Area Forecast Discussion
Issued by NWS Great Falls, MT
Issued by NWS Great Falls, MT
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752 FXUS65 KTFX 102335 AFDTFX Area Forecast Discussion National Weather Service Great Falls MT 535 PM MDT Fri May 10 2024 .Aviation Section Updated... .SYNOPSIS... Upper level ridging will result in above average temperatures across the region this weekend. Weak disturbances moving through the ridge will result in isolated showers and perhaps a few thunderstorms in the afternoon this weekend, mainly near terrain and across North-central Montana. Flooding concerns will remain in areas where significant snowmelt is occurring. && .DISCUSSION... Through Sunday... An upper level ridge will slowly shift eastward from the west coast toward the central CONUS this weekend, allowing for temperatures to climb back above average in most areas. Although temperatures will warm at the surface, a relatively cool northwesterly flow will be in place aloft. This will combine with a weak disturbance to result in isolated to widely scattered showers and thunderstorms, primarily across North-central Montana, late Saturday evening into Sunday. Isolated afternoon showers will be around near terrain this weekend, but the probability of these at any one location is quite low at this point. -AM Monday through Tuesday...Ensemble clusters are in relatively good agreement with a shortwave within initially zonal flow, and an associated Pacific front, digging east/southwest and over/across the Northern Rockies during the period. High temperatures ahead of the shortwave and Pacific front on Monday will once again warm well above normal and into the 70s, but fall back below normal and into the 60s on Tuesday. Surface winds will be on the increase through the morning hours on Monday ahead of the aforementioned Pacific front, becoming breezy and gusty during the afternoon and evening hours on Monday. While the latest NBM probabilistic data does not support high winds materializing over this timeframe; most lower elevations across Southwest through North Central Montana have between a 20-50% chance of seeing wind gusts in excess of 35kts. Light precipitation is also expected to accompany and follow the passage of the Pacific front Monday afternoon/night, lingering into the day on Tuesday as the upper level disturbance digs into the Central Rockies. While widespread, heavy precipitation is not expected over this timeframe, NBM probabilistic data does support between a 40-70% chance for QPF amounts to reach or exceed 0.10" across most of Southwest through North Central Montana. Wednesday through next Friday...ensemble clusters diverge drastically throughout the period, with the main difference between the clusters being the timing of shortwave ridging and troughing. The multi-model ensemble favors a more zonal pattern, with temperatures near normal and daily chances for showers. - Moldan && .AVIATION... 530 PM MDT Fri May 10 2024 (11/00Z TAF Period) VFR conditions will prevail over the CWA through period. Expect passing high clouds to move from north to south through the CWA through the period. Otherwise, no other aviation impacts are expected at this time. Brusda/thor Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .HYDROLOGY... A Flood Warning remains in effect for Clear Creek in North Central Montana through Saturday morning, with water levels expected to slowly fall from minor flood stage to action stage over this timeframe. Additionally, a Flood Watch remains in effect for the nearby Bears Paw Mountains from this afternoon through the weekend as warming temperatures and subsequent snowmelt runoff, and remaining runoff from rainwater, could push creeks and streams out of their banks. Further south across the Island Ranges of Central Montana (i.e. Highwood, Moccasin, Judith, Little Belt, and Snowy), increased snowmelt and subsequent runoff into creeks and streams is expected from Saturday through Monday as overnight temperatures and dewpoint temperatures remain above freezing. This runoff could result in waterways nearing bankful by Saturday night/Sunday morning. Hence, a Flood Watch has been issued for the Little Belts eastward toward the Lewistown area. - Moldan/AM && .PRELIMINARY POINT TEMPS/POPS... GTF 44 78 45 79 / 0 0 20 20 CTB 47 78 44 79 / 0 10 20 20 HLN 42 79 50 81 / 0 0 0 0 BZN 34 75 43 77 / 0 0 0 10 WYS 29 67 34 69 / 10 10 0 10 DLN 37 73 42 76 / 0 0 0 0 HVR 46 79 47 77 / 0 0 40 20 LWT 40 72 44 71 / 0 0 30 40 && .TFX WATCHES/WARNINGS/ADVISORIES... Flood Watch through Sunday morning for Bears Paw Mountains and Southern Blaine. Flood Watch from Saturday afternoon through Monday morning for Cascade County below 5000ft-Fergus County below 4500ft-Judith Basin County and Judith Gap-Little Belt and Highwood Mountains- Meagher County Valleys-Snowy and Judith Mountains-Western and Central Chouteau County. && $$ http://www.weather.gov/greatfalls