208
FXUS61 KLWX 041433
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1033 AM EDT Thu Jul 4 2024

.SYNOPSIS...
A nearby frontal boundary will bring daily shower and thunderstorm
chances through the weekend. The cold front will move through the
area on Saturday before stalling overhead allowing for precipitation
chances to continue through midweek.

&&

.NEAR TERM /THROUGH TONIGHT/...
Mid-morning update: Very little change in thinking with respect
to the forecast this morning. Skies have cleared out to the east
of I-81, allowing for strong daytime heating. Mid-high level
clouds are making their way into western portions of the
forecast area, and should overspread the rest of the forecast
area this afternoon. Some cumulus are also starting to develop
over the mountains. 12z IAD sounding shows a very moist profile
above 850 hPa, with a precipitable water value of 2.09 inches
and a freezing level of 4.77 km. The high freezing level should
allow for efficient warm rain processes in any storms today, and
the high precipitable water values will provide ample moisture
to storms. Both of these factors should make very heavy rainfall
possible in association with storms today. Previous discussion
follows...

For the 4th of July, expect showers and thunderstorms along
with hot and humid conditions. A surface trough overhead
combined with shortwave energy aloft will provide plenty of
instability to initiate convection. With little CIN, latest CAMs
have convection beginning as early as noon in the western
portions of the area and moving through the metro areas in the
afternoon. Should convection initiate earlier, the atmosphere
could recover leading to lingering showers becoming more
organized.

The primary threats with thunderstorms today will be damaging
wind gusts and flooding in urban areas. CAPE values of 1000-2000
J/kg and up to 30 knots of Bulk Shear will be just enough to
lead to pulse and multicell cluster convection. Precipitable
water values nearing record levels of over 2 inches will lead to
heavy rain and wet microbursts potential. Steering flow is
enough to lower the risk of flooding in rural areas, but urban
areas with lower flash flood guidance could see flooding with
heavy rain. The flooding threat is expected to primarily stay
contained to urban areas and those prone to flash flooding,
however, if convection lines up oriented from west to east,
training could lead to prolonged periods of heavy rain over
areas. This is not expected, but cannot be ruled out.

Temperatures today will be in the low to mid 90s for
those east of the Blue Ridge with those west of the Blue Ridge
in the 80s. Humid conditions will have heat indices rising into
the low 100s for metro areas and the southern portions of the
forecast area. Overnight low temperatures will stay in the 70s
for most. Those in the metro areas will find little relief from
the heat overnight with heat indices remaining in the upper 70s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Daily shower and thunderstorm chances continue Friday and Saturday
with the aforementioned cold front moving through the forecast area
on Saturday. A surface trough will remain overhead on Friday
providing lift and instability. The setup for Friday looks
similar to Thursday with afternoon showers and thunderstorms and
even warmer temperatures, however coverage of storms looks to be
less widespread.  Temperatures will be in the 90s for most with
high humidity leading to heat indices up to 105 for those east
of the Blue Ridge. Overnight low temperatures will be in the mid
60s to 70s.

On Saturday, a weak cold front moving through the area will
continue precipitation chances. The forecast continues to trend
drier with highest PoPs in the eastern portions of the area. We
will continue to monitor the threat for severe weather and
flooding, though thunderstorms look to remain scattered and
confidence is low. High temperatures will be a few degrees
cooler than Friday with heat indices remaining in the low 100s
for those east of the Blue Ridge. Overnight low temperatures
will be in the 60s to low 70s.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
A weak surface ridge builds south into the area Sunday, bringing
less humid conditions. The weak frontal boundary that was stalled
over our area earlier in the weekend is pushed to southeast VA.
While a couple of thunderstorms are possible in Central VA and far
southern MD, expect conditions to be dry for most. Near-normal highs
as temperatures reach the upper 80s to low 90s.

A warm front lifts north through the area Monday, ushering in a much
more humid airmass. Dew points reach around 70F Monday, then
widespread low to mid 70s for the middle of next week. Afternoon
highs in the low to mid 90s Monday and Tuesday. The hottest
conditions are forecast on Tuesday when peak heat indices reach
between 100-105. Increasing cloud cover brings temps down a bit on
Wednesday to the upper 80s to around 90F. Muggy overnight lows in
the far upper 60s to mid 70s.

Daily afternoon showers and thunderstorms return to the forecast,
likely for much of next week. Shower/t`storm chances Monday focus in
the central Shenandoah Valley and central VA, then become widely
scattered Tuesday and Wednesday afternoons.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Prevailing VFR conditions are expected for all terminals through
Saturday with winds expected to remain light out of the
south/southeast. Daily shower and thunderstorm chances peak each
afternoon with primary hazards being heavy rainfall, gusty
winds, and frequent lightning. Sub-VFR conditions are possible
during precipitation.

VFR conditions are expected Sunday as high pressure builds into the
region. A warm front lifts north across the area Monday, bringing a
return to daily showers and thunderstorms. Still, most activity
Monday looks to be around CHO, with much lower chances for storms at
the other terminals. Any storm that moves over a terminal will be
capable of producing brief periods of sub-VFR conditions, in
addition to gusty winds.

&&

.MARINE...
A Small Craft Advisory is in effect for the southern portions
of the Chesapeake Bay through tonight with sub-SCA criteria
winds expected elsewhere. SMWs are possible over the waters each
afternoon through Saturday with daily chances of showers and
thunderstorms.

Weak high pressure builds into the area from the north to end the
weekend, bringing lighter winds and dry conditions. A warm front
lifts north through the waters on Monday, with southerly channeling
possibly leading to near-SCA winds in the open waters of the
Chesapeake Bay Monday evening. A few thunderstorms are possible over
the waters Monday afternoon, though most should be well inland.

&&

.TIDES/COASTAL FLOODING...
Steady southerly winds through Saturday night are likely to result
in minor coastal flooding at the more sensitive locations each day.
This is going to be during the highest diurnal tide, which is
currently in the morning. Annapolis is most likely to hit minor
flooding each day, with DC SW Waterfront, Havre de Grace, and
Baltimore needing a close watch.

A weak front pushes south of the area Sunday, bringing light
northwest/north winds and a brief reprieve from coastal flooding.
However, stronger southerly flow is expected again next week, likely
leading to additional periods of coastal flooding.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Heat Advisory from noon to 8 PM EDT Friday for DCZ001.
     Heat Advisory until 8 PM EDT this evening for DCZ001.
MD...Heat Advisory from noon to 8 PM EDT Friday for MDZ008-011-013-
     014-016>018-504-506-508.
     Heat Advisory until 8 PM EDT this evening for MDZ011-013-014-
     016-504-506.
     Coastal Flood Advisory until 11 AM EDT this morning for MDZ508.
VA...Heat Advisory from noon to 8 PM EDT Friday for VAZ050-051-
     053>057-502-527.
     Heat Advisory until 8 PM EDT this evening for VAZ053>056-527.
WV...None.
MARINE...Heat Advisory from noon to 8 PM EDT Friday for ANZ530.
     Small Craft Advisory from 3 PM this afternoon to 8 PM EDT this
     evening for ANZ533-537-541.
     Small Craft Advisory until 1 AM EDT Friday for ANZ534-543.

&&

$$

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