247
FXUS66 KPQR 190953
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
252 AM PDT Thu Sep 19 2024

.SYNOPSIS...
High pressure will maintain dry weather with temperatures more
typical of late September for today into Saturday. The next front
will bring a chance of showers Sunday into Monday. Warmer weather
returns for later next week, possibly.
&&

.SHORT TERM...(Today through Saturday)...
High pressure will site offshore for the next several days. As such,
will maintain variable onshore flow. This will keep areas of
overnight/morning clouds, with afternoon sunshine. Thermal trough
will build on the south Oregon coast Thu night into Fri. At the same
time, a weak upper system will push inland. No rain expected, but it
will act to increasing the northwest flow into the region. As such
expect breezy west to northwest winds for Friday, especially over the
higher terrain and through the Columbia Gorge. Otherwise, morning
clouds will give way to partly to mostly sunny skies on Friday. Less
wind, less clouds and tad warmer for Saturday, as high pressure
builds inland.

Will keep temperatures closer to MOS guidance, with highs along the
coast in the 60s, and lower to middle 70s farther inland such as the
Cowlitz Valley southward through the Willamette Valley.  /Rockey

.LONG TERM...(Sunday through Wednesday)...
Lingering uncertainty for later this weekend into the early next week
as medium and long range guidance continues to diverge with respect
to how the pattern will evolve during that time. That said,
ensemble clusters have started to slightly favor a warmer and
drier pattern for Sunday and beyond, with about two thirds of
solutions now indicating a ridgier pattern while the other third
still depict troughing or more zonal flow. As a result, NBM
interquartile ranges for temperatures have narrowed to show
inland high temperatures most likely residing in the mid to
upper 70s for Sunday through Monday. Precipitation chances have
also gone down as models hint at upper level ridging, but NBM
mean guidance still carries chance to slight chance PoPs across
mainly the northern half of the area late Sunday into early
Monday, which reflects the below normal forecast confidence.
Model agreement actually increases towards the beginning of next
week as ensemble clusters show about 90 percent of solutions
favoring some degree of upper level ridging over the Pacific
Northwest for Monday and Tuesday. As such, Tuesday looks to be
the warmest day in the next week with highs possibly reaching
into the mid 80s in the interior valleys. Models start to
diverge again beyond Tuesday as guidance is split between
another trough and a more gradual breakdown of the ridge. /CB

&&

.AVIATION...Transient upper level ridge crossing the region today.
Low level onshore flow with a shallow marine layer at the coast.
Satellite shows extensive stratus

Northeast flow aloft as upper ridge of high pressure
gradually builds over the region headed through Thursday. Stratus
has already begun to build along the coast with conditions likely
(60-80%) deteriorating to IFR tonight into Thursday morning.
Stratus also likely (40-80%) back-builds off the Cascade
foothills towards the inland terminals after 10-12z Thursday with
MVFR CIGs trending toward 1500-2000 ft - highest likelihood at
PDX and TTD. Fortunately any low status inland will dissipate
around midday. Generally expect north to northwest winds,
increasing during the afternoon.

PDX APPROACHES...Predominately VFR expected through the overnight
hours as broken stratus has lifted to around FL040-050. MVFR
stratus likely (70-90% chance) to redevelop after 12z Thursday
before breaking up around 18z. Expect northwest winds to around
6-8 kt Thursday afternoon. -Schuldt/DH

&&

.MARINE...High pressure has returned to the coastal waters,
resulting in increased northerly winds today, likely continuing
through the week. Winds may gust up to 20-25 kt at times tonight,
especially over the outer coastal waters. Wind gusts to 25 kt
becomes more likely by Thursday afternoon as the thermal trough
strengthens over the southern Oregon coast. Have issued a Small
Craft Advisory to cover the increased winds and choppy seas
expected through Thursday night. Pressure gradients across the
coastal waters weaken somewhat over the weekend, likely resulting
in a decrease in north to northwest wind speeds.

A persistent northwest swell around 5 to 7 ft is expected to
continue through late week. Seas around 5 to 6 ft today likely
increase to around 7 to 8 ft Thursday through Friday, with a
dominant period of around 8 to 9 seconds. Seas then expected to
subside back to around 5 to 6 ft for the weekend. /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from noon today to 11 PM PDT this evening
     for PZZ253.

     Small Craft Advisory from noon today to 5 AM PDT Friday for
     PZZ271>273.
&&


$$

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