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Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
819 FXUS65 KMSO 171841 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1241 PM MDT Sat Aug 17 2024 .DISCUSSION...High pressure remains over the region today, bringing generally sunny skies, light winds and warm temperatures to the region. Cloud cover will increase tonight into Sunday as a wave of mid level monsoonal moisture advects northwards into western Montana and north central Idaho. Forecast models have begun to show potential for some light showers and isolated thunderstorms associated with this wave as it moves through northwest Montana early Sunday morning, thus the probability of precipitation has been increased for these areas. In addition, with high pressure generally off to the east and low pressure to our west, a north east to easterly gradient will develop tonight. It doesn`t look overly strong, but will be enough to help limit any fog development for Sunday morning. Monsoonal moisture will continue to be drawn northwards into the Northern Rockies region Sunday into Monday. Afternoon and evening showers and thunderstorms are anticipated both days, primarily across western Montana, though a few storms could form in the higher terrain of north central Idaho near the Bitterroot Divide. The main threats with storms will be gusty outflow winds of 40 to 50 mph, lightning, small hail and brief heavy rain. For Tuesday and Wednesday next week, forecast models show the upper level flow becoming more southwesterly as a persistent area of low pressure develops off the west coast of Washington and high pressure shifts slightly east of the Four Corners area. While afternoon and evening thunderstorms will be possible in this pattern, the region largely appears to get cut off from monsoonal moisture surges, and thus convection looks to be more isolated and focused across southwest Montana. Near normal temperatures and breezy conditions can be expected area wide. There is still significant spread in the forecast models with how the low pressure system in the Pacific Northwest will eject inland mid to late next week. Differences exist both in the timing of this occurring as well as how it occurs (weaker open wave vs a more significant closed low type feature). Most solutions lean towards cooler temperatures, but the amount of precipitation (and timing of when precipitation may occur) is very much in flux. && .AVIATION...High pressure will bring mostly sunny skies through this evening across western Montana and north central Idaho. Local/regional fires in Idaho will likely send another plume of elevated smoke into central Idaho and Northwest Montana, which may result in locally lowered visibility. A wave of mid level monsoonal moisture will move into the region late tonight into Sunday morning, bringing an increase in cloud cover for the mid levels. A few showers and possibly even a thunderstorm are being shown by high resolution models across northwest Montana late tonight between 18/0600z and 18/1200z. Also of note, a northeast to east gradient is expected late tonight into early Sunday, which could produce some breezes up to 10 to 15kts for exposed locations, including KGPI and KMSO. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$