694
FXUS66 KPQR 140416 AAA
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR
816 PM PST Thu Nov 13 2025

Updated Aviation Discussion

.SYNOPSIS...Low pressure moves along the West Coast bringing
periods of rain over the next several days. Will see periods of
breaks, but will be short lived as short wave after short wave
passes over. The big weather shift will be early next week as a
long wave pushes eastward over the coast. Cold air wraps around
the trough and will cause temperatures to drop. Increased
probability for lowering snow levels and Cascade Pass snow.

For those who may have noticed, the NEXRAD Radar at KRTX is down
for a mechanical issue. The time of restoration is unknown at
this time. We apologize for the inconvenience.

&&

.SHORT TERM...Now through Saturday night...Satellite imagery
shows a closed low pressure system centered just off of the
Oregon/California border this afternoon. This low has ushered in
persistent rain with showery conditions this afternoon. The
main rain band has since passed but expecting a series of steady
rain showers over the next several hours. This low will slowly
advect southward through tomorrow and stall over central
California. Will see a continuation of non-impactful
precipitation. Snow will not be a concern through Saturday as
the warmer air ushered in from the south from this low will
maintain snow levels well above the passes (9000 ft+).


Another frontal system will swing through British Columbia and
far northwest Washington Friday evening into Saturday. High
resolution models for 24 hour precipitation ending Saturday
afternoon are showing nearly a 40-70% chance of 0.25" of rain
along the coast, less than a 10% chance for the Willamette
Valley, with higher probability from Clark County north where
chances are closer to 60%. This is due to the track of the
secondary short wave troughs which are pushing just to the
north. If they shift southward though prepare for heavier ran.
Overall, the weather over the next few days is nothing to write
home about.-27


.LONG TERM...Sunday through Thursday... A slightly more complex
scenario for early next week that is being driven by a broad low
pressure system sitting over British Columbia. This low will
push a robust long wave trough southward along the coast. This
trough will usher in slightly colder air starting on Sunday with
overnight temperatures dropping through mid-week. As the
temperatures lower, will see snow levels fall suit. In the
current forecast, snow levels will reach pass level late
Sunday night or early Monday morning. However, if one were to
look at the ensemble long range models there is much more
uncertainty. This is due to a) the depth of the trough, and b)
whether a closed low forms at the base. If the low does in fact
form, the lift will be amplified with more impacts. Wrap around
cold air will be more robust as will sinking air. In contrast
though, if the low does form but further north then there will
be active weather but less cold air intrusion. The second option
is the low not manifesting. If this is the case, the cold air
plunge will be less than if it were to. The same trend of a
north or south track rings true in this case too.

With all that said, the timing of the cold air is going to have
a major impact on if/when we get snow in the Cascades which
could lower to pass level. The deterministic GFS has snow levels
reaching pass level nearly 24-hrs later than the ECMWF at this
point. Let`s dive into the snow potential for advisory level
snow on Monday into Tuesday. If we look at the probability of 6"
or greater snow at the Cascade passes in the 48-hrs ending
Tuesday afternoon, the probability has decreased significantly.
At this point there is around a 35% chance of >6" of snow at
Santiam and Willamette Passes. There is less than a 5% chance at
Government Camp and even lower probability to the north. In
fact, the highest probability that exceeds 50% is only along the
volcanoes of the central Oregon Cascades.

There continues to be significant disagreement towards mid-
week. -27

&&

.AVIATION...Light showers continue to dissipate over the next few
hours, this will result in lingering mid/high level clouds. This
will result in generally VFR conditions, but could see intermittent
MVFR/IFR (15-25% probability) conditions through 15Z Friday.
Higher probs of IFR along the coast. Light rain/aggressive drizzle
could also persist through the TAF period, but better chances for
rain don`t return until 08Z-10Z Friday for the coast and 10Z-12Z
Friday for inland locations. VFR conditions are expected to
persist as the rain returns for the remainder of the TAF period.
Winds generally out of the south less than 10 kt.

KPDX AND APPROACHES...VFR with lingering mid/high level clouds,
along with intermittent MVFR/IFR (15-25% probability) conditions
through 15Z Friday. Light rain/aggressive drizzle could also
persist through the TAF period, but better chances for rain return
around 10Z Friday. Winds generally out of the south less than 10
kt. /42

&&

.MARINE...Winds are beginning to ease behind a frontal system
that moved through the central Oregon waters this afternoon.
Winds remain from the south, mainly less than 10-15 kts, though
zone Pzz273 will see gusts up to 20-25 kts through around 5 PM
PST tonight. Seas are building towards 10-12 feet at 12-15
seconds for all waters due to an increasing westerly swell. The
area south of Cape Falcon and beyond 20 NM off the coast will
also have a 50-70% chance for seas building towards 13-15 ft
tonight. Therefore, the current Small Craft Advisory for all
marine zones remain in effect through at least 7 AM Friday,
mainly due to seas. Seas gradually subside to 8-9 ft at 13
seconds Friday morning.

Another frontal system will swing through British Columbia and far
northwest Washington Friday afternoon, maintaining relative
breezy southwesterly winds over our coastal waters. There is a
30-50% chance for southwesterly winds with frequent gusts of 21 kt
or stronger across the waters north of Cape Falcon including the
Columbia River Bar by late Friday afternoon and evening. South of
Cape Falcon, these chances drop to 15-30%. Winds ease on Saturday
before another frontal system may bring another round of
increased winds on Sunday. Seas continue falling Friday afternoon
to 7-9 feet at 11-12 seconds, remaining here through Saturday
before increasing to 9-11 feet at 12-14 seconds on Sunday. -10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 7 AM PST Friday for PZZ210-251>253.

     Small Craft Advisory until 1 PM PST Friday for PZZ271>273.
&&

$$

www.weather.gov/portland

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