Marine Weather and Tide Forecast for Grand Ronde, OR

SHORT TERM
Light, intermittent rain continues across the area this afternoon and evening as a weak upper disturbance moves over the region within southwest flow aloft. Rainfall amounts will be minimal, from a few hundredths to a tenth of an inch. Will continue to ease into fall-like weather as a cold front moves across the area on Wednesday. Associated with more upper level support, this somewhat stronger front will bring a period of widespread rain late tonight through Wednesday morning. Model QPF amounts for this system are expected to remain around 0.10-0.25 inch across the interior valleys and 0.25-0.50 inch along the coast and in the higher terrain.

The cooling trend will continue as the upper level trough drops over the Pacific NW Wednesday night into Thursday. This will enhance shower activity across the area by late Wednesday night while 850 mb temps fall to around 0 degrees C through Thursday. These cooler temperatures aloft will bring lowering snow levels to the mountains, as well as a slight chance for thunder, beginning Wed night at the coast. There is potential for this system to be the wettest of the week, but amounts will likely vary widely across the area due to the showery nature of the precipitation. There is high confidence (greater than 80%) of widespread QPF exceeding 0.25 inch, while the coast and mountains will most likely see amounts generally around 0.50-1.00 inch through Thursday afternoon.

There is also high confidence of snow falling at the higher Cascade passes, beginning early Thursday morning. Snow levels are expected to fall to around 4000-4500 ft Wed night into Thursday. The probability of snowfall exceeding 6 inches has fallen slightly to around 30-50% but there is still fairly high confidence (70-80%) of around 3 to 6 inches of total snowfall at the Willamette and Santiam passes. The chance of snowfall exceeding a foot has decreased to below 10%. Although the Winter Storm Severity Index indicates low probability of minor impacts (likely due to the warmer road temps), still be prepared for possible winter driving conditions through Cascade passes on Thursday. /DH

LONG TERM
Friday through Monday...Friday into Saturday is setting up as the driest period within the coming week as ensemble clusters show good agreement in a low amplitude ridge building into the Pacific Northwest behind the departing trough late in the week. As such, could see temperatures on Saturday rebound into the upper 60s to perhaps 70 degrees in a few interior valley locations. But, uncertainty increases on Saturday especially for northern portions of

the forecast area with clusters indicating at least 20% of ensemble members bringing rain farther south. Precipitation chances increase again by Sunday as the ridge starts to flatten out and a potential atmospheric river focused on coastal British Columbia and the Olympic Peninsula sags south across western Oregon on Sunday.
Precise forecast details and timing will have to be narrowed down in the coming days, but the weakening and progressive nature of the system would seemingly limit the potential for higher end precipitation amounts or hydro concerns at this time. DH/CB

AVIATION
Flight conditions remains mixed this evening as SW Washington and NW Oregon are positioned between two fronts; one departing to the east and one approaching from the west. The worst flight conditions are currently along the south coast where predominately IFR conditions can be expected through the night.
The north coast and inland areas are mostly VFR with occassional MVFR conditions with shower activity. IFR conditions are likely to develop along the whole coast late tonight into Wed morning as HRRR forecasts a 50-80 percent chance of ceilings below 1000 feet.
There is around a 30% chance for MVFR ceilings in the Willamette Valley Wednesday morning with the front passage with less than 10% chance for IFR conditions. VFR chances increase around midday Wed in most locations as west winds increase behind the front.

PDX APPROACHES...MVFR conditions likely with showers through 5z Wed. MVFR cigs may return (30-50% chance) 12-18Z Wed. Also worth mentioning is a 10-20% chance for IFR cigs 14-17Z Wed. VFR conditions expected Wed afternoon and evening. ~TJ

MARINE
Weak surface high pressure over the waters this afternoon will give way to a front that will move through the waters later tonight into Wednesday morning. This front is associated with a parent low off the coast of British Columbia and will shift winds southerly. Expect a return of breezy southerly winds tonight with gusts up to 20 kt. Isolated gusts up to 25 kt are possible overnight across the waters, however opted against issuing a new Small Craft Advisory for now as those gusts currently forecast to be short-lived and not widespread. Winds turn westerly Wednesday after the front moves through.

Wednesday night into Thursday, the aforementioned low near British Columbia dips southward into the Pacific Northwest, shifting winds northwesterly with gusts up to 20 kt. Late in the week, another robust low pressure system in the NE Pacific will follow and track towards British Columbia. Model guidance currently shows the associated surface front reaching the Pacific Northwest this weekend, returning breezy southerly winds to our waters.

Seas remain in the 7 to 9 ft range through Wednesday and may rise just above 10 ft Thursday. Also, persistent northwest fetch sets up off the B.C. coast Wednesday into Thursday which may generate a fresh northwest swell to bring choppier seas to the coastal waters. /mh -Alviz

PQR WATCHES/WARNINGS/ADVISORIES

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