Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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140 FXUS65 KTFX 231612 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 1012 AM MDT Mon Sep 23 2024 .SYNOPSIS... A disturbance passing over North Central and Southwest Montana today will cool temperatures a few degrees and bring breezy conditions, but there is only a slight chance for even mountain precipitation. High pressure aloft will then bring warmer and drier conditions through Friday, with Wednesday likely being the warmest day. && .Update... No morning update is needed or planned as the on-going forecast is handling current conditions well. Breezy southwest to northwest winds will once again be experienced today, but these speeds and gusts will be lower than what was observed yesterday. Otherwise, high temperatures will be within several degrees of yesterday`s highs, with decreasing clouds towards the late afternoon/early evening hours. - Moldan && .AVIATION... 23/12Z TAF Period Primarily VFR conditions are expected for the next 24 hours, but there will be periods of mid- and higher level cloudiness. Mountain wave turbulence and gusty westerly surface winds are also expected at times, mostly over Central/North-central MT. KHVR and KLWT will be impacted by low level wind shear through 23/16Z. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 543 AM MDT Mon Sep 23 2024/ Today through Tonight... A weak disturbance in the northwest flow aloft will move clouds over North Central, Central, and Southwest Montana today. A few light mountain showers are possible, but breezy westerly downslope winds behind a weak frontal passage will likely keep any showers from reaching the ground. Winds will generally have a 30 to 40 percent chance of exceeding 30 mph at times over the plains, but the chance for gusts 40 mph or greater increases to over 60% on the Rocky Mountain Front. The frontal passage will also cool temperatures a few degrees over yesterday, but they will remain slightly above normal. Tuesday through Wednesday... An unseasonably strong high pressure ridge is forecast to move east into the Rocky Mountain region for Tuesday, then an approaching Pacific low pressure trough will shift the ridge axis more so over the northern Great Plains on Wednesday. This should keep the forecast area dry with significant warming, with Wednesday likely being the warmest day of the week. The current NBM has forecast highs on Wednesday well into the 80s for lower elevations, but there are areas along the Missouri River from Great Falls east that have at least a 20 percent chance of exceeding 90 degrees. However, the shift in the ridge axis will put much of the area under an increasing southwesterly flow aloft, and the warm air mass will aid in mixing those winds down to the surface. Areas along and west of the Interstate 15 corridor on the plains and through north-south oriented valleys will generally have a 30 to 50 percent probability of gusts exceeding 30 mph at times on Wednesday. This, combined with temperatures up to 20 degrees above normal and afternoon humidity falling below 30 percent, could elevate fire weather conditions. Thursday through Friday... The Pacific trough will weaken as it moves east across the area Thursday into Friday, but it will be strong enough to break down the high pressure ridge and move a weak cold front through the area. The breakdown of the ridge will put the forecast area under a stronger westerly flow aloft, and these winds will mix down to the surface at times in the wake of the cold front; much of the area will have at least a 30 percent probability of gusts exceeding 30 mph, but the Rocky Mountain Front will have at least a 30 percent probability of 40+ mph gusts. Although temperatures will cool down a bit closer to seasonal averages, moisture will be somewhat lacking, so humidity will remain on the low side, continuing fire weather concerns. The downsloping winds will limit any potential for precipitation to the mountains of the Rocky Mountain Front. Saturday through next Monday... The NBM is showing that another low pressure trough from the Pacific is forecast to approach and move through the area this weekend into early next week, potentially bringing more unsettled weather and cooler than normal temperatures. However, ensemble forecast model clusters continue to be in disagreement between this scenario and one with a broad high pressure ridge that would favor a less cool and unsettled pattern. As a result, confidence is only moderate in the forecast for this time period for now. -Coulston && .PRELIMINARY POINT TEMPS/POPS... GTF 74 50 83 54 / 10 0 0 0 CTB 71 49 82 49 / 10 0 0 0 HLN 75 49 82 53 / 10 0 0 0 BZN 73 43 80 46 / 10 0 0 0 WYS 64 32 72 35 / 0 10 0 0 DLN 69 42 77 45 / 0 0 0 0 HVR 73 50 82 51 / 10 10 0 0 LWT 68 46 78 52 / 10 10 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls