textproduct: Portland

SYNOPSIS

A gradual warming trend continues through the end of the work week as weak ridging holds over the Pacific Northwest. Most areas west of the Cascade foothills remain dry through Thursday, while shower and thunderstorm chances increase over the central Oregon Cascades Thursday afternoon before expanding northward on Friday. A few storms may drift west toward the Willamette Valley and Coast Range late Friday. A cooler, more unsettled pattern returns this weekend with widespread showers.

LONG TERM...Saturday through Tuesday night

Confidence is high that a broader trough will settle over the Pacific Northwest this weekend, bringing cooler temperatures and widespread showers. Ensemble cluster analysis indicates some uncertainty in the southern extent of the trough axis, with roughly 75% of solutions digging the trough into southern Oregon and about 25% keeping the core farther north over Washington. Regardless of the exact placement, precipitation probabilities increase markedly.

PoPs rise to 60-90% Saturday and Sunday, highest across the Cascades and foothills. Probabilistic QPF guidance suggests a 50-80% chance of 0.25+ inches of rainfall between 5 AM Saturday and 5 AM Sunday for most locations, except 30-50% along the south Washington and north Oregon coast. For the 24-hour period ending 5 AM Monday, probabilities of 0.25+ inches decrease to 25-50% west of the Cascades and remain higher, around 50-75%, in the Cascades where orographic enhancement is favored. While confidence is high that measurable rain will occur over the weekend, total amounts will vary given the showery, convective nature of the precipitation.

Temperatures trend notably cooler under the trough. Inland highs moderate to the mid 50s to low 60s Saturday, then cool further into the low to mid 50s Sunday. Shower activity diminishes Monday, with precipitation chances dropping below 10% as heights gradually rise. May see a return of precipitation on Tuesday. Overall, the weekend and into early next week will feel substantially cooler compared to the mild conditions observed today and forecasted through Friday. ~12

AVIATION

Westerly flow aloft continues with widespread VFR conditions under mostly clear skies. High clouds will infiltrate into the airspace through the overnight hours, but no impacts are expected. Overall, predominately VFR conditions through the TAF period. The only exception to this, is that some "bog fog" could develop along the coast resulting in IFR/LIFR conditions at KAST and KONP. However, the probability of that occurring is 5-10% and would start around 14Z-16Z Thursday if it were to occur. Any lowered flight conditions that do develop should improve to VFR by 18Z-20Z Thursday. Winds generally out of the north/northwest around 3-6 kt.

KPDX AND APPROACHES...VFR flight conditions through the at least the remainder TAF period with FEW/SCT high clouds. North/northwesterly winds 3-6 kt. /42

MARINE

Seas of 5 to 7 ft at 10 to 12 seconds, with little in the way of active weather expected through the remainder of the week and into the weekend. It should be noted that a series of lows, passing south of the OR/CA border will bring rain showers to all waters starting on Friday and continuing through the weekend. The second low on the weekend will also result in a 15-20% chance for gusts up to 25 kt across all waters Saturday and Sunday. We will continue to monitor the situation as the path of the lows will dictate if Small Craft Conditions would have a higher probability of occurrence. /42

PQR WATCHES/WARNINGS/ADVISORIES

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