textproduct: Portland

SYNOPSIS

Generally onshore flow with weak ridging at the mid levels. Will continue to see near normal temperatures over the weekend. Temperatures warm above normal next week with dry weather.

UPDATE...Saturday morning

Areas of drizzle and light rain are being observed over portions of the Portland/Vancouver metro and south WA/north OR Cascade foothills this morning. Updated the forecast to increase the probability of precipitation in these areas through the morning hours and ensure the forecast mentions areas of drizzle. No impacts are expected with this light and spotty precipitation. -23

LONG TERM...Monday through Friday

Confidence remains high next week starting out with a warm-up as ridging over the Central Plains builds and heights aloft increase over the region. Temperatures expected to jump into the mid to upper 80s (localized 90s) on Monday and upper 80s to low 90s on Tuesday for the interior lowlands. Coastal areas will see temps jump into the mid 60s to low 70s. Tuesday continues to look like the warmest day next week and has the highest and most widespread probabilities for 90 degrees. Chances are 30-50% along the I-5 corridor and around the Portland metro with lower chances of 15-30% within the Cascade and Coast Range Foothills. There is also a low (10-20%) chance for isolated locations to reach 95, mainly around the Central Willamette Valley and Tualatin Valley. Moderate HeatRisk for Tuesday and Wednesday has increased across the Portland/Vancouver Metro, Willamette Valley, and within the Columbia River Gorge. Chances for major HeatRisk remain less than 10%.

However, temperatures for Wednesday show a nearly 20 degree spread between the 10th-90th percentiles in some areas, ranging from the mid 70 to the mid 90s. This is due to uncertainty regarding a short wave trough that is expected to drop southward from the Gulf of Alaska. Timing and location of this feature vary drastically among the models and ensembles, leading to a large range of possible temperatures. Current forecast temperatures for Wednesday would yield a moderate HeatRisk but there remains around 5-10% for most locations. Confidence in the trough moving into the PacNW on Thursday increases with a a dip in high temperatures. For Friday and beyond, cluster analysis depicts the trough progressing northeast toward south-central Canada while the ridge rebuilds into the West Coast. This would lead to another warm-up in the area but given the long lead time, the details are unclear at this time. -19

AVIATION

Satellite shows widespread stratus over the area below 1000 ft with most areas under MVFR conditions. Winds will generally be onshore today then transition to the north this afternoon as skies clear. Due to a lack of mixing, it will take a few more hours to at least lift to VFR, and there is around a 30% chance that we will not see clear skies inland. Along the coast, tracking the stratus is a bit more difficult as it continues to bounce between MVFR and IFR.

Overnight, models suggest significantly less cloud cover and this is due to the disturbance that ushered in higher moisture levels being well to the north and inland. Therefore, will see VFR conditions. The uncertainty remains along the coast where there is around a 40-60% chance of MVFR CIGs returning.

KPDX AND APPROACHES...MVFR under a 2000 ft cloud deck. High uncertainty in regards to when exactly it will burn off, but models suggest it should start lifting here in the next few hours to VFR. Northerly winds will ramp up in the afternoon with diurnal heating but are not expected to exceed gusts of 20 kt. -27

MARINE

High pressure rebuilds over the coastal waters through the weekend, returning northerly winds later Saturday and increasing pressure gradients on Sunday. Chances for gusts up to 25 kt return Sunday afternoon, mainly across the central and southern waters out to 30-40 NM. Seas are expected to remain around 4 to 6 ft as relatively benign conditions persist through the weekend and into the start of next week. -19/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.