733
FXUS66 KPQR 191806 AAA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
1105 AM PDT Thu Sep 19 2024

Updated Aviation discussion

.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...Upper level ridge with dry northwest flow aloft
persists through Thursday night. Shallow marine layer with onshore
flow in the lower levels will maintain stratus through this
morning. IFR to lower MVFR CIGs at the coast likely to dissipate
by 21z this afternoon. Inland stratus is expected to scatter out
with widespread VFR by 19-20z. Expect mostly sunny skies with
variable high clouds through this evening. With similar conditions
expected late tonight into Friday morning, will likely see a
similar repeat of stratus redevelopment by 02z at the coast
(60-80%) and after 12z inland (40-70%), especially across northern
parts of the forecast area. Generally expect north to northwest
winds, increasing during the afternoon.

PDX APPROACHES...MVFR stratus around FLO15 will gradually erode by
around 19-20z this afternoon. Then, VFR expected with variable
high clouds through this evening. There is around a 50% chance of
MVFR redevelopment after 12z Friday. Expect northwest winds to
around 6-8 kt Thursday afternoon. /DH

&&

.MARINE...High pressure over the coastal waters, resulting in
increased northerly winds today, likely continuing through the
week. Winds may gust up to 20-25 kt at times, especially over the
outer coastal waters. Wind gusts to 25 kt becomes more likely this
afternoon as the thermal trough strengthens over the southern
Oregon coast. Small Craft Advisory continues to cover the
increased winds and choppy seas expected through tonight.
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 6 to 8 ft through Friday,
with a dominant period of around 8 to 10 seconds. Seas then
expected to subside back to around 5 to 6 ft for the weekend.
/mh /DH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 4 PM this afternoon to 8 PM PDT this
     evening for PZZ210.

     Dense Fog Advisory until 11 AM PDT this morning for PZZ252-253.

     Small Craft Advisory until 11 PM PDT this evening for PZZ253.

     Small Craft Advisory until 5 AM PDT Friday for PZZ271-272.

     Small Craft Advisory until 5 AM PDT Friday for PZZ273.
&&


$$

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