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000
FXUS61 KLWX 201858
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
258 PM EDT Mon Aug 20 2018

.SYNOPSIS...
High pressure will build across the northeastern United States
through the rest of today while a front remains stalled to the
south. Low pressure will pass northwest of the area Tuesday,
lifting a warm front northward. A cold front will then push
eastward on Wednesday, with high pressure building in from the
west for the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A stalled frontal boundary is positioned well to the south of
the region this afternoon while high pressure builds into the
northeastern United States. Northeasterly flow and moisture in
the low levels have led to widespread stratus across much of the
region into this afternoon. Breaks have begun to develop and
this trend will continue through the rest of the day, but in
general mostly cloudy skies are expected. Some instability has
also developed across portions of eastern WV, central VA, and
into southern MD, and with that, isolated to scattered showers
and a rumble or two or thunder. The greatest coverage has been
across southern MD and the middle Chesapeake Bay.

Shower/storm coverage will trend downward at first this evening,
but as the warm front lifts northward and forcing increases
aloft from the south/west, additional showers and a possible
rumble of thunder become possible late tonight and towards
Tuesday morning. Low clouds are expected once again, as well as
some patchy fog. Lows tonight in the 60s/70s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
The warm front will gradually lift northward during the day
Tuesday. Low clouds and a few showers/drizzle will likely start
the morning for much of the region prior to warm frontal
passage. By the mid-afternoon hours, the warm front is expected
to have made some progress northeastward, although the extent
of which is still in question. At the same time, an upper trough
and cold front will be approaching from the west, with passage
during the evening and overnight hours. MLCAPE values on the
warm side of the boundary are progged to reach into the
1000-1500 J/KG range, with shear values of 30-40 knots atop it.
This will provide for an environment where strong to locally
severe thunderstorms are possible, and the Storm Prediction
Center has continued to highlight portions of the region in a
Slight Risk for severe thunderstorms, although the extent of the
event is still uncertain given instability questions and frontal
timing. With deep moisture, noted by forecast precipitable
water values in excess of 2", heavy rain and flooding is also a
concern, although storm motion won`t be all that slow. Highs
Tuesday will be in the low to mid 80s, with lows in the 60s and
70s.

A secondary front will cross the region on Wednesday, with
additional chances for scattered showers and isolated
thunderstorms. Highs Wednesday will be in the 80s. Much cooler
and drier air will push in behind the front for Wednesday night,
with lows in the 50s and 60s.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Thursday into Friday, an upper level ridge will build over the
region from the west. Surface high pressure will also move into
our area starting Thursday from the midwest. Skies will be
mostly clear with light west to northwesterly winds. Daytime
temperatures will be mild and below average in the mid to upper
70s on Thursday and the upper 70s to mid 80s on Friday.

Saturday through Sunday, a weak upper level shortwave trough will
approach the region from the west and move through over the weekend.
A weak frontal boundary associated with the shortwave will attempt
to move through late Saturday into Sunday. The 00Z Euro and the 12Z
GFS both agree that this front will be mostly dry leading to little
to no precipitation occurring over the weekend. The best chance for
precipitation will be near the mountains. Day time temperatures
for the weekend will hover in the upper 70s to mid 80s. Winds
will be light out of the south.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
A mix of VFR/MVFR currently exists across the region this
afternoon, and gradual improvement to VFR is likely at most
sites by the late afternoon and evening hours.

Ceilings will again be an issue tonight into Tuesday morning with
widespread MVFR/IFR returning. Patchy fog and a few showers are
also possible.

A warm front will lift northward Tuesday, followed by a cold
front Tuesday night. In between, ceilings will likely lift, but
showers and thunderstorms will become likely, some of which
could be strong with gusty winds. A secondary front will cross
on Wednesday and may produce some showers as it crosses.

On Thursday and Friday, winds will be light out of the west to
northwest with mostly clear skies. VFR conditions expected.

&&

.MARINE...
Generally sub-SCA winds are expected through tonight, with
easterly flow up to around 15 knots. Scattered showers and a few
thunderstorms may produce brief gusty winds over the waters this
afternoon and evening.

A warm front will lift north Tuesday and flow will turn
southerly. Wind speeds through the day may be marginal for SCA,
but the strongest winds are likely Tuesday evening and Tuesday
night, as an initial front passes across. A Small Craft Advisory
has been issued for this period. Showers and thunderstorms will
also become increasingly likely during the afternoon and
evening and could contain gusty winds.

A cold front will cross the area early Wednesday, and winds
don`t look particularly strong behind it. However, a secondary
cold front will pass late in the day with potential for a few
showers and storms. In its wake, SCA conditions will be
possible.

On Thursday and Friday, winds will be light out of the
northwest with no marine weather hazards expected.

&&

.TIDES/COASTAL FLOODING...
Onshore flow will continue through Tuesday morning, then turn
southerly as a warm front lifts north Tuesday afternoon. Minor
coastal flooding is possible tonight through Tuesday night,
especially at the climatologically favored sites. A Coastal
Flood Advisory has been issued for St. Mary`s county for
tonight`s high tide cycle and additional advisories may be
necessary.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Coastal Flood Advisory from 7 PM this evening to 2 AM EDT
     Tuesday for MDZ017.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 PM Tuesday to 6 AM EDT Wednesday
     for ANZ532>534-537-540>543.

&&

$$
SYNOPSIS...MM
NEAR TERM...MM
SHORT TERM...MM
LONG TERM...JMG
AVIATION...MM/JMG
MARINE...MM/JMG
TIDES/COASTAL FLOODING...MM