276
FXUS61 KLWX 300800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Sun Jun 30 2024

.SYNOPSIS...
Low pressure will move across the Great Lakes region early this
morning. A cold front will then push through this afternoon and
evening. A strong area of high pressure settles over the area
Monday and Tuesday before drifting offshore the second half of
the week. A warm front nears the region by mid-week yielding a
warming trend.

&&

.NEAR TERM /THROUGH TONIGHT/...
A residual pool of elevated instability continues to spark off
isolated to scattered showers and thunderstorms early this
morning. What has developed has not been terribly organized, but
has been stout enough to produce locally heavy rainfall and
frequent lightning strikes. The 0720Z radar imagery shows a
loosely organized line tracking east of the Baltimore area toward
the Chesapeake Bay. Farther upstream, a shield of decaying
thunderstorms have begun to march toward the I-81 corridor. With
the atmosphere downstream largely worked over per ample
inhibition (100-150 J/kg) on the 06Z RAP objective analysis.
Based on how much shower activity is occurring back over central
West Virginia, expect some threat of showers during the morning
hours.

It will be a warm and muggy start to the day given current
temperatures in the 70s to low 80s and dew points in the low/mid
70s. The latest radar trends and hourly update high-resolution
models support showers during portions of the morning. This
would introduce a hefty amount of cloud cover which will
influence how afternoon convection unfolds. The 00Z HREF mean
shows plenty of clouds through the lunch hour before some breaks
become evident west of the Blue Ridge. If this is the way things
play out, the forcing from a formidable mid-level trough should
help ignite some convection by the early afternoon. 500-mb wind
fields are fairly healthy this afternoon, generally running
around 40 to 45 knots. The forecast surface-based CAPE values
along and east of U.S. 15 run between 1,500-2,500 J/kg. Thus,
expect convection to further intensify when pushing from U.S. 15
and points eastward. Thunderstorms are expected to coagulate
into an eastward surging squall line. A Slight Risk continues
across from I-81 eastward with damaging winds and large hail
being the primary threats. However, cannot rule out a brief
tornado from I-95 eastward given some interactions with local
bay/river breezes. All of this activity exits into the lower
Chesapeake Bay by the mid/late evening hours as a cold front
ushers in drier air in the wake.

Regarding the threat of daytime heat and humidity, there is a
lot of question marks in whether heat indices are able to push
to advisory thresholds (105 east of the Blue Ridge and 100 to
the west). There has been a subtle cooling trend in the guidance
which caps high temperatures to around 93 to 95 degrees. This
is in response to the extensive cloud cover which may hinder
some of the afternoon heating. Based on the air mass in place,
dew points in the low/mid 70s should stick around much of the
day. Some vertical mixing could lower dew points by a couple
degrees. The net combination of heat and humidity carries heat
indices into the 100 to 104 degree range. Despite falling short
of a Heat Advisory, the public should ensure to stay hydrated,
find shade or the indoors to escape the heat, and wear light
clothing.

For the night, expect cooler temperatures than the past several
nights. Lows will be in the mid 50s to low 60s, locally falling
into the mid/upper 40s along the Alleghenies. This comes with
northerly winds that gusts up to 10 to 20 mph at times.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A seasonably strong area of high pressure will advance from the
Upper Midwest toward the northeastern U.S. on Monday and
Tuesday. This ushers in an air mass characterized by below
average temperatures and lower humidity levels. Ample sunshine
is likely on Monday, accompanied by high temperatures in the
upper 70s to low 80s. 60s to low 70s will be more commonplace
for those in mountain locations. Along the eastern extent of the
ridge of high pressure, a steady northerly wind is expected
through the day with afternoon gusts up to 20 to 25 mph. By
Monday night, the ridge settles over interior New England down
into the Mid-Atlantic region. This helps lower overnight
temperatures into the 50s to low 60s. A few mid 60s are possible
along and east of the I-95 corridor.

