Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 210120
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
920 PM EDT Fri Apr 20 2018

.SYNOPSIS...
Strong high pressure will slowly migrate eastward into the
northeastern states by Sunday, and off the coast on Monday.
Unsettled weather is expected to return by the middle of next
week as low pressure approaches the area from the southeast U.S.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Strong high pressure is centered over the Great Lakes and upper
Midwest this evening. Satellite shows clear skies extending to
the Ohio Valley, with only a few thin cirrus propagating
eastward later tonight at worst.

Below normal temperatures are expected tonight with lows in the
30s. Went with cooler guidance as light winds are expected for
most areas (except a persistent light breeze over central MD/DC
metro). A Freeze Warning has been issued for much of the same
area as last night. Overall, temperature forecast seems to be on
track. Low levels remain dry, so any frost should be patchy.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Benign weather conditions are expected this weekend as high
pressure slowly shifts eastward from the Great Lakes into the
northeastern U.S. Light winds and below normal temperatures are
expected as a result. Mid to high level clouds will move
overhead Saturday afternoon and may persist into Sunday as a
jet max and mid level energy moves across our area. High
temperatures will be in the 60s with lows in the 30s and 40s,
though it should be warm enough to preclude frost/freeze issues
in areas where the growing season has started.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
High pressure will shift offshore on Monday as a mid-level cutoff
trough and associated surface low move across portions of the
Southeast. Conditions should remain mainly dry, with slightly
below normal temperatures.

On Tuesday, the aforementioned area of low pressure will slowly
track north toward our CWA. The latest deterministic guidance has
trended slightly slower with the northward progression of this area
of low pressure, suggesting it`s possible that we remain dry much of
the day Tuesday as well. On the other hand, both the GEFS and
EPS have many ensemble members that move the system along
faster, bringing precipitation in during the day Tuesday.

It appears as though the most likely time period for steadier
rainfall across the area will be Tuesday Night, when both
deterministic and ensemble model guidance point toward a cool,
soaking rainfall across the region.

Forecast confidence decreases considerably for Wednesday and
Thursday, but the potential for active weather remains.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR expected through the weekend with light winds as high
pressure passes to the north of the terminals.

VFR conditions are expected during the day on Monday. MVFR
conditions likely begin to develop Mon night as easterly flow
ensues. Flight restrictions are likely Tuesday and Wednesday as
an area of low pressure approaches from the south bringing rain.
Winds will increase out of the east during this time as well.

&&

.MARINE...
Winds subsided quickly early this evening, but a subtle
pressure surge on the east side of ridging building to the north
will likely result in marginal SCA conditions in northerly
channeling over the Maryland portion of the Chesapeake Bay.
Given trends in hi-res guidance, reconfigured the Small Craft
Advisory, as the surge may enter northern portions of the Bay by
10 PM and exit by 1-3 AM. As high pressure builds further to
our north, light winds are expected over the weekend.

Sub SCA conditions are forecast Monday as a departing ridge of
high pressure will keep winds light over the waters. SCA
headlines may be needed Monday night through Tuesday as easterly
flow strengthens thanks to low pressure developing/approaching
from the southeast U.S.

&&

.TIDES/COASTAL FLOODING...
Persistent onshore flow is expected to result in increased tidal
anomalies and possible coastal flooding during the middle part
of next week.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Freeze Warning from 2 AM to 9 AM EDT Saturday for MDZ003>006-
     503-505-507-508.
VA...Freeze Warning from 2 AM to 9 AM EDT Saturday for VAZ025>031-
     038>040-051-501-502-505>508.
WV...Freeze Warning from 2 AM to 9 AM EDT Saturday for WVZ051>053.
MARINE...Small Craft Advisory until 3 AM EDT Saturday for ANZ531>533-
     539>541.
     Small Craft Advisory until 6 AM EDT Saturday for ANZ534-537-
     543.

&&

$$
SYNOPSIS...IMR/DHOF
NEAR TERM...ADS/IMR/DHOF
SHORT TERM...IMR/DHOF
LONG TERM...KJP
AVIATION...IMR/DHOF/KJP
MARINE...ADS/IMR/DHOF/KJP
TIDES/COASTAL FLOODING...DHOF



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