Area Forecast Discussion
Issued by NWS Missoula, MT
Issued by NWS Missoula, MT
814 FXUS65 KMSO 242018 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 218 PM MDT Fri May 24 2024 .DISCUSSION...Current radar trends this afternoon have depicted an increase in showers across northwest Montana. The meso-analysis portrays up to 100 J/kg of CAPE instability, which could be enough juice to cause a shower to grow tall enough to produce a lightning strike. There is a 40 to 50 percent probability for lightning occurrence with one of the showers through 7 pm, generally across northwest Montana. Another area that will need to be watched is over in north-central Idaho. The lightning occurrence probabilities range from 20 to 40 percent generally from Grangeville and points south and west from 5 to 11 pm PDT. So if you are recreating on the Snake River or along US-95, have a safe place in mind before you go. These showers could also produce wind gusts in excess of 30 mph (25% probability). The incoming upper trough will be much different than the heavy snow-producing system from Thursday. Ensemble means suggest that this will be more of an open wave moving quickly across the region Saturday into Sunday morning. Total precipitation ranges in the western Montana valleys go from nothing to several hundredths in the lower range, and up to 0.10 to 0.20" in the upper range. The mountains of north-central Idaho range from 0.10 to 0.50" and the western Montana mountains could range from a few hundredths up to a couple of tenths. Snow levels could be as low as 5000 feet, but probabilities for an inch or greater are mainly confined to the passes along the Idaho/Montana border including Lost Trail Pass. As the trough exits the region Sunday, a drying trend will start, but it will end up being a breezy afternoon across the region. The mean wind speeds will range from 10 to 25 mph across western Montana. Temperatures will rebound into the 70s and 80s by Monday and Tuesday. Ensembles show around a 70 percent probability that the cold front on Tuesday will be into north-central Idaho by evening time...55% northwest Montana. There is an 80% probability that the wind shear will be greater than 35 knots in these areas. And lastly the mean instability values are around 500 J/kg which could be enough to trigger a few strong thunderstorms along this cold frontal boundary. Any thunderstorm could be capable of producing gusty winds over 40 mph, hail, lightning and heavy rain. && .AVIATION...Instability showers have begun to pop up this afternoon, especially across northwest Montana. There is a roughly 30 percent chance that these showers could produce a lightning strike through 25/0300z, mainly from Flathead Lake northward to the Canadian border. Another area of showers and thunderstorms will be possible through north central Idaho, including Grangeville and the Camas Prairie after 25/0000z. Winds will be relatively light overall across western Montana and north central Idaho but gusts of 15-25 kts will occur near showers/storms. Precipitation will become more widespread through central Idaho into western Montana late tonight into Saturday with relatively widespread obscurations of the higher terrain anticipated. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$