Johnson Trail Oregon Weather Forecast Discussion

766
FXUS66 KPQR 111058
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
358 AM PDT Sat Oct 11 2025
.SYNOPSIS...A broad upper-level trough and embedded coastal low
continues to drive cool and unsettled weather across the
Pacific Northwest through the weekend. Expect periodic rain,
mountain snow, and below-normal temperatures. Conditions
gradually moderate midweek as a ridge builds over the region,
though model uncertainty grows toward late week.
&&
.DISCUSSION...Now through Friday...Satellite and radar imagery
early this morning depict a compact upper-level low now centered
near the Oregon coast, with widespread cloud cover and
intermittent light to moderate rain inland. As of 4 AM,
overnight temperatures have dipped into the low 50s to upper 40s
across the interior valleys, and a Frost Advisory remains in
effect for Hood River County until 8 AM this morning.
Uncertainty persists regarding additional frost or freeze
headlines over the next few nights. For Saturday night into
Sunday, frost formation hinges on whether clouds sufficiently
clear - confidence remains low to moderate. The Sunday night
into Monday period could see near-freezing conditions as cold
air lingers, though thicker cloud cover may limit frost
formation. Monday night into Tuesday currently appears to hold
the highest potential for a Freezing Warning, given cloud cover
is forecasted to clear through Monday.
As the coastal low drifts slowly inland today, expect another
period of widespread rain, tapering to showers by late afternoon
and evening. Rainfall totals through today are forecast to range
from 0.10-0.20 inches in the interior valleys to 0.20-0.40 inches
along the coast, Coast Range, and Cascades. Probabilities for
24 hour accumulation exceeding 0.50 inches sit around 15-30% for
the Willamette Valley and 40-80% for the coast, Coast Range,
and Cascades.
The upper low begins to move eastward late tonight into Sunday,
allowing for a transition to more showery and convective
precipitation. Model soundings and ensemble guidance suggest
around a 15% chance for isolated thunderstorms through much of
Sunday, primarily along the coast but still possible inland. By
Sunday night, a colder post-frontal air mass settles into the
region. Highs Sunday and Monday will remain in the mid 50s to
low 60s for most lowland areas and upper 30s to upper 40s
across higher terrain. Snow levels lower to around 3500-5000
ft, bringing the potential for 2 to 5 inches of wet snow near
pass level, with up to 6 to 12 inches at higher elevations above
5000 ft.
For Saturday through Monday, ensemble 72 hour total
precipitation probabilities indicate a 50-75% chance for 1 inch
or more across the interior lowlands and 75-95% for coastal and
mountainous areas. For 1.50 inches, probabilities drop to 20-40%
for the valleys and 50-80% for higher terrain.
Tuesday into Wednesday, a transition toward higher pressure and
drier weather is expected as ensemble cluster guidance favors a
ridge building over the northeast Pacific. This will bring
moderating temperatures, highs climbing into the 60s and PoPs
dropping to 10-20%. Uncertainty increases toward Thursday and
Friday. Several ensemble members rebuild the offshore low and
push it back toward the coast. If that scenario materializes,
weak onshore flow and increasing cloud cover could return,
bringing PoPs back up into the 30-50% range. Confidence in this
late week pattern remains low as ensemble spread continues to
widen regarding the strength and placement of the reemerging
trough.
~12
&&
.AVIATION...An upper level low pressure system pushes inland
through today, absorbing into an upper level trough located to
the north by the end of the TAF period. As a result, expect
showers and a mix of MVFR/VFR conditions throughout the airspace
through the period. Guidance suggests a 30-50% chance for MVFR
CIGs at most terminals at any given hour after 12Z Saturday.
Otherwise, expect southerly winds 5-10 kt overnight, shifting more
southwesterly/westerly around 21-23Z Saturday. Afternoon wind
gusts up to 20 kt possible for coastal terminals.
KPDX AND APPROACHES...Persistent showers with a mix of MVFR/VFR
conditions through the TAF period. Guidance suggests a 20-40%
chance for MVFR CIGs between 12Z Saturday and 06Z Sunday. Expect
southerly winds 4-8 kt, shifting southwesterly by 01-03Z Sunday.
~12
&&
.MARINE...A low pressure system currently moving onshore will
weaken further through today. Southwesterly winds this morning
will turn westerly to northwesterly this afternoon into the
evening, increasing winds to 15-25 kt with gusts up to 30 kt.
Seas are expected to increase to 10-13 ft with dominant periods
around 10 seconds late today into early Sunday bringing a period
of hazardous seas.
Late Sunday into Monday, a low pressure system will drop
southward along the coast, bringing another round of northerly
winds. Seas decrease below 8 ft during the middle half of next
week as high pressure builds back across the northeast Pacific.
The end of next week has a fair amount of uncertainty as guidance
suggests an 80% chance that significant wave heights will be
between 7 and 14 ft across the waters on Friday.
~12
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory until 8 AM PDT this morning for ORZ121.
WA...None.
PZ...Small Craft Advisory from 5 PM this afternoon to 11 PM PDT this
     evening for PZZ210.
Small Craft Advisory from 3 PM this afternoon to 11 PM PDT this
     evening for PZZ251>253-272-273.
Hazardous Seas Watch from this evening through Sunday afternoon
     for PZZ251>253-272-273.
Small Craft Advisory from noon today to 5 PM PDT this afternoon
     for PZZ271.
Hazardous Seas Watch from this afternoon through Sunday
     afternoon for PZZ271.
&&
$$
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NWS PQR Office Area Forecast Discussion