Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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367 FXUS66 KOTX 161219 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 519 AM PDT Thu May 16 2024 .SYNOPSIS... Today will be the last day of well above average temperatures for the next week or two. The arrival of a vigorous cold front this afternoon will produce widespread windy conditions, with gusts as high as 40 to 50 mph in parts of central and eastern Washington. Gusty west winds will continue into Friday, with significantly cooler temperatures. Seasonably cool and showery weather is expected this weekend into next week. && .DISCUSSION... ...GUSTY WEST WINDS TODAY AND FRIDAY WITH A TRANSITION TO COOLER AND SHOWERY WEATHER BY THE WEEKEND... Today and Tonight: The first half of May has had its fair share of breezy days across the Inland Northwest, but today and tomorrow will feature the most widespread windy weather so far this month. The Polar Jet will descend from B.C. and the Gulf of Alaska today and push a vigorous cold front across Washington and Idaho this afternoon. By late in the day, low pressure deepening east of the Continental Divide will lead to an increasingly tight westerly pressure gradient across the region. West winds will peak late in the afternoon and early this evening as cool maritime air spills through the Cascade gaps. Along and behind the cold front, the NAM and GFS advertise 850mb winds around 40kts suggesting gust potential of 40 to 50 mph from Vantage and Wenatchee across the Waterville Plateau and along the Highway 2 corridor from Coulee City to the West Plains. A Wind Advisory is in effect from 2 PM to 10 PM emphasizing isolated power outages, patchy blowing dust near recently worked fields, and treacherous driving conditions for high profile vehicles. Afternoon highs in the 70s will tumble into the 40s tonight as west winds continue to gust in the 20 to 35 mph range across the Columbia Basin, West Plains, and Palouse. Exposed ridge tops in north Idaho and in the Cascades have the potential of 40 to 50 mph gusts through the night and into Friday morning as the upper level jet sets up overhead. Friday: Additional Wind Advisories may be necessary Friday for the Palouse, Lewiston-Clarkston area, and the Winchester/Craigmont areas. The tight surface pressure gradient will continue to support windy conditions well into Friday afternoon. As the wind direction becomes more northwesterly, southeast Washington and portions of the southern Idaho Panhandle will experience the brunt of the winds with gusts of 35 to 45 mph. Cooling aloft under the 500mb trough (-25 to -28C) will generate showers over the Idaho Panhandle and eastern third of Washington. The National Blend of Models (NBM) advertises a 30 to 50 percent chance of measurable precipitation across the eastern third of Washington and a 60 to 80 percent chance for the mountainous terrain of the northern and central Idaho Panhandle. Some of the strongest cells Friday afternoon will be capable of producing lightning, small hail, and wind gusts up to 50 mph. High temperatures on Friday will be a solid 10 to 15 degrees cooler than Thursday with readings mainly in the 60s. As winds diminish Friday night, temperatures will tumble into the 30s and 40s by sunrise on Saturday. Our typical cold spots in our sheltered valleys of north Idaho and northeast Washington like Deer Park, Springdale, and Republic may flirt with freezing temperatures. /GKoch Saturday to Wednesday: The periods with a trough digging into the West, before weak and short-lived ridge moves in for the start of the new work week. Then another low moves in toward next Tuesday or Wednesday, models start to disagree over the precise timing and track of that low but they do show it having some impact on the area. First this weekend, a mid-level trough slides down the BC coast and deepens as it move into the Pacific Northwest. Moisture starts to move in early, but the atmosphere really moistens going into late Saturday into Sunday as it wraps into the low. This will bring increasing clouds and rain chances. The best rain chances remain near the Cascades and northern mountain Saturday morning, then expand across throughout more of the Inland NW later Saturday into Sunday with the deeper Columbia/lower lee of the Cascades having smallest chances. The best chances for wetting rains (>=0.10) will be near the Cascade crest and the NE WA and ID mountains zones. Some embedded thunderstorms are also possible during the afternoon hours over the weekend, with the best chances toward the northern mountains. Additionally, look for breezy conditions especially in the lee of the Cascades and western basin, with gusts of 25-35 mph possible. The breeziest time appears to be around late Saturday and Saturday evening. Heading into Monday the weak ridge builds in, with a west- northwest flow. The primary shower chances retreat to the mountains. It will remain a little breezy again especially near the Cascades. Then Tuesday into Wednesday a deeper and wetter low drops down the coast and into the Pacific Northwest. Models take it in slightly different directions and at different speeds, but generally starts to really impact the area later Tuesday as it starts to drop down the WA coast and then tries to make its way inland, wrapping moisture into it. This will bring broader and higher over precipitation chances across the region. There will be a broader opportunity for wetting rains. Temperatures will be below normal much of the period between Saturday and Wednesday. High will largely be in the upper 50s and 60s, with some areas near 70 in the deeper Columbia Basin and L-C valley. Overnight lows will be in 30s and 40s, with some potential for some pockets of frost in a few sheltered valleys across the northern mountains early Saturday, early Sunday, and maybe early Monday. Overall the warmest day of the period appear around Monday, but Tuesday could be similar if the low is slower to move in. /Solveig && .AVIATION... 12Z TAFS: Scattered rain showers will develop over the Cascades and mountainous terrain near the Canadian border north of Colville and Sandpoint after 18z as the cold front moves inland. Post frontal showers will increase over the Idaho Panhandle and southeast Washington overnight with ceilings above 5000 feet. The Pullman, Lewiston, and Coeur d`Alene TAFs have mention of these showers after 08z. West winds are expected to produce gusts to 30kts along and behind the cold front this afternoon and evening. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Visibility reduction to 6SM with blowing dust has been added to the Moses Lake TAF. This is a low confidence forecast. Dust is just as much a function of recent field work as it is wind speed. This is the season for planting corn and beans in the irrigated fields near Moses Lake so the potential is there for localized visibility reduction with dust. /GKoch ----------------------- 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 75 44 63 40 62 40 / 0 10 30 10 10 20 Coeur d`Alene 74 44 59 39 61 39 / 0 20 60 10 10 30 Pullman 72 43 58 39 61 39 / 0 40 20 0 0 20 Lewiston 82 52 67 44 71 45 / 0 20 10 0 0 10 Colville 75 37 63 34 61 36 / 0 20 50 10 50 60 Sandpoint 72 43 56 37 58 39 / 10 30 80 20 40 60 Kellogg 70 44 53 40 57 42 / 10 50 80 20 20 40 Moses Lake 80 44 69 40 69 40 / 0 10 0 0 0 0 Wenatchee 74 46 64 45 65 44 / 0 10 0 0 0 0 Omak 77 42 69 39 66 40 / 0 10 0 0 20 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Wind Advisory from 2 PM this afternoon to 10 PM PDT this evening for Moses Lake Area-Upper Columbia Basin-Waterville Plateau- Wenatchee Area. && $$