SHORT TERM
Now through Friday Night...Water vapor satellite imagery reveals a potent upper level trough located offshore of the Pacific Northwest early this morning. An attendant surface cold front is analyzed over the coastal waters as of 2 AM Wednesday, with numerous rain showers spreading inland across northwest Oregon and southwest Washington. A few embedded thunderstorms are also noted over the coastal waters. Widespread showers will continue through the day as the upper trough moves inland across the region, with the heaviest rain likely to fall through later this morning along the coast and into the Willamette Valley, shifting to the Cascades this afternoon and evening. Rainfall amounts so far range from a few hundredths to as much as a quarter inch in a few spots. Expected rainfall totals remain more or less on track from previous forecast packages, with guidance depicting 0.50-0.75 inches in the interior valleys and 0.75-1.00 with locally as much as 1.25" for the Coast, Coast Range, and Cascades through late this evening.
A few embedded thunderstorms will also remain possible into this evening with a 15-25% chance across the area. May see a bit of an uptick in thunderstorm potential in the afternoon if any clearing materializes behind the front to generate some surface based instability. Overall, thunderstorm concerns remain minimal as locally heavy rain will accompany any storms that do develop.

Showers and thunderstorms diminish tonight as the trough shifts east of the Cascades, though northwest flow in the wake of the trough will keep the threat of a few showers over the area into Thursday afternoon. Expect these showers to mostly favor the higher terrain, with model QPF amounts still limited to around a tenth of an inch across most of the area and perhaps slightly higher to around a quarter inch for orographically favored spots in the Cascades. Expect a general clearing trend from west to east through the afternoon with highs inching back upwards into the low 70s. Temperatures will continue to incrementally increase into the low to mid 70s on Friday as shortwave ridging moves overhead and brings an end to any lingering shower activity. /CB

LONG TERM
Saturday through Tuesday...Medium range guidance has slightly sped up the arrival of the next trough into the region on Saturday, which will bring about another period of showery conditions and cooler temperatures this weekend into the early part of next week. Model suites then show some notable differences on how the trough evolves from Sunday into Monday which will have implications on the extent of shower coverage and potential additional rainfall amounts during the period.
European guidance is favoring keeping the trough offshore and digging towards northern California, whereas the GFS tends to move the trough directly overhead and Canadian guidance splits the difference between the two. The farther south solution would lead to generally less shower coverage and thus lower precipitation amounts, with the farther north solution representing the higher end solution for both shower coverage and precipitation amounts. For now, favored a broad brushed, ensemble based approach keeping a chance of showers over the region through much of the period until guidance comes into better agreement. Regardless, the presence of upper level troughing will favor cooler temperatures into the long term, with guidance depicting highs in the 60s in the inland valleys for the start of next week. /CB

AVIATION
A front is currently in the process of passing through the region, producing generally a mix of VFR/MVFR cigs. Rain showers as well as a few isolated thunderstorms near the coast will continue while the frontal passage continues. Possibility of thunderstorms at coastal terminals is around 30%, though any thunderstorms will end by 12z Wed. Southerly winds will generally remain under 10 kt, though any passing thunderstorms or heavier showers could produce isolated gusts up to 20 kt. While frontal passage is ongoing, confidence in inland TAFs deteriorating to IFR or lower is 0-20%.

The front finishes moving through the area around 20z Wed, after which VFR conditions will return to inland terminals with 75% confidence. This will be accompanied by a shift in winds to more westerly, remaining under 10 kt. Coastal terminals will still see around a 40% chance of remaining MVFR, increasing to 80% by 06z Thu. Of note, with post-frontal instability, currently seeing around a 10-20% chance of very isolated thunderstorms at all terminals Wednesday during daytime hours, from around 20z Wed to 03z Thu.

PDX APPROACHES...A mix of VFR and MVFR conditions are currently in place as a front continues to move through the area. Rain showers and southerly winds up to 10 kt are possible while this front is passing through. Chance of MVFR cigs essentially ends once the front finishes moving through the area around 20z Wed, and winds will shift westerly around this time. Around a 20% chance of an isolated thunderstorm Wednesday afternoon, between 20z Wed to 03z Thu. /JLiu

MARINE
A front is currently in the process of moving through the area. Any elevated southerly winds over 21 kt caused by the leading edge of the front should end by 12z Wed, after which winds will remain below SCA for the foreseeable future. Before 12z Wed, a stray thunderstorm or two could be possible in the southern and central waters, but by 12z this ends. Winds will thereafter slowly shift westerly, with max gusts remaining below 15 kt.

High pressure returns to the northeast Pacific late in the week and brings a brief period of northerly winds Friday. Currently around 20% chance that winds of greater than 21 kt work their way northward into the waters off the central coast of Oregon Friday afternoon and evening while winds will be even weaker farther north towards the mouth of the Columbia River. Uncertainty in the forecast details and timing of storm systems grows thereafter, but another low pressure system and attendant front or two will drop southeastward across the waters during this time. Given the relatively weak winds across the waters over the next week, expect seas to generally hover between 4-7 ft through early next week.
/Neuman/JLiu

PQR WATCHES/WARNINGS/ADVISORIES
OR...None.
WA...None.
PZ...None.