139
FXUS66 KPQR 101038
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
238 AM PST Fri Jan 10 2025

.SYNOPSIS...A frontal system will push through the region today,
bringing light rain and light mountain snow. Expect lingering
scattered snow showers over the mountains this weekend while
most locations remain dry. Seasonable, dry weather prevails
Monday through Wednesday as high pressure re-builds. Overnight
temperatures will likely be colder early next week, leading to
potentially frosty mornings.

&&

.DISCUSSION...Now through Thursday night...Satellite imagery as
of 230 AM PST reveals the next frontal system approaching the
Pacific Northwest, moving east of 130W as an upper level
shortwave trough drops over the region. This system will bring
light rain to the area Friday morning, followed by showers as
the cold front quickly sweeps across the area. 24 hour rain
amounts ending 4 AM Saturday are forecast around 0.15-0.40
inches for interior valleys and 0.50-0.75 inches along the
coast, west slopes of the Coast Range, and Cascade foothills.
With snow levels expected to remain above 5000 feet through
Friday morning, snowfall at pass level will likely be associated
with the post-frontal showers. 24 hour snowfall accumulations
are forecast around 2-4 inches through the Cascade passes.
Expect higher amounts (5-10 inches) above 5500 feet.

Will also need to monitor temperatures Friday morning across
the Upper Hood River Valley, where some light freezing rain will
be possible before westerly winds bring warmer temps Friday
afternoon. As of 230 AM PST, temps still remain above freezing
from Odell to the Columbia River, however, Parkdale is already
around 30-31 degrees. If precipitation arrives while surface
temps are still freezing, then freezing rain would be a
potential impact for that area.

More seasonal weather expected Saturday and Sunday. Weak upper
level disturbances embedded within northwest flow aloft will
maintain scattered showers mainly across the higher terrain
through the weekend. Snow levels are forecast to remain lower
around 2000-3000 feet through the weekend, with minimal impacts
expected. 48 hour weekend snow totals are around a trace to 3
inches through the passes.

High pressure returns early next week with another period of dry
weather and mostly clear skies as offshore winds re-develop.
With cooler air in place, colder overnight temperatures become
more likely next week with lows dropping into the upper 20s to
lower 30s. Radiational cooling will be most effective in areas
of calm winds and clear skies, which will support frost
development. Most ensembles maintain dry weather through
Thursday, with around a 30-50% chance of a weak front
approaching late next week.        -Alviz/DH

&&

.AVIATION...VFR prevails across most of the area as of 10z Fri
ahead of a front approaching the north OR Coast, with MVFR cigs
being reported at KAST. Locally dense fog which had been in place
earlier in the evening in the south Willamette Valley has quickly
been scoured out as southerly flow increases and mid/high level
clouds thicken ahead of the front. Rain pushing into the coastal
terminals around 12z will spread to the inland sites by around
15z, bringing mainly MVFR conditions through late morning. The
front moves into the Cascades by 18-20z Fri, leaving showery
conditions and a mix of VFR and MVFR across the area through much
of the rest of the TAF period. Conditions may trend more solidly
MVFR after 06z Sat as stratus backbuilds into the interior valleys
from the Cascades.

PDX AND APPROACHES...VFR early this morning ahead of an
approaching front moving onto the coast as of 12z Fri. Expect
rain to move into the terminal around 15z accompanied by MVFR
cigs. Steady rain exits the terminal 18-19z Fri, with conditions
trending back towards VFR with scattered rain showers in the wake
of the front. Wind turn westerly 18-20z as flow transitions to
onshore behind the front. Guidance depicts a 50-60 percent chance
for MVFR cigs after 06z Sat. /CB

&&

.MARINE...A surface cold front is crossing the coastal waters
early this morning accompanied by 10-15 kt south-southwest winds
and seas around 4-6 ft per latest available buoy observations.
Winds will shift northwesterly this morning in the wake of the
front and will become quite gusty at times through early Saturday
as cold air advection allows stronger winds aloft to mix down to
the surface at times, with widespread gusts of 25-30 kt expected
across the waters through tonight. Blustery conditions will be
compounded by a building westerly swell entering the waters later
this morning, which will push seas into the 11-14 ft range by this
afternoon. Small Craft Advisories have been extended through
Saturday afternoon, but it is possible that seas could linger at
or above 10 feet into Sunday even as gusty winds diminish. Expect
relatively benign conditions for the first half of next week as
high pressure rebuilds over the region and promotes lighter
offshore breezes across the waters. Seas will remain dominated by
mid period westerly swell, generally in the 7-9 ft range. /CB

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory from 10 AM this morning to 10 AM PST
     Saturday for PZZ210.

     Small Craft Advisory until 3 PM PST Saturday for PZZ251>253-
     271>273.
&&

$$

www.weather.gov/portland

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