155 
FXUS66 KPQR 191208
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
407 AM PST Fri Jan 19 2024

.SYNOPSIS...Precipitation has mostly diminished this morning across
SW Washington and NW Oregon. The Columbia River Gorge and Hood River
Valley remain encased in snow and ice. Portions of the Portland metro
area, being closest the Gorge, saw areas of freezing rain and gusty
winds overnight. Meanwhile, spots of ice are possible this morning
farther south in the Willamette Valley as temps approach freezing and
potentially refreeze wet roads. A slow thaw will resume today as
temperatures gradually climb a few degrees above freezing, but the
emphasis is on the word slow. Temps will continue to slowly moderate
through the weekend, but likely too slowly to mitigate freezing rain
concerns for the Columbia Gorge as the next system spreads rain into
the region Saturday afternoon and evening. Temperatures likely return
to seasonal normals by early next week.

.SHORT TERM...Today through Sunday...Latest radar and surface
observations indicate precipitation has mostly come to an end early
this morning across SW Washington and NW Oregon. Cold, dry air has
moved back into the Willamette Valley, more or less eliminating the
threat of freezing drizzle for the Portland metro area. That said,
surfaces remain very icy and slick across much of the metro, and
temperatures will only slowly climb back into the mid to upper 30s
today. This is enough to allow minor progress in thawing the region,
but it will go slow given mostly cloudy skies and temps just a few
degrees above freezing. Meanwhile, the freezing level from the 12z
Salem sounding is 9100 ft, so temperatures in east Portland are the
same if not a couple degrees colder than the present temperature of
34 deg F at Timberline's Magic Mile near 7000 ft elevation.

The Columbia Gorge and the Hood/Wind River Valleys remain encased in
ice as temps have fallen into the upper teens and 20s. MSLP gradients
from KTTD-KDLS remain an impressive -12 mb, and the larger scale
KOTH-KGEG gradients are an impressive -18 mb. This environment
continues to produce easterly wind gusts of 35-45 mph along a
corridor that goes across Gresham, south and east Portland, Capitol
Hill/Tigard, and Chehalem Mountain. This is also the coldest portion
of the PDX metro this morning, as they have seen the most effective
cold advection from the Gorge. This corridor is also the most likely
to have ice impacts lingering into this morning's commute. Meanwhile,
temperatures have quietly fallen into the mid 30s throughout the
remainder of the Willamette Valley, so it is not out of the question
that a couple colder valley locations could dip below freezing and
see wet secondary roads turn icy. However by 2 PM this afternoon, the
00z HREF only shows a 10% chance of temps below 32 deg F anywhere in
the Portland metro area. That said, HREF probs suggest a 30-40%
chance the Willamette Valley will dip back below freezing tonight,
but roads should be drier in general. 

With no fresh batches of arctic air expected west of the Rockies the
next 7-10 days, it appears today will finally be the beginning of the
end of the arctic air intrusion into SW Washington and NW Oregon.
Without a surge of south or west wind, temperatures will have to
moderate in-situ and that will be a slow process. Low-level flow will
remain offshore in general as a series of low pressure systems lift
northward off the coast. The offshore flow will continue to draw
surges of east wind through the Columbia Gorge, but they will be less
and less effective at advecting cold air back into the Willamette
Valley. However it appears unlikely the cold air will retreat enough
to prevent concern for freezing rain, snow, or sleet in the Columbia
River Gorge and Hood River Valley as the next low pressure system
spreads rain back northward across the forecast area Saturday night.
Based on latest soundings, it appears enough cold air may linger to
allow mostly snow for the Hood River Valley and central Gorge, with
freezing rain dominating between between Multnomah Falls and Cascade
Locks. QPF remains uncertain for this system, but latest guidance
seems to support 0.25-0.50" of liquid equivalent, so we will probably
need to issue at least a Winter Wx Advisory for this event. Will
allow the day shift to take a gander at this situation before issuing
any highlights.  Weagle 

.LONG TERM...Monday through Thursday...Deterministic and ensemble
guidance continues to suggest a continued moderation in temperatures
next week as a series of low pressure systems and their occluding
warm fronts continue to chip away at our old arctic air mass. In
fact, latest NBM suggest a 90% chance temperatures will be above
normal in the Willamette Valley by Tuesday. Subtropical moisture will
become increasingly involved with these frontal systems, raising the
concern that some rivers may reach minor flood stage due to rain and
snowmelt. At the moment, no mainstem rivers are expected to reach
flood stage, but some such as the Pudding River will be a close call.
 Weagle 

&&

.AVIATION...Widespread VFR conditions throughout the period, with
occasional drizzle through Friday morning. An exception to these 
conditions is the south Willamette Valley, currently with IFR 
conditions due to an inversion, expected to improve to VFR around 
19-21z Friday.

Gusty easterly winds expected to continue through the Columbia 
River Gorge, occasionally reaching into the east Portland Metro, 
with winds gusting up to 25-30 kts near KPDX and 40-45 kts near 
KTTD. Probabilistic guidance suggests chances of wind gusts above
45 kts to be around 20% for areas near KPDX and around 40% for
areas near KTTD.

PDX AND APPROACHES...Predominately VFR conditions through the TAF
period with high overcast skies. East winds will continue gusting
Friday up to 25-30 kt. Possible light drizzle through early 
Friday morning.
-JH

&&

.MARINE...Trailing cold front approaching the waters Fri. Pressure
gradients not quite as potent, and seem to be favoring more east 
to southeast flow. Small Craft Advisory continues through today 
for all waters, then only outer waters beginning 4pm PST Friday. 
More systems follow over the weekend but will appear to be weaker 
than recently passed systems.

Seas remain around 10-15 ft, with choppy conditions given the 
forecasted winds over the next few days. -JH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...Small Craft Advisory until 4 PM PST this afternoon for Coastal 
     waters from Cape Shoalwater WA to Florence OR out 10 
     NM-Columbia River Bar.

     Gale Warning until 7 AM PST this morning for Coastal waters 
     from Cape Shoalwater WA to Florence OR from 10 to 60 NM.

     Small Craft Advisory from 7 AM this morning to 4 AM PST 
     Saturday for Coastal waters from Cape Shoalwater WA to Florence 
     OR from 10 to 60 NM.

&&

$$

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