Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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708 FXUS65 KTFX 040248 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 848 PM MDT Wed Jul 3 2024 .SYNOPSIS... Shower and thunderstorm chances will linger through the remainder of the work week, most notably over Central and North Central Montana. The best chance for showers and thunderstorms over the Independence Day holiday will be during the afternoon hours, with decreasing chances through the evening hours. Below to near normal temperatures will continue through the weekend, with hot temperatures arriving by the middle of the next work week. && .UPDATE... Current forecast is performing well; therefore, no updates are made, at this time. - Fogleman && .DISCUSSION... Rest of today through tonight...Strong shortwave currently moving overhead, which was within a moist and unstable northwest flow regime, will depart to the southeast of the Northern Rockies through midnight tonight. This will lead to a gradual decrease in the coverage of precipitation through the evening hours, but before then, scattered to numerous showers and thunderstorms will continue across much of North Central through Southwest Montana. Isolated showers and thunderstorms will remain possible beyond midnight tonight northeast of a Bozeman to Helena line as a weak embedded wave within the overall flow dives southeast. A few of the storms through this evening hours could become strong and produce wind gusts of between 45-55 mph, small hail, and even a cold air funnel (mainly during the afternoon hours). Additionally, while PWATs are not anomalously high, slow storm motions of generally 10-20 mph could lead to periods of moderate to heavy rainfall. This could lead to ponding of water in low lying and poor drainage areas. Independence Day through Friday...moist, unstable northwest flow aloft with embedded shortwaves diving southeast within the flow will help to maintain chances for showers/thunderstorms and below, albeit slightly warmer than the prior day, normal temperatures. Best chances for showers and storms on Thursday look to be be during the afternoon hours northeast of a Bozeman to Helena line, with decreasing chances through the evening hours. As has been the case for the previous two days, slow storm motions will lead to brief heavy downpours beneath relatively small showers and storms. Saturday through Monday...ensemble clusters favor the upper level ridge axis remaining just west of the Northern Rockies through the weekend before shifting east towards the Northern Rockies on Monday. This would keep Southwest through North Central Montana beneath continued northwest flow aloft, which would help to keep chances for precipitation and near normal temperatures for the weekend before drying and warming conditions arrive on Monday. Leading mode(s) of uncertainty through the weekend and early next week will be the exact position and/or timing of the ridge axis, with any deviation east of the ridge axis by ~200-400 mile having a totally different outcome (i.e. much warmer and drier), especially on Saturday and Sunday. None-the-less, NBM trends over the past several days with respect to temperatures have been for "cooler", near normal highs vs the previously above normal highs. Tuesday through next Wednesday...ensemble clusters strongly favor upper level ridging over the Northern Rockies through the period and beyond, with the leading mode(s) of uncertainty on Tuesday and Wednesday being the position and/or timing of the ridge. This will ultimately affect when the hot temperatures arrive to the Northern Rockies; however, confidence is high that well above normal temperatures of at least 10 degrees will occur by the middle to end of next (work) week, with normal high temperatures at Cut Bank (CTB), Havre (HVR), Great Falls (GTF), Lewistown (LWT), Helena (HLN), Bozeman (BZN) and Dillon (DLN) ranging from the upper 70s to mid-80s. NBM probabilities for temperatures of 95 degrees or warmer at the aforementioned sites range from 15% (CTB), 20% (HVR), 20% (GTF), 5% (LWT), 70% (HLN), 30% (BZN), 10% (DLN) on Tuesday and 25%, 30%, 40%, 10%, 85%, 55%, 20% on Wednesday respectively, with these probabilities increasing further for Thursday and Friday. It is not out of the realm of possibilities that some sites by the middle to end of the upcoming work week may string together multiple consecutive days of 100-105 degree high temperatures. People, especially those with medical conditions exacerbated by hot temperatures, should begin to prepare for this heatwave. - Moldan && .AVIATION... 04/00Z TAF Period Note: The NWS Great Falls Weather Forecast Office manages the following TAFs: KCTB, KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS. Showers and thunderstorms continue to move through the area, this evening. Generally, VFR conditions are forecast. Toward the end of this TAF period, another round of general thunderstorms develops, impacting our north central and central Montana airfields. Thunderstorms are forecast across southwest Montana, as well; however, there is a low (<20%) probability that these storms impact our southwest Montana airfields. Periods of mountain peak obscuration are forecast in associated with the convective weather. Aside from thunderstorm, light winds are forecast. As always, all hazards are assumed in and near thunderstorm. - Fogleman Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 47 74 47 77 / 40 30 20 20 CTB 46 72 45 77 / 30 40 20 20 HLN 50 79 50 85 / 50 20 10 10 BZN 42 73 45 80 / 60 20 10 10 WYS 33 67 33 73 / 20 20 20 10 DLN 39 73 42 79 / 20 10 10 0 HVR 50 74 50 79 / 20 40 20 40 LWT 44 68 45 73 / 40 50 20 40 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls