138 
FXUS66 KPQR 071015
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
315 AM PDT Thu Aug 7 2025

.SYNOPSIS...Seasonably cool temperatures continue today while
lingering rain showers dwindle this afternoon. A marked pattern
shift will see robust ridging develop offshore, bringing a 
warming trend through early next week. Heat is expected to reach 
hazardous levels Sunday and Monday, before cooling midweek.

&&

.DISCUSSION...Now through Wednesday...An upper-level low 
apparent on satellite imagery over Vancouver Island will 
continue to track eastward along the Canada-US border through 
the end of the week. Its associated cold pool aloft will keep 
temperatures some 5-10 degrees below normal today. A few 
isolated to scattered rain showers remain possible as the low 
makes its nearest approach through this afternoon, but chances 
remain low, only 15-25% this morning and less than 15% this 
afternoon, with the highest likelihood along the coast and the 
western slopes of the Cascades.

Starting on Friday, a major pattern shift will see robust 
upper-level ridging and surface high pressure begin to build 
over the northeast Pacific. As heights aloft rise overhead, 
surface temperatures will steadily warm through early next week.
While unseasonably warm temperatures should be expected along
the coast and in areas of high terrain by Sunday and Monday, 
the heat will reach hazardous levels within inland valleys.
Afternoon high temperatures will very likely exceed 90 degrees
along the Willamette Valley and Columbia Gorge, and in the 
Portland/Vancouver metro: 75-95% chances on Sunday and 85-100% 
on Monday, with higher likelihoods to the south. Slightly lower
chances extend into the Lower Columbia and Cowlitz Valleys, 
60-85% on Sunday and 75-90% on Monday. Some locales may also 
record their first triple digit temperatures of the year:
chances to exceed 100 degrees are 10-25% on Sunday and 25-45% on
Monday in the Portland/Vancouver metro and Columbia Gorge,
40-60% on Sunday and 65-85% on Monday in the Willamette Valley,
and less than 15% on Sunday and 15-35% on Monday in the Lower
Columbia and Cowlitz Valleys. Dewpoints in the low to mid 60s
will additionally make conditions feel noticeably humid each
afternoon. Temperatures will also be very mild on Sunday night,
generally in the low to mid 60s, and similar or a few degrees 
cooler on Monday night.

The combination of hot daytime temperatures and lack of 
sufficient overnight cooling can raise the cumulative heat 
stress and elevate the risk for heat illness, resulting in areas
of Major HeatRisk most prevalent across inland valleys. An 
Extreme Heat Watch has therefore been issued from noon Sunday 
through 8 PM Monday throughout the Portland/Vancouver metro, 
Columbia Gorge and Lower Hood River Valley, Lower Columbia and 
Cowlitz Valleys, and the Willamette Valley. All residents, but 
especially those without access to adequate cooling or hydration,
should make plans for this period of hazardous heat.

By Tuesday and Wednesday, long-range ensemble solutions begin 
to diverge quite a bit. In the mean, the pattern deamplifies 
and shifts west away from the region as upper-level troughing 
develops over the Pacific Northwest, allowing temperatures to 
ease cooler back toward more seasonal values. The amplitude of 
potential troughing remains very uncertain, and some members 
instead maintain upper-level ridging, which could prolong heat 
impacts through more of the workweek. -Picard

&&

.AVIATION...Currently as of 10Z Thursday, stratus lingers
throughout the airspace, continuing to bring moments of
deteriorated conditions at most terminals. Looking ahead, inland 
terminals will stay mostly VFR through the TAF period, with the 
exception being a low chance (20-30% chance) of MVFR conditions 
until 17-18Z Thursday. Breaks in stratus could lead to fog/mist 
development at some locations, as observed at KHIO with IFR/LIFR
conditions. Confidence is low on exactly when and where 
foggy/misty conditions may develop, but any formation of such 
conditions will likely be brief. 

Along the coast, conditions differ from KAST to KONP, with
MVFR/VFR conditions at KAST and LIFR conditions at KONP. 
Guidance suggests deteriorated conditions to persist until 
around 18-19Z Thursday, with a 40-60% chance for MVFR CIGs at 
KAST, and a 40-60% chance for LIFR conditions at KONP. 
Conditions should improve to VFR thereafter, but there is a 
20-40% chance that coastal terminals will see a return of MVFR 
conditions after 00Z Friday.

Otherwise, expect northwesterly winds through the period. Inland 
will see winds generally under 10 kt and coastal terminals will 
see winds around 10-14 kt with gusts up to 20 kt during the 
afternoon.

PDX AND APPROACHES...Mostly VFR through the period, with a low 
chance (20-30%) of CIGs lowering to MVFR before 18Z Thursday. 
Thereafter, VFR conditions and northwesterly winds under 10 kt.
												~Hall

&&

.MARINE...Seas will stay around 6 ft at 10 seconds through at 
least Friday as a result of a passing front yesterday. Winds
will remain elevated around 10 to 15 kt with gusts up to 20 
kt, mostly in the southern waters today into Friday afternoon. 
Friday night and through the weekend, a ridge will build with a 
northerly wind reversal and conditions will take on a typical 
summer pattern. As temperatures warm considerably through the 
weekend, expects winds to ramp up throughout all the waters, 
with combined seas being dominated by wind wave. Moderate to 
high probability of Small Craft Advisory conditions in the 
southern waters starting Friday afternoon, then a high 
probability of Small Craft conditions in all waters by Saturday 
afternoon. ~Hall/Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...Extreme Heat Watch from Sunday afternoon through Monday 
     evening for ORZ108>118-120>122.
WA...Extreme Heat Watch from Sunday afternoon through Monday 
     evening for WAZ204>207-209-210.
PZ...None.

&&

$$

www.weather.gov/portland

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