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Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
314 am EDT sun Oct 22 2017

Synopsis...

High pressure will push eastward into the northwest Atlantic
through Monday. Low pressure will move up the Appalachians
Monday night into Tuesday. Upper troughing will remain over the
region through the second half of the week.

&&

Near term /today/...

Patchy fog early this morning, mainly near the Chesapeake Bay and in
sheltered river valleys.

Another delightful day is in store for the mid-Atlantic. Basically
a Carbon copy of Saturday with some high cirrus, light winds,
and unseasonably warm temperatures in the 70s. Enjoy it while it
lasts, because the area of high pressure responsible for the
gorgeous weather packs its bags and heads into the North
Atlantic by tonight.

&&

Short term /tonight through Tuesday night/...

As high pressure sails away into the North Atlantic Sunday
night into Monday, low pressure will begin to move northeastward
up the Appalachians. This area of low pressure will be re-
invigorated by a digging shortwave trough diving across the
Great Lakes and Ohio Valley. The result will be widespread
beneficial rain Monday night into Tuesday across the region
(generally 0.50-1.00", locally 2" in heavier downpours/on the
ridges). Model guidance has unanimously trended quicker which
reduces the already meager outlook for flooding potential. Gusty
winds and a few claps of thunder are still possible, though a
little less likely given unfavorable timing in the diurnal
cycle.

The low will depart to the northeast Tuesday sending a cold front
through. This will knock temperatures back to more seasonable levels.

&&

Long term /Wednesday through Saturday/...

We have been running over ten degrees above normal for
temperatures for much of October, but finally things should
trend toward "normal" in the long term. Cold front will push off
the coast Wednesday and an upper level trough will briefly move
over the northeastern. Skies will probably see increasing
cloudiness Wednesday afternoon with isolated showers as cooler
air moves into the region. Highs in the lower 60s east of the
mountains, 50s west.

Lows at this time of year should be in the lower 40s outside of
the cities, which is close to what Wednesday night will be.
Temperatures west of the Blue Ridge expected to drop into the
mid to upper 30s. Frost advisories may be needed Page/Warren/
Clarke/Frederick into the eastern Panhandle of WV.

Trough will be lifting out Thursday allowing for sunshine but
cool temperatures. After that high pressure will be developing
offshore while a trough moves over the upper Midwest. This will
palce the eastern Seaboard in warmer southerly flow. By Saturday
expect to see temperatures up near 70. GFS is bringing the next
front into the forecast area late Saturday while the Euro is
significantly slower. Will add 30 pops to Saturday afternoon
but these may need to be removed depending on later model runs.

&&

Aviation /07z Sunday through Thursday/...

Brief patchy fog possible early this morning and again Monday
morning at outlying terminals (cho/mrb/iad). Lower ceilings/visibilities
likely Monday night in showers as low pressure passes to the
west dragging a cold front through. Low level wind shear possible Monday night
as well, along with a few gusts to 20+ kts. Conditions improve
by Tuesday afternoon as winds become westerly.

VFR conditions expected Wednesday and Thursday.

&&

Marine...

Light winds until late Monday/Monday night in southerly
channeling as low pressure develops and passes west of the waters.
Gale force gusts possible, especially in heavier downpours late
Monday night into Tuesday morning. Winds become west after cold
front crosses Tuesday afternoon with Small Craft Advisory gusts possibly lingering
into Wednesday.

&&

Tides/coastal flooding:

A period of southerly winds will cause anomalies to rise early
this week. Minor tidal flooding is likely Monday into Tuesday
before winds become west and water levels recede.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...none.

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