Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
628 FXUS65 KMSO 231828 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1228 PM MDT Sun Jun 23 2024 .DISCUSSION...A trough moving over the region today will set up zonal (west to east) flow for tomorrow. Overall, the impact of this pattern is breezy conditions in the valleys with stronger winds gusting near 30 or 40 mph at some mountain locations. Along with the increased winds, the region is under a very dry air mass, so relative humidity will be dropping down below 20 percent at most low elevation locations. Monday through Wednesday a ridge builds in over the region, causing some of the hottest and driest conditions we`ve seen so far this summer. For several days, many valley locations will have relative humidity drop below 20 percent. Also, under the influence of the ridge a phenomena called thermal belts will intensify. Thermal belts cause low humidity to persist on the mid-slopes and sometimes the upper slopes in the mountains. While land management agencies are currently still reporting fire danger at moderate levels across the northern Rockies, these are the weather conditions that start the transition to a drier time of the Summer. And the end of June and early July is a very typical time of year for this to occur. A recent change in the models has been to show the ridge starts breaking down late Wednesday into Thursday. Previously, even the ensembles weren`t indicating a breakdown starting until Thursday. But the timing has been trending earlier with successive model runs the last few days. This will bring more wind again, cooler temperatures, and the chance for lightning later this week. The probability of a good, wetting rain with this system has been trending down. So while portions of northwest Montana still have a roughly 50 percent chance of getting 0.10 inches or more of rain Thursday or Friday, most of the rest of the region less than a 25 percent chance of picking up that much moisture. && .AVIATION...A trough moving over the region today and tonight will bring gusty westerly winds this afternoon and increasing cloud cover. There is a slight chance of thunderstorms this evening, but dry air moving in from the west is really making just virga much more likely with more thunderstorms east of the Continental Divide. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$