Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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209 FXUS65 KTFX 141142 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 542 AM MDT Sun Jul 14 2024 ...AVIATION SECTION UPDATED... .SYNOPSIS... A passing weather system will bring a period of gusty winds, along with isolated to scattered showers and thunderstorms this afternoon and evening. The strongest storm potential will be along the Hi- Line. Temperatures hold steady or even cool a few degrees during the first half of next week before heating back up mid- week and beyond. Daily chances for isolated scattered shower and thunderstorm activity with little rainfall will persist for much of the week. && .DISCUSSION... Shortwave energy and a cold front will bring a round of west to northwesterly breezes and isolated shower and thunderstorm chances later this afternoon and evening. The winds actually look to expand in coverage, including much of North-central MT, but wind speeds will generally be less and there will be a shorter temporal opportunity for the windier conditions, mostly around 3 to 4 hours or less. Regardless, this will create difficulties for those working on containment of ongoing wildfires given the combination of the winds with the continued hot and dry weather. Today`s shower and thunderstorm activity looks most widespread along the Hi-Line and then over the southwest and central areas south of the highway 200 corridor. Moisture, instability, and shear along the Canadian border will be favorable for a few stronger to possibly severe storms with forecast soundings highlighting ML CAPE values around 1,000 to 1,500 J/kg, PWATS approaching 1 inch, and bulk shear north of 30 kts. Primary thunderstorm hazards from the stronger storms will be gusty winds, hail, and brief heavy downpours in addition to lightning. The storms farther south will be weaker and mostly an isolated gusty wind and lightning threat. Activity decreases later this evening, but a few showers and storms may linger into the overnight hours. Temperatures cool down by a few degrees on Monday in the wake of the passing weather system, but many locations will be breezy with minimum relative humidities dipping critically low again. Isolated shower thunderstorm activity with little rainfall relief can also be expected. The latest 3 to 7 day cluster analysis still favors the upper level ridge amplifying mid- late week, yielding more hot and dry conditions while lingering moisture bring daily chances for isolated to scattered showers and storms. - RCG && .AVIATION... 14/12Z TAF Period A passing weather system will bring west to northwesterly breezes this afternoon and evening, along with isolated to scattered showers and thunderstorms. Shower/thunder activity will be mostly concentrated over Southwestern MT and along the Hi-Line (KCTB, KHVR). The storms along the Hi-Line will have the potential to be the strongest, but any shower or storm may initiate brief periods of gusty, erratic winds and isolated lightning. Overall, VFR conditions are expected for this TAF period save for patchy fog development over the river valleys near KHVR through 15Z, periods of mostly mid- and higher level cloudiness associated with any shower/thunder activity, and lastly hazy skies impacting slantwise visibility over the southwest. Very warm to hot afternoon temperatures will continue to cause density altitude concerns. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .FIRE WEATHER... A passing weather disturbance will bring increased northwesterly winds, hot temperatures, and critically low relative humidity this afternoon and evening. There will also be isolated to scattered shower and thunderstorm activity generally offering little in the way of rainfall while initiating isolated instances of gusty, erratic winds in the presence of a few lightning strikes. Even without the thunderstorm wind gusts, the northwesterly breezes may gust up to the 25 to 30 mph range for a short period this afternoon while relative humidity is critically low. looking ahead, the overall very warm to hot and dry pattern looks to persist into next week with little to no relief from daily chances for scattered showers and storms. These conditions will increase the risk for new wildfires. Be mindful of the deteriorating conditions and avoid activities involving sparks or open flames. - RCG && .PRELIMINARY POINT TEMPS/POPS... GTF 94 57 92 58 / 10 10 0 0 CTB 91 52 89 54 / 40 30 0 0 HLN 98 60 96 60 / 10 10 0 0 BZN 95 56 92 55 / 20 20 0 0 WYS 85 46 82 44 / 40 40 30 20 DLN 91 55 89 53 / 20 20 10 0 HVR 92 56 88 58 / 20 40 0 0 LWT 89 54 85 55 / 10 10 10 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls