textproduct: Portland

SYNOPSIS

Generally onshore flow with weak ridging at the mid levels. Will continue to see near to slightly above normal temperatures over the weekend, with the potential to warm further early next week. Overall, will see minimal change in the forecast from day to day though.

LONG TERM...Monday through Friday

High pressure at the surface really begins to take hold over the northeast Pacific on Monday which will trend conditions towards warmer and drier conditions. 850 mb temperatures continue to rise through at least Wednesday with the peak being Tuesday and Wednesday. around 15-17 deg C. There is an extensive ridge aloft building inland, with around half of the ensembles suggesting weak trough forming near the coast line. This pattern orientation will have a significant impact on just how hot conditions will be. The spread of possibilities is quite wide with around a 8-10 deg F spread between the 10th-90th percentile along the coast and around a 12 deg F spread in the interior valleys. Lets dive into a few of the locations for an example of the level of uncertainty we are dealing with. I will note that models have fluctuated quite a bit over the last 24-hours.

For Tuesday, Portland is showing a 10% chance of high temperatures of 85 deg F, and equal chances of them being 98 deg F. Elsewhere in the Willamette Valley shows similar ranges. The Upper Hood River Valley ranges from around 85-95 deg F, and Longview 82-95 deg F. Moving into Wednesday though the uncertainty grows significantly. In fact, the range from the coolest high temperature to the warmest (10th to 90th percentile) is around 20 deg for the Willamette Valley and 10 deg for the coast. In fact there is around a 10% chance of highs of 70-75 deg F for the coast, and 100-105 deg F for the inland valleys including some areas like Estacada and Stayton. With this being said though, there are equal chances of temperatures in the lower 80s. Therefore, not biting on any specific outcome in particular and have moreso stuck with the median within the forecast to account for some of the outliers. A similar trend occurs thus far on Thursday.

If these temperature forecasts remain, we are looking at the potential for Moderate HeatRisk with a 20% chance of Major HeatRisk for urban areas on Wednesday. -27

AVIATION

A weak upper level trough digs south towards airspace, turning the flow aloft more southwesterly. Expect VFR conditions to continue through the TAF period for inland terminals. For coastal terminals, Satellite continues to show patchy MVFR clouds south of KTMK, with more pervasive cloud cover around KAST. Will note that conditions are beginning to lift along the north coast so will see some improvement over the next few hours. West to northwesterly winds 5-10 kt at all terminals, highest during the afternoon. Possible gusts up to 20 kt at a few inland terminals.

Overnight, high resolution models are suggesting a return of MVFR CIGs to the coast with another marine push. Inland too is showing around a 40-60% chance of MVFR CIGs, while other models are keeping areas hovering right around 3500 ft. Back building off of the Cascades will be the main driver on whether we see the deep stratus.

KPDX AND APPROACHES...VFR conditions with a 40-70% chance of MVFR CIGs; though confidence is low as they instead could remain just above 3000 ft. Northwesterly winds around 5-10 kt, with gusts up to 20 kt possible during the afternoon. -27

MARINE

High pressure rebuilds over the coastal waters through the weekend, returning northerly winds later Saturday and increasing pressure gradients on Sunday. Chances for gusts up to 25 kt return Sunday afternoon, mainly across the central and southern waters out to 30-40 NM. Seas are expected to remain around 4 to 6 ft as relatively benign conditions persist through the weekend and into the start of next week. -19/DH

PQR WATCHES/WARNINGS/ADVISORIES

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