textproduct: Portland

SYNOPSIS

Low pressure moving over the area will send a weak cold front through the area today. Expect near average temperatures today and tomorrow. Chance for light rain shower along the coast, coast range and north of the WA/OR border. Ridging builds back into the area early next week, increasing temperatures back into the mid to upper 80s across the interior lowlands.

DISCUSSION...Today through Friday

An upper level trough will continue to progress northeast today, sending a weak cold front through the area early Saturday. This will support temperatures near or slightly below average both today and Sunday in the upper 70s to low 80s across the interior lowlands. Surface pressure gradients tighten as the cold front moves through, supporting relatively gusty winds up to 20 mph inland and up to 25 mph along the coast. Strongest winds expected through the western Columbia River Gorge where gusts around 30 mph are expected with a 30-40% chance for isolated gusts around 35 mph Saturday afternoon. There is also a chance for light showers this evening and overnight as the trough axis passes overhead. Best chances for any precipitation will be along the coast and coast range and along and north of the WA/OR border. Most likely timing is between 5 PM Saturday through 5 AM Sunday.

Zonal flow aloft develops Sunday as the upper level trough continues to trek northeast away from the region. Looking ahead into early next week, ensemble clusters favor ridging over the central CONUS and the PacNW. Warmer temperature are expected to return for Monday and Tuesday. Model spread for high temperatures between the 10th- 90th percentiles range from the low 80s to low 90s for the interior lowlands. Clusters favor another trough influencing the region by the middle of the week but exact timing and upper level pattern are uncertain but onshore flow and seasonable or below average temperatures would be favored. Currently, the 10th-90th percentiles range from the low 70s to low 80s. There is also no clear signal for any precipitation associated with the mid week trough. approximately 20-30% of members show very light rain possible during the Thursday- Friday timeframe but nothing significant at this time. -19

AVIATION...Through 12z Sunday

An upper-level low tracking to the north offshore will bring periods of vis/cig restrictions to area terminals throughout the period. Along the coast, widespread low stratus coverage will bring persistent IFR/low-end MVFR cigs at 500-1500 ft. Highest confidence in IFR cigs to the south at KONP (70-80% chance) while MVFR conditions are more likely at KAST. Periods of MVFR vis are likely overnight at coastal terminals. Cigs will tend to lift to 1.5-2.5 kft after 15-18z Sat while south-southwesterly winds increase to 12-16 kt with gusts of 20-25 kt through the afternoon. Cigs look to trend downward again late this afternoon and into the evening.

VFR conditions inland with increasing chances for MVFR conditions through 18z. Chances for MVFR cigs are 40-60%, with the highest confidence in the southern Willamette Valley (KEUG) where MVFR CIGs are already being reported. Chances are lower in the central Willamette Valley and Portland area. South to southwest winds will build to 6-12 kt with gusts 15-18 kt during the afternoon.

KPDX AND APPROACHES...VFR conditions favored but low clouds are starting to develop around the metro. Chances for MVFR cigs are 30-50% through 18z. As low clouds mix out, VFR conditions are again highly favored after 18z Sat. South to southwest winds of 3-5 kt overnight will build to 8-10 kt by Saturday afternoon. -19/36

MARINE

South winds continue today as a low pressure system moves over the northeast Pacific. A cold front moving through later today is expected to bring maximum wind gusts to exceeding 21 kt to the inner waters, including the Columbia River Bar. A Small Craft Advisory has been issued for the inner waters from 5 AM to 5 PM Saturday and for the Columbia River Bar from 11 AM to 5 PM today. For the outer waters, chances are 20-50% with the highest values of that range between 10 and 30 NM.

High pressure and northerly winds return by Sunday, with a 40-70% chance for northerly wind gusts to exceed 21 kts in the evening and continuing into Monday. Seas of 4-6 ft persist through the period. -19/12

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Small Craft Advisory from 11 AM this morning to 5 PM PDT this afternoon for PZZ210.

Small Craft Advisory until 5 PM PDT this afternoon for PZZ251>253.