Area Forecast Discussion
Issued by NWS Spokane, WA
Issued by NWS Spokane, WA
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253 FXUS66 KOTX 102247 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 347 PM PDT Mon Jun 10 2024 .SYNOPSIS... A dry cold front arrives Tuesday afternoon ushering gusty westerly winds across the region. Breezy conditions continue into Wednesday with cooler temperatures. Temperatures rebound on Thursday then a pattern shift late in the week will lead to cooler temperatures, another round of gusty winds, and shower chances for Friday into the weekend. && .DISCUSSION... Tonight through Wednesday night: A progressive, spring weather pattern will continue across the Northwest through this period. During the next 12 hours, shortwave ridging will be passing through. This is delivering stable weather conditions, temperatures a handful degrees of average, and light breezes of 15-20 mph. Quickly on its heels, the next area of low pressure is swinging to the coast and will begin crossing 130W by midnight. This wave will swing into the Northwest on Tuesday delivering our next bout of gusty winds. The system will largely be moisture deprived with just a 10-20% chance for showers along the immediate Cascade Crest and immediate Canadian Border. The more impactful element of the system will be strong winds arriving with the cold front in the afternoon and early evening. The Inland Northwest should brace for another round of sustained winds of 15-30 mph with gusts of 30-45 mph. The windiest locations will be found in the lee of the Cascades and into the Western Columbia Basin. Wind advisories have been issued to address these areas although, some of these stronger winds will likely expand across the Upper Columbia Basin along Highway 2 into Wilbur and Davenport. The foothills of the Blue Mountains will be another wind prone area. The sheltered northern valleys will experience lower sustained speeds of 10 mph or less but afternoon mixing will likely transport wind gusts up to 30 mph at times into the valley floors. The winds will be driven by a 16 mb cross-cwa pressure gradient and enhanced by cold air advection late in the day into the evening. Impacts: Use caution around dry grasses with the potential for new fire starts to become problematic for local resources. Grasses on south aspects and in the Western Columbia Basin are quickly curing and will support fire spread. Those venturing on area lakes in small vessels such as kayaks should be prepared for choppy, changing conditions throughout the afternoon. Winds will remain elevated Tuesday night but speeds will be significantly lighter compared to the early evening. Much drier air will continue to flood into the region. Locations that decouple from the winds will cool sharply with overnight temperatures dipping into the upper 30s to lower 40s; otherwise the winds will keep temperatures in the 40s and 50s. Zonal or westerly flow will remain over the region on Wednesday with continued breezy conditions. Wind gusts in the afternoon will be lower, only topping out near 25 mph. Temperatures on Wednesday will be nearly 10 degrees cooler than Tuesday topping out in the 70s. /sb Thursday to Monday: The Inland NW starts off this period dry and mild, before the next system moves in with cooler temperatures, breezy conditions and, for some, a chance of showers and thunderstorms and even be some high terrain snow. Patchy frost is also possible toward Saturday night/Sunday morning in some of the sheltered northern valleys. First Thursday a shortwave ridge migrates across the Pacific Northwest and pushes toward the northern Continental Divide Thursday night, while a deep low approach the Pacific Northwest coast. Highs are forecast to reach the upper 70s to mid-80s. Skies will be mostly clear to partly cloudy during the day, then clouds start to increase heading into later Thursday into Thursday night. Friday into Saturday a couple shortwave disturbances pivot around the approaching low and cross the region, thickening clouds and another increase in winds. Winds actually start increasing overnight into Friday morning near the Cascades and increase throughout the region heading through the day, peaking once in the evening, subsiding some overnight and then increasing again through Saturday afternoon. Speeds of 15-30 mph, with gusts of 30 to 40 mph will be possible, strongest around the lee of the