textproduct: Portland

SYNOPSIS

Seasonably cool and showery conditions continue through the workweek as repeated weather systems support persistent chances for rain. A drying trend beginning Friday may bring better trick-or-treating conditions by late Saturday. A more active pattern looks to return by the start of next week as a broad area of low pressure moves southward our of the Gulf of Alaska.

LONG TERM...Thursday through Monday

Another, broader closed upper low and its associated surface low will drop south from the Gulf of Alaska over Vancouver Island and into the Pacific Northwest Wednesday night into Thursday. This will bring another round of precipitation to the region through Friday. 850 mb temperatures will continue to slowly fall towards -1C to -2C thus bringing snow levels further down towards 3000-3500 ft by Thursday. While cooler temperatures remain in the forecast, QPF has decreased sharply with the Thursday system. Currently, the ensembles are supporting a 40-60% chance for an additional inch of snow for the Cascade passes. For lower elevations, another 0.10-0.25 inches of rain is most likely across the CWA.

From Friday through the weekend, WPC 500 mb clusters support a broad low remaining offshore of the Pac NW, while weak ridging looks to develop over the Great Basin. This looks to bring some drier air into the region, which is cutting the overall QPF for the latter part of this week and into the weekend. However, 15-30% PoPs remain in the forecast. While a drying and clearing trend is expected for the end of the week and weekend, there continues to be a slight chance for lingering rain showers Friday and Saturday. So, for all those Halloween trick-or- treaters just be aware that some very light rain could impact any festivities. Given the clearing trend along with the influx of cooler temperatures expect overnight lows in the upper 20s to mid 30s most likely for most inland valleys through the weekend and into early next week. /42

AVIATION...Through 12Z Wednesday

Moist, westerly flow aloft continues as an upper level trough moves over the region. This will maintain showers across the airspace along with a mixture of VFR to MVFR conditions. Brief periods of IFR/LIFR conditions will also be possible, though generally just a 10-20% chance at any given hour through the TAF period. Conditions are likely to improve after 18Z-21Z Tuesday as showers decrease and CIGs lift toward VFR. Winds generally remain west to southwest at 5-10 kt. After 02Z Wednesday, winds are expected to increase along the coast with gusts up to 20 kt through the remainder of the TAF period.

KPDX AND APPROACHES...Showers expected to continue along with a mixture of VFR to MVFR conditions. 10-20% chance for intermittent IFR/LIFR conditions at any given hour through the TAF period. After 18Z-21Z Tuesday conditions likely to improve as showers decrease and CIGs lift toward VFR. West to southwest winds 5-10 kt. /42

MARINE

A surface low pressure system will move through all waters today bringing elevated winds with gusts approaching 25-30 kts and seas building towards 7-10 ft at 8-10 seconds. As such, have issued a series of Small Craft Advisories for all waters and the Columbia River Bar through at early Wednesday morning. Conditions will slowly subside after Wednesday with gusts below 15 kt and seas subsiding towards 4-6 ft at 10-12 seconds through the weekend. Looking towards the start of next week, another low pressure system from the Gulf of Alaska looks to bring building seas and winds that could result in Small Craft conditions for the start of next week. /42

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 8 AM this morning to 11 AM PDT Wednesday for PZZ210-251-252.

Small Craft Advisory from 8 AM this morning to 8 AM PDT Wednesday for PZZ253.

Small Craft Advisory from 5 AM early this morning to 5 PM PDT Wednesday for PZZ271-272.

Small Craft Advisory from 5 AM early this morning to 8 AM PDT Wednesday for PZZ273.