textproduct: Portland

SYNOPSIS

A fairly progressive upper-level weather pattern remains in place as a series of weak frontal systems parade into the Pacific Northwest through the early to middle portion of next week. This'll keep temperatures generally below normal with on/off shower and weak T-storm chances at times, especially at the coast and across our elevated terrain features. However, these conditions won't last in perpetuity as a growing number of models depict a ridge of high pressure building overhead towards the end of next week - welcome news for those craving some warming/drier weather.

LONG TERM...Monday through Thursday

After our one day of near normal and mostly dry June weather on Sunday, the vast majority of deterministic and ensemble models depict broad troughing and below-average 500 mb heights returning to the area for Monday. While models capture the progression of the overall trough feature early next week, there still remains some uncertainty in the exact amplitude and track of this system which would modulate precipitation amounts and placement, especially across the inland valleys. All in all, around ~75-80% of ensemble members keep some sort of troughing and the associated cooler/wetter conditions over the Pacific Northwest through Tuesday and Wednesday. During this period, the NBM projects chances to exceed 1 inch of liquid precipitation in 48 hours between 5 AM Monday to 5 AM Wednesday at around 50-55% across the west slopes of the Cascades and adjacent foothills, and 15-25% in the Coast Range/Willapa Hills. Less than a 15% chance elsewhere. By Thursday there is greater uncertainty as ensemble guidance is half and half on whether or not troughing lingers overhead or exits the area to the east. Either way, any precipitation that falls will likely be light and non-impactful by this point. Then there is growing consensus among ensemble members (~55-65%) for a ridge of high pressure over the eastern Pacific to begin shifting into the Pacific northwest around Friday which would lead to completely dry weather and a noticeable warming trend to end next week. This scenario is also being depicted by AI based model guidance as well adding some additional confidence to an eventual warm-up at the end of the forecast period. -99/10

AVIATION

Expect VFR conditions to generally persist while a trough over the Gulf of Alaska slowly drifts southeast toward the region supporting increasing moisture and cloud cover. Surface observations show cloud decks across the inland sites holding near 4-5kft while the coast has been a mix of MVFR and low-end VFR CIGs. For the latter area, periods of MVFR ceilings continue at times through 18-20Z accompanied by some light showers before CIGS trend back to VFR into the evening. Inland terminals likely maintain low-end VFR CIGs through the period. Southwesterly winds turn more westerly this afternoon but maintain speeds between 5-10 kt at most sites. It's worth quickly noting there'll be a 15% chance for thunderstorms this afternoon mainly for KAST and the Portland Metro Terminals - limited impacts.

KPDX AND APPROACHES...VFR conditions are expected to persist through the forecast period as CIGs hold around 4-5kft locally. There will be a chance for light showers this afternoon (19-00z) but they don't appear to be frequent enough to be a prevail condition should they pass overhead. -99

MARINE

Overall fairly benign conditions are expected through the weekend into next week while several weak frontal systems move through the region. This first of these frontal systems arriving today allow seas to build into the 6-8 ft range at 10-11 seconds with westerly winds generally gusting in the 13-18 knot range, highest across the outer waters. Then a secondary front arrives on Saturday, bringing a shift to northwest winds in the afternoon and evening hours. Winds only increase marginally with only a 15-35% chance for Small Craft Advisory wind gusts - highest probabilities across the outer waters. After a lull during the day on Sunday, winds likely increase yet again on Monday as a comparatively stronger system moves over the waters, bringing south wind gusts up to 20-25 kt and seas approaching 6-8 ft. Conditions then gradually calm into the middle the of the week as a ridge of high pressure attempts to build overhead and northwesterly winds return while seas hold around 5-6ft around 9-10 seconds. -99

PQR WATCHES/WARNINGS/ADVISORIES

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