textproduct: Portland

SYNOPSIS

Areas of fog and low clouds Sunday morning will give way to sunny and warm conditions in the afternoon. Temperatures trend cooler Monday through Friday as upper level troughing develops over the Gulf of Alaska. Chances for rain have increased Thursday night into Friday to 40-60% as troughing attempts pushing into western Washington and western Oregon.

LONG TERM...Wednesday night through Saturday night

The forecast remains dry and mild Wednesday night through Thursday afternoon as dry southwest flow aloft persists. However, chances for rain Thursday night into Friday have increased due to an uptick in the number of ensemble members showing at least some QPF over the area with an approaching upper level trough. Chances for precipitation falling within a 24-hour period ending at 5 PM Friday have increased to 40-60%. Exact timing and rain amounts remain uncertain, and around 30-40% of ensemble guidance continues to show no rain at all over the Willamette Valley. Therefore, confidence is only moderate and it is too soon to tell if Friday will for sure be a wet day or not. Regardless of the outcome, chances for rain decrease significantly Friday night into Saturday to less than 15%, suggesting multiple days with rain are unlikely.

It is also worth mentioning that chances for frost increase over the Upper Hood River Valley Friday night and Saturday night when there is a 30-50% chance for overnight lows around 37 degrees or colder, mainly in the Parkdale area. Probabilities are around 10% in Odell and 1-5% in Hood River. Those with sensitive outdoor vegetation in this area should monitor the forecast over the coming days. -23

AVIATION...Through 06Z Monday

Late this evening satellite and surface observations show generally VFR conditions across the region outside of some low clouds/fog along portions of the Oregon coast, Coast Range, and southern Willamette Valley (including KEUG). This low cloud/fog layer should continue expanding up the coastline as the night progresses with widespread degraded CIGs/VIS by 12-14Z Sunday. Expect gradual improvement to MVFR at coastal terminals by the midday hours with decent chances for at least some clearing during the mid to late afternoon.

Inland terminals have increasing chances for a period of fog and low stratus between 13-18Z Sunday, with KEUG already observing dense fog with LIFR flight conditions as of 09Z Sunday. Outside of the south Willamette Valley, KSLE, KUAO, and KTTD are other sites which could see some degraded conditions (40-50% chance) between 13-18Z but confidence in the exact placement of the fog remains too low to add it as a prevailing condition at this time. High confidence (90%) in widespread VFR conditions at inland sites Sunday afternoon and evening. Winds stay fairly light overall outside of the coast where increasing northwesterly winds at sites like KONP likely gust up around 15-25 knots Sunday afternoon.

KPDX AND APPROACHES...VFR conditions prevail through late tonight. However, there is a chance of fog and/or low stratus between 13-18Z Sunday (10-15% chance for surface visibilities of 1 SM or lower during that time, and a 40-50% chance for ceilings of 1000 ft or lower). The latest guidance continues showing the highest probabilities for fog and low stratus to the east and south of the KPDX terminal. Confidence in fog and/or low stratus development directly over the terminal remains too low to reflect in the TAF. Otherwise, high confidence in VFR conditions 18-19z onward with fairly light winds (less than 10 knots) through the TAF period. -99/23

MARINE

High pressure over the waters will maintain northerly winds through this weekend. Northerly winds peak in strength Sunday afternoon and evening when there is a 50-90% chance for maximum wind gusts of 21 kt or slightly stronger across the waters, with the highest chances across the inner waters out to 10 NM offshore. Given wind gusts of this magnitude are not expected to be frequent or widespread, Small Craft Advisories are not anticipated at this time. Significant wave heights will remain around 3 to 5 ft through the weekend, mainly driven by a persistent northwesterly swell with a dominant wave period near 7 seconds.

Northerly winds are expected to linger Monday through Wednesday, with wind gusts generally staying under 20 kt. A long period west-northwesterly swell is set to arrive either Monday afternoon or evening, pushing seas up by one to two feet. However, seas will not be particularly steep as the dominant wave period with this swell will be around 11-13 seconds. -23

PQR WATCHES/WARNINGS/ADVISORIES

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