textproduct: Portland

SYNOPSIS

A series of frontal systems continue progress through Pacific Northwest into next week facilitating cooler than normal temperatures and periodic rounds of showers through Wednesday, June 10. There is also a 15-35% chance of short- lived thunderstorms this afternoon and a 10-20% chance Tuesday afternoon. Upper level ridging will bring a warming and drying trend Thursday onward (June 11-15), with a growing potential for heat related concerns June 12-15.

LONG TERM...Tuesday through Friday

The long term forecast starts out with cooler than average temperatures and occasional showers followed by growing confidence in a substantial warming and drying trend late in the week. Despite the model timing differences discussed above with the arrival of a frontal system late Sunday into Monday, ensemble guidance is in good agreement the area will be solidly within a post-frontal shower environment Tuesday through Wednesday under a broad upper level trough parked overhead. Expect the continuation of cooler than normal temperatures and occasional rain with high temperatures most likely in the 60s. As the axis of the larger trough feature passes overhead around Tuesday, temperatures aloft bottom out with the NBM suggesting a 10-20% chance of thunderstorms during the Tuesday afternoon time period. The latest NBM 48-hr probabilities for rain amounts over 0.50" peak between 5 PM Sunday and 5 PM Tuesday, showing anywhere from a 50-75% chance for most locations in southwest WA and northwest OR, except an 80-90% chance in the Cascades and in the coast range/Willapa hills.

Our focus then shifts to a noticeable warming and drying trend from Thursday onward. Cluster analysis for June 11-15 for 500 mb heights generally suggest upper level ridging will gradually develop over the region. This will bring a prolonged stretch of dry weather, with temperatures likely warming each day. While confidence is high temperatures will warm significantly compared to early in the week, confidence is low regarding exactly how warm temperatures will get. The NBM ensemble spread reflects this uncertainty well, for example the NBM 10th-90th percentile for high temperatures Saturday June 13 through Monday June 15, range from low 80s to near 100 degrees for the inland valleys and upper 60s to upper 80s for coastal locations. But, compared to prior NBM runs yesterday this spread has shrunk by 2-5 degrees, albeit in the "warmer" direction. Probabilities for major HeatRisk begin to hit 10-25% across in the inland valleys starting Saturday June 13 before increasing to 20-45% by Monday June 15th. Those who are sensitive to heat and/or have outdoor plans should definitely keep an eye on the forecast over the next week. -99/23

AVIATION

Expect mainly VFR conditions across the region today although with some caveats. Early this morning radar imagery shows ample shower activity beginning to push inland with CIGS generally holding around 4-6kft as of 11z. Headed through the day some of these showers could be heavier, causing brief periods of MVFR cigs or vis. Additionally, there's a 20-35% chance of thunderstorms near and north of KSLE and KTMK and 10-20% chance elsewhere west of the Cascades between roughly 16-18z through 00z Sun. Best chances will be in the 18-22z time period with shower and thunderstorm chances diminishing after. Any stronger activity could produce heavy rain that could cause brief periods of MVFR/IFR conditions, small hail, gusty and erratic winds, and lightning. Confidence is high lingering showers taper off around inland sites by 03-05z Sun with dry conditions afterward. Winds may be a bit breezy at times with a southerly component this morning in the Willamette Valley before turning more westerly late in the afternoon.

KPDX AND APPROACHES...VFR conditions are favored through the TAF period. Showers likely continue at times through the day with a 30-35% chance of thunderstorms between 18-22z Sat. Any stronger shower or thunderstorms could produce heavy rain that could cause brief periods of MVFR conditions, small hail, gusty/erratic winds, and lightning. Shower and thunderstorm chances diminish around 00-03z Sun. Winds remain out of the southwest this morning, increasing and shifting westerly after 18-22z. -99

MARINE

A fairly progressive weather pattern continues into next week as a series of frontal systems bring increasing winds and building seas. Seas this morning currently hold in the 5-8 ft range at ~10 seconds . Another system moves through today bringing a slight increase in northwesterly winds. However, wind gusts only have around a 10-35% chance for Small Craft Advisory wind gusts with the highest probabilities in this range across the outer waters. Minimal confidence in Small Craft conditions. After a lull during the day on Sunday as high pressure briefly returns, winds increase yet again on Monday as a comparatively stronger system moves over the waters bringing south wind gusts up to 21-25 kt and seas approaching 5-8 ft. Conditions then gradually calm into the middle the of the week as a ridge of high pressure attempts to rebuild overhead and northwesterly winds return while seas hold around 5-7ft around 9-11 seconds. Towards the end of next week, those northwesterly winds likely (60-80%) push above 21 knots across the outer waters south of Cape Falcon and will be a feature to watch in the long-term. -99

PQR WATCHES/WARNINGS/ADVISORIES

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