Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
420 FXUS65 KMSO 250759 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 159 AM MDT Tue Jun 25 2024 .DISCUSSION...Warm and dry conditions continue through Wednesday morning, then things become interesting. Currently, there is an air mass of anomalous PWs over Arizona and southern California. When we use the term PW or in this case anomalous PW, we are talking about precipitable water, this is the amount of available moisture for precipitation. This air mass will drift northward tomorrow and into Wednesday morning. Expect high clouds during the morning Wednesday and a couple high resolution models are introducing warm frontal showers before noon, although a dry surface may only allow for virga showers or sprinkles. By the afternoon, mid-level instability increases across the region and showers and thunderstorms develop. Looking at the makeup of the atmosphere 2 things stand out, initially a dry surface layer and then a deep saturated layer late afternoon. Initial showers or storms will likely have gusty outflow winds especially from southwest MT, Butte, through Lemhi County, ID. Then as the atmosphere moistens up there is the potential for heavy rainers. These storms should have good movement off to the northeast so at this time isolated, brief but heavy showers is the threat late afternoon. Thursday as the low pressure moves north of our region, jet dynamics along the base of the trough will allow for widespread precipitation. Due to the convective nature of this system, exact precipitation totals are difficult but the mountains have a 50% chance of receiving 0.25 inch, while valleys especially north of I-90 have a 10 to 20% chance. Friday showers and thunderstorms continue along the Continental Divide, while the rest of us enjoy a not as warm day with north to northeasterly breezes. Saturday a transient ridge will allow for a drier day, with temperatures 70s and 80s in western Montana (mostly cloudy) and upper 80s and 90s in north-central, ID (mostly sunny). July 1st and 2nd, another system affects the region but details are still lacking. && .AVIATION...The Northern Rockies air space will be under the influence of a transient ridge today. Expect light breezes and VFR conditions. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$