Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 230747
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
347 AM EDT Sun Apr 23 2017

.SYNOPSIS...
A cold front will stall out over the Carolinas today. Low
pressure will develop along the front tonight and it will track
toward the Mid-Atlantic Coast Monday and it will remain nearly
stationary through Tuesday before finally weakening and moving
off to the north and east on Wednesday. A cold front will
approach the area Thursday but it will stall out nearby or just
to our north for Friday. The cold front may move into the area
next weekend.

&&

.NEAR TERM /THROUGH TODAY/...
Persistent northerly flow from elongated ridge over the eastern
Great Lakes has shunted frontal boundary and deeper moisture
south of much of the area this morning. A few showers do
remain across central Virginia, but most areas are rain-free. As
clouds thinned overnight, areas of fog have developed, mainly
from the Blue Ridge/Catoctins west.

As low pressure system moves through the southeastern US during
the day today, additional rain will break out across portions
of the lower Appalachians and try to push northeastward.
However, low level dry air will continue filtering southward on
northeasterly flow. This will keep most areas dry through much
of today. The exception will be parts of central VA where rain
will gradually expand through the day, reaching into portions of
southern Maryland towards the evening hours.

Otherwise, any breaks of sun this morning in northwestern areas
will fill back in as dense high clouds move back overhead.
High temperatures will range from the mid/upper 50s in central
VA to low 60s in northern areas.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
Low pressure system will work towards the SE US coast tonight
and move to a position near the NC/SC border on Monday. Rain
will continue to overspread the region from south to north
tonight and persist through Monday with strong moisture
advection. Periods of rain will continue through Monday night,
although intensity likely to experience a downtrend later Monday
and Monday night as forcing lessens.

As the low pressure system then slowly trudges up the Mid-
Atlantic coastline, to a position near the Outer Banks/Norfolk
by later Tuesday, rain will continue, with an uptick in
intensity/coverage likely again. Low pressure will slowly fill
and weaken Tuesday night with steady rain tapering off to
showers.

Additional rain amounts from this morning through Tuesday night
expected to range on average from 1-2", with somewhat less in
northern/western areas to locally 2-3" south, especially along
the eastern facing slopes in Nelson County and along the Blue
Ridge.

Temperatures during this time period will see limited diurnal
change with solid overcast and periods of rain. Highs Monday
will hold in the low/mid 50s, possibly nearing 60F on Tuesday.
Lows tonight/Mon night from the mid 40s to low 50s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Cutoff low pressure along the Mid-Atlantic Coast Wednesday
morning will finally get drawn into the jet stream and move off
to our north and east. Morning clouds and perhaps even a light
rain should give way to some sunshine Wednesday afternoon.
However...clouds may be stubborn to give way to sunshine across
eastern areas depending on how quick the low moves away from the
area. Noticeably warmer conditions are expected
Wednesday...especially west of the Blue Ridge Mountains where
confidence is higher in more sunshine.

High pressure will build over the Atlantic for Wednesday night
through Friday. A cold front to our west will approach our area
Thursday...but it will likely stall out nearby or just to our
north as it runs into the blocking high over the Atlantic.
Therefore...much warmer and more humid conditions are likely
during this time. A few showers and thunderstorms are
possible...but coverage may be isolated or scattered due to most
of the mid and upper-level forcing remaining well off to the
north and west. A backdoor cold front may impact the area next
weekend.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Areas of fog have developed this morning across portions of
eastern WV, northern VA, and central/western MD. This is
currently affecting the MRB terminal with LIFR conditions, and
this will continue through the early morning hours, before
improvement after sunrise. Elsewhere, fog not significantly
impacting the TAF sites, however some MVFR is possible early
this morning at IAD/BWI.

Otherwise, mainly VFR is expected today with thickening and
lowering high/mid clouds. A few showers will move near CHO
this morning, with rain then affecting the site by the
afternoon, before gradually spreading northward across all sites
this evening and tonight. Conditions will deteriorate as the
rain/stratus overspread with MVFR/IFR developing later tonight
and on Monday. Rain/stratus and associated reductions expected
to continue through at least Tuesday, possibly Tuesday night.
Winds will be out of the northeast through the period.

Low clouds may impact the terminals Wednesday morning.
Conditions should gradually improve later Wednesday. High
pressure over the Atlantic will cause southerly winds and mainly
VFR conditions for Wednesday night and Thursday. A few showers
and thunderstorms are possible Thursday.

&&

.MARINE...
SCA conditions being observed early this morning will gradually
taper through the first half of the day, with SCA-winds confined
to only portions of the central Chesapeake by this afternoon.
This will however be a short-lived break as northeasterly winds
re- intensify tonight and continue through Tuesday night as
coastal low intensifies and slowly moves up the east coast.

Low pressure will move away from the waters Wednesday. High
pressure over the Atlantic will cause a southerly flow for
Wednesday night through Friday. A Small Craft Advisory may be
needed for portions of the waters during this time. A few
showers and thunderstorms are possible Thursday and Friday...but
coverage may be isolated or scattered since forcing will be
weak.

&&

.TIDES/COASTAL FLOODING...
A persistent onshore flow will continue over the waters through
Tuesday. Elevated water levels are expected during this time.
Most areas should remain below minor flooding thresholds through
the high tide cycle this afternoon. Will have to watch Straits
Point...but as of now confidence was not high enough for an
advisory since the next tide will be the lower of the two and
the onshore flow may lighten up just a bit.

The onshore flow will strengthen a bit for tonight through
Tuesday. Minor flooding is possible near times of high tide. The
flow should gradually turn north Tuesday night into Wednesday as
the low moves away from the area. Water levels should decrease
during this time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for
     ANZ531>533-536-537-539>542.
     Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ530-
     531-535-536-538>540-542.
     Small Craft Advisory until 6 PM EDT Monday for ANZ534-543.
     Small Craft Advisory from 11 PM this evening to 6 PM EDT
     Monday for ANZ532-533-537-541.

&&

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



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