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513
FXUS61 KLWX 220900
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EST Wed Jan 22 2020

.SYNOPSIS...
High pressure will move overhead today and gradually transition
offshore by Friday. Low pressure will approach from the central
United States on Friday night, then slowly move toward New
England during the second half of the weekend. High pressure
will return early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure center is nearing the central Appalachians
this morning while the mid and upper ridge axis is over the
Mississippi Valley. Skies are clear to start, but some cirrus will
be encroaching from the west as the day progresses, and especially
into tonight. After starting in the teens and 20s this morning,
daytime temperatures will moderate compared to the past two days due
to the rising heights. Highs will range from the upper 30s to mid
40s. With the high remaining nearby through tonight, winds will
remain light, thought cooling may be tempered a bit by the advancing
clouds. Am still allowing some teens in the typically colder
locations, with 20s elsewhere.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Ridging will advance to the east on Thursday. Mid and high clouds
will continue to advance ahead of a trough digging into the center
of the country. High temperatures will be a bit warmer, with most
locations will reach the 40s. Low pressure will be developing in the
Mississippi Valley Thursday night. While a few ensemble solutions
offer a faster solution, there is good consensus among deterministic
models that the nighttime hours will remain dry in our CWA (and in
fact probably well into the day Friday). Lows will be warmer but
still below freezing in many locations.

Moisture/lift associated with the low will spread into the area on
Friday. There will be some dry air to overcome, so a slow onset
makes sense. And most of the day could turn out dry along and east
of roughly US 15. If precipitation begins quickly enough, there
could be some spots below freezing west of the Blue Ridge, though am
unsure if it would be valley locations, or on some of the ridges
depending on how the column saturates to the wet bulb. It should be
warm enough aloft for any such precipitation to be freezing rain
versus snow. At this time, however, am expecting the bulk of the
area to just see rain on Friday, with temperatures largely in the
40s by afternoon.

As the closed upper low moves into the Ohio Valley Friday night, a
new low is expected to develop along the trailing frontal zone,
likely somewhere near Virginia. There will be a good surge of
moisture and lift with this low, and at a minimum, a period of
moderate to briefly heavy precipitation is expected. Rainfall totals
could near an inch in some locations. What is uncertain is the
thermal profiles during this time, and how quickly cold air will
arrive on the back side of this system. Eventually, a changeover to
snow will occur along the Allegheny Front. The question is whether
the cold air can arrive east of there before precipitation begins to
exit. Even so, were there to be snow Friday night, the chances
should be confined along and west of the Blue Ridge, and most likely
at the higher elevations. The event will turn more upslope in nature
as the low pulls away, which is discussed further in the long term
section.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Mid to upper level trough and its cut-off low will be pushing ENE
from the Midwest on Saturday. At the surface, occluded low pressure
system will move from the Tennessee Valley into the Ohio Valley and
Mid-Atlantic. Precipitation will be pushing from west to east on
Saturday but conditions will be drying gradually through the day
(except for the upslope areas). As this low pressure moves over our
area and approaches the Mid-Atlantic coast, it will take a more NE
track as it deepens. Lingering rain or snow showers possible into
Saturday night. Greatest chance for any snow is at higher
elevations, rain is expected elsewhere.

Low pressure will continue to move away from us Sunday into Monday.
NW flow and shortwave energy aloft could bring additional upslope
showers through Monday. High pressure will build over our area
Monday night into Wednesday.

Temperatures during this period will be near or above normal for
this time of the year with highs in the 40s and 50s (except at time
over the ridges). Lows will be in the 20s and 30s.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will continue through Thursday as high pressure moves
across the area. Northwest winds this morning will become light and
variable as the day progresses, eventually taking on an east or
southeast component.

Clouds will lower late Thursday night with MVFR ceilings and
increasing rain chances Friday as low pressure approaches. IFR
becomes more likely Friday night, along with a period of moderate
rain, as the low moves overhead.

Sub-VFR conditions on Saturday with a low pressure system impacting
our region. Conditions should improve later Saturday as the system
moves away. Winds will increase on Sunday with VFR conditions
remaining into Monday.

&&

.MARINE...
North/northwest winds are finally starting to diminish on the waters
as high pressure approaches from the west. By later today into
Thursday, winds will become more northeasterly and should remain 10
kt or less. Winds will gradually increase Friday as low pressure
approaches from the west, with Small Craft Advisory conditions
becoming possible Friday night.

Periods of SCA conditions possible Saturday into Monday with low
pressure moving across our area Saturday. Winds will increase behind
this system Sunday and remain it into Monday with SCA conditions
possible during this time.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...IMR
AVIATION...ADS/IMR
MARINE...ADS/IMR