Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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304 FXUS65 KTFX 190935 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 335 AM MDT Thu Sep 19 2024 .SYNOPSIS... A few showers linger this morning across north-central Montana before drier conditions and seasonable temperatures develop across the area this afternoon. Temperatures cool slightly for Friday and Saturday, though mainly dry conditions are expected through the weekend with just some showers moving east along the Canadian border on Friday. Another weak weather system moves through the area Monday before a warmer and drier weather pattern develops next week. && .DISCUSSION... A few showers continue to track across north-central MT early this morning within a corridor of lower level (850MB) convergence from eastern Glacier county southeast through Judith Basin county. Lingering showers and cloud-cover will gradually diminish through the morning period as the storm system that brought significant precipitation to the area yesterday continues to move out of southeast SK. By this afternoon, mainly dry but somewhat breezy conditions are expected across the area with seasonable temperatures. A progressive weather pattern develops through Monday with a series of lower amplitude troughs in the upper level flow moving east across western Canada. The first trough and its associated low at the surface already move east across southern AB tonight with a cooler airmass sliding south in its wake across north- central tomorrow, expanding into southwest MT Saturday. Breezy west winds this evening and overnight on the plains will shift to the north and northwest on Friday with a few showers possible near Glacier NP and along the US/Canadian border but most areas will remain dry. While afternoon temperatures are only slightly below seasonal averages, the cooler airmass and clearing skies later Friday night and again Saturday night will allow temperatures to fall to the 30s at many locations and bring the risk of frost to some areas. Dry and warmer conditions develop Sunday as upper level ridging transits the area before breezy conditions develop with the arrival of the next upper level wave Sunday night and Monday. There is some uncertainty still with precipitation associated with the wave moving through the area Sunday night and Monday, but this is a fast moving system with current probabilities around 20-30% for showers on Monday. Medium range model ensembles seem to be in reasonable agreement in the depiction of upper level ridging building across the western US by the middle of next week, likely resulting in a return to near and above average temperatures. Hoenisch && .AVIATION... 19/06Z TAF Period A few lingering light showers are possible for the next few hours across North Central MT. There`s a 40% for dense fog (1/2SM or less) at the KWYS terminal starting around 12z. However, there`s a chance cloud cover limits fog development. Due to the uncertainty, I`ve kept a TEMPO for LIFR conditions at KWYS this morning. Other terminals have a low fog potential due to the cloud cover. Otherwise, VFR conditions are expected through the TAF period. Cloud cover clears moderately around 12z. Lower clouds along the mountains will keep mountains obscured through 12z. -Wilson Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... Little additional rainfall is expected this morning but some minor flooding from the recent heavy rainfall may persist before more noticeable improvement develops today. The flood advisory has been cancelled for Cascade and Meagher counties, where stream gauges indicate the elevated flows have passed, but the advisory contiues for Chouteau, Hill, Blaine, Judith Basin and Fergus counties, where heaviest rainfall totals were observed and minor flooding impacts, including standing water in low-lying areas and surface water hazards near some roads could linger through this morning. Hoenisch && .PRELIMINARY POINT TEMPS/POPS... GTF 73 48 69 39 / 10 0 10 30 CTB 71 45 62 35 / 10 0 50 40 HLN 74 48 72 40 / 0 0 0 10 BZN 71 42 72 35 / 0 0 10 10 WYS 60 31 63 27 / 10 0 10 20 DLN 68 41 69 34 / 0 0 0 0 HVR 72 47 66 38 / 10 0 20 30 LWT 66 45 66 35 / 20 0 10 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls