Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 231527

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1027 AM EST Thu Jan 23 2020

High pressure will continue to move offshore throughout today.
Low pressure will move into the region tomorrow, before slowly
moving northeastward into New England during the second half of
the weekend. High pressure returns Sunday and lingers into early
next week.


High pressure continues to maintain control of the region,
resulting in mainly dry weather continuing through early Friday
AM. The upper level ridge associated with the high will continue
to slide offshore, allowing a weak shortwave to travel along
the ridge axis and pass over the region tonight. As a result,
high clouds will continue to increase through tonight. Weak
southerly winds are expected to develop by this afternoon,
before flipping back to northerly tonight. Daytime temperatures
across the region are expected to reach the low 40s.

Precipitation will be approaching from the SW portion of our
CWA very late tonight in which some patchy fog/drizzle may
develop for the lower section of the Potomac Highlands. Hi-res
modeling is iffy with this idea as a decent amount of dry air
remains in the BL. With overnight temperatures expected to dip
towards the freezing mark, if any patchy freezing fog/drizzle
does develop, it may result in some slick spots developing



The low pressure and the mid level cutoff
low will be moving east across the Ohio Valley on Friday.
Precipitation associated to this system will be approaching our
region Friday morning. Depending on the timing, wintry
precipitation could take place, mainly over areas west of the
Blue Ridge, but most high-res guidance moves the precipitation
late Friday morning over our western zones. As the system keeps
moving east precipitation will overspread across our region in
the form of rain as temperatures remain in the 40s across most
of our region. Moderate to heavy rain is possible at times.

A secondary low pressure will develop overhead on Friday night and
will move NE and away from us Saturday into Saturday night.
Precipitation will continue during this time with plenty of lift
over us as frontal boundary moves across late Friday night. Rain
will continue over most areas, but some snow is also possible over
higher elevations. Total QPF values are near an inch across most of
our CWA, with higher elevations near 2 inches. Precipitation will
gradually decrease on Saturday from west to east behind the front,
but upslope snow will continue through Saturday night.


By Sunday low pressure, both surface and aloft, will be migrating
toward New England. The forecast area will be experiencing northwest
flow with scattered upslope snow showers Sunday and Sunday night...
possibly extending into Monday. Winds will be on the gusty side as
well, especially during the daytime hours when cold advection will
have a better chance to mix to the surface.

Tuesday into Wednesday will be the lull when a ridge axis
passes across the eastern CONUS. Thereafter, another transitory
upper level closed low and surface reflection will approach at
the end of the forecast period. Its too soon to get caught up
in the details for this system.


VFR conditions will continue through Friday as high pressure moves
offshore with light and variable winds. High level clouds are moving
in this morning, and CIGs will be decreasing Thursday night with
some terminals possibly reaching MVFR conditions. Low pressure
system will approach from the west Friday and will move overhead
Friday night into Saturday. This system will bring rain across our
area, which will be heavy at times. Periods of reduced VSBYs and
CIGS are anticipated Friday into Saturday. Winds will be increasing
Friday night and remain breezy into Saturday night, gusts up to 20
knots. Conditions will improve Saturday afternoon into the

VFR should prevail across the terminals Sunday and Monday.
Winds will be from the west/northwest, with 20-25 kt gusts
Sunday resulting in the bigger operational impact.


Winds will remain light across our region today and through Friday
with high pressure in control. Periods of SCA conditions possible
Friday night into Saturday night with low pressure impacting our

Small Craft Advisory possible Sunday (and maybe into Monday) in cold
northwest flow permitting 20+ kt gusts to mix to the water`s




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