Marine Weather and Tide Forecast for Manson, WA

UPDATE
The first atmospheric river is bringing steady rains to the Cascades and ID Panhandle as forecast. Based on radar trends, and the new 00z high resolution models, confidence is high that a significant rain shadow will persist across most of Central and Eastern Washington tonight with little to no precipitation from Omak south to Ephrata eastward to near the WA/ID border.
This is due to strong downslope flow east of the Cascades. Thus made some adjustments to lower POP's for the rest of tonight across much of Central and Eastern WA.

Besides heavy rain in the Cascades, which will be decreasing overnight as the atmospheric river begins to sag south, winds remain a concern. 00z model guidance has not changed much, with wind advisories in place for much of the region. Models continue to show very strong winds at 850mb of around 55-65 kts between 9 PM - 2 AM. Higher resolution model guidance continues to reflect these higher winds having a difficult time mixing down except in a localized basis. We have already had a few reports of small branches coming off trees in Spokane and near Plummer with 35-45 MPH wind gusts. Some downed trees and power outages are possible overnight as winds pick up more. High wind gusts (58 MPH or greater) are still expected to be isolated in coverage but something we will be keeping a close eye on through the evening hours. JW

SYNOPSIS
An active weather pattern will impact the area through the week.
A series of warm and wet weather systems will result in periods of heavy mountain rain, lowland rain, high mountain snow, and gusty winds. Widespread strong wind gusts are expected Monday night into Tuesday which may result in downed trees and power outages.

DISCUSSION
STRONG LONG DURATION ATMOSPHERIC RIVER EVENT TO BRING POTENTIAL FOR FLOODING, ROCK/MUD SLIDES THROUGH THURSDAY, AS WELL AS GUSTY WINDS TONIGHT...

Tonight through Thursday: The first wave of two separate AR events is ongoing today. A warm front has pushed through Eastern Washington and now into the Idaho Panhandle at 2:30 pm this afternoon.
Precipitaiton intensity over much of the region has been light to moderate with heavier intensity being observed closer to the Cascade crest. Much of the precipitaiton for tonight will largely remain now at the Cascade crest and in the Idaho Panhandle. The Cascade crest will see an additional 1.5 to 3.0 inches and the Idaho Panhandle up to an additional quarter plus inches of precipitation. The higher terrain of the Panhandle will more likely see upwards of an additional half of an inch with mountains more likely to receive an additional inch or so.
The main concern with the precipitation tonight that will largely fall as rain over the Cascades will be for rock/mud slides, especially so in steep terrain and near newer burn scars including the Pioneer above Stehekin, Sugarloaf, and Labor Mountain burn scars. A flood watch will remain in effect for Chelan County and we have actually extended this flood watch to include the next round of precipitation Tuesday through Thursday as well.

A potentially more impactful hazard will be winds mixing down later this evening and overnight. Model guidance is in good agreement with strong winds aloft with 50-60 mph winds up around 2,000 feet above ground level. Where the uncertainty comes is how effectively will we be able to mix down these winds in the warm sector. Typically this is difficult to do to its fullest potential. The surface gradient isn't necessarily significant to the point of what we would expect to achieve high wind criteria (sustained speeds of 40+ mph and/or gusts 58+ mph). The GEFS is on the higher end when compared to the ECMWF Ensemble members. The GEFS is progged to have a MSLP of near 16 mb between Portland, OR and Glacier, MT, whereas the ECMWF ensemble mean is more around 12 mb. There is uncertainty with the potential for how strong winds may actually get. The HRRR mean wind guidance is in line with what our forecast has been portraying with sustained winds in the 25-35 mph range across the Columbia Basin and gusts up to 50-55 mph. This is in the high end range for a wind advisory. It's entirely possible, if not probable, that we will see isolated spots that meet high wind criteria. An additional factor to consider is soils being fairly saturated and this may lead to more downed trees than what we typically would expect with winds of this magnitude.

