Marine Weather and Tide Forecast for Moscow, ID

SYNOPSIS
Areas of rain will linger into Friday. Saturday will bring a brief break. A weak system moves in Sunday bringing light rain the mountains. Confidence is increasing for another round of rain and high mountain snow Monday before snow levels begin to decrease by the middle to end of next week.

DISCUSSION
Today through Sunday: What is left of a weakening atmospheric river will continue to produce areas of light rain today mainly along the Cascades crest and ID Panhandle. Most rivers have crested or will so early this morning. Given ongoing flooding several flood warnings remain in place in the Cascades and the ID Panhandle. Then a flat ridge will be the story for Saturday giving the region a much needed break in the rain. Yet southwest flow will bring in very mild air aloft as 850mb temperatures climb to near 10C in the Central Cascades and over SE Washington, and 3-7C over northern WA and the ID Panhandle. This will contribute to more mountain snow melt. The break in the rain and less mountain snow left to melt will allow rivers and streams to continue falling, but they will still be elevated.
The mild southwest flow continues into Sunday but the next system approaches giving the Cascades and NE Mountains a chance for light rain with snow levels around 6000 feet.

Monday: Another atmospheric river punches in with precipitable water values increasing to 200-300% of normal. While this one will not be as long lived, ensembles are showing another 1-3 inches of rain along the Cascade crest which is likely to give another rises to area rivers and streams. With levels already elevated, additional flooding is possible with the Stehekin River forecast to rise above flood stage again by Tuesday. Yet, given time for levels to recede prior and it being shorter lived the flooding is not expected to be as significant as what is occurring this week. This atmospheric river will have another punch of wind and very mild air as 850mb temperatures climb to 5-9C with 850mb winds out of the southwest at 40-50 kts. It's too far out to say with much confidence how much wind will mix to the surface, but currently the ECMWF ensemble mean shows gusts of 30-45 mph mixing down across the Columbia Basin into the Spokane area and Palouse.

Tuesday through Thursday: A very active pattern is expected as a deep low in the Gulf of Alaska results in a an active jet stream aimed at Washington, Oregon, and north Idaho. There is some indication that the enhanced jet will help bring down the snow levels, dropping to 3500-5000 feet Tuesday, and between 2000-4000 feet Wednesday and Thursday (lowest over northern WA/N Idaho Panhandle). The strong jet and waves tracking through is a good pattern for heavy snow in the Cascades and ID Panhandle. The NBM Tuesday evening through Thursday is giving Stevens Pass a 75% chance of 2 FEET or more of snow! For Lookout Pass there a 40% chance of a foot or more during this same time. There is also the potential for strong winds in this pattern. Some model solutions have been developing a 985-990mb surface low and tracking across southern BC with a strong cold front Tuesday into Wednesday. Yet the majority of the GFS and ECMWF ensemble members support gusts in the 40-50 MPH range across the region. This is supported by the NBM with a 60-70% chance of gusts exceeding 40 MPH Tuesday for Moses Lake, Spokane, Pullman, and Lewiston. The chances for gusts exceeding 50 MPH in these same areas is around 30%. JW

AVIATION
18Z TAFs: IFR-LIFR conditions across much of central/eastern WA and north Idaho (except PUW-EAT) will slowly improve over the next few hours into the early afternoon. Low confidence for exact timing of improvements. Lingering boundary layer moisture may lead to fog/low cigs again tonight but confidence is low.

.FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Low confidence for exact timing of improvements and potential for degraded conditions again tonight into Saturday.
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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 51 40 52 35 50 41 / 10 10 0 0 10 20 Coeur d'Alene 50 41 51 35 50 40 / 30 20 10 0 20 30 Pullman 53 39 52 37 50 40 / 10 0 0 0 10 10 Lewiston 60 42 55 38 54 43 / 10 0 0 0 0 0 Colville 44 35 45 32 45 35 / 30 30 10 0 10 30 Sandpoint 47 40 47 33 46 38 / 60 40 20 0 30 50 Kellogg 49 41 51 40 50 42 / 60 20 10 0 20 20 Moses Lake 55 38 50 35 49 39 / 0 0 0 0 0 10 Wenatchee 55 41 51 39 50 42 / 10 0 0 0 10 30 Omak 47 37 46 36 45 38 / 10 10 0 0 10 30

OTX WATCHES/WARNINGS/ADVISORIES
WA...None.
ID...None.