Vancouver, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

359
FXUS66 KPQR 090342 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
842 PM PDT Tue Oct 8 2024

Updated aviation discussion.


.SYNOPSIS...A weak front dropping southeastward across the area
will bring spotty light rain to the area tonight into early
Wednesday. Building high pressure will bring a return to above
average temperatures later this week into this weekend.

&&

KEY MESSAGES:

- Weak front to bring spotty light rain to portions of southwest
  Washington and northwest Oregon through early Wednesday

- Light offshore flow Wednesday night/Thursday and again Friday
  night/Saturday will allow smoke from eastern Lane County
  wildfires to drift downriver

- Rain chances increase substantially early next week


.DISCUSSION...Water vapor satellite imagery shows a shortwave
trough over the northeast Pacific while large scale ridging is
centered downstream over the central US this afternoon. This is
placing the Pacific Northwest under broad southwesterly flow
aloft and has allowed a weak front to slide southeastward into
the area. This front will continue to progress southeastward
across the area overnight with rain chances mainly being
limited to our far northwest coast this evening and across the
Cascades later tonight into Wednesday.

As the aforementioned shortwave trough over the northeast
Pacific slides eastward across southern Canada, 500mb heights
will build back over the Pacific Northwest and result in a
warming and drying trend Thursday into Friday. Ensemble systems
are in relatively good agreement a shortwave trough currently
over the Aleutians will dive southeastward and form a weak
cutoff low pressure off the southern Oregon and northern
California coast late Thursday into Saturday. About 10-20% of
the global ensemble membership brings this upper level low
northeastward into the Pacific Northwest and generates some
light precipitation. However, the vast majority of the ensemble
guidance keep the area dry and suggests the main impact from
this weak storm system will be a brief increase in cloud cover
and weak easterly winds developing in the Columbia River Gorge
and across the Cascades Friday night into Saturday.

There is still relatively good agreement in the large scale
weather pattern among the global ensemble members early next
week. The general consensus is that a large shortwave trough
will return to the eastern Pacific and shortwave ridging will be
located over Rocky Mountain states. However, subtle differences
in when the shortwave ridge shifts east and allows a front to
push into the Pacific Northwest exist between members. For
those that want rain, the good news is that greater than 80-90%
of the EPS, GEFS and GEPS membership suggest the front will
bring at least some rain to the region at some point beginning
as early as late Monday or as late as early Wednesday. The main
reason our official PoP forecast is not that high is due to it
only focusing on the probability of precipitation in any given
12-hour time period.


&&


.AVIATION...The weak front that brought isolated showers is
pushing inland leaving behind stratus and light winds. Cannot rule
out a stray shower or two over the next 12 hours, but will have
minimal to no impact on conditions. IFR/MVFR stratus continues
along the coast, with a 50% chance of those CIGs persisting
through 11Z Wednesday. Visibility remains degraded in these areas
as a combination of mist and dense low stratus. Inland sites will
be at risk for ground fog formation after 10Z Wednesday due to a
lack of cloud cover allowing for radiational cooling. However,
high level clouds will insulate just enough that the probability
is low. Onshore flow will increase through the night pushing air
up to the Cascades. This damming will cause CIGs to back build and
fill into the Willamette Valley terminals through 17Z Wednesday.
High pressure slowly develops late Wednesday which will cause CIGs
to lift considerably.

PDX APPROACHES...VFR with back building CIGs in the morning.
Stratus that does develop will be short lived though as the lower
levels dry and force clouds to lift and clear. Once CIGs lift to
VFR levels, they will stay there for the remainder of the forecast
period. Winds will shift to the northwest which could bring
isolated periods of increased winds but will not be persistent
enough to include in the TAF. -Muessle

&&

.MARINE...Generally light winds expected over the coastal waters
through Wednesday as a pair of weak fronts traverse the region.
Light southerly breezes being observed over the nearshore waters
this afternoon will shift around to the northwest this evening in
the wake of the first front moving onshore. Winds will briefly
turn southerly again on Wednesday north of about Cape Falcon as
the next weak front arrives. Overall, expect winds to remain at or
below 10 kt across the waters into Wednesday night. Thursday will
bring a return of 10-15 kt northerly breezes in response to a
tightening coastal pressure gradient, but winds quickly weaken and
turn more southeasterly Thursday night into Friday ahead of a low
passing south of the region towards northern California.
Southerly breezes then persist into the weekend. Seas will remain
in the 6-8 ft range through Thursday, driven mainly by a mid
period westerly swell. /CB

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

www.weather.gov/portland

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