As the ridge slowly nears the New England coast, the surface
winds will respond to become more east-southeasterly in nature.
Tuesday`s high temperatures will be a tad warmer as they rise
into the low/mid 80s. This comes with a few more clouds, but sky
conditions should still be mostly sunny across the area.
Humidity levels remain on the low side for early July standards.
Wind fields become southerly overnight yielding a milder night
than the previous two. Forecast lows will be in the low/mid 60s,
with mid/upper 50s across mountain locales.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Return flow from surface high pressure offshore will usher in warm
and moist air on Wednesday. High temperatures will be in the upper
80s to low 90s for most with overnight low temperatures staying in
the upper 60s to low 70s. With high pressure in charge, dry weather
is expected throughout the day. As an area of low pressure north of
the Great Lakes tracks eastward, the associated cold front will
approach the area. This will bring a slight chance to a chance of
showers and thunderstorms to the area beginning Wednesday night.
Shower and thunderstorm chances will remain confined to along and
west of the Blue Ridge overnight Wednesday into Thursday, before
becoming areawide Thursday afternoon. With upper level ridging over
the east coast on Independence day, temperatures will warm to the
mid to upper 90s for those east of the Blue Ridge. With high
relative humidities, heat indices are expected to rise into the low
100s in the afternoon.

Similar pattern continues Friday and Saturday as the cold front
looks to stall to our northwest. This will allow for daily chances
of showers and thunderstorms, with highest chances in the
northwestern portions of the forecast area. High temperatures each
day will rise into the upper 80s to mid 90s with higher elevations
staying in the upper 70s to low 80s.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Ongoing convection activity across northeastern Maryland has
maintained some restrictions across the Baltimore terminals. The
reduced visibility should improve with any lightning activity
pushing toward northern/central Delaware. Isolated showers and
thunderstorms also persist near KMRB which should exit to the
east in the next hour.

Strong to severe thunderstorms may erupt this afternoon and
evening in response to an approaching cold front. While much of
the day will feature VFR conditions, a 2 to 4 hour window of
restrictions are likely sometime in the early afternoon to early
evening timeframe. Gusty and erratic winds, frequent lightning,
and reduced visibility/ceilings are possible in such
thunderstorms. Any threat wanes by the mid-evening as the cold
front pushes off to the east. Winds shift to northwesterly with
gusts up to 15 to 20 knots tonight.

VFR conditions are expected on Monday and Tuesday as high
pressure takes control of the weather. Northerly winds may gust
up to 20 knots during the afternoon to early evening. As the
ridge of high pressure pushes off toward the New England coast,
winds shift to east-southeasterly on Tuesday, before becoming
southerly at night.

Prevailing VFR conditions are expected Wednesday and Thursday
at all terminals. Shower and thunderstorm chances increase
Thursday morning, mainly for western terminals, with
precipitation possible at all terminals in the afternoon.

&&

.MARINE...
Small Craft Advisories remain in place until 6 AM across wider
portions of the Chesapeake Bay down into the lower tidal Potomac
River. Southerly winds persist through the day which could near
Small Craft Advisory thresholds. However, these should fall
short and be handled by Marine Weather Statements. Eventually,
hazardous weather could impact the waterways late this afternoon
into the evening. Strong to severe thunderstorms are possible as
a cold front migrates east toward the waters. Thus, Special
Marine Warnings may be needed at times, mainly between 3-10 PM
(southern waters would be on the later side of this range).

In the wake, a gusty northwesterly wind eventually shifts to
northerly on Monday. Small Craft Advisories are likely needed
late tonight through Monday during period of cold advection.
Winds turn more east-southeasterly on Tuesday, largely staying
below advisory thresholds.

Southerly winds on Wednesday shift to westerly on Thursday. Small
Craft Advisories are likely across the Chesapeake Bay on Wednesday
with winds gusting 15-20 knots. Winds decrease to below SCA criteria
for Thursday.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies begin decreasing this morning as winds become
more southwesterly. No tidal sites are expected to reach minor
flood stage, but DC Waterfront, Straits Point, and Annapolis may
reach action stage in the new couple high tide cycles. As winds
shift to northwesterly Sunday night, tidal anomalies continue
to fall with all tidal sites expected to stay below action
stage.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 AM EDT early this morning for
     ANZ530>534-537-539>541-543.

&&

$$

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