181 FXUS66 KOTX 281757 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1057 AM PDT Sun Apr 28 2024 .SYNOPSIS... Sunday and Monday will be windy with gusts around 35 mph. Showers will focus in the mountains today then expand into the lowlands overnight and Monday with the passage of a frontal system. This system will also bring snow to the Cascade mountain passes Sunday night and Monday morning. Temperatures will trend cooler with areas of frost returning Tuesday morning. Unsettled conditions return for the remainder of the week. && .DISCUSSION... Today through Monday night: Unsettled weather pattern continues over the Inland Northwest as shortwaves continue to drop into the region from the Gulf of AK. Surface analysis indicates heights falls are ongoing over south-central Alberta resulting in a 6 mb pressure gradient across the forecast area as of 2AM. These gradients will continue to increase today closer to 9 mb resulting in stronger winds than those experienced on Saturday. Winds will generally be out of the south and southwest this afternoon with speeds across the Okanogan Valley, Waterville Plateau, Columbia Basin, West Plains, and Palouse close to 20 mph. HREF places the highest probabilities for these speeds from Omak to Waterville and from the Tri-Cities to Airway Heights. Accompanying wind gusts will be on the order of 30 mph. It will also be noticeably breezier for our northern mountains and Idaho Panhandle with sustained speeds of 10-15 mph and gusts near 25 mph except some higher gusts on the higher peaks. Precipitation will once again focus over the rising terrain of NE WA and N ID as scattered showers. Not ruling out a few weak thunderstorms though instability parameters and calibrated thunder chances are lower than those predicted on Saturday. A more robust shortwave drops into the Northwest overnight into Monday ushering a potent cold front through the region with 850mb temperatures cooling from 4C to 0C. Stronger dynamics will lead to more widespread showers which will mix or change to snow for elevations as low as 2500 feet Monday morning. The most impactful snow will be on the Cascade passes where several inches of snow will be possible overnight into Monday morning bringing a return to winter travel conditions. Winter weather advisories were issued to address these concerns. Monday will feature another shot of strong winds with a shift toward a westerly direction. HREF probabilities for sustained winds of 20 mph are 50-90% for a much larger area stretching from the foothills of the Cascades, across the COlumbia Basin, and into the lower Idaho Panhandle including the Palouse and L-C Valley. Sustained winds on the order of 20-25 mph will be accompanied by gusts of 30-40 mph. Locally stronger winds 30 G 45 mph are possible on the Waterville Plateau and in the foothills of the Blue Mountains. Hi-res models are also indicating isolated gusts 35-40 mph with short-lived downdrafts near convective showers that develop in the Basin Monday around midday to early afternoon. Thinking these showers are very possible given the projected lapse rates and midlevel forcing. Patchy blowing dust will also be possible near freshly tilled fields around Moses Lake, Othello, and Warden as afternoon humidity values dip near 20% though this comes with low confidence. Winds will weaken Monday evening and overnight with clearing skies. Several areas will carry a risk for freezing temperatures. There is at least a 30-40% chance along and north of a line from Pullman to Mose Lake for freezing temperatures. Probabilities increase closer to 50% across the upper Basin and Okanogan Valley then 60-90% for the northern mountain valleys. /sb Tuesday through Saturday...Looking ahead to the latter half of the week, the forecast becomes somewhat uncertain, characterized by a split in ensembles starting Wednesday night. Before that, a shortwave will slide through the region bring an unsettled pattern to the region Tuesday. There is a widespread chance of showers on and with the instability with afternoon heating, thunderstorms are not out of the question during the afternoon and evening. Winds will also be a bit breezy, but will not be as high as what is seen Monday. As we move into Tuesday night, the threat of showers will decrease along with temperatures dipping into the low to mid 30s, leaving a heightened risk of frost across the area. Those with sensitive plants should take precautionary measures, particularly as temperatures flirt with freezing. Showers will increase again Wednesday afternoon, mainly over the ID Panhandle and mountainous terrain. Winds will continue to decrease Wednesday from what is seen Tuesday. High temperatures will warm into the mid 50s to low 60s However, the picture becomes muddled as we move into Wednesday night, as differing ensemble models paint contrasting scenarios. While some models indicate a continuation of a troughing pattern accompanied bu the arrival of a shortwave ridges, others suggest the intrusion of a ridge into the region. Should the ridge remain offshore, temperatures are poised to be cooler than initially anticipated, with the area remaining unsettled within the trough. Nevertheless, there is a growing consensus that the ridge will make landfall ushering in warmer temperatures. /KM && .AVIATION... 18Z TAFS: Showers are expanding once again across the ID Panhandle and will develop in the mtns of NE WA as well. Cigs will continue to improve at GEG, but under showers cigs to 3000 feet will be possible. Otherwise, winds will increase region wide with a general south to southwest direction. Gusts around 30-35 mph will be possible in the Okanogan Valley, Columbia Basin, and near the Blue Mountains. A potent cold front tonight into Monday will bring more widespread precipitation to the Idaho Panhandle and Eastern third of WA. Rain will transition to wet snow for elevations around 2500 feet and higher which includes Pullman, Spokane, and Coeur D Alene. Higher confidence for GEG to see snow mix in and have that in the TAF, but not for PUW/COE because of lower confidence. Confidence is moderate for little to no accumulations with steady winds keeping temperatures above freezing during this time. Winds will become gusty Monday from the west as well with potential for brief gusts around 40-45 mph. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: A lightning strike or two will be possible again in Northeastern WA and North Idaho. The threat is lower than Saturday but tough to rule out completely. ----------------------- 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 58 39 51 32 53 36 / 20 30 70 10 30 10 Coeur d'Alene 54 38 48 31 50 35 / 40 40 90 20 30 20 Pullman 55 37 48 31 49 33 / 20 30 90 30 60 20 Lewiston 64 44 55 37 56 37 / 20 30 80 20 40 20 Colville 58 34 51 26 55 31 / 40 30 80 10 30 10 Sandpoint 52 38 47 32 48 35 / 80 70 90 40 50 20 Kellogg 51 39 44 33 45 35 / 70 60 100 50 70 30 Moses Lake 63 39 59 34 60 36 / 10 10 30 0 10 0 Wenatchee 60 39 55 37 57 38 / 10 20 20 0 10 0 Omak 63 37 57 32 58 36 / 10 10 30 0 10 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...Winter Weather Advisory from 11 PM this evening to 11 AM PDT Monday for Western Chelan County. && $$