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000
FXUS61 KLWX 191332
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
932 AM EDT Thu Oct 19 2017

.SYNOPSIS...
High pressure will remain across the Mid Atlantic through this
weekend. A low pressure system will affect the region early
next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
An elongated area of high pressure is located from the southern
Appalachians northeastward off of the southern New England
coastline, and will generally remain in control of the weather
through the day, providing mostly sunny skies with only a few
cirrus around. Temperatures will rise rapidly this morning, and
peak n the low to mid 70s this afternoon.

A very weak cold front will cross the region this evening. This
will result in a bit more wind overnight, but little more than
that. Because of the wind keeping it stirred up, temps should be
a bit higher than the last few nights. In areas where the wind
diminishes late, patchy fog could redevelop.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
High pressure will remain over the region through the short
term. It will be centered just to our southwest Friday, then
slowly migrate northeastward to a position off Cape Cod by
Saturday night. WInds may be a little breezy Friday in the wake
of the previous night`s cold frontal passage, but should be very
light Saturday as the high drifts on by. Temps will remain warm
during the day thanks to minimal air mass change, with 70s
common both Friday and Saturday, with lows falling back into the
40s each night thanks to good radiational cooling under the
high and limited if any cloud cover. Patchy fog will be possible
late each night.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
A significant change to the synoptic height pattern is forecast
to take place across the Northern Hemisphere this period. A
large/deep upper-level low will retrograde out of northern
Canada into the Bering Strait/western Alaska over the weekend.
This will force a building ridge over western North America, and
lowering heights across the eastern CONUS. With a blocking
ridge downstream over the North Atlantic, interaction between
the northern and southern streams seems likely early next week.
The exact evolution is, of course, uncertain at this time range.
But the pattern should transition from warm/dry to cool/stormy
over the Mid-Atlantic early next week. Latest 00z deterministic
runs and their respective ensembles continue to show this
overall evolution, with spread in finer scale details which will
be ironed out in the coming days.

&&

.AVIATION /13Z THURSDAY THROUGH MONDAY/...
Patchy fog possible at MRB/CHO/IAD over the next few mornings,
but chances are low and any fog would be brief. Otherwise, VFR
through Saturday night all terminals with light winds under high
pressure.

Some low CIGS/VSBYS may develop early Monday morning as
moisture returns around departing high pressure. Otherwise
guidance in agreement with pattern which would favor VFR Sunday
into Monday.

&&

.MARINE...
High pressure will generally keep winds below SCA criteria
through Saturday night. The exception will be tonight into
Friday morning, when a weak passing cold front will produce a
temporary increase in winds. Soundings show winds of 20-30
knots just above the surface, and while near shore areas will
likely have a surface inversion and less wind, with the warm
water temps some of that wind will mix down over the open waters
later tonight into Friday morning. As temps warm and the winds
aloft diminish during the day Friday, gusts should drop below
SCA criteria.

Southerly channeling to SCA levels possible by Monday as high
pressure moves offshore.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 9 PM this evening to noon EDT Friday
     for ANZ531>534-537-539>541-543.

&&

$$
SYNOPSIS...RCM
NEAR TERM...MM/RCM
SHORT TERM...RCM
LONG TERM...DFH
AVIATION...MM/RCM/DFH
MARINE...MM/RCM/DFH