Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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827 FXUS65 KTFX 262022 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 222 PM MDT Sun May 26 2024 .SYNOPSIS... Showers and isolated thunderstorms associated with a weather disturbance moving east along the Canadian border will diminish this evening as the disturbance exits the area. Winds diminish tonight as high pressure builds across the Northern Rockies and brings dry conditions with warming temperatures through Tuesday. The next weather system moves into the region Tuesday night and Wednesday with a risk for some strong Thunderstorms Tuesday evening and Wednesday along with cooler temperatures for the second half of the work week. && .DISCUSSION... A compact shortwave disturbance will continue to track east across the Hi-line/Canadian border region this afternoon with numerous showers and a few isolated thunderstorms in its vicinity but only isolated showers further south across the central and southwest MT mountains. These should diminish fairly quickly this evening as the disturbance moves off to the the east with clearing skies across most areas overnight as upper level ridging builds across the Northern Rockies. Gusty west winds across much of the area this afternoon will decrease tonight as well, beginning early this evening across southwest MT with a more gradual decrease through the overnight period further north across the Plains. The upper level ridge axis shifts east across the State Monday and Tuesday for a mainly dry period with temperatures climbing above seasonal averages Monday and likely to the warmest levels so far this season on Tuesday. Probability of Max Temperatures 80F or Warmer Tuesday: Cut Bank 80% Havre 90% Great Falls 90% Lewistown 45% Helena 95% Bozeman 90% Dillon 30% By late Tuesday, southwest flow aloft behind the departing upper level ridge will begin to import moisture into the region ahead of a cold front associated with the next upper level trough moving into the Northwest US. The cold front and upper level trough continue east across north-central and southwest MT Tuesday night through Wednesday with cooler and windy conditions likely across the area by Wednesday afternoon. Thunderstorm development is likely across Idaho and western MT late Tuesday afternoon ahead of the cold front, translating east of the continental divide Tuesday evening. There is a marginal (5%) risk for severe thunderstorms Tuesday evening across western portions of north-central and much of central/SW MT with primary threat being strong winds. There is some spread among models in the timing of the cold front however, which will be key to the risk of strong to severe thunderstorms late Tuesday and potentially again on Wednesday for eastern portions of central and southwest MT. Hoenisch Thursday through next Sunday... On Thursday the upper-level trough remains in place over North-central, Central, and Southwestern Montana. Showers and thunderstorms are possible across the area on Thursday. The thunderstorms will not be severe. On Thursday there is a 20 - 40% chance for locations across North-central, Central, and Southwestern Montana receiving a tenth of an inch of rain (total liquid for mountain locations) or more. On Thursday for the mountains of North-central, Central and Southwestern Montana there is 40 - 60% chance for receiving a tenth of an inch of snow or more. On Friday clusters indicate that an upper-level trough remains in place over North-central, Central, and Southwestern Montana which will keep unsettled weather in place for the area on Friday. On Saturday two clusters (66% of ensemble members) have an upper-level ridge in place over North-central, Central, and Southwestern Montana. The other two clusters (44% of ensemble members) have the upper-level trough remain in place over the area on Saturday. This indicates uncertainty in the weather for Saturday at this time. Next Sunday three clusters (80% of ensemble members) have an upper-level ridge over North-central, Central, and Southwestern Montana. Next Sunday one cluster (20% of ensemble members) has the upper-level trough remaining over the area. This indicates that by Sunday the weather pattern will most likely change to have warm and calm weather for North-central, Central, and Southwestern Montana. -IG && .AVIATION... 26/18Z TAF Period VFR conditions are expected to prevail through the TAF period. Windy conditions will be the immediate concern across all terminals for the first half of the TAF period. The highest gusts up to 40 kts are expected at KCTB with both KGTF and KHVR having gusts as high as 35 kts possible. Winds are expected to decrease after 27/04Z as the shortwave trough exits the region. The only other concern will be a minor chance for thunderstorms in the vicinity of KHVR between 26/22Z and 27/03Z. Gusty and erratic winds may accompany stronger showers and there is a slight chance of pea-sized hail along portions of the hi-line east of KHVR this afternoon. Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 40 72 45 82 / 0 0 0 10 CTB 39 69 42 79 / 0 0 0 10 HLN 43 75 48 84 / 0 0 0 20 BZN 36 70 41 80 / 0 0 0 10 WYS 30 64 33 71 / 10 0 0 0 DLN 37 71 42 78 / 0 0 0 10 HVR 43 73 44 83 / 30 0 0 0 LWT 37 66 42 77 / 0 0 0 0 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && $$ http://www.weather.gov/greatfalls