textproduct: Portland

SYNOPSIS

Temperatures will gradually cool each day Thursday through the weekend as onshore flow strengthens ahead of a low pressure system set to bring widespread rain to the area on Saturday. Showers dissipate on Sunday, with dry and mild conditions expected early next week.

LONG TERM...Monday through Wednesday

The long term forecast is highlighted by dry conditions and the continuation of below average temperatures, albeit a bit warmer than what is expected on Saturday. The vast majority (>90%) of ensemble guidance suggests the upper level low over the area will continue to push eastward and move towards the Northern Plains late Sunday into early next week. A weaker secondary trough on the backside of this low looks to remain over Oregon and Washington through at least Tuesday. On Monday, NBM temperature spread ranges from the mid 60s to upper 70s for the interior lowlands, with low 70s being the most likely outcome. Spread increases a bit on Tuesday, as highs could range anywhere from the mid 60s to the mid 80s. By Wednesday, uncertainty increases in the overall pattern as around 50-60% of ensemble members suggest the low pressure weakening over the PacNW with high pressure over the southern US trying to push northwest into the area, allowing for warming temperatures. The other 40-50% of guidance suggest some level of troughing remaining over the PacNW, which would keep temperatures on the cooler side. The total temperature spread indicates highs could range anywhere from low 70s to upper 80s. Overall, there are no signs of any high impact weather on the horizon. -03/23

AVIATION...Through 12z Friday

At 11z Thu, widespread VFR conditions at inland terminals through the period while low cloud coverage is producing MVFR/IFR vis/cigs at most coastal terminals. KAST is forecast to fall to MVFR/IFR conditions by 12-13z Thu. Low clouds over the coast will then tend to decrease in coverage through Thursday afternoon, though areas from KTMK northward are more likely to maintain MVFR cigs through much of the day. Increasing high cloud coverage is expected from north to south through the period. VFR conditions expected through the majority of the period for inland terminals, though chances for MVFR/IFR cigs increase around 12z Thu for terminals around and north of KUAO. Light north to northwest winds will build to 5-10 kt inland and 10-15 kt with gusts as high as 20-25 kt along the coast by Thursday afternoon, becoming light after 04-06z Fri.

KPDX AND APPROACHES...VFR conditions expected throughout the period with increasing coverage of high clouds today. Chances for MVFR cigs increase near the end of the period around 12z Fri. Northwest winds of less than 5 kt will rise to near 10 kt by after 21-23z Thu, decreasing by 06z Fri. -03

MARINE

High pressure offshore will maintain predominately northerly winds across all waters through at least Friday. Breezy north winds with gusts up to 25 kt at times are possible through this evening. A Small Craft Advisory remains in effect for all zones excluding the Columbia River Bar from 5 AM to 8 PM PDT today. Seas 6 to 8 ft through Friday with period of 9 to 11 seconds. Another weaker system is expected to approach the coastal waters from the north late Friday into Saturday. This will result in a southerly wind shift along with seas subsiding towards 4 to 6 ft and gusts below 20 kts. -03

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 8 PM PDT this evening for PZZ251>253- 271>273.