Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 150750

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
350 AM EDT Tue Aug 15 2017


A series of disturbances will move across the region today bringing
a chance of showers or an isolated thunderstorm. High pressure
will build into the region tonight through Wednesday night. A
cold front will approach from the west late in the week.



With low cloud deck it is interesting to look off to the east
and see the light of a town/city is reflecting onto the bottom
of the clouds. DC is probably too far; Reston (6 miles away)
seem more likely.

Showers over over the middle portion of northern NC/southern VA
will be tracking NE. This will likely impact a line from CHO to
Lower Southern MD during the middle portion of the day.
Convective possibilities look low. Further north will maintain
chance PoPs.

Otherwise skies will be mostly cloudy...perhaps some clearing in
the NW part of the forecast area in the latter stages of the
afternoon. Given the cloud cover and fact that Monday was a rare
day when the temperatures were cooler than guidance we`ll stay
on the lower end of guidance. Highs generally around 80.



Tonight through Wednesday night area will be under the influence
of high pressure. Lows tonight and Wednesday night in the upper
60s west of I-95, lower 70s east. Highs Wednesday around 90.

Thursday morning should be dry. It appears that a warm front
will approach the area during the day bringing a chance of
showers and thunderstorms to the region during the aftenoon,
although the models appear to be slowing down the approach of
this system so PoPs may have to be pushed back with later
forecast packages.



Several chances for showers/thunderstorms exist for late this week
and into the weekend, although no washout days are expected.

We`ll likely be sitting in the warm sector of a frontal system
Thursday night as the primary low pushes through the Great Lakes and
into southern Canada. Thus a mild and muggy night is likely in store
with lows in the low to mid 70s.

A cold front will progress towards the region on Friday with humid
and very warm to hot conditions out ahead of it. This will lead to
the development of instability and therefore chances for scattered
showers and thunderstorms. High temperatures should peak in the
neighborhood of 90F.

Uncertainty then exists as to how far south/east the front will make
it before stalling out. Model guidance has trended less progressive
over the past several cycles and 00z/0815 suites of both the
ECMWF/GFS keep the frontal boundary near or over the region. This
would allow for continued chances of isolated-scattered
showers/thunderstorms, especially as an upper trough traverses
overhead. That being said, run to run consistency is still low, so
will keep PoPs slight to low chance. Temperatures/humidity values
are also dependent on the frontal evolution, but have trended them

By Monday, both model suites are in good agreement with high
pressure building in.



Cloudy at all TAF sites for the majority of the day. CHO should
see the most impacts with ceilings in the MVFR category along
with periods of rain. Further north in the forecast area periods
of rain will also be possible.

Entire region will go back to VFR conditions this evening and
remain that way into Thursday.

Predominantly VFR is expected Thursday night through Saturday with
potential for brief periods of reductions in isolated to scattered
showers/thunderstorms, especially afternoon/evening.



Winds expected to remain below SCA values today through

South winds will be on the increase Thursday night and Friday ahead
of a frontal system, and Small Craft Advisory conditions are
possible. Sub-SCA conditions should then return by Saturday.
Isolated to scattered showers and thunderstorms are also possible
each day, mainly afternoon/evening.




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