textproduct: Portland

SYNOPSIS

Dry weather is expected to continue through most of the weekend as high pressure stubbornly holds over the region. Gusty winds persist through the Columbia Gorge. Expect cold overnight lows in the low to mid 20s through Saturday night in the lowlands. Clear skies and light winds away from the Columbia River Gorge will result in frost and/or freezing fog formation for a decent swath of the interior lowland valleys and coast range Valleys. Chances for precipitation return by the middle of next week, but details on the exact timing and impacts remain rather uncertain at this time.

LONG TERM...Sunday through Thursday

Models and their associated ensembles are starting to show a pattern shift next week as a trough digs across the Pacific. This may weaken the anchored ridge enough to finally see a substantial change later in the week. Ensembles agree that a weak short wave and associated cold front will pass through the region during the Sunday night through Monday night timeframe. However, precipitation is almost negligible for the area with at most a few hundredths. Even if this system brings little in the form of precipitation, it will still play an important role in breaking the ridge down and setting the stage for more beneficial precipitation toward the middle/end of next week. Ensemble guidance remains in agreement that a moderate, Pacific low will finally break down the strong ridging over the region by midweek, though details are still unclear. At this time, model ensemble guidance is pointing towards a moderate PoP (35-60% chance) with relatively low/moderate QPF (0.10-0.50 inches total) event. At this point, there are no major impacts expected with this weather system, and if precipitation does occur, it would be more beneficial than impactful, especially after the recent dry spell. -19/42

AVIATION

Expect dry weather to prevail across the region through the TAF period with broad northerly flow aloft and high pressure attempts to rebuild overhead. Near the surface a cross- Cascade pressure gradient remains in place helping to drive east winds through the Columbia Gorge into portions of the Portland Metro, most noticeable at KTTD. Tonight into Saturday morning, temperatures will drop below freezing for most inland areas with frost accumulation possible on surfaces. We'll need to keep an eye on a slight chance (20-30%) for fog formation in the far southern Willamette Valley approaching sunrise which would impact KEUG. For now, there is not enough confidence in the timing and/or placement to add a mention into the 18z TAF package.

KPDX AND APPROACHES...VFR over the next 24-hours. Minimal change as easterly winds dominate. Gusts will begin to increase this afternoon coinciding with daytime heating. 10-20% chance of gusts as high as 30kt at KPDX. Aloft at 2000 ft, easterly gusts as high as 35-40 kt can be expected through today. -99/27

MARINE

Rather benign conditions continue across the coastal waters. East to northeasterly winds increase through Friday evening as the thermal trough along the coast expands northward and high pressure rebuilds inland. Winds generally increase to around 10-15 kt with gusts up to 20 kt, but isolated gusts to 25 kt will be possible extending from gaps in the coast range and across the coastal waters. Winds ease again through the weekend as pressure gradients decrease. Weak low pressure drifting offshore will cause the winds to turn southerly by Monday. The next frontal system is likely to approach the waters by the middle of next week returning increasing chances for Small Craft Advisory conditions on Wednesday. Seas are expected to persist at around 4 to 6 ft with wave periods varying between 11-15 seconds through the weekend. Not much change to the overall sea state into early next week. -19/DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...Cold Weather Advisory until noon PST today for ORZ104>125. WA...Cold Weather Advisory until noon PST today for WAZ202>210. PZ...None.