Marine Weather and Tide Forecast for Troy, MT

SYNOPSIS
A cold front passage this afternoon into Wednesday will bring lowland rain, mountain snow, and breezy to windy conditions. Some snow will make it down to the lowlands Wednesday night into Thursday morning on the tail end of the mid-week system.

DISCUSSION
Today to Thursday: Low pressure in the Gulf of AK drops into our area through Wednesday and gradually shifts out Thursday. This brings modest chances for precipitation, along with a trend toward cooler temperatures. Highs will largely in the mid 40s and 50s.
Lows will be in the mid-30s to low 40s tonight, then drop into the mid-20s to mid-30s Wednesday and Thursday night which means some freezing temperatures.

Rain and mountain snow chances increase through today from the west as the low approaches, becoming likely in the Cascades and northern counties by late morning to afternoon and over most of the remaining CWA late Tuesday afternoon/evening into Wednesday.
The exception will be over central WA where the shadowing will keep PoPs to around 40-50%, highest Tuesday overnight into early Wednesday. Overall chances start to wane from the west Wednesday night into Thursday and then start to end completely heading into Thursday night. There is about 15 percent chance for embedded t-storms over the northeast CWA Wednesday afternoon/early evening.
Snow levels around 3.5-4.5kft Tuesday afternoon drop to 2-3kft Wednesday afternoon and 1-1.5kft by Thursday morning. So look for mountain snow and lowland rain to start, changing to a lowland mix or even all snow overnight Wednesday into Thursday morning.
Precipitation chances start to wane by then, but it still leave the potential for some accumulation in the lowlands that time frame.

The biggest snow impacts are expected in the mountain passes.
Here are some probabilities from Tuesday to Thursday morning (48-hours):

2 4 6 8 12 Stevens Pass 100% 95% 85% 65% 20% Snoqualmie Pass 100% 85% 65% 45% 15% Lookout Pass 100% 80% 50% 35% 10% Sherman Pass 50% 20% 5% 0% 0%

Winter storm warnings remain in effect over western Chelan county and Winter Weather Advisories are in place over western Okanogan County this afternoon and tonight; over the higher elevations of the Okanogan Highlands this afternoon through Wednesday, and now over the central ID Panhandle, above 3000 feet, from this evening through Wednesday night.

The chance for 0.1 inches of snow at select locations outside the mountains for Wednesday night into Thursday AM: Pullman 60%, Sandpoint 55%, Spokane 20%.

Rain amounts around 0.25 to 0.60 inches are forecast around the east third of WA and ID, with higher amounts in the higher terrain. This could cause some minor flooding around small streams and creeks and lead to some ponding of water in poor drainage areas and field flooding. The NWRFC forecast some rises on mainstem rivers into midweek, though none reach action stage.
Paradise Creek, however, could approach action stage toward later Wednesday afternoon into evening. So this will be monitored, because it could easily push above action stage (or more).

Winds will remain breezy/gusty through this period. Southwest winds today at 10-20 mph with gusts of 25-40 mph. Winds turn more west-northwest Wednesday and Thursday, with similar speeds but gusts around 20-30 mph.

Friday to Monday: High pressure and drier weather comes in Friday, but another low approaches for the latter part of the weekend increasing rain and mountain rain/snow chances Saturday night into Monday. The primary low stays off the coast until Monday, so PoPs are 20-40%, up to near 60% at the immediate Cascade crest and central Panhandle Mountains on Monday. It will be a bit breezy and temperatures will be near normal, except Sunday when values are forecast to be slightly above normal.
/Solveig

AVIATION
18Z TAFS: The next system moves in today into tonight with rain and a return to MVFR at GEG/SFF/COE/PUW. Downslope flow off the Cascades will keep conditions VFR at KEAT/KMWH, while similar effects off the Blue Mountains keep LWS VFR until after the cold front passage Wednesday morning. CIGS are expected to degrade further as well for KPUW, becoming IFR around 15z Wed. The system will also usher in gusty west-southwest winds through the TAF period, shifting to west-northwest behind the cold front in Central WA Wednesday morning.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate confidence in CIGS dropping to MVFR for KGEG/KSFF/KCOE/KPUW tonight. Moderate confidence in KPUW dropping to IFR 15-18z Wed. High confidence that VFR conditions persist through the TAF period at KEAT/KMWH. JW

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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 38 49 30 49 29 / 50 90 70 30 30 0 Coeur d'Alene 49 37 46 30 47 29 / 50 100 90 50 50 10 Pullman 51 38 44 29 44 29 / 20 90 100 60 50 10 Lewiston 58 44 52 34 50 34 / 10 80 100 50 40 10 Colville 52 35 51 28 53 26 / 80 90 60 30 30 0 Sandpoint 46 37 44 30 45 28 / 80 100 90 60 70 20 Kellogg 46 37 43 29 41 28 / 60 100 100 70 80 30 Moses Lake 57 40 56 30 58 31 / 30 30 30 10 0 0 Wenatchee 55 37 52 34 55 34 / 40 50 20 10 0 0 Omak 56 37 53 31 58 31 / 60 60 30 10 0 0

OTX WATCHES/WARNINGS/ADVISORIES
WA...Winter Weather Advisory from 11 AM this morning to 5 PM PDT Wednesday for Okanogan Highlands.
Winter Storm Warning from 11 AM this morning to 5 AM PDT Wednesday for Western Chelan County.
Winter Weather Advisory from 11 AM this morning to 5 AM PDT Wednesday for Western Okanogan County.
ID...Winter Weather Advisory from 8 PM this evening to 5 AM PDT Thursday for Central Panhandle Mountains.