Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 160053

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
853 PM EDT Thu Jun 15 2017

A nearly stationary front will meander across the region through
Friday before lifting back northeast of the area as a warm front
over the weekend. A cold front is forecast to cross the area
Monday into early Tuesday.


Frontal boundary remains stalled across the region this evening,
as noted by east/southeasterly winds and dew points in the mid
60s east of a line from roughly CJR to MRB, and more
southwesterly flow and dew points near 70F west of the line.
This had also led to quite the CAPE gradient as well earlier
today, which dictated much of today`s shower/thunderstorm
development. Following earlier rounds of convection and the loss
of daytime heating, instability is lessening, and much of the
activity has weakened. Exception currently is across portions of
Albemarle and Nelson counties where strong thunderstorms with
heavy rain (and localized flash flooding threat) will continue
for the next couple of hours. Elsewhere, scattered showers and
isolated embedded thunderstorms remain possible, mainly west of
the previously mentioned boundary, although a few may make it

Overnight, low stratus, fog, and drizzle development is likely,
especially in areas that saw rain this afternoon/evening and dew
points remain elevated.

Lows tonight from the mid 60s to low 70s.


The stationary boundary Friday morning will gradually shift
north and east as a warm front Friday afternoon. More popup
showers and thunderstorms are expected...but coverage will be
more widespread across central and eastern portions of the CWA
compared to Thursday. Limited shear profiles suggest that the
severe threat will be low. Locally heavy rain is expected with
thunderstorms due to high amounts of atmospheric moisture and
the fact that storm motion will be slow. Coverage of convection
should dissipate Friday night due to the loss of daytime
heating. Patchy low clouds and fog are expected overnight into
early Saturday morning.

Bermuda high will develop for Saturday and a south to southwest
flow around this system will continue to usher in warm and humid
conditions across our area. The warm and humid airmass will lead
to more showers and thunderstorms...especially during the
afternoon and evening hours. Warm and humid conditions are
expected Saturday night with patchy low clouds and fog.


Hot and humid conditions continue into Sunday with
heat indexes reaching the mid to upper 90s. Scattered showers
and thunderstorms possible, mainly diurnally driven.

PoPs increase Monday and into early Tuesday ahead of a cold front
that could bring additional showers and thunderstorms, with the
potential for strong storms. Heavy rain is also possible with PW
near the 2 inches.

Weather conditions will improve behind the cold front on Tuesday
and into Thursday. Some showers may linger into Tuesday night,
while another weaker system may allow for some other showers on


Scattered showers and thunderstorms will gradually lessen in
intensity and coverage this evening, with MRB/CHO having the
greatest risk of seeing activity. Mainly VFR although some brief
reductions in the showers/storms possible.

Low clouds will develop late tonight along with areas of fog and
drizzle. IFR conditions are expected late tonight through mid-
morning Friday before CIGS gradually improve. More popup showers
and thunderstorms are expected Friday afternoon and evening.
Coverage will be farther north and east compared to Thursday.
Warm and humid air will remain in place through Saturday night.
Popup showers and thunderstorms are likely...especially during
the afternoon and evening hours Saturday. Areas of low clouds
and fog are possible during the overnight and early morning
hours Friday and Saturday.

Showers and thunderstorms possible Sunday into early
Tuesday due to diurnal heating and an approaching cold front.
Sub-vfr conditions possible at times during this period.
Conditions improve/vfr Tuesday into Tuesday night.


Small Craft Advisory continues for portions of the middle and
lower tidal Potomac as well as portions of the central
Chesapeake Bay through 10 PM this evening. Easterly wind gusts
near 20 knots expected across these areas through the evening
hours. Elsewhere winds should largely stay below SCA criteria,
however gusts may still approach 20 knots for a brief window
until 10 PM this evening.

Winds should remain below SCA criteria overnight through Friday
night. The gradient will strengthen as Bermuda high sets up
late Saturday and Saturday night. An SCA may be needed for
portions of the waters during this time. Popup showers and
thunderstorms are likely Friday and Saturday...especially during
the afternoon and evening hours.

Showers and thunderstorms possible Sunday into early
Tuesday due to diurnal heating and an approaching cold front.
Wind gusts will be near or above the small craft advisory
threshold Sunday into Monday night, and improving into Tuesday
behind the front.


Tidal anomalies have increased to around 1 to 1.5 feet above
normal due to an onshore flow. The onshore flow will continue
through tonight and into Friday. With the high tide this evening
and tonight being the lower of the next two high tides, minor
flooding is not expected at most locations...however have issued
a Coastal Flood Advisory for St. Mary`s County where water
levels are likely to just reach minor flood stage.

Minor flooding is then possible during the next high tide early
Friday morning which will be the higher of the two. Have
extended the Coastal Flood Advisory for St. Mary`s County to
cover this, and will Anne Arundel may need to be added as well.

Elevated water levels are expected through the weekend. Minor
tidal flooding will be possible for sensitive areas near high


MD...Coastal Flood Advisory until 10 AM EDT Friday for MDZ017.
MARINE...Small Craft Advisory until 10 PM EDT this evening for


TIDES/COASTAL FLOODING...BJL/MM is the U.S. government's official web portal to all federal, state and local government web resources and services.