FXUS66 KOTX 182041 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 141 PM PDT Mon May 18 2026 .KEY MESSAGES... - Pop up showers and isolated thunderstorms primarily Northeastern WA and North Idaho Tuesday afternoon. - Chilly overnight temperatures will bring an isolated threat of morning frost Tuesday. This could impact sensitive plants or crops. - Conditions trend drier and warmer through the workweek regionwide, with periodic breezy winds for the Cascades and central WA. && .SYNOPSIS... Showers with isolated afternoon thunderstorms will continue Tuesday. Precipitation chances decrease and afternoon highs trend warmer through the workweek, climbing back into the 70s and 80s by Thursday and continuing through next weekend. Breezy winds are expected at times through the Cascade gaps and across the western Columbia Basin. && .DISCUSSION... Tonight - Wednesday: The combination of afternoon heating and residual moisture will keep a threat for showers and thunderstorms this evening across Northeastern WA and North. Storm motion to the south and southeast does bring a small threat for a few cells to drift off the higher terrain and into the Upper Columbia Basin and Spokane-Cd'A area. The depth of the convection is slowly shrinking at temperatures warm 2-3 Celsius at 500 mb so updrafts are largely growing to -25C versus -35C on Sunday. Ideally, this will result in less lighting strikes across the area. The strongest cells will be capable of brief downpours of rain/small hail and wind gusts around 30 mph. Overnight lows will be a few degrees warmer Tuesday morning but still cooling into the 30s to 40s. The threat for frost will be more localized. If you experienced temperatures in the low 30s and frost Monday morning, may want to consider taking actions to protect sensitive plants again. Given the complex terrain of our region, many observation platforms are not dipping to freezing given the placement of the sensor above ground but frost has been reported nearby, especially where there are low spots. The current frost forecast has a 20-25% chance for frost in the valleys of NE WA and N ID (down from 40-50% Monday). One change for tonight will be the potential for midlevel clouds moving through NE WA and N ID overnight which would support the idea of warmer temperatures. On Tuesday, temperatures continue to warm aloft for most areas away from far NE WA and N ID. This will equate to less shower activity region-wide and mainly fair cumulus build ups. Upper levels will be slower to warm over far NE WA and N ID. Locations like Ione, Porthill, and Bonners Ferry will maintain a 15-25% chance for showers and t-storms. High pressure begins to amplify along the coast Wednesday. Midlevel flow buckles from northwest to north over the INW. A cooler shortwave will drop down the eastern flank of the ridge and along the Northern Rockies. This will bring a threat of showers and thunderstorms back to the ID/MT border Wednesday afternoon. If the wave is a bit deeper and further west, the threat for convection may need to be expanded as far west as the ID/WA border. Breezy northerly winds will develop Wednesday night with this system with gusts of 20-30 mph for locations like Omak, Ephrata, and Wilbur. Thursday-Monday: There is moderate confidence for the upper-level ridge to build into the region Thursday and linger into Friday delivering a warming and drying trend. Details become a bit more uncertain over the weekend and early next week when additional shortwaves begin swinging into the region from the Gulf of AK. There are many variations with timing and strength of these systems. Any systems will need to be monitored closely for potential showers and thunderstorms along with gusty winds, especially if thereis a quick exchange of air masses. Ensemble means are hinting wind gusts around 30 mph right now across the Basin and Spokane Area with a handful of members in the 40-45 mph range. Monday is the windiest day at this time. /sb && .AVIATION... 18Z TAFs: Antecedent boundary layer moisture and surface heating will result in developing cumulus fields 18-20Z. There is 40% chance for cells to develop showers and 10-25% for convection to grow deep enough for lightning. Greatest risk will be over the mountains of northern WA and the Idaho Panhandle though cells drifting south will pose a small risk into the upper Columbia Basin and Spokane-Cd'A area. Given the latest output from the cam models, did introduce prob30 for KGEG-KSFF-KCOE for -shra with a 10-15% chance for -tsra. Any thunderstorms will bring a threat for brief downpours of rain/small hail, lightning, and erratic outflow winds to 30 mph. Pending where rain falls, areas of valley fog will be possible overnight. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is a small risk for MVFR cigs mainly around KGEG-KSFF- KCOE-KPUW this morning as cumulus clouds are developing and cloud bases are slowly lifting. Main uncertainty this afternoon will be if thunderstorms survive off the higher terrain into KGEG-KSFF-KCOE as we have seen the last two afternoons. /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 41 68 44 71 43 72 / 20 0 0 0 0 0 Coeur d'Alene 41 66 44 68 43 70 / 20 10 0 0 0 0 Pullman 39 64 42 66 41 69 / 0 0 0 0 0 0 Lewiston 43 70 46 72 46 75 / 0 0 0 0 0 0 Colville 36 70 40 74 38 75 / 20 20 10 0 0 0 Sandpoint 40 65 43 67 41 70 / 20 10 10 10 0 0 Kellogg 39 65 43 67 42 70 / 20 10 0 10 30 0 Moses Lake 41 74 45 78 48 79 / 0 0 0 0 0 0 Wenatchee 48 73 50 77 53 78 / 0 0 0 0 0 0 Omak 43 74 47 77 48 78 / 0 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$