


Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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131 FXUS65 KTFX 162045 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 245 PM MDT Wed Jul 16 2025 .KEY MESSAGES... - Reduced visibilities due to fog are once again possible tonight through Thursday morning, mainly over the plains of Central and North Central Montana. - Temperatures trend closer to normal by the end of the week. - Increased chance for afternoon and evening showers and thunderstorms beginning Thursday. && .DISCUSSION... - Meteorological Overview: Transient ridging within overall northwest flow aloft was moving over the Northern Rockies this afternoon, with surface high pressure centered over Southern Saskatchewan, Northeast Montana, and Northern North Dakota. Dry conditions have and will continue to prevail through the overnight hours as the aforementioned ridge and surface high slowly slide and move, respectively, further east towards the Upper Mississippi River Valley through Thursday morning. An abundance of boundary layer moisture thanks to recent precipitation and/or overall low level flow from the southeast to northeast combined with clearing skies will help to set the stage for another night for fog development. Overnight low temperatures will once again fall well below normal, with most locations falling into the 40s while some cold prone valleys in Central and Southwest Montana dip into the 30s. - Moldan Northwesterly flow remains heading into Thursday, with another wave within the flow crossing northern portions of the region in afternoon and evening. Lingering moisture, sufficiently warm surface temperatures, and forcing from the troughing will support scattered shower and thunderstorm development by early afternoon across the Hi-Line. There is uncertainty as to just how supportive the environment will be for severe weather, which will be discussed further in the confidence section. Nonetheless, the showers and thunderstorms that form will generally move east or southeast across the plains through the afternoon and evening. Flow aloft becomes slightly more zonal Friday into the weekend. That said there appears to be several embedded waves within this flow that will help afternoon and evening thunderstorms develop. Temperatures continue to trend closer to normal by Saturday, which looks to be the warmest day of the forecast period for most. Thereafter a period of troughing is favored, though specifics as to precipitation chances as well as how much cooling occurs is low confidence at this time. -AM - Forecast Confidence & Scenarios: Fog Tonight through Thursday morning : Hi-Res Ensemble Forecast (HREF) guidance supports increasing chances (i.e. greater than 10%) for reduced visibilities (i.e. 6 miles or less) due to fog development beyond 3AM MDT (09z) Thursday along and northeast of a Browning, to Choteau, to Carver, to Roy line; with the highest probabilities of 30-50% for reduced visibilities (i.e. 6 miles or less) occurring near Browning and Cut Bank between 6AM and 9AM MDT (12-15z) Thursday. Furthermore, HREF probabilities support a 10-30% chance for visibilities to fall to or below 1/4 mile between 5AM and 9AM MDT (11-15z) Thursday from Browning to Cut Bank, with generally a 10-20% chance within the Milk River Valley across Western Hill County and in Eastern Pondera County over this same timeframe. For now we will hold off on issuing any Dense Fog Advisories given low confidence on when skies will clear enough to support fog development (earlier clearing would allow for the best chance of seeing the lowest visibilities), but satellite trends will need to be monitored and a short notice Dense Fog Advisory may be needed. - Moldan Thunderstorms Thursday: The main source of uncertainty for Thursday`s severe thunderstorm chances is related to just how much instability develops across the Hi-Line and vicinity. Forcing appears to be favorably timed, with vertical wind shear near or in excess of 35 kts also supportive of a few more organized thunderstorms. Guidance with the most instability features afternoon temperatures on the warmer side of the envelope, while less aggressive guidance is cooler. Neither scenario seems unreasonable at this time. Troughing early next week: Ensemble support is still high for troughing early to mid next week, with cluster guidance giving at least an 80% chance for troughing across the Northern Rockies each of Tuesday and Wednesday. Specifics such as how cool it looks to get as well as precipitation amounts remain low confidence. Probabilistic guidance gives areas in and near the Golden Triangle the best chance for a quarter of an inch of precipitation, though that chance is only in the 20-30% range at this time. -AM && .AVIATION... 16/18Z TAF Period Marginal VFR conditions across central Montana continue to improve. Ceiling becomes scattered through afternoon, then clearing overnight. Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 47 80 52 80 / 0 10 10 0 CTB 45 71 48 75 / 10 40 30 0 HLN 47 87 51 86 / 0 0 0 0 BZN 44 88 47 88 / 10 0 0 10 WYS 37 80 39 80 / 0 0 10 20 DLN 43 86 46 87 / 0 0 0 20 HVR 49 78 51 80 / 10 30 20 0 LWT 42 77 49 77 / 0 10 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls