Damaging Wind in Oregon, April 30, 2022

Area Forecast Discussion
National Weather Service Portland OR
244 PM PDT Sat Apr 30 2022

.SYNOPSIS...Showers, along with a slight chance of thunderstorms
continue through this evening. High pressure brings warmer and drier
weather Sunday ahead of the next system. Rain returns Sunday night
and continues through Monday. Another stretch of warmer and drier
weather appears likely Tuesday and Wednesday. Thursday and continuing
into next weekend, the next round of precipitation is on order.

&&

.SHORT TERM...Tonight through Monday night...Showers, along with the
slight chance of thunderstorms continue through this afternoon. Also,
any thunderstorm that does manifest, will have the chance to produce
small hail. Diving into the model soundings, there is a clear pool of
colder air aloft will help to steepen mid level lapse rates, which
will support the widespread, marginal instability. Current satellite
imagery is showing some clearing along the coast and if that clearing
continues inland, will increase the overall instability. Will
continue to watch the situation as this evolves over the remaining
daylight hours. Also, snow levels will settle around 4000 to 4500 ft,
this will likely bring a few more inches of snow to the Cascade
passes through tonight. Showers will quickly dissipate tonight as an
upper level ridge starts building in across the Pac NW. This will
result in a much warmer and drier trend through the remainder of the
weekend. Given that a ridge will build in, the chances of fog
development will be possible thanks to increasing subsidence and
recent rainfall.

Sunday, daytime temperatures will be in the mid 50s to mid 60s.
However, don't get used to the warm and dry environment as the next
round of cool, wet weather is expected by Sunday night/Monday morning
as a frontal system will greet the region for the start of the
upcoming week. Monday daytime temperatures will be cooler, climbing
into the mid 40s to mid 50s. Precipitation will start out as
stratiform and become more showery by Monday afternoon. Total
rainfall for this next system is noticeably less, with guidance
having around 0.25" to 0.50" for most locations, with slightly higher
amounts around 0.50" to 1.00" for higher elevations by the time the
precipitation ends on Monday night. /42

.LONG TERM...Tuesday through Friday...High pressure is set to build
over the forecast area on Tuesday with some possible lingering post
frontal showers from the system on Monday. Will likely still see a
bit of that northwesterly flow which will maintain the cool air
aloft. However, once the ridge shifts inland with the axis setting up
over the coast, skies will begin to clear and any showers will
dissipate. Warmer air will be ushered into the forecast area with
temperatures rising up to near normal. There is quite a bit of
variability with ensemble outputs in regards to temperatures on
Tuesday with values ranging from 55-60 degrees F. The outcome will
greatly depend on where skies clear and when. If we seeing that
clearing in the morning, will likely have enough daytime heating to
reach those warmer temperature.

Wednesday is another story as the ridge will reach its maximum
intensity with the ridge shifting over eastern Oregon and becoming
positively tilted. With this orientation, winds will become
southwesterly and will keep temperatures warmer. Looking at above
normal temperatures on Wednesday possibly reaching into the lower 70s
inland with the warmest values in the southern portions of the
forecast area. Models are actually in better agreement in regards to
this outcome than Tuesday even with it being a day later. Looks to be
a beautiful spring day if you like that sort of thing.

Late in the week, a few different shortwave troughs and cold fronts
will pass over the area each bringing periods of rain and wind. These
fronts are associated with a developing closed low from the Gulf of
Alaska which is wrapped in quite a bit of cold air. Friday night
appears to be the wettest time frame at this time. Temperatures will
once again cool through Friday. 		  -Muessle

&&

.AVIATION...00z TAFs: Numerous showers continue across the area
in the unstable, post-frontal air mass as of 2130z Saturday. VFR
conditions remain predominant, though heavier bursts of rain have
brought ceilings into the MVFR category temporarily at many
terminals. This is expected to continue the next several hours,
but shower activity should gradually taper off this evening with
both (1) the loss of solar heating and (2) the gradually increase
in subsidence associated with high pressure building in from the
west.

HREF guidance continues to suggest low clouds will build westward
off of the Cascades in the weak, westerly low-level flow pattern
late tonight to bring 80% or greater probabilities for MVFR
ceilings to the northern and eastern Willamette Valley. In
addition, given the saturated soils from recent rain, light winds,
and lack of dense clouds to significantly inhibit radiational
cooling, chances for areas of fog in the southern and central
Willamette Valley are still there - especially between 10z and 17z
Sunday morning.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR conditions remain predominant despite
numerous showers across the area. In the periodic, more intense
bursts of rain, MVFR ceilings are likely, though VFR is expected
to be most prevalent until around 07z to 09z Sunday, when MVFR
ceilings are expected to approach the terminal from the east.
-Bumgardner

&&

.MARINE...Winds and seas remain low outside of showers Saturday
afternoon as high pressure gradually overtakes the eastern
Pacific. Southerly winds will increase Sunday afternoon as a cold
front approaches from the west, and Sunday night westerly winds
behind the front could reach Gale Force in portions of the waters.
Considerable uncertainty surrounds the strength and track of the
low pressure system which has the potential to bring these strong
winds, but confidence was high enough to warrant a Gale Watch for
the northern outer waters and all of the central waters. There,
mean model guidance was suggesting peak wind gusts approaching 40
knots, though again spread among model guidance is vast. Given
this uncertainty, it would be prudent to continue checking the
forecast throughout the next couple days for updates.

Significant wave heights were observed around 6 to 7 feet at 7 to
8 seconds at Buoys 29 and 50 at 2 PM Saturday. This generally
relaxed sea state is not expected to undergo drastic changes
between now and Sunday evening, but wind driven seas will jump
rapidly Sunday night with significant wave heights over 15 feet
possible through Monday afternoon in at least a section of the
waters. -Bumgardner

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Gale Watch from Sunday evening through Monday evening for
     Coastal waters from Cascade Head to Florence OR out 10 nm-
     coastal waters from Cape Shoalwater WA to Florence OR from
     10 to 60 nm.

&&

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