Cascades through the Waterville Plateau and Upper Columbia Basin. In terms of fire weather concerns, afternoon RH values will hover near critical values, especially Friday so this will be need to be monitored. Wind gradually decline late Saturday night into Sunday morning. Precipitation-wise, the main precipitation chances lay near the Cascade crest Friday and perhaps skimming near the Canadian border. By Saturday the atmosphere moistens up some and the threats of showers expands over most of the Cascades and northern mountains and central Panhandle mountains, with a risk for snow in the higher terrain. Some snow may be found near Washington Pass and a rain/snow mix could even be seen near Stevens and Sherman Pass. It is borderline for showers outside of those mountain zones. Places like Spokane and Coeur d`Alene and the Palouse were held to just a ten percent chance. Thunderstorms are possible around the northern mountains Saturday afternoon. Some could be locally stronger and could enhance the synoptic scale winds. Sunday and Monday the area remains in a troughy pattern, but models really start to diverge over the details of where the individual features lay. The overall pattern will favor continued shower chances around the mountain zones and at least a slight chance around the eastern third of WA and lower ID. As the models start to settle on a solution confidence in who will have the higher risk will start to come into focus. A limited risk for t-storms will linger over the northern mountains too. Wind will still remain a bit breezy, but not as much as previous days with gusts near 10-20 mph strongest near the Cascades to Waterville Plateau. As for temperatures they being to drop heading into Friday and especially the weekend. Highs on Friday are forecast in the 70s to near 80, then 60s to mid-70s for the weekend, then warming a couple degrees on Monday. Lows are forecast to be in the 50s Friday morning, the 40s to near 50 Saturday morning, then the 30s to mid-40s Sunday morning, moderating slightly Monday morning. These latter cooler temperatures could bring some frost to the sheltered valleys near the Cascades and Canadian border counties. Overnight Saturday into Sunday morning has the highest risk. As we get closer we will have more confidence, but could impact anyone with sensitive plants or crops. /Solveig && .AVIATION... 00Z TAFS: A few sprinkles are falling from fair cumulus around Bonners Ferry, otherwise, shortwave ridging passing through the region will deliver stable weather conditions and VFR skies. Fair cumulus clouds across N Idaho will dissipate this evening by 04z. Winds which are gusting 15-20 mph will also decrease after 02z. A dry cold front presses through the region on Tuesday with winds increasing around 18z then becoming strong from 21-02z. Sustained winds 20-30 mph with gusts around 40 mph expected for most sites across the Basin and within the aligned Cascade valleys. This includes Wenatchee, Chelan, Ritzville, Pullman, and Spokane. The sheltered northern valleys will experience sustained winds closer to 10kts or less with infrequent gusts 20-30 mph. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence is high for VFR skies today and tomorrow but this will come at the cost of strong winds. There is high confidence for windy conditions Tuesday afternoon and early evening. Confidence is high for wind gusts to 30 mph and moderate for wind gusts in excess of 40 mph. Highest probabilities for gusts in excess of 40 mph is around Wenatchee, Moses Lake, Douglas, and Ephrata. The strong jet crossing the Cascades will result in wave clouds at times and potential for clear air turbulence. We will need to monitor localized blowing dust given these wind speeds but time of year is not favorable for widespread impacts. /sb ----------------------- 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 55 83 46 74 45 79 / 0 0 0 0 0 0 Coeur d`Alene 53 79 45 71 44 79 / 0 0 0 0 0 0 Pullman 51 78 45 69 44 77 / 0 0 0 0 0 0 Lewiston 58 89 54 79 50 87 / 0 0 0 0 0 0 Colville 48 80 40 74 40 79 / 0 10 0 0 0 0 Sandpoint 51 78 44 70 42 77 / 0 10 0 0 0 0 Kellogg 55 76 48 67 47 77 / 0 0 0 0 0 0 Moses Lake 55 87 47 79 46 83 / 0 0 0 0 0 0 Wenatchee 60 80 50 76 49 82 / 0 0 0 0 0 0 Omak 55 84 46 79 47 83 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Wind Advisory from noon to 8 PM PDT Tuesday for Moses Lake Area- Waterville Plateau-Wenatchee Area. && $$