Area Forecast Discussion
Issued by NWS Glasgow, MT
Issued by NWS Glasgow, MT
489 FXUS65 KGGW 292011 AFDGGW Area Forecast Discussion National Weather Service Glasgow MT 211 PM MDT Mon Apr 29 2024 .DISCUSSION... KEY MESSAGES: - High probability (70-90%) for a wetting rain for most of northeast Montana with a moderate probability (40-70%) for 0.5 inches of rainfall for the northwest zones. - Strong west winds develop Tuesday morning with gusts to 50 mph possible, elevating fire weather concerns through Tuesday evening mainly in the southeast. - Cooler and slightly unsettled weather continues into next weekend. WEATHER PATTERN OVERVIEW: A low pressure system moves across northern Montana over the next few days, resulting in cooler, wetter and windier weather for tonight into Tuesday. The low will be slow to move east, lingering over southern Saskatchewan on Wednesday before slowly wobbling east into the weekend. This will keep cooler and unsettled weather over northeast Montana. The strong winds will also increase fire concerns in areas that don`t get much precipitation. For now this will mainly be the southern portion of FWZ122, but also into eastern portions of FWZ136/137 to be considered. Even without much QPF, partly cloudy skies and cold air convective potential could keep RH from dropping much below 20%. Will continue with Fire Weather Watch for now, taking into consideration how much rain falls tonight over this area and the latest forecast trends in RH. CONFIDENCE AND POTENTIAL DEVIATIONS FROM BASE FORECAST: There is high confidence for at least a wetting rain for the northwest zones from late this afternoon through Tuesday morning. Models have a tendency to overestimate rainfall, so uncertainty increases for higher QPF and away from the developing 700mb low. Blended in NBM90 winds with the NBM due to tendency for underestimation of speeds for tonight and Tuesday. This still gives low confidence for a High Wind Warning being needed toward the Little Rockies, but a solid Lake Wind Advisory has been issued for much of Tuesday. Following the initial frontal passage, the upper low lingers over the northern plains. Cooler and unsettled weather is likely, but with highly variable positioning of the low in the ensembles, confidence for precipitation chances is low into the weekend. && .AVIATION... VFR dropping to MVFR or lower late tonight with rain moving across the region behind a cold front. West winds will also increase behind the frontal passage, with gusts up to 40kts possible Tuesday afternoon. && .GGW WATCHES/WARNINGS/ADVISORIES... Lake Wind Advisory from 3 AM to 9 PM MDT Tuesday for Central and Southeast Phillips-Central and Southern Valley-Garfield-McCone- Petroleum. Fire Weather Watch from Tuesday morning through Tuesday evening for Dawson/McCone/Prairie/Richland/Wibaux Counties. && $$ weather.gov/glasgow