Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 280037

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
837 PM EDT Sat Aug 27 2016

High pressure surface and aloft will hold through Monday then
move offshore. A cold front will move through the area Wednesday
night. High pressure then builds for the second half of next week.


High pressure is stretched south into the Mid-Atlantic region
from northern New England this evening. Light easterly flow will
continue off the Atlantic tonight. Low clouds are expected to move
into the Chesapeake Bay/ I-95 region by Sunday morning however
uncertainity exists as to how far west they get by sunrise. Clouds
will dissipate shortly after sunrise.

Previous discussion...
There will be a slightly better chance of t-storms far west over
the Appalachians Sun, but most of the area will remain dry.
Slightly cooler with temps in the low 90s.


Ridge of high pressure begins to weaken over the area Mon as it
moves offshore and a shortwave-trough digs across the northeastern
states. Increasing warmth and humidity will generate more
instability with showers and t-storms becoming more probable over
the mtns. Activity will drift east during the late afternoon
and/or early evening before dissipating, but is not likely to
reach the metro areas. Hot and humid with temps in the mid 90s and
heat indices aoa 100F.


Warmer than normal temperatures should persist through the middle
part of the week. A few showers and thunderstorms are possible
Tuesday afternoon over the higher terrain in a warm and humid
airmass but with little forcing outside of terrain circulations. A
cold front dropping into the area may be able to bring a threat for
showers and thunderstorms closer to the metro areas Wednesday
afternoon and evening.

A shower or thunderstorm will remain possible Thursday across
southern portions of the area as some models/ensembles are slower
with the southward progress of the cold front.

An unseasonably strong area of high pressure will dive into the
region later in the week bringing cooler and drier weather which
looks to persist into the first part of next weekend.


Low clouds possible late tonight at BWI, MTN, and DCA as
increasing moisture on easterly flow becomes trapped beneath
nocturnal inversion. This was advertised well by early afternoon
runs from high-res ensemble guidance (e.g., HRRR-TLE, NARRE).
Climatologically, certainty of IFR is higher at BWI and MTN than
at DCA. Brief period of MVFR visibilities possible at KCHO, though
latest guidance/persistence suggest they may remain VFR. Any low
clouds or patchy fog would mix out quickly tomorrow after 13Z.

Mainly VFR expected with southwesterly winds around 10 knots
Tuesday into Wednesday. A thunderstorm is possible Wednesday as a
cold front approaches.


Sub-SCA conditions through Mon. No t-storms expected.

The pressure gradient will remain relatively weak Tuesday
into Wednesday despite an approaching cold front, with winds likely
staying below Small Craft Advisory levels during this time.


Ranking of summer 2016 in terms of average temperature (JUN 1 - AUG 26)

Site          Rank                    Average Temperature

DC   3   80.5
Balt          19  77.2
IAD            3                            77.3




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