Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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137 FXUS65 KTFX 241417 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 817 AM MDT Tue Sep 24 2024 .SYNOPSIS... Much warmer and dry conditions are expected for the next couple of days before a fast moving weather system brings periods of breezy to windy conditions, a few showers or storms, and cooler temperatures to close out the week. && .UPDATE... Winds this morning were coming in a little higher than previously forecasted so some adjustments were made using the latest model guidance to better fit what is expected through the rest of today. Otherwise the going forecast remains on track. -thor && .AVIATION... 24/12Z TAF Period VFR conditions will continue through at least 25/12Z across North Central (KCTB, KHVR), Central (KLWT, KGTF, KHLN), and Southwest (KBZN, KEKS, KWYS) Montana. High pressure aloft will only allow a few high clouds to pass overhead. Breezy west to southwest surface winds will shift more southerly after 18Z; occasional gusts will mostly stay between 20 and 30 kt. -Coulston Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PREV DISCUSSION... /ISSUED 442 AM MDT Tue Sep 24 2024/ High pressure builds in for the next couple of days for a return of well above average temperatures and dry conditions. Expect afternoon highs to warm into the 80s for most lower elevation locations today, with the warmest areas making a run for 90 on Wednesday. A trough moves onto the Pacific NW coast and displaces the upper level ridge in favor of a southwesterly flow aloft by late Wednesday. This will increase west to southwesterly surfaces winds, though the strongest winds look to hold off until Wednesday night and Thursday when the trough ejects eastward and sends a Pacific cold front racing through the CWA. Isolated shower activity, mountain wave activity, and the transfer momentum of the front itself looks to help mix 40 to 50 kt H500/H700 winds to the surface along the Rocky Mountain Front and adjacent plains Wednesday night. This will be followed by the maintenance of the windier conditions into Thursday thanks to deep layer mixing and cold air advection. Current probabilistic guidance for wind gusts in excess of 55 mph are running over 50% for locations along the Rocky Mountain Front eastward onto the northern high plains near the Cut Bank area. These chances fall well below 30% for other areas, but there are typically some concerns for stronger bursts of winds along the Hi- Line in this type of set up as well. Given the aforementioned factors, a High Wind Watch was issued for the Rocky Mountain Front, their adjacent high plains zones, and the eastern Toole and Liberty zone. Timing of the cold front Wednesday night and the overall strongest mixing winds on Thursday still needs to be fine tuned, but going with 26/03Z (9 pm Wed) to 26/21Z (3 pm Thurs) run time seems reasonable for now. A stronger west to southwesterly flow aloft continues through at least the first half of the weekend for more breezy to windy conditions and above normal temperatures. probabilities for sustained winds/gusts exceeding 40 mph/55 mph remain low, but those with outdoor recreation plans should still expect windy conditions along the Rocky Mountain Front. Forecast certainty is still a bit murky for the weekend, though more ensembles are now favoring the passage of an open wave and attendant cold front sometime between the late Saturday and Monday timeframe. While there are still differences among ensemble members, most yield temperatures cooling closer to average and slight chances for precipitation. - RCG && .PRELIMINARY POINT TEMPS/POPS... GTF 83 55 88 53 / 0 0 0 0 CTB 82 49 85 51 / 0 0 0 20 HLN 83 52 89 53 / 0 0 0 0 BZN 80 47 87 48 / 0 0 0 0 WYS 73 35 75 36 / 0 0 0 0 DLN 78 47 83 47 / 0 0 0 0 HVR 82 51 89 54 / 0 0 0 0 LWT 78 53 85 52 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Wednesday evening through Thursday afternoon for East Glacier Park Region-Eastern Glacier, Western Toole, and Central Pondera-Eastern Toole and Liberty-Northern High Plains-Southern High Plains-Southern Rocky Mountain Front. && $$ http://www.weather.gov/greatfalls