Detroit Lake Oregon Weather Forecast Discussion

673
FXUS66 KPQR 151032
AFDPQR
Area Forecast Discussion
National Weather Service Portland OR
332 AM PDT Wed Oct 15 2025
.SYNOPSIS...A ridge of high pressure continues to facilitate
dry conditions through today and much of Thursday across the
interior valleys - limited impacts. Beginning later Thursday
into Friday the pattern become more progressive starting with a
weak frontal system ushering in chances (30-50%) for light
showers, more likely near the coast. Then confidence is high
widespread rain moves overhead for the second half of weekend
into early next week thanks to an upper-level trough. Lower
forecast confidence by the middle of next week.
&&
.SHORT TERM...Now through Saturday...Headed through today a
positively-tilted upper-level ridge continues to slide
eastward building heights aloft before finally passing overhead
and deamplifying during the day on Thursday. This pattern will
allow portions of the coast-range through the interior valleys
to begin the day with rather cool temperatures, especially for
spots like the Hood River Valley, wind-sheltered coast
range/Cascade valleys, and portions of the central/southern
Willamette Valley. Frost Advisories and a Freeze Warning (Upper
Hood River Valley) continue through 9 AM this morning.
While an offshore component to the wind is present to start to
day, more seasonable onshore north-northwesterly flow returns
this afternoon. There remains some uncertainty as to just how
low temperatures will drop again Wednesday night into Thursday
morning with most ensemble model guidance showing a slight
warming trend in the mean albeit with a larger spread -
dewpoints trend higher as well. Whether we see frost at our
more prone areas which have been impacted the last couple of
nights may come down to two main factors: the proliferation of
mid to high cloud cover this evening and tonight in addition to
any clouds associated with a weak marine surge Thursday
morning, and whether winds can stay light enough to allow the
near surface boundary layer to decouple. It would be a fairly safe
bet (60-80% chance) for yet another night of temperatures in
the low to mid 30s across the Upper Hood River Valley, Cascade
valleys, higher coast range valleys (think Vernonia area), and
more protected areas in the central/Southern Willamette Valley
tonight, but locations which have been on the fringe (mid to
upper 30s) the last two nights may be just a hair too warm for
impacts tonight. Once the current round of frost/freeze
products expire this (Wednesday) morning be on the lookout for
the potential of additional frost advisory issuance tonight
into Thursday morning.
Then later on Thursday into Friday morning a weak/decaying
trough and accompanying frontal system attempt to swing into the
region from the northwest ushering in a few rain showers, most
likely along the coast and across the higher terrain of the
north Oregon Coast Range, Willapa Hills, and Washington/North
Oregon Cascades. The immediate shorelines of Willapa Bay, Long
Beach Peninsula, and coastal Clatsop County, as well as upstream
in the Columbia Estuary to Cathlamet/Wauna, may see a 20-40%
chance of 0.25" of rain or more, while chances of a wetting rain
elsewhere and inland along the I-5 corridor is less than a 5%
chance. At least the added cloud cover and westerly flow
drastically lowers the threat for frost concerns for most
locations sunrise Friday morning.
Behind this weak disturbance, a quickly moving transient ridge
of high pressure aloft shifts overhead on Saturday while the
flow aloft turns northwesterly to southerly in the afternoon
hours. Expect a bump in high temperatures and prevailing dry
weather through most of the day across the I-5 corridor
Portland/Vancouver metro southward. However, a frontal system
will be lurking just off the coast by the afternoon hours.
There`s some uncertainty as to how quickly the rainfall
associated with this front shifts into southwestern Washington
and western Oregon during the afternoon/evening hours Saturday
which is responsible for the ~15-30% PoPs Portland northward
through Cowlitz County during this period. The ECMWF based
solutions in particular are bit faster bringing in precipitation
compared to the GFS and Canadian; something to watch. -99
.LONG TERM...Saturday night through Wednesday...There remains
good consensus between deterministic and ensemble modeling
systems that a trough over the northeastern Pacific digs
overhead, bringing a return to wetter weather across the Pacific
Northwest. At this lead time, there is high confidence in the
occurrence of rain in the Saturday night/Sunday time period
while the main mode of uncertainty is the amplitude of the
trough and progression thereafter. Around 40-45% of global
ensemble members favor a deeper trough and a resultant wetter
outcome in addition to a slower progression eastward on Monday,
while the other 55-60% favor a less amplified and quicker
moving trough and thus a drier scenario overall (we`ll still get
some rain). The amplitude of the trough will also heavily
modulate snow levels with the former deeper trough scenario more
favorable for a period of Cascade pass level snowfall late
Sunday into Monday. Beyond this point ensemble models suggest
some sort of ridge feature attempts to build into the region
around Tuesday followed by another trough Wednesday/Thursday.
Although, uncertainty abounds regarding the exact amplitude and
longitudinal placement of these two features helping to drive
lower forecast confidence late in the forecast period. -99
&&
.AVIATION...VFR conditions generally prevail today with minimal
impacts. Cooler temperatures to start this morning will
increase chances for frost formation within the interior valleys
potentially impacting Willamette Valley terminals from KUAO
southward. Freezing temperatures expected around K4S2 in Hood
River. Easterly flow aloft to start the day likely turns more
onshore and gains a northerly component in the afternoon before
switching a light southerly overnight - winds likely remain 5-10
knots or less. However, late in the forecast period there is a
growing chance (30-50% after 06-08z Fri) for fog and/or low
stratus formation along the coast around KONP to KAST. That
said, confidence is low in the exact timing of any degraded
conditions.
KPDX AND APPROACHES...VFR through the next 24 hours. Light winds
remain variable near the surface into the sunrise hours this (Wed)
morning but more predominate east winds aloft around 2000-3000ft
AGL will exist with gusts up to 20-25 kt; these wind speeds may
be impactful for flow into the terminal. Fortunately these
east winds a couple thousand feet above the surface will
rapidly drop-off 14-17z Wed. -99
&&
.MARINE...High pressure remains in place the next couple of days
with winds continuing the decrease into Wednesday morning. Expect
north to northwest winds to persist through Thursday morning while
seas hold around 4-6 ft with a dominate period of 14-15 seconds.
Our next time-period of concern arises on Friday into Saturday
with the onset of a frontal passage. Will see a quick surge of a
northwesterly fresh swell and elevated winds, in addition to a
nearly an 80% chance based on the GEFS WAVE models for seas of 10
ft. The pattern remains rather active through the latter half of
the weekend into early next week as another, albeit stronger,
frontal system progresses into the coast waters. Conditions will
quickly amplify as a result with a 40-60% chance of seas greater
than 15 ft late Sunday into early Monday. -99/27
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory until 9 AM PDT this morning for ORZ104-115>118.
Freeze Warning until 9 AM PDT this morning for ORZ121.
WA...Frost Advisory until 9 AM PDT this morning for WAZ204.
PZ...None.
&&
$$
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NWS PQR Office Area Forecast Discussion