548
FXUS66 KPQR 110924
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
224 AM PDT Tue Jun 11 2024

.SYNOPSIS...High pressure will shift eastward as a weak front
pushes through the region today. This may lead to drizzle or
light rain along the coast this morning, while inland locations
remain dry. Onshore flow will keep things cool, and clearing
skies tonight will lead to much cooler Wednesday morning lows.
High pressure brings dry and warm conditions Wednesday and
Thursday. Friday through early next week, troughing enters the
region, resulting in increased precipitation chances and cooler
temperatures.

&&

.SHORT TERM...Today through Thursday...A high pressure ridge
aloft will push eastward this morning as an upper level trough
approaches British Columbia. Satellite imagery as of 1 AM PDT
depicts the associated surface low around 49N/132W, with a cold
front draped southward along 128W. This weak front is progressing
toward the Pacific Northwest, which is beginning to deepen the
marine layer along the coast. The front will push inland around
8-11 AM today, which may result in some morning drizzle or light
rain along the coast (15-30% chance).

It doesn`t appear that this front will be robust enough to lead
to any precipitation within the Willamette Valley, but do
expect increased broken/overcast cloud cover inland in this
morning. An exception would be the Eugene area, where the front
may be slow enough to arrive such that the first half of the day
has plenty of sunshine before the front arrives early this
afternoon. Given the increased cloud cover today, expect
afternoon high temps for interior valleys to be a few degrees
cooler than yesterday. Forecast highs are in the mid 70s for
interior valleys and upper 50s/low 60s along the coast. While
most locations will experience northwesterly winds with gusts
up to 20 mph this afternoon, westerly winds in the Central
Columbia River Gorge could gust up to 40 mph.

Tonight, high pressure will re-build as the weak front dies off.
As a result, expect a decrease in cloud cover and lighter winds.
It`ll be a pretty cool night for June, with tomorrow morning
lows in the mid to upper 40s for lowlands and upper 30s for
higher terrain. Though we`ll start off Wednesday pretty cool,
the air mass will warm up later in the day with sunny skies so
tomorrow afternoon highs should end up seasonable.

High pressure will persist through Thursday, leading to another
cool night Wednesday night, but probably not quite as cold as
Tuesday night. As the air mass continues to warm Thursday, it
appears likely Thursday afternoon will be a few degrees warmer
than mid-June normals. Based on NBM guidance, it appears there
is a 40-50% chance of the Portland Metro Area reaching 80 deg F
Thursday afternoon, while chances for the same in Eugene are
closer to 10-20%.       -Alviz/Weagle

&&

.LONG TERM...Friday through Monday...The upper ridge begins to
shift east of the forecast area on Friday as another trough near
the Gulf of Alaska dips southward toward the Pacific Northwest.
This will lead to a cooling trend and return of precipitation
chances. It currently looks like a weak front will brush the
coast and northern part of our CWA, so Friday`s PoPs are pretty
low (15-40% chance) and confined to the coast, Coast Range, and
southwest Washington.

Saturday, most ensemble members agree on troughing entering the
region with below-normal 500 mb heights. In this scenario, we
would see increasing chances for widespread precipitation and
below average temperatures. For now, the NBM`s 25-60% chance of
PoPs across northwest Oregon and southwest Washington at the end
of the week look reasonable. Sunday to Monday, the majority of
ensemble members (>85%) continue to show broad troughing over
the Pacific Northwest, maintaining a generally cool and
potentially wet start to next week.     -Alviz

&&

.AVIATION...At 2 am, VFR with scattered high clouds across the
region. But, do have widespread IFR to lower end MVFR along the
coast as marine stratus blankets the coastal areas. Increasing
onshore flow today, as front approaches. This will push stratus
deep into the coast range/Willapa Hills valleys, and into parts of
the interior by 12Z to 13Z. Do not think entire Willamette Valley
will cloud over, but will have areas of MVFR against the Cascades
foothills. As morning progresses, marine layer near surface will
deepen, and as such, will see increasing marine stratus spread
across much of the interior, but will likely be lower VFR (3000 to
4000 ft clouds). Even coast will likely lift to VFR this
afternoon. Once the front passes, will see winds turn more
northwesterly, with CIGS gradually breaking up towards evening.

With the uptick of onshore flow, expect breezy west winds in the
mid/eastern Columbia Gorge, and over higher terrain in Cascades.

PDX AND APPROACHES...At 2 am, still VFR with scattered high
clouds. Should see patchy MVFR to north and east of PDX from 12Z
to 16Z, possible backbuilding enough to form a BKN-OVC CIGS after
14Z. As front draws closer, will see increasing clouds by mid to
late morning, with CIGS mainly 3000 to 4000 ft. CIGS will slowly
break part late in the afternoon into the evening. /Rockey

&&

.MARINE...Not a lot of change. Even though weak front will push
across the region, high pressure will quickly restrengthen over
the offshore waters behind the front this afternoon through
tonight. As such, northerly winds will pick up again later today,
but mainly tonight and remain gusty at times through Wed evening.
Have Small Craft Advisory on the waters, spreading from north to
south as the front moves across region and pressure gradient
tightens. Seas mainly 5 to 7 ft, but will see seas up around 10 to
12 ft for a time later today into early Wed am as fetch of large
swell moves from northeast Pac into the north Washington waters.

High pressure will maintain northerly gradients through Thu,
though the north winds will be bit less, generally 10 to 20 kt,
with strongest in afternoons/evenings. Seas stay in the 5 to 6 ft
range. Next front will arrive later Fri, with flip back to W or SW
winds of 10 to 15 kt for late Fri into early Sun.  /Rockey

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT
     Wednesday for PZZ210.

     Small Craft Advisory from 11 AM this morning to 11 PM PDT
     Thursday for PZZ251-252-272.

     Small Craft Advisory from 5 PM this afternoon to 11 PM PDT
     Thursday for PZZ253-273.

     Small Craft Advisory from 8 AM this morning to 11 PM PDT
     Thursday for PZZ271.
&&

$$

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