textproduct: Portland

SYNOPSIS

Dry and warm weather is expected across the region through the weekend with high pressure over the NE Pacific spreading east over the Pacific NW. Rain and cooler temperatures return to the area late Sunday into early next week, which could impact any outdoor Memorial Day plans.

DISCUSSION...Today through Wednesday

The upper level ridge that has been persistent over the NE Pacific will slide across the Pacific NW today as shortwave trough over the Gulf of Alaska sends a weak impulse toward the region. 850 mb temps rise to around 12-13C this afternoon while a weak surface thermal trough pushing into the Willamette Valley this morning shifts over the Cascades. With drier, offshore flow in the foothills, there are lower chances for morning stratus developing. This should allow mostly sunny skies to help warm surface temperatures into at least the lower 80s for inland areas today, which is around 10-15 degrees above normal for today. Record high temps are generally in the upper 80s to mid-90s through the Memorial Day Weekend, so we are not expecting any record high temps to be broken at this time.

Conditions are expected to remain dry through the end of the week and into the weekend as high pressure continues across the region. The upper level ridge re-amplifies over the NE Pacific tonight and sags back over the PacNW region on Friday. Broad upper level ridging on Friday becomes more zonal aloft Saturday into Sunday. Expect a slight cooling trend in temperatures through the weekend, but still likely to remain above seasonable averages. Coastal locations will experience a brief warmup today into the 60s to lower 70s before onshore flow brings typical temperatures there.

There remains good agreement that Sunday will remain mainly dry and warm, though could begin to see increasing cloud cover ahead of an approaching weather system. About 90% of ensemble members indicate a frontal system will push into the PacNW sometime late Sunday night into Monday, with chances of rain increasing for Monday, followed by showers into Tuesday. Some uncertainty still remains in the general timing of rain as well as rain totals, but latest consensus is that rain will hold off until at least late Sunday night along the far N OR and SW WA coast, then spread southeast Monday morning. Temperatures will also drop substantially Monday and Tuesday with high temperatures in the lower to mid 60s for the interior lowlands. Conditions are likely to rebound back to seasonable norms by the middle of next week, though some uncertainty remains due to low chances of precipitation. DH/03

AVIATION

A ridge of high pressure shifts over the region today which should help maintain predominately VFR conditions for inland terminals. Shallow marine stratus offshore continues to spread inland near KAST with IFR CIGs with around a 30-40% chance of persisting through 17z. IFR to LIFR stratus may also push into KONP between 10-17z this morning (40% chance). Light north to northwesterly winds become breezy again in the afternoon and evening hours. As of 09z this morning, satellite imagery has not shown any stratus forming along the Cascade foothills yet. But there does remain around a 10-30% chance for inland terminals to be impacted by MVFR stratus through 18z.

KPDX AND APPROACHES...VFR conditions are likely to persist through the TAF period, aside from a 10-20% chance of MVFR stratus developing this morning. Light northwest winds increase again to around 8-10 kt this afternoon. /DH

MARINE

High pressure offshore will maintain breezy northerly winds through the end of the week. The strongest winds are expected during the afternoon and evening periods as the surface thermal trough strengthens over the northern CA/southern OR coast. Small Craft Advisories remain in effect for the waters south of Cape Falcon through tonight for northerly wind gusts up to 25 kt. Will note that there may be a brief lull in the winds between 5-11 AM Thursday for the inner water and northern outer water zones before increasing again this afternoon. Gusty northerlies are again likely south of Cape Falcon on Friday. Seas 6 to 9 feet are expected across all waters through this weekend. The summer- like pattern is expected to break down Sunday night as a front approaches the waters and returns southwesterly winds by Monday. 10/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 7 AM this morning to noon PDT today for PZZ210.

Small Craft Advisory until 5 AM PDT Friday for PZZ252-253- 271>273.