Marine Weather and Tide Forecast for Troy, MT

SYNOPSIS
Active pattern continues through the weekend. Blowing dust concern returns for Sunday. The colder air this weekend and early next week will bring freezing low temperatures to many areas. Drier weather next week, with moderating temperatures.

DISCUSSION

Morning update: Update sent to address shower chances which are a bit more expansive this morning and tweak wind gusts down some to reflect the current wind gusts. Peak wind gusts will be this morning and early afternoon and slowly wane this evening. The Blowing dust advisory was also delayed to start closer to 11AM due to the showers this morning. We have gotten a report of blowing dust near Ritzville but visibility has only been reduced to 3 miles.

Sunday through Monday night: A cold upper-level low centered over the Pacific Northwest, combined with surface high pressure building east of the northern Rockies, will strengthen the regional northeast pressure gradient. The Cranbrook, BC to Pasco, WA (YXC-PSC) gradient is forecast to tighten from ~7 mb Saturday evening to ~12 mb early Sunday morning. This will generate gusty northeast winds through the Purcell Trench into the Spokane area and Columbia Basin through Sunday afternoon. Coupled with a dry air mass (precipitable water values 60-80% of normal; dew points in the mid 20s to low 30s), these winds will increase the risk for blowing dust and localized visibility reductions across the central and western Columbia Basin, including Moses Lake, Coulee City, Wilbur, and Ritzville on Sunday.

Additionally, these winds will draw cold air from the northeast into the Inland Northwest, with snow levels falling to between 2500 to 3000 feet across northeast Washington and north Idaho Sunday morning. Precipitation wrapping around the upper-level low as it drifts southward Sunday will fall as snow primarily across the mountains of the central Idaho Panhandle, though isolated flakes could fall to higher elevations across the Palouse early Sunday morning.

Sunday will be the coldest day of this week with highs mostly in the upper 40s to upper 50s. Low temperatures will fall into the mid to upper 20s across the northern Valleys Sunday and Monday nights.
Winds may be strong enough across the Columbia Basin and Spokane area Sunday night to keep temperatures above freezing with a 30-60% chance for temperatures below 32F. As the low moves south of the area Monday, building upper-level ridging will bring lighter winds and clearing skies. With dry air remaining in place, the probability of sub-freezing temperatures across the Spokane area and Columbia Basin increases to 60-80% Monday night. The Palouse has better chances for freezing temperatures both nights with a 70% chance Sunday night and a 100% chance Monday night.

Tuesday through Saturday: Temperatures begin to trend warmer for the rest of the week as an upper-level ridge builds over the Pacific Northwest. A weak front on Wednesday flattens the ridge temporarily and brings an increase in clouds, a 15% chance for showers across the north Cascades and breezy mountain winds. The ridge strengthens Thursday through Saturday with afternoon temperatures warming into the mid 60s to low 70s by Friday. These temperatures are 8-13 degrees above normal for this time of year. Overnight lows will remain chilly though, with values in the upper 20s to low 30s across the northern values and in the low to mid 30s elsewhere. Ensembles begin to show the next weather system moving into the Pacific Northwest between late Friday night and Saturday, though there remains differences on the timing and strength. The main message at this point is that this will be the next period to monitor for breezy winds and mountain showers. /vmt

AVIATION
18Z TAFS: The main aviation impact today will be gusty northeast winds coming through the North Idaho Panhandle and spreading across the Columbia Basin. Sustained speeds of 10-20kt with gusts 15-27 kts. Peak gusts will be 18-22z with speeds slowly waning 22-01z. This has potential for localized BLDU around Moses Lake, Ephrata, and Ritzville. Winds will largely come from the north through Omak and into Wenatchee. Showers wrapping around an area of low pressure drifting toward NE Oregon will impact southeast WA and the southern and central ID Panhandle through this afternoon. Ceilings will range between 4-6kft AGL.
The showers will continue to impact KLWS overnight and at times, skirt KPUW. There is a 30% chance for cigs at KLWS to lower into MVFR cigs, otherwise VFR conditions will be in prevail.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for primarily VFR conditions through the period. High confidence for gusty north to northeast winds through this afternoon. Low confidence for BLDU at KEPH/KMWH and if cigs will reach MVFR at KLWS overnight.

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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 54 35 51 33 56 30 / 20 20 0 0 0 0 Coeur d'Alene 55 35 50 32 55 30 / 20 20 0 0 10 0 Pullman 52 34 50 31 53 28 / 0 30 20 10 10 0 Lewiston 59 40 54 38 57 34 / 0 10 30 30 30 0 Colville 58 28 56 25 59 24 / 40 30 0 0 0 0 Sandpoint 55 32 47 29 54 26 / 20 30 0 0 0 0 Kellogg 52 32 44 30 53 28 / 10 60 10 10 10 0 Moses Lake 59 38 59 32 60 29 / 10 10 0 0 0 0 Wenatchee 60 44 59 37 61 40 / 20 50 0 0 0 0 Omak 55 38 60 31 61 33 / 20 60 0 0 0 0

OTX WATCHES/WARNINGS/ADVISORIES
WA...Blowing Dust Advisory from 9 AM to 5 PM PDT Sunday for Moses Lake Area-Upper Columbia Basin.
ID...None.