Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Baltimore Maryland/Washington District of Columbia
845 PM EDT sun Sep 15 2019
high pressure will continue to build into the area tonight,
before pushing to our southeast on Monday. Warm on Monday, as
southerly flow returns ahead of another cold front that will
push through the region tomorrow night into Tuesday morning,
with showers possible. High pressure then builds across the
northeastern US through the end of the week, leading to dry
weather and cooler temperatures.
Near term /until 6 am Monday morning/...
high pressure will slide overhead tonight, with mostly clear
skies expected to continue across the majority of the region.
Some patchy fog is expected to develop in the favored rural and
valley locations. Additionally, latest guidance is indicating
that some low clouds/fog may also try to develop across much of
central Virginia towards Richmond, and may reach up into the
central Virginia Piedmont, and even possibly into southern Maryland. Lows
tonight will be in the low 60s for much of the area, with the
usual urban hot spots holding in the upper 60s.
Short term /6 am Monday morning through Tuesday night/...
surface high pressure shifts to the southeast on Monday, pushing
offshore. This will result in warm southeasterly flow, which
will lead to a warmer day tomorrow. Monday is likely to be the
warmest day of the forecast period with highs reaching the upper
80s to near 90. Temperatures could be somewhat limited up north,
as a cold front will be pushing into the region late Monday into
Tuesday morning. Clouds ahead of this front could keep things
slightly cooler along the Mason-Dixon line, depending on
exactly when they arrive. Additionally, guidance has Bee
persistently showing some showers across the Potomac Highlands
Monday afternoon in association with this front, so have upped
pops a bit to show this. Not seeing a lot of convective
potential though, as moisture return to that region likely won't
be quick enough. Keeping with slight chance to low end chance
pops through the afternoon.
Increased cloud cover elsewhere late Monday into Tuesday
morning as the frontal boundary pushes through, but thinking it
will be too dry for showers to make it east of the Blue Ridge.
Low temperatures on Monday night will be in the mid 60s.
A much drier air mass pushes into the region behind this cold
front, with northwest flow returning. Clouds should quickly
clear on Tuesday, with abundant sunshine expected into the
afternoon. High temperatures will only reach the mid to upper
70s. Clear and cooler on Tuesday night, with low temperatures
down into the mid 50s.
Long term /Wednesday through Sunday/...
the extended will feature high pressure along with a continuation of
the recent dry weather and slightly below normal temperatures. From
mid-week through the first part of the weekend...a strong ridge of
high pressure will extend from New England down the eastern Seaboard
to the mid-Atlantic and dominate conditions here. Precipitable water
values during the extended will be less than 0.75 inches...and on
thur and Fri below 0.5 inches. The only challenge will be the
direction of low level flow off the Atlantic. If parcel trajectories
can pick up enough Atlantic moisture...that could cause some
cloudiness to be banked up east of the Blue Ridge late in the week.
But the airmass will be very dry. Vertical 12z GFS profiles suggest
some clouds during the day Wednesday into Wednesday night. Other
than that, clear weather is expected.
Aviation /01z Monday through Friday/...
should remain mainly VFR through Monday evening, although some
patchy fog and reductions are possible at cho/mrb overnight into
early Monday morning. A backdoor cold front will push south
later Monday night into Tuesday morning, and may bring some
brief sub- VFR intervals, most likely with regards to cigs, but
these likely are transient and return to VFR by Tuesday
High pressure is expected Wednesday into the later part of next
week. Expecting VFR for the extended with brief localized MVFR/IFR
conditions possible due to morning fog at cho/mrb.
light winds are expected tonight with high pressure overhead.
Winds may increase a bit on Monday afternoon ahead of another
cold front. Best chance of Small Craft Advisory looks to be overnight Monday into
Tuesday as that front passes and northeasterly flow strengthens
Winds are expected remain below Small Craft Advisory levels through the extended.
District of Columbia...none.