By Tuesday, we see the next AR move into the region, and this one will be similar in magnitude as today's and also be a bit longer in duration on the order of 36-48 hours. The peak of the AR event will be the first 24 hours Tuesday night through Wednesday, and then see precipitation rates come down a bit for the latter half Wednesday night into Thursday. However, this next round coming on the heels of a healthy amount of rain over the Cascades and Idaho Panhandle will be one to watch for hydrology related impacts. An area of concern in addition to Chelan county will be the headwaters across the Central Panhandle Mountains and drainages downstream. This includes the Coeur d'Alene River, St. Joe River, and, to a lesser extent, Paradise Creek. Rainfall with this next AR will range from around an inch to as much as 3+ inches in the Idaho Panhandle with heaviest amounts being across the Central Panhandle Mountains. Additional rainfall in combination with snowmelt is expected to result in rapid rises to rivers, small streams, and creeks. Minor flooding is forecast along the Coeur d'Alene River, and I wouldn't be surprised if the St. Joe River sees flooding impacts as well. A Flood Watch is in effect for Tuesday through Thursday. If you're in a low lying area, or along a stretch of the river, small stream, or creek take precautions to protect property for the potential of flooding. Steep terrain will also be prone to mud/rock slides as well. This second AR will continue to pound the Cascades with additional rain as well. We will have a good idea of how burn scars responded to the first round of rain tomorrow. Those traveling along Highway 97 over Blewett Pass should be advised that there may be some debris that comes out on the road with several days of soaking rain on the Labor Mountain burn scar.

These AR events will mainly bring impacts due to rain and melting snow, but the cold front passage tonight will see snow levels lower that light snow will accumulate over Stevens Pass and Lookout Pass.
Accumulations will be in the neighborhood of 1-3 inches. That will be the case at Stevens Pass on the back edge of the cold front tonight and then also a couple of inches or so expected as snow transitions back to rain with the second AR event.

Thursday night through Monday: Weather turns more benign at the end of the week as a high pressure ridge builds over the eastern Pacific. The ridge looks transitory though and model guidance does indicate a frontal system pushing across over the weekend. However, the ridge will give a reprieve to the wet weather on Friday at least and allow levels on rivers and streams to decrease.
Precipitation over the weekend won't be nearly of the scale as over the next few days. Temperatures remain mild with any snow remaining over the mountains. /SVH

AVIATION
00Z TAFs: The steady rain that has been impacting TAF sites through much of the day is on its way out. Rain will impact KCOE, KPUW, and KLWS for the next couple of hours before exiting to the east. Southwest winds will become the primary focus of the forecast this evening and into tomorrow morning with speeds 20-30kts and gusts 30-40kts. Low level shear is expected at times over the next couple of hours for KPUW and KEAT.

.FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for wind gusts greater than 40 kts from the southwest from Pullman to Spokane (KPUW/KGEG/KSFF/KCOE) and moderate confidence that wind gusts will increase to around 50 kts between 05-12Z.

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Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,please refer to the Aviation Dashboard on our webpage: https:/ www.weather.gov/otx/avndashboard

Preliminary Point Temps/PoPs
Spokane 42 49 39 53 45 51 / 20 30 100 80 70 60 Coeur d'Alene 42 47 38 51 45 49 / 70 40 100 90 80 70 Pullman 44 49 41 54 47 52 / 80 80 100 90 80 80 Lewiston 50 55 46 60 54 57 / 30 80 100 80 70 60 Colville 35 45 32 47 35 46 / 20 10 100 70 60 50 Sandpoint 39 45 35 46 41 46 / 80 30 100 100 80 70 Kellogg 40 46 38 50 46 49 / 100 80 100 100 90 90 Moses Lake 42 49 41 57 44 55 / 10 50 90 50 40 40 Wenatchee 40 47 41 54 43 52 / 80 50 100 70 60 60 Omak 35 44 36 48 36 46 / 30 10 100 60 50 40

OTX WATCHES/WARNINGS/ADVISORIES
WA...Flood Watch through Thursday afternoon for Central Chelan County-Wenatchee Area-Western Chelan County.
Wind Advisory until 7 AM PST Tuesday for Lower Garfield and Asotin Counties-Northeast Mountains-Spokane Area-Upper Columbia Basin-Washington Palouse.
ID...Flood Watch through Thursday afternoon for Central Panhandle Mountains-Coeur d'Alene Area-Idaho Palouse-Northern Panhandle.
Wind Advisory until 7 AM PST Tuesday for Central Panhandle Mountains-Coeur d'Alene Area-Idaho Palouse-Lewiston Area- Northern Panhandle.