Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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731 FXUS65 KTFX 242350 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 549 PM MDT Tue Sep 24 2024 Updated Aviation Discussion .SYNOPSIS... Much warmer and dry conditions are expected over 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. && .DISCUSSION... Key Points: - Well above normal temperatures on Wednesday with lower elevations reaching the upper 80s to low 90s. - A strong cold front will move through the region Wednesday night into Thursday morning bringing gusty winds along the Rocky Mountain front and the Hi-Line. - Warmer temperatures will continue through the weekend before another cool off at the start of next week. 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. Updated model guidance has been split on how strong this event will be and has reduced some of the probabilities further along portions of the Hi-Line. Current probabilistic guidance for wind gusts in excess of 55 mph ranges from 50 to 70% for locations along the Rocky Mountain Front. East of Cut Bank these probabilities start to drop off below 30% fairly quickly, however, the decision was made to keep the Hi-Line portions of the High Wind Watch in order to wait for confirmation with future model runs as typically there are some concerns for stronger bursts of winds along the Hi-Line in this type of set up as well. Generally, the strongest wind gusts are expected between midnight and noon on Thursday. But stronger wind gusts outside of that time frame cannot be ruled out, thus the decision was made to keep the watch timing the same for now. - RCG/thor Friday thru Monday... 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 && .AVIATION... 25/00Z TAF Period Flow aloft gradually turns more southwesterly through Wednesday as upper level high pressure shifts east of the area with just some increase in high level clouds. VFR conditions prevail with south to southwesterly surface winds increasing at most terminals Wednesday afternoon. Increased flow over the Rockies may also lead to some Mountain wave turbulence on Wednesday. Hoenisch Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 57 87 53 75 / 0 0 0 0 CTB 49 84 51 67 / 0 0 20 0 HLN 54 89 53 78 / 0 0 0 0 BZN 48 87 48 80 / 0 0 0 0 WYS 36 74 38 71 / 0 0 0 0 DLN 47 82 48 77 / 0 0 0 0 HVR 52 89 54 74 / 0 0 0 10 LWT 54 85 51 74 / 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