s east of the Alleghenies and low 80s
in the immediate Baltimore/Washington DC metros.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Excessive heat and humidity continue into midweek with the
persistent upper level ridge remaining amplified over the
southeast U.S and stalled front nearby. Southerly flow will
return at the surface allowing for a continued uptick of
moisture into the region. This will result in another day of
high heat and humidity with additional heat advisories likely
being needed for areas east of the Blue Ridge. High temperatures
Tuesday will push up into the mid to upper 90s east of the
mountains with heat indices once again over 100 degrees. Showers
and thunderstorms will also be a concern during the afternoon
and evening hours especially with the stalled front wavering
nearby. CAM guidance pegs slightly better coverage for
convective activity over central MD and central VA as well as
the terrain Tuesday afternoon and evening. Uncertainty remains
though given the flow will be more westerly aloft ahead of the
approaching upper level trough and remnants of Beryl from the
central CONUS region. For now kept 20-30 percent PoPs in for the
peak heating period Tuesday afternoon into early evening. Any
thunderstorm activity Tuesday will diminish with the loss of
peak heating. Once again it will be another night with no relief
with lows in the mid to upper 70s and low 80s east of the
mountains. Areas of patchy fog remain where clearing and
rainfall occur.

By Wednesday, the upper level ridge flattens allowing the upper
level trough over central CONUS (which ultimately absorbs the
remnants of Beryl) to move east into the Great Lakes and Ohio River
Valley. Meanwhile, the stalled boundary over our region lifts
further north as a warm front driving more moisture into the region.
Dewpoints will get back into the mid 70s making it truly feel like
"air you can wear". High temperatures will also remain in the low
mid 90s especially east of the Blue Ridge. This will force heat
indices back between 100-105 degrees. Flow aloft will switch back to
the southwest allowing for the eventual progression of several
shortwave disturbances and fronts to cross the region. Some
uncertainty remains in regards to the timing and placement of these
pieces of energy as well as the relation to the moisture tied up
within the remnants of Beryl. Both the 00z GEFS/EPS show PWAT
anomalies 1.5 to 2 standard deviations above normal Wednesday.
Forecast soundings also show higher CAPES on Wednesday with slightly
stronger 0-6km bulk shear values. These probabilities are also
highlighted with the learning machine probabilities signaling a
broad low end risk for both severe weather and localized flash
flooding. For now, keeping high POPs, more closely aligned to the
NBM, in place for Wednesday. Areas of heavy rain and localized flash
flooding is possible, especially if storms form/move over urban and
poor drainage areas.


&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Increasing heat and humidity will help to fuel the threat for
showers and thunderstorms Thursday through Friday night. A front
could stall across the central portions of our CWA late Thursday and
Thursday night. Along with this front, the remnants of Beryl could
bring a renewed or prolonged period of showers and thunderstorms
along and east of this stalled front. There is a lot of uncertainty
on position of the stalled front, amount of instability present, and
the exact track of Beryl. It does look like we could get some much
needed rainfall late this week into early in the weekend with this
setup. Highs Thursday could be in the lower to middle 90s. Highs
Friday, depending on cloud and shower coverage may reach the middle
80s. Then we could be right back into the 90s during the weekend. It
is during the weekend of Saturday and Sunday that high pressure
becomes reinforced and brings us more Summer heat and humidity.


&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Prevailing VFR conditions are expected through Tuesday. The stalled
front over the western Delmarva, eastern VA, and central NC will
eventually lift northward as a warm front later this afternoon and
evening. As the front, pushes north an isolated shower or
thunderstorm cannot be ruled out. The best opportunity for showers
and thunderstorms appears to be at terminals near terrain (KMRB/KHGR)
and down across the Shenandaoh Valley/central VA Piedmont
(KCHO/KSHD) between 2-7pm. Have went ahead and put VCTS in the TAF
for these locations. I also opted to put VCTS in for KIAD although
confidence is much lower for thunderstorm development and hinges on
the placement of the frontal boundary. Additional showers and
thunderstorms are possible on TUesday although confidence remains
low on coverage given westerly flow aloft and the remnant moisture
from Beryl sitting over the Great Lakes/Ohio River Valley. Winds
will remain light out of the south and southeast today before
switching to the south Tuesday.

Slightly higher opportunities for sub-VFR conditions exists
Wednesday and Thursday as remnants of Beryl pass through.Restrictions
remain possible especially during the afternoon and evening hours.
This is due in part to thunderstorms development along with the
potential for heavy rainfall. MVFR conditions possible in terms
of ceilings Thursday through Friday night with a stalled front,
tropical remnants and developing showers and thunderstorms.
Wind gusts in thunderstorms could exceed 40 knots.


&&

.MARINE...
Light southerly winds this morning will gradually increase late
tonight and into the day Tuesday. Sub-SCA conditions are expected
during this although a brief period of southerly channeling could
occur especially over the open waters Tuesday afternoon and Tuesday
night. isolated showers and thunderstorms are possible both Monday
and Tuesday afternoon as a front wavers nearby. Storms will be
fairly isolated with frequent lightning and gusty winds as the
primary concerns.

Periods of southerly channeling look to continue Wednesday and
Thursday. SCA may be needed during this time to encompass this
threat. Additionally, convective chances also increase as a front
and the remnants of Beryl approach from the west. Special Marine
Warnings may be needed for any of the stronger thunderstorms. This
boundary stalls nearby on Friday leading to continued opportunities
for showers and thunderstorms.

&&

.TIDES/COASTAL FLOODING...
Tides will gradually increase throughout the week but should still
remain below action stage everywhere at this time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from noon today to 8 PM EDT this evening for
     DCZ001.
MD...Heat Advisory from noon today to 8 PM EDT this evening for
     MDZ004>006-008-011-013-014-016>018-503>508.
VA...Heat Advisory from noon today to 8 PM EDT this evening for
     VAZ039-040-050-051-053>057-501-502-505-506-526-527.
WV...None.
MARINE...Heat Advisory from noon today to 8 PM EDT this evening for
     ANZ530.

&&

$$

SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...EST
LONG TERM...KLW
AVIATION...KLW/EST
MARINE...KLW/EST
TIDES/COASTAL FLOODING...KLW