Mt. Bachelor

000
FXUS66 KPQR 011112
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
412 AM PDT Sat Aug 1 2026

.SYNOPSIS...A weak cold front moving through the region today 
ushers in cooler temperatures, chances for light rain, and 
locally gusty west winds. Wind related impacts are highest in 
the central Columbia Gorge. The below normal temperatures won't
last long however. Warmer and drier conditions are expected by 
the middle of next week with a period of northerly to 
northeasterly winds Mon/Tue as well. Elevated temperatures peak
on Tuesday before gradually moderating towards seasonable norms
the remainder of the week.

&&

.SHORT TERM...Now through Sunday Night...A frontal boundary is
beginning to push into the Pacific northwest this morning
helping to rapidly spread stratus from the coast into the I-5 
corridor. This feature and the added westerly flow it brings
will help facilitate below normal temperatures and even some 
chances for light rain/mist, mainly this morning along the coast
and midday inland areas. This is a fairly high probability of 
precipitation but low accumulation scenario with around an 
60-80% chance along the coast and coats range north of 
Tillamook, but less than a 20% chance inland. Areas within 
southwest Washington will see higher probabilities relative to 
the rest of the CWA as the bulk of the system appears to stay to
our north.

Another facet of the weather today worth highlighting is the 
westerly wind potential, albeit fairly localized in scope. 
While it is not expected to be widespread, we will see stronger
winds as the front passes as the cross-Cascade pressure 
gradient tightens. These winds will mostly be observed through 
east-west aligned terrain like the Columbia River Gorge, Upper 
Hood River Valley, and the gaps of the Coast Range. The Cascades
too will see these gusty west winds. Not much changes on Sunday
as a residual short wave trough rotating around the large 
upper-level low feature to our north swings into the region 
maintaining similar conditions minus the precipitation chances. 
High temperatures hold in the mid 70s across the inland valleys 
with 60s along the coast. -99/27

.LONG TERM...Monday through Friday Night...Early next week the
proverbial weather pendulum begins to rapidly swing the other 
direction. On Monday confidence continues to grow for a large 
scale ridging pattern building just off the coast of the 
Pacific Northwest. While there continue to be a small handful
of ensemble models that favor a trough or zonal flow, nearly all
of the 500 mb clusters show at least some form of a ridge 
forming. This ridge will lead to warming temperatures and lower 
relative humidity on both Monday and Tuesday - lowest on the 
latter day.

The one weather feature we continue to closely watch is the 
near surface thermal trough early next week which this time of
year helps to dictate our fire weather concerns. Typically it 
builds overhead from southwestern Oregon (dry northerly winds 
when this occurs) then it modulates diurnally back-and-forth 
from the coast/coast range (AM) towards I-5 and/or the Cascades
(PM) helping to influence the magnitude and placement of offshore
flow. Currently it forms along the coast then moves inland 
through the afternoon on Monday as it builds northward from 
southwestern Oregon. This progression would cause northerly 
winds to amplify in the lower elevations, and increase easterly 
winds at 850 mb (around 5000 ft). These easterly winds will 
bring in drier air from east of the Cascades and the downsloping
action will increase drying in the lower elevations and in the 
Willamette Valley. Combine this with daytime heating and a deep 
layer of dry air, we will see relative humidity drop within the 
interior lowlands on Monday. Therefore, could see gusts up to 
25 mph within the Willamette Valley, Clark County lowlands, and 
along the coast. In the southern Willamette Valley around Eugene
there is a higher probability of seeing these wind speeds than 
in the north. This is likely due to more of a channeling/fetch 
component and a tighter north-south pressure gradient. These dry
and windy conditions may lead to elevated fire weather concerns
as they overlap mid/late afternoon into the early evening on 
Monday. That said, confidence is not yet high enough to pull 
the trigger on any fire-weather related watches/warnings at this
time - we'll see how the model guidance continues to evolve the
next few forecast cycles. 

Temperatures the peak on on Tuesday with most areas seeing at 
least a 75-80% chance of meeting of exceeding 90 degrees F. 
Moderate HeatRisk remains for much of the Willamette Valley and 
the lower I-5 corridor. Mid to late week it'll all come down to 
the exact pattern amplification and longitudinal placement of 
the ridge over the far eastern Pacific. In the warmer solutions 
(favored by GFS and more GEFS members), stronger inland ridging 
and the resulting coastal thermal trough may be sufficient to 
drive decent offshore flow and potential gusty north to 
northeast winds along the coast and within the Willamette 
Valley. The EPS keeps this ridge flattened comparatively but 
still shows a signal for north to northeast winds. The majority of
of deterministic and ensemble guidance depict a return to W-NW 
winds by late Thursday and Friday signaling moderating 
conditions. -99/27

&&

.AVIATION...Through 12Z Sunday...Widespread MVFR conditions are 
in place early this morning as marine stratus ahead of a weak 
frontal boundary fills in across the Willamette Valley and 
southwest Washington. While inland CIGs may fluctuate between low 
end VFR and MVFR through much of the morning, beyond 18-20z 
conditions should gradually trend more VFR as the cold front moves
through - similar trend at coastal sites. That said, as the 
aforementioned frontal feature moves overhead can't rule out some
light rain, especially along the coast this morning. Expect south
to southwesterly winds this morning to shift more westerly this 
afternoon behind the front. 

KPDX AND APPROACHES...MVFR conditions are in place the start the
TAF period with CIGs likely fluctuating between 2.5-3.5kft. VFR
conditions are expected to prevail by 19-20z as CIGs jump towards
3.5-4.5kft but confidence is only moderate regarding the timing.
Southerly winds turn more west-northwesterly around this 18-21z 
time period as well. -99

&&

.MARINE...A frontal systems will traverse the waters this morning
slightly increasing winds and bringing decent chances for light 
rain/mist. At least any chances for precipitation decrease in the
afternoon hours. Westerly flow behind the frost will then shifts 
northerly by Sunday as surface high pressure builds offshore. 
Chances for maximum wind gusts of at least 21 kt are around 85-95%
from Sunday afternoon/evening through at least Tuesday night with
the highest relative probabilities across the outer waters. Given
this high confidence in Small Craft conditions, a Small Craft
advisory was issued for the inner and outer waters, including the
Columbia River Bar, starting Monday mid/late afternoon. Once we
get in to the middle of the week these Small Craft concerns
primarily shift to the outer waters but likely persist through the
end of the week. Wave heights through the forecast period remain 
around 5-8 ft at 7-9 seconds. -99

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 5 PM Sunday to 2 AM PDT Monday for 
     PZZ210.
     Small Craft Advisory from 5 PM Sunday to 5 AM PDT Tuesday for 
     PZZ251-252-271-272.
     Small Craft Advisory from 2 PM Sunday to 5 AM PDT Tuesday for 
     PZZ253-273.
&&

$$

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