textproduct: Portland

SYNOPSIS

Warmer than normal and dry conditions expected to continue through the middle of next week. Confidence is increasing that hot temperatures peaking Monday and Tuesday will support Moderate to Major HeatRisk, however there remains uncertainty in the temperature forecast at this time.

DISCUSSION...Tonight through Wednesday

There has been very little change in the forecast since the last package. An upper- level ridge axis currently centered over the northeastern Pacific will shift eastward and inland through the end of the week, bringing warmer temperatures with a typical summertime northerly wind pattern. Temperatures peak on Friday for inland locations as troughing aloft supports a return to stronger onshore flow Friday into Saturday. As daytime highs reach to near 70 degrees on the coast and 80s to near 90 degrees on Friday, this will result in Minor HeatRisk for most areas within our CWA and locally Moderate HeatRisk from Salem, OR northward towards Kelso/Longview, WA and across the greater Portland/Vancouver Metro area. Aforementioned troughing and onshore flow will yield cooler temperatures near 60 degrees for Friday along the coast, with persistent onshore flow will help to cool inland locations down, which will bring daytime highs into the upper 70s to low 80s on Saturday.

Ensemble guidance remains in good agreement that renewed ridging will develop from Sunday into early next week, raising the chances for another period of hot temperatures for the start of next week with the warmest days looking to be Monday and Tuesday. Uncertainty in the position and amplitude of the ridge axis remain, leading to uncertainty in the temperature forecast, but given the model consensus, there is 85-95% probability for daytime highs to exceed 90 degrees F throughout inland valleys Monday and Tuesday. The chances to exceed 95 degrees similarly peak at generally around 40-85% chance Monday and Tuesday, while the chances to reach 100 degrees reach 25-40% only from Salem, OR north to Vancouver, WA on Monday and 20-40% from Corvallis, OR north to Kelso/Longview, WA.

These daytime temperatures combined with overnight lows in the upper 50s to low 60s support widespread Moderate HeatRisk inland both Monday and Tuesday, with the coverage of Major HeatRisk largely dependent on the occurrence of overnight low temperatures falling into the mid 60s. Looking beyond, towards the middle of next week. Long-range guidance is favoring a cooling trend beginning Tuesday night and continuing into later next week, but there's still a 30-50% chance for temperatures above 90 degrees to persist on Wednesday. It should also be noted that there are no strong signals for any precipitation through the entire forecast. /42-03

AVIATION

Expect dry conditions throughout the airspace over the next 24 hours. While inland terminals will continue to see VFR conditions through the TAF period, coastal terminals will likely see a mix MVFR/IFR/LIFR marine stratus development along the coast beginning around 10-12Z Fri. From 10Z onward to at least 18Z Fri, there is a 40-60% chance of MVFR, 30-40% chance of IFR, and a 10-20% chance of LIFR conditions for coastal terminals.

Expect another breezy day with northerly to northwesterly winds, with wind gusts up to 25 kt along the coast until 04Z Fri. Wind through the Willamette Valley will not be as gusty (therefore have kept wind gusts out of the TAFs for most terminals), however infrequent gusts up to 20 kt are possible between 20Z Thu and 02Z Fri.

KPDX AND APPROACHES...VFR and dry conditions through the next 24 hours. Northwest winds around 8-12 kt with gusts up to 18-20 kt expected between 20Z Thu and 02Z Fri. ~12

MARINE

High pressure offshore will maintain a summertime pattern through this week. Diurnally driven northerlies are expected to peak each afternoon and evening through at least Friday. Winds are expected to peak each afternoon and evening with gusts to 25-30 kts, decreasing a bit in the late overnight to morning hours. Winds will likely ease over the weekend as high pressure weakens and low pressure moves into northwest WA, turning winds more northwesterly on Saturday. Seas around 7 to 9 ft at 8-9 seconds are expected to build to 9 to 11 ft at 9-10 seconds later Thursday into early Saturday as a fresh northwesterly swell persists across the coastal waters. Seas are expected to subside later Saturday into Sunday. /DH/03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory until 5 AM PDT Friday for PZZ251>253. Small Craft Advisory until 5 AM PDT Saturday for PZZ271>273.