textproduct: Portland

SYNOPSIS

Cooler temperatures through Saturday before building high pressure brings a warming trend Sunday through Tuesday. Warmest day will be Tuesday with Moderate HeatRisk in the lowlands north of Salem. Dry weather persists through Tuesday. Cooler temperatures return Wednesday with a slight chance of rain.

LONG TERM...Monday through Thursday

Monday starts the first of two days of drastically increasing temperatures. Ensemble models are in good agreement of the ridge of high pressure intensifying, and the ridge axis shifting closer to the shore. In fact, the differences between 500 mb ensemble clusters is minimal. This ridging is combined with widespread east flow aloft will bring significantly warmer temperatures in the midlevels. 850 mb temperatures will rise to around 12-14 deg C. This pattern will cause temperatures to spike once again by about 10-15 deg F with highs forecast to be in the low to mid 80s for the interior lowlands, in the upper 60s to low 70s along the coast, and the Cascades in the 60s. There is currently around a 25-45% chance of the greater Portland-Vancouver Metro area seeing highs of 90 deg F or more on Monday, with the central Willamette Valley sitting closer to 15-25%. Elsewhere, chances are less than 5%. The big component to consider on Monday is the urban heat island effect and thus why Portland will be warmer. Overnight temperatures will still cool, but there's a 25-35% chance they remain above 60 degrees in the greater Portland metro area. This is due to the easterly flow aloft causing a weak downslope feature which will cause warming from compression within the lower elevations.

Tuesday is marked to be the hottest day of the week. There is a 60-75% chance that the Portland-Vancouver area will see highs of 90 deg F or higher, around 40-50% in Salem, 45-55% in Longview, and 15-20% in Eugene. If we were to bump up that temperature to 95 deg F or greater, the Portland area remains the highest around 20-35% chance while other urban areas and along the I-5 corridor have less than a 10% chance. There's a 25-35% chance low temperatures remain above 60 degrees in the Portland-Vancouver metro area, increasing to 40-60% chance in the Columbia River Gorge. Elsewhere, lows of 50-55 deg F are expected. There is currently Moderate HeatRisk for the greater Portland-Vancouver metro area, lower Cowlitz and Columbia Valley, and Columbia River Gorge. However, the chance of Major HeatRisk in the greater Portland- Vancouver Metro has lowered to less than 10% due to a combination of high temperature probabilities lowering slightly and low temperatures remaining below 60 degrees. Moderate HeatRisk means that those without access to sufficient cooling and hydration may be impacted by the heat. Therefore, take precautions on Tuesday if participating in outdoor activities - especially in the afternoons during peak heating.

Luckily this heat will be short lived as a low pressure system from the Gulf of Alaska deepens in the northeastern Pacific and pushes the high pressure east. Guidance indicates a weak upper shortwave and surface front will push through the region late Tuesday into early Wednesday, which will usher in cooler temperatures for Wednesday and Thursday. There's 70-90% that interior lowland temperatures will fall below 80 degrees into the low to mid 70s. Some uncertainty in the exact pattern leaves that 10-20% chance of temperatures remaining in the 80s. There are slight chances of light precipitation late Tuesday into Wednesday morning, mainly limited to the coast and Coast Range as the dry airmass in place will likely cause the front to weaken as it approaches land. On Thursday, the shortwave moves east and 500 mb clusters are in pretty good agreement that zonal flow takes over briefly with dry weather and similar temperatures to Wednesday. -03/27

AVIATION

Overall persistent onshore flow continues overnight through Saturday with VFR conditions favored at all sites. Expected CIGs near 5kft with a layer of SCT-BKN 25kft into Saturday morning before skies trend clearer late morning into the afternoon hours. Given the prevalence of the aforementioned cloud layers tonight any sunrise fog formation across the region should remain rather isolated (less than a 10% chance at most sites). Expect northwest winds to persist, increasing at the coast around midday with gusts around 20-25 knots at times into Saturday evening.

KPDX AND APPROACHES...VFR conditions continue tonight through Saturday with CIGs near 5kft generally decreasing 18-20z. Winds remain out of the northwest around 5-10 knots, although infrequent gusts ~20 knots are possible 23z Sat through 04z Sun. -99

MARINE

High pressure remains over the area with a persistent northwesterly swell and north/northwest winds. North/northwest winds 10-13 kt with gusts up to 20 kt through Sunday morning. Winds expected to increase on Sunday with gusts up to 25 kt across all waters as high pressure strengthens and results in a more summer like pattern. Cannot rule out gusts as high as 30 kt in the waters south of Lincoln City, OR on Sunday. As Monday approaches, winds are expected to fall below Small Craft Advisory Criteria. Seas 9 to 11 ft will gradually subside to 6 to 8 feet by late this afternoon/tonight and look to hold through at least the start of next week.

A series of strong ebbs will take place on the Columbia River Bar each evening through at least Sunday. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 7 AM PDT Saturday for PZZ210.