textproduct: Portland

SYNOPSIS

Overcast clouds continue to mix out this afternoon, leaving a mainly dry and increasingly sunny finish to today. High pressure then strengthens over the region Wednesday and Thursday, delivering the warmest weather of the week with widespread 70s inland and a reasonable chance of 80 degrees in the Greater Portland metro Thursday. A weak, moisture-limited trough brushes the Pacific Northwest Friday into Saturday, bringing a small cool-down and only low-end shower chances focused on the Cascades. Warmer and largely dry conditions look to return for Sunday and Monday. With the late-week warm-up, continue to keep cold water safety in mind, as local rivers remain cold enough for cold water shock.

DISCUSSION...Now through Monday

As of this afternoon, overcast clouds continue to mix out, giving way to increased sunshine. Expect the rest of the day to stay dry, but still with temperatures near to slightly below average (low 60s inland and mid 50s along the coast) given the cool start this morning. Winds remain mostly light, though the usual afternoon funneling through the Columbia River Gorge and Upper Hood River Valley will persist into early evening with gusts in the 25-30 mph range.

Tonight into Wednesday, a Frost Advisory is in effect for the Upper Hood River Valley (notably above 1000 ft in elevation) from 1 AM to 8 AM Wednesday. Lows there are expected to drop into the 33 to 36 degree range, which is cold enough for frost development. Frost may harm sensitive outdoor vegetation; protect or bring in sensitive plants.

Wednesday and Thursday bring a sharp turn toward warmer, sunnier weather as high pressure builds overhead and a drier air mass settles in. Confidence is moderate to high (greater than 60%) that inland highs reach the upper 60s to low 70s Wednesday, then climb into the upper 70s to near 80 Thursday. The Greater Portland metro down to Aurora still has the best odds of hitting 80 on Thursday (about 50-80%), while the remainder of the I-5 corridor is lower (roughly 20-40%). Overnight lows should continue to drop comfortably, keeping heat-related impacts limited.

Friday into Saturday, model and ensemble guidance remains consistent in showing the ridge weakening as a weak trough drops in from Canada. Moisture with this feature appears limited, so most areas should stay dry. The only location with a meaningful precipitation signal remains the Cascades (including the Cascade foothills), where chances for light showers are around 20-40%; elsewhere probabilities remain below 15%. Temperatures ease back a few degrees but remain seasonably warm.

Sunday into Monday, many ensemble solutions depict a closed low shifting southeast towards California while high pressure rebuilds across the Pacific Northwest. That favors another warm- up locally with dry weather for most lower elevations; the Cascades could still see occasional light showers if any moisture wraps north. Guidance continues to support high confidence (>90%) for greater than 80 degrees along the I-5 corridor Sunday, with Monday maintaining a 50-80% chance, again highest near the Greater Portland metro.

With late-week warmth, river recreation becomes more likely, but river temperatures remain cold enough for cold water shock, even on hot afternoons. Wear a life vest and use extra caution around fast, cold water.~12

AVIATION

High pressure gradually builds over the area today with northwest flow aloft. As of 20z, satellite imagery reveals a mostly overcast stratus layer with lower-end VFR CIGs beginning to become more broken. Expect conditions to remain predominately VFR through tonight with CIGs gradually lifting and clouds becoming more broken to scattered as mixing increases. Light winds become NNW this afternoon around 5-10 kt.

KPDX AND APPROACHES...VFR conditions expected through the TAF period as stratus continues to break and CIGs gradually lift. Northwest winds expected around 4-8 kt through this evening. /DH

MARINE

Northwesterly winds today turn northerly by Wednesday as high pressure persists offshore. Northerlies strengthen each afternoon and evening as pressure gradients tighten over the coastal waters due to strengthening surface thermal trough near the southern Oregon coast. Wind gusts are expected to remain below 20 kt through Wednesday morning. From Wednesday evening through at least Friday, there is a 70-90% chance for at least isolated small craft wind gusts up to 20-25 kt. The strongest gusts would mainly be south of Cape Falcon. The highest probabilities for SCA winds are for Thursday and Friday. Seas of 6 to 8 ft are expected to persist through the week with a northwesterly swell. Mid-period swells of 13-16 seconds will also result in a moderate sneaker wave threat at beaches Wednesday and Thursday. Those participating in razor clam digs should take extra precaution. DH/10

PQR WATCHES/WARNINGS/ADVISORIES

OR...Frost Advisory from 1 AM to 8 AM PDT Wednesday for ORZ121.

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