Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 221408

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1008 AM EDT SUN MAY 22 2016

A low pressure near Cape Hatteras today will head northeast
through Monday. High pressure will slide southeastward from the
Ohio Valley on Monday into the southeast on Tuesday and then move
off the coast Wednesday, where it will remain for the rest of the


Shortwave energy evident on water vapor loop across western
Pennsylvania this morning. Corresponding light rain and drizzle
has moved south into the forecast area. Database has been updated.
Already had periods of rain in there; timing and areal coverage
were adapted to account for latest trends, and increased PoPs to
near 100 percent. Otherwise, forecast looks to be on track. It`s a
wet and gloomy day across much of the area. There may be a few
breaks in the overcast across central Virginia, but guidance
suggesting that these will fill in by mid-afternoon.

Slightly drier air will begin to wrap into the low this afternoon.
Simulated reflectivity suggest precip will become more showery by
this time. In addition, some weak instability may build generally
west of I-81, so can`t rule out a few thunderstorms there. Expect
another day where temperatures struggle to reach 60, especially the
eastern half of the area where rain is expected to persist longest.

By tonight, the upper low will be drifting to SE VA, and combined
with the diurnal trend, precip should diminish in coverage,
eventually becoming focuses in the Fredericksburg-S MD vicinity. Low
clouds and light fog will develop again, and can`t rule out some
drizzle. Close to persistence for lows...upper 40s to mid 50s.


The upper low will be pivoting near the Outer Banks and offshore on
Monday as it spawns a surface low pressure. This will keep a
moisture feed into the area and would thus expect mostly cloudy
skies to continue. Models insist on higher cloud bases though and
perhaps even a few glimpses of sun. This deeper mixing is giving
highs in the upper 60s to perhaps lower 70s, but I`m a little
skeptical it gets that warm. Also with this heating, there should be
some instability building by afternoon, so showers will likely
develop with perhaps a few thunderstorms, especially the further
west you go.

By Monday night, the low will be moving toward Cape Cod, so expect
showers to diminish, with any lingering activity east of the Blue
Ridge. Unfortunately, there will still be enough moisture wrapping
around the low to keep a small chance of showers east of I-95
through midday Tuesday, perhaps extending into the afternoon (along
with an isolated rumble of thunder). However, with diminishing cloud
cover, it looks like a majority of the area will make it into the
70s. Ridging at the surface and aloft arrives in earnest Tuesday
night with lows in the 50s to near 60.


Generally warmer and more humid through the long term as a much
more summer-like pattern develops. Ridge axis will remain to our
west on Wednesday with a northwest flow aloft likely suppressing
any convection despite increased instability. By Thursday the
ridge axis is passing and a weak shortwave is approaching.
Combined with the still increasing warmth and
moisture...thunderstorm chances over the higher terrain to the
west will increase. Some may try to reach the lower elevations to
the east before dissipating. Another ridge axis approaches Friday
but by this point instability may be great enough thanks to
continued increase in warmth and humidity that convection may
develop along the terrain to the west regardless. Saturday a ridge
of high pressure aloft looks to develop directly overhead...but
the excessive warmth and moisture may still overcome any
suppressive effects and cause spotty showers and thunderstorms to
develop over the mountains and potentially advect east before
dissipating. By this point highs in the lower elevations may reach
90 for the first time this year...notably later than normal by
several days. Lows will be sultry with 70s possible in the urban


MVFR/IFR flight conditions across the area at this time. The lower
cloud deck has been intermittent, which is only part of the
reasoning behind the variable conditions. Light rain and drizzle
have developed; its intensity varies, which also is a contributing
factor. Expect similar conditions through the midday hours.

Precip may become more showery by late afternoon, and this may be
the best chance for a solid push of MVFR. However, expect low
clouds and fog to redevelop tonight. Have limited this to MVFR for
now though. Winds light and generally N or NW.

Monday will remain cloudy, but models insist on higher cloud bases,
perhaps VFR at times. Showers will redevelop quickly by midday
though and there could be a thunderstorm. As precip diminishes
Monday night, there is a chance of lower clouds and perhaps fog,
especially eastern areas. Conditions will improve Tuesday as high
pressure builds with light NW winds.

VFR later next week.


North winds generally around 10 kt this morning. With a second
area of low pressure developing offshore, winds will remain
northerly through Monday night or so, but at this time, magnitudes
appear to be less than 15 kt. High pressure will begin building
Tuesday with winds become NW then W.

Light winds overall thru late next week.




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