South Beach, Oregon Weather Forecast Discussion

255
FXUS66 KPQR 211321
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
621 AM PDT Sun Sep 21 2025
Updated hazards and marine discussion.
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.SYNOPSIS...A Fall-like front will bring a quick shot of rain
to the region tonight into Sunday before drier and milder
weather return early next week and persist through at least the
middle of next week.
&&
.SHORT TERM...Now through Tuesday...
Now through Tuesday...The previously discussed
cold front has made landfall bringing southerly gusty winds and
rain to the area. The coast and Coast Range will see the
heaviest rain. While initially it will be stratiform, it will
quickly transition to showers which will lead to variability in
the accumulation. For example, in Astoria the 10th percentile
shows a 24-hr rainfall total of 0.5 inch, while the 90th
percentile shows around 1.5 inches. This wide range will vary
based on location and terrain. Along the north Oregon and south
Washington Coast amounts will be highest while the central coast
around Lincoln and Lane Counties will see slightly less. This
trend will follow inland. One challenge will be the amounts
within the Willamette Valley. Winds will initially start
southerly then shift to the northwest with the frontal passage.
This switch will increase rain shadowing so there is a high
probability that portions of the valley will see less rain than
the coast and both ranges.
This front is quickly moving eastward as high pressure builds in
behind it. 500 mb heights shows ridging developing as early as
late tonight. The ridge will amplify through Monday bringing in
drier and warmer air - slightly higher than we typically think
of with September. Monday`s high temperatures will be highest in
the central and southern Willamette Valley where 850 mb
temperatures reach around 14-17 deg C. These temperatures will
set the stage for Tuesday`s weather.
On Tuesday the ridge will amplify further becoming positively
tilted. In contrast, a low aloft forms in the northeast Pacific
and another over Rockies. A thermal trough will form at the
surface as well increasing the temperature gradient within the
area. Highs are expected to be in the mid to upper 80s inland,
and in the 70s along the coast. The combination of these
features will promote easterly winds once again. At this point,
the pressure gradient between Troutdale and The Dalles is around
-3 mb to -4 mb which is consistent with gusty winds from the
 east. This will be most evident through the Columbia River
 Gorge, the coastal gaps, and the passes of the Cascades. Some
 component of downsloping is possible leading to locally gustier
 winds and higher temperatures (like around Tillamook). A
 challenge is the intensity of these patterns. In regards to
 wind, the ECMWF is trending stronger with ensembles suggesting
 gusts at Troutdale Airport around 25-35 mph. The GFS though is
 trending closer to 15-20 mph (a more typical easterly wind).
 Have decided to nudge towards the 90th percentile of the NBM in
 our typical "windy" locations to account for terrain and trends
 for these types of scenarios. -Muessle
.LONG TERM...Tuesday Night through Saturday...Ensembles are in
fairly good agreement in the ridge remaining within the general
area through Thursday morning then becoming more zonal. By
Friday though there is high uncertainty in the overall pattern.
2 of the 4 ensembles are showing troughing in the vicinity as
early as Friday, while the remainder show the troughing on
Saturday. Ultimately, this troughing is correlated with the
strong low pressure system over the northeast Pacific. If this
low advects further south and east, another rainy system is
likely. However, based on current ensembles, only 2 are showing
that rainy scenario on Friday/Saturday. For the next 6-10 days,
the Climate prediction center shows around 30-40% chance of
above normal temperatures and a 40-50% chance above normal
precipitation. With this level of uncertainty and probability,
it very much feels like a coin toss on whether we will see a
rapid cool down and rain, or lingering dry air and moderate
temperatures.-Muessle
&&
.AVIATION...A cold front will continue to push through the region
today bringing widespread MVFR CIGS and gusty north to
northwesterly winds. Along the coast conditions will be the most
reduced due to heavier rain and more pervasive stratus. The
combination of gusty winds up to 25 kt with heavy rain will cause
at least MVFR VIS, while saturation will cause CIGs to fall to low
end MVFR or high end IFR. Reduction has been slow this morning so
will continue to track. Inland, precipitation will be less as
will wind so VIS challenges are not expected to be as widespread.
Within the central and southern Willamette Valley (south of KSLE)
will be windier.
Because this will be a fairly fast moving front, wind and rain
will end early and CIGs will rebound to VFR inland and high end
MVFR along the coast. Some models are suggesting fog formation
after 06Z Monday due to building high pressure. However, winds
will remain elevated which will aid in keeping any fog at bay.
KPDX AND APPROACHES...Rain with southwesterly winds through the
next 8-12 hours which will cause CIGs and VIS to reduce to MVFR
levels at times. There is around a 10-20% chance of IFR CIGs at
the terminal but confidence is low that it will prevail. After
15Z, winds at 1000-2000 ft AGL will increase with speeds around 25
kt. A lack of directional shear means that LLWS is not expected.
Return to VFR in the later half of the forecast. -Muessle
&&
.MARINE...Update: Winds have held on longer than forecast, and
are gusting stronger in the central waters. Have issued a short
durration Small Craft Advisory for PZZ273/253, and extended the
others. Previous discussion follows:
A cold front moving over the waters are causing
conditions to ramp up. Seas are currently 6-8 ft with a 10-11
second period. These conditions will prevail over the next week
with minimal change. Currently, winds are southerly around 15-20
kt with gusts up to 25 kt in the inner waters, northerly outer,
and through the Columbia River Gorge. However those conditions
will decline with the passing of the front when they become
northwesterly. High pressure builds through mid- week.
A summer northerly wind pattern in store starting Monday night
into Tuesday as a thermal trough builds. Will see winds increase
once again, especially in the southern waters of PZZ273/253. At
this time there is uncertainty in how strong they will be. With
this shift, the westerly swell will combine with the northerly
wind and thus could see periods of seas closer to 9 ft. High
probability of small craft advisory wind conditions Tuesday
through Wednesday. -Muessle
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 9 AM PDT this morning for PZZ210-
     251>253-271-273.
&&
$$
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NWS PQR Office Area Forecast Discussion