textproduct: Portland

SYNOPSIS

Hot weather will intensify through midweek as high pressure strengthens over the region. Inland temperatures are expected to peak Tuesday and Wednesday, when many valley locations rise into the mid to upper 90s, while coastal areas remain substantially cooler. Dry conditions will continue, and heat impacts will increase across the interior lowlands before a noticeable easing of temperatures arrives later in the week.

DISCUSSION...Now through Saturday

The early morning pattern remains dominated by a broad ridge centered over the Great Basin and extending northwest into the Pacific Northwest. That feature will continue to support a warm and dry stretch through at least Wednesday, with only weak marine influence lingering near the coast. As a result, inland areas will keep warming day by day, while coastal locations stay noticeably cooler but still edge upward a few degrees.

Forecast confidence remains highest in the broader temperature trend and somewhat lower in the details for the middle of the week. One source of uncertainty continues to be the timing and northward extent of moisture associated with offshore low pressure and southerly flow aloft. Current guidance suggests the better potential for deeper moisture and any associated precipitation would hold off until late Wednesday into Thursday, which would lessen its influence on daytime heating Tuesday and likely much of Wednesday as well. Even so, some increase in high clouds, haze, or smoke remains possible before then, and that could still have a modest effect on temperatures. Cluster guidance remains less than ideal in its agreement, so while the most likely outcome still favors a hotter and drier solution through midweek, some forecast uncertainty remains.

Today will mark the beginning of the hotter stretch for the interior lowlands, with widespread upper 80s to lower 90s expected. The coast should remain considerably cooler, generally in the 70s. The hottest conditions are still expected Tuesday and Wednesday, when many inland valleys reach the mid 90s and some of the traditionally warmer locations may push the upper 90s. While there remains some spread in the guidance, the odds continue to support widespread mid to upper 90s both days, and there is still a lower-end chance (15-30%) that a few spots approach 100 degrees if clouds and haze remain limited.

Heat-related impacts will become more of a concern as this stretch continues. Multiple days of above normal heat combined with limited overnight relief will support widespread Moderate HeatRisk across much of the interior. The greatest concern remains centered on the Portland/Vancouver metro, the Columbia River Gorge including Hood River County, and the Kelso/Longview area, where a Heat Advisory is in effect from Tuesday morning through at least Wednesday evening. Within those areas, Major HeatRisk appears increasingly likely Tuesday and Wednesday, especially in locations that see the warmest afternoons and the least nighttime cooling. Those with outdoor plans or without effective cooling should be prepared for elevated heat impacts. So, drink plenty of fluids, stay in a cool place during the heat of the day, stay out of the sunshine, and check up on relatives and neighbors.

By Thursday and Friday, the ridge is expected to weaken somewhat as a broader trough begins to press into the Pacific Northwest. That should allow temperatures to ease a few degrees late in the week, though values may still remain somewhat above average for late July. Beyond Friday, there is currently no strong signal for meaningful precipitation. ~12

AVIATION

Currently as of 11Z Mon, marine stratus maintains LIFR conditions at coastal terminals while inland terminals remain VFR. Through the TAF period for coastal terminals, guidance suggests LIFR/IFR conditions until 17-19Z Mon, potential VFR conditions afterward, then more LIFR/IFR conditions by 01-03Z Tue. While guidance suggests a 70-90% chance to improve to VFR at KAST between 19Z Mon and 01Z Tue, KONP only has a 50-70% chance to improve to VFR. In other words, there is a 10-30% chance for coastal terminals to maintain IFR CIGs between 19Z Mon and 01Z Tue. Inland terminals will maintain VFR conditions through the TAF period, especially with drier conditions expected through the TAF period. Otherwise, expect northwesterly winds between 5-10 kt at all terminals.

KPDX AND APPROACHES...VFR conditions with northwesterly winds below 8 kt through the period. ~12

MARINE

A typical summertime pattern will continue through the middle of this week with persistent north to northwest winds over the coastal waters. Gusty winds and steep seas will gradually decrease this morning, bringing an end to hazardous conditions for small craft across all waters. As such, Small Craft Advisories for all the waters will remain in effect until 11 AM this morning. Benign conditions expected late today into late this week. ~12

PQR WATCHES/WARNINGS/ADVISORIES

OR...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for ORZ108-109-111-112-115-120>122.

WA...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for WAZ204>207-209-210.

PZ...Small Craft Advisory until 11 AM PDT this morning for PZZ251>253- 271>273.