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000
FXUS66 KPQR 161723 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
1023 AM PDT Tue Apr 16 2024

.SYNOPSIS...Onshore flow continues today, along with a few light
showers. But, high pressure will build over the region later today
into tonight, with clearing skies. Will be cool tonight, and with
light winds, will see rather chilly night with areas of frost. After
a cool start, a mild Wednesday is on tap. High pressure remains over
the region for later this week, with mild temperatures and even a bit
of offshore winds for Thu and Fri. Clouds and cooler weather  with
return of onshore flow expected for next weekend.
&&

.SHORT TERM...(TODAY through WEDNESDAY)...
Westerly flow aloft, with moderate onshore low level flow remains
intact across the region, as evident by the extensive clouds. A weak
upper disturbance in the flow will maintain scattered light showers
over the area today, though these mostly over the higher terrain and
along the coast. Interior lowlands still being somewhat rain-shadowed
(thanks to the westerly flow aloft). As such, any shower would be
rather hit-n-miss, with not much rainfall expected.

Overall, today will be similar to yesterday, with plenty of clouds.
Will see bit more in way of breaks in the clouds, but will likely not
be until later this afternoon (such as across Lane County) into this
evening (areas around Portland and northward) before see any big
clearing. As such, still on cool side, with highs 55 to 60.

High pressure offshore will build inland tonight, with clearing skies
through this evening. Winds will be light, and with the clearing,
will see temperatures drop back into the 30s and lower 40s. Air mass
remains cool, and think high potential that many areas will see
overnight lows in the 30s, with warmest along the coast. Do think
will see temperatures in the upper 20s to lower 30s (sub-freezing)
for many higher locations, as well as the lowlands of the Cascades
foothills, Hood River Valley, and in the Willamette Valley south of
Corvallis-Albany line, including Eugene. As such, will expand Freeze
Warning for those areas. Rest of the area will be cool, but think
will just be above freezing. Will cover that area with Frost
Advisory. Anyone with outdoor vegetation that is sensitive to cold
temperatures should bring their plants indoors if possible, or take
other appropriate actions to prevent freeze or frost damage.

After a cool start on Wednesday, should be a rather pleasant day,
with highs warming into the mid and upper 50s along the coast, and
lower to middle 60s across interior lowlands east of the Coast Range
and Willapa Hills.
/Rockey

.LONG TERM...(THURSDAY THROUGH SUNDAY)...WPC 500 mb cluster
analysis indicates that ensembles are in agreement that upper level
ridging will continue building over the eastern Pacific and shift
east to just off the West Coast Thursday into Friday. At the
surface, high pressure strengthens off the coast with a thermal
trough building north from California into western Oregon. Due to
this, sunny skies and a warming trend will continue across NW Oregon
and SW Washington. Inland valley temperatures will inch towards the
70s once again with NBM indicating 55-75% of temperatures exceeding
70 degrees on Thursday and a 70-85% probably of the same on Friday.
This pattern will also result in increased surface pressure
gradients over the Cascades and Columbia River Valley, producing
increased offshore (easterly) winds for areas near the Columbia
River and Cascades, strongest through the Columbia River Gorge. NBM
indicates roughly 50-70% probability of wind gusts exceeding 30 mph
Thursday and Friday for the Cascades and locations north of Salem.
Additionally, NBM indicates a 60-80% probability for wind gusts to
exceed 45 mph for the Columbia River Gorge Friday.

Beyond Friday, ensembles are still uncertain at the exact pattern.
About 30% of the 500 mb clusters indicate ridging will continue
through the weekend, which would allow for warm and dry conditions
to continue. About 50% of the clusters indicate ridging will begin
to weaken or even become more zonal flow, which would allow
temperatures to cool somewhat, potentially back to seasonal normals
(low 60s for inland locations, upper 50s for the coast). The other
20% or so of the clusters indicate weak troughing will impact the
region, bringing near to below normal temperatures and light
showers. No matter which solution winds up occurring, no impactful
weather is expected in the extended period.     /HEC
&&

.AVIATION...Expect predominately VFR conditions to continue with
widespread mid and high level clouds gradually decreasing through
the TAF period, with clearer skies by tonight into Wednesday
morning. North to northwest winds at all locations with gusts up
to 20 knots along the coast through at least 00Z before
decreasing afterwards. Otherwise, winds generally remain 5-10
knots or less. Clear skies along with near to below freezing
temperatures will result in the possibility for frost build up on
exposed and elevated surfaces. Not expecting significant build up
with these conditions.

PDX AND APPROACHES...Expect predominately VFR conditions .
Northwest winds around 5-10 kt, strongest during afternoon and
early evening hours. Clear skies along with near to below
freezing temperatures will result in the possibility for frost
build up on exposed and elevated surfaces. Not expecting
significant build up with these conditions. /42

&&

.MARINE...Today an upper-level trough grazes the region to the
northeast and while impacts remain fairly minor overall, northerly
winds are expected to increase in the afternoon with gusts
reaching up to 25 kt. Thus, a Small Craft Advisory was issued for
all waters starting afternoon and continuing into the evening. On
Wednesday and Thursday as the upper-level trough progresses
eastward and a ridge of high pressure amplifies over the eastern
Pacific winds increase further out of the north with the NBM
projecting a 75-95% chance for wind gusts to once again meet Small
Craft Advisory criteria for the inner and outer waters generally
around and south of Cape Falcon each day. Then late week into the
weekend the axis of the upper- ridge moves overhead allowing winds
to turn more offshore while seas sit around 4 to 6 feet at 13 to
15 seconds. -Schuldt/42

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Frost Advisory from 11 PM this evening to 9 AM PDT Wednesday for

     ORZ101>105-108>115-119-120-122.

     Freeze Warning from 11 PM this evening to 9 AM PDT Wednesday for

     ORZ106-107-116>118-121-123>125.

WA...Frost Advisory from 11 PM this evening to 9 AM PDT Wednesday for

     WAZ201-202-204>207-209-210.

     Freeze Warning from 11 PM this evening to 9 AM PDT Wednesday for

     WAZ203-208.

PZ...Small Craft Advisory from 2 PM this afternoon to 11 PM PDT this
     evening for PZZ251>253-271>273.
&&

$$


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