004
FXUS61 KLWX 290800
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT Sat Jun 29 2024

.SYNOPSIS...
As high pressure departs, a warm front lifts through the region
this morning which will bring showers and thunderstorms back to
the region. A cold front will then push through on Sunday,
bringing yet another chance for afternoon showers and
thunderstorms. A strong area of high pressure settles over the
area during early portions of next week leading to cooler and
drier conditions. A more summerlike pattern returns by the
middle of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Persistent low-level warm advection has sufficiently moistened
the boundary layer early this morning. This is evident on
GOES-16 nighttime imagery, surface observations, and aircraft
soundings. The result is a broken to overcast stratus deck
generally between 1,000 to 1,500 feet. Current temperatures are
holding steady in the upper 60s to low 70s, accompanied by dew
points in the mid/upper 60s. Expecting little change in the
current conditions with south to southeasterly winds persisting
around 5 to 10 mph.

A stationary front currently analyzed over northeastern
Tennessee down into the Carolinas is forecast to lift
northeastward today. This boundary should push through the local
area during the morning hours which leads to additional
moistening. Forecast dew points rise into the low 70s, which
coupled with highs in the low 90s will support heat indices
between 98 and 103 degrees. This net contribution will increase
instability levels across the area, especially west of the Blue
Ridge. The latest guidance increases surface-based CAPE values
to around 2,000 J/kg, while instability is weaker and more
capped off to the east. Thus, have the initial threat of showers
and thunderstorms confined to west of the Blue Ridge. This will
be accompanied by some risk of severe thunderstorms. However, an
additional round looms which may impact more of the region.

While high-resolution models are somewhat at odds with another
in terms of storm coverage, a few solutions carry a squall line
of sorts tracking into western Maryland by around 8-9 PM. This
forward propagating line is set to track across the Shenandoah
Valley. Areas farther downstream have more unknowns as the
convection may decay while crossing the Blue Ridge. However,
given the degree of heating/moistening of the atmosphere coupled
with some modest perturbations in the flow aloft, have kept a
threat for storms across the I-95 corridor. Confidence is lower
with this aspect of the forecast though. As of right now, the
Storm Prediction Center has a Slight Risk in place from north-
central Maryland back into the eastern West Virginia panhandle
and western Maryland. The main threats are damaging wind gusts,
frequent lightning, and a brief isolated tornado.

Nighttime lows will be very warm with mainly 70s across the
area. 80 degrees is possible over D.C. and Baltimore, with mid
60s to low 70s in the higher terrain.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Some residual showers are possible to start off the morning,
with some cloud cover possibly lingering into the core heating
period. However, do think any cloud cover should erode in enough
time to allow ample heating of the boundary layer. Persistent
warm advection is expected to further moisten the low levels
which yields mid 70s dew points across the region. With high
temperatures rising up into the mid 90s, heat indices could
easily rise to 105 degrees and slightly above. This would
warrant Heat Advisories so this bears watching as the next round
of guidance arrives in the mid-morning.

Besides the excessive heat and humidity, another round of strong
to severe thunderstorms may impact the area. The culprit is a
seasonably strong cold front which arrives during the peak in
the diurnal heating cycle. Forcing aloft is more pronounced than
the previous day, although the better height falls are confined
to upper portions of the Mid-Atlantic. Multiple rounds of
showers and thunderstorms are possible, especially east of the
Blue Ridge. The Storm Prediction Center has maintained a broad
Slight Risk area extending from I-81 eastward. All severe
hazards are possible, but damaging wind gusts stand out as the
most likely threat. The eastward progressing cold front reaches
the Chesapeake Bay during the evening hours before settling
into the coastal Atlantic by late Sunday night. Shower activity
should come to an end as winds shift to northwesterly in the
wake. While most see lows in the 60s, many can expect
temperatures in the 50s to the west of the Blue Ridge.

A strong dome of surface high pressure advances from the Upper
Midwest toward the Great Lakes. A seasonably cool air mass
arrives on Monday with 850-mb temperatures falling to around
10-12C. The well-mixed boundary layer yields dry adiabatic
profiles down to the surface. This favors high temperatures in
the upper 70s to low 80s which is around 5 to 10 degrees below
average for early July. Expect plenty of sunshine with northerly
winds gusting up to 20 mph. Cooler nighttime conditions push
into locations to the east with lows in the upper 50s to mid 60s
east of the Blue Ridge. This is accompanied by clear skies as
the surface high is positioned over the northeastern U.S.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The long term period will start will begin with mild and dry
conditions as high pressure and upper level ridging build over the
region. Temperatures will be slightly below normal with highs in the
mid 80s for most(70s at higher elevations) and lows in the upper 50s
to low 60s. Temperatures warm to the upper 80s to mid 90s Wednesday
and Thursday as high pressure shifts off the east coast and
southerly flow ushers in warm and moist air. A nearby warm front
will bring renewed precipitation chances, mainly to those along and
west of the Alleghenies on Wednesday.

For the Fourth of July, a nearby cold front will bring precipitation
chances to the forecast area. There is a chance of showers and
thunderstorms throughout the area, with chances peaking in the
afternoon as instability increases with daytime heating. Shower and
thunderstorm chances continue Friday as the aforementioned frontal
boundary remains nearby. Precipitation chances peak in the afternoon
with the greatest chance of precipitation remaining in the
northwestern portions of the forecast area.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Many terminals are starting to see the influences of the low-
level southerly moisture advection. A band of low stratus have
settled over much of the area with near IFR ceilings being
observed. These should stick around through the mid-morning
before becoming scoured out as a warm front pushes through. Any
convective threats likely are delayed across the terminals,
mainly after 00Z. Have placed a 4-hour VCTS group at all
locations, generally during the late evening to early overnight
hours. Some showers possibly linger through the night.

Sunday brings another potential active weather day, all ahead of
an approaching cold front. Restrictions are again possible as
these storms races across the area. Right now the afternoon to
early evening would be the most likely timing of such activity.
Any convective activity should diminish by later in the evening
with northwesterly flow ensuing in the wake. For Monday, VFR
conditions are expected with northerly gusts up to 15 to 20
knots.

VFR conditions and light winds are expected at all terminals Tuesday
with high pressure overhead. There is a slight chance of
precipitation at KMRB on Wednesday with all other terminals expected
to remain dry.

&&

.MARINE...
Southeasterly winds have continued to gust up to 20 knots early
this morning. While not constant, it is persistent enough to
maintain advisories across all waters outside of the upper
tidal Potomac. With southerly channeling likely enusing today,
additional Small Craft Advisories may be needed for late this
morning through the afternoon/evening hours. Some convective
potential late in the evening to early overnight may require
Special Marine Warnings. However, confidence is pretty low at
this time.

Small Craft Advisories may be needed early Sunday and again
behind a cold front late Sunday into Monday. In between, strong
to severe thunderstorms could impact the waters during the late
afternoon to early/mid evening. Special Marine Warnings become
likely with this activity before the convection pushes off to
the east overnight.

Light and variable winds Tuesday morning before southwesterly in the
afternoon and are expected to remain below SCA criteria. Small Craft
Advisories are possible Wednesday as southerly winds gust over 15
knots in the afternoon.

&&

.TIDES/COASTAL FLOODING...
Tidal anomalies rise today in southerly flow. Winds shift to more
southwesterly Sunday afternoon, allowing for tidal anomalies to fall
slightly. During southerly flow, most tidal sites will reach Action
stage while Havre de Grace and Annapolis reach minor flood stage
during the high tide cycle early Sunday morning.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 8 AM EDT this morning for
     ANZ530>534-536>543.

&&

$$

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