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FXUS65 KBYZ 072130 AFDBYZ

Area Forecast Discussion National Weather Service Billings MT 230 PM MST Thu Dec 7 2023

DISCUSSION

Tonight through Friday night...

Light rain showers will continue to progress east across the area this afternoon. While this precipitation will remain predominantly rain, a brief rain/snow mix is possible (overall low chance) over the higher hills in the plains. This activity will exit into the Dakotas this evening, leaving a dry night for most.
Over the mountains, the ongoing snow showers will also lighten up this evening, ending over most areas overnight.

With this precipitation, a frontal passage is bringing increased winds across the area this afternoon. Overall, peak wind gusts will be between 30 to 50 mph, with the best chance to see 50 mph or greater existing over the western foothills from Big Timber to Harlowton. Current guidance for seeing a 50 mph gust is around 90 percent for Harlowton and 70% for Big Timber this evening. By late this evening, the stronger winds will back off for most areas outside of far eastern MT.

In far eastern MT, a tight west to east pressure gradient will persist into Friday, allowing 25 to 45 mph wind gusts to continue.
With these winds, another round of scattered snow showers will drop south through eastern MT during the day tomorrow (40-60% chance, mainly east of Billings). While temperatures will be near freezing during this time, accumulating snow is possible (mainly on grassy surfaces). At this time, areas in eastern MT (east of Billings) have a 40 to 70 percent chance to see at least an inch of snow. Chances for 2 inches back off quickly, with only a 30 to 50 percent chance over portions of Fallon County and northern Carter County. This falling snow, with increased winds, will likely reduce visibilities at times, creating hazardous driving conditions for both the morning and evening commutes. This prompted a Winter Weather Advisory to be issued for Fallon and Carter Counties for Friday, from 5 AM to 5 PM.

Mountain snow will pick up again on Friday as well with light amounts expected in the Beartooth/Absaroka Mountains (moderate chance for 1 inch) and a few inches expected in the Bighorn Mountains (moderate chance for 3+ inches of snow). If you have outdoor plans in the high country late this week, make sure to prepare for winter weather conditions.

Low temperatures tonight will be in the upper 20s to lower 30s before temperatures warm into the mid 30s to lower 40s on Friday.
Overnight lows Friday will be in the upper teens to mid 20s.
Arends

Saturday through Thursday...

A weak shortwave dropping south and east through the area on Saturday is expected to be mainly dry, keeping seasonal temperatures in place (30s to lower 40s). Behind the wave, ridging building into the region from the west, along with lee-side troughing will help increase the surface pressure gradients along the western foothills Saturday night into Sunday. 700 mb winds will be on the increase as well, with westerly winds of 40-50 kts by Sunday. Surface winds will likely increase from Livingston to Nye Saturday night, with latest ensembles showing the KIDA-KLWT pressure gradients increasing to around 18mb by late Saturday night into Sunday morning. Latest local wind guidance for these areas shows the chance of 50+ mph winds near 100 percent, with winds of 58+ mph up near 90 percent. Heading into Sunday, the surface pressure gradients become aligned more west to east, which becomes favorable for Big Timber, up to Harlowton. Local wind guidance on Sunday has around a 90 percent chance of 50+ mph winds at Harlowton, with 58+ mph winds at around 60 percent. For Big Timber, the probabilities of 50+ mph winds are near 80 percent, with 58+ mph winds around 40 percent. Will be monitoring for potential wind highlites over the next couple of days.

At the same time, moisture will be working into the southwest mountains, and areas near Cooke City could pick up a few inches of snow into Sunday. Heading into Monday, another shortwave is progged to drop into the area from the northwest, bringing a moderate chance of rain and snow showers. Current precipitation chances range from 30 to 60 percent over the mountains, to 15-30 percent over the lower elevations, highest near the western foothills. Snowfall amounts look to be light at this time. Upper ridging looks to build back over the region for the middle part of the week bringing above normal temperatures (highs in the 40s to maybe 50s) and periods of gap winds. STP

AVIATION

A weak disturbance moving through the region will bring rain and snow showers into the evening hours. MVFR to local IFR conditions are possible with the rain and snow. Mountain obscurations can be expected due to snow. Gusty northwest winds (25-40 kt gusts, strongest along the western foothills) will decrease into the overnight hours, lingering over the far east. Another disturbance dropping in from the north will bring light snow and gusty northwest winds to areas mainly east of KBIL on Friday. STP

PRELIMINARY POINT TEMP/POPS

Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 030/042 027/041 027/047 032/043 026/042 028/049 030/049 13/S 20/U 00/N 13/O 20/B 00/U 00/U LVM 026/037 020/036 025/042 029/042 026/042 024/047 027/048 13/S 10/U 11/N 33/O 20/B 00/U 00/U HDN 028/042 024/043 021/049 030/044 024/044 021/049 022/050 15/S 30/U 00/E 22/O 21/B 00/U 00/U MLS 031/037 022/037 021/044 027/039 021/039 023/046 024/047 25/S 00/U 00/B 11/B 10/B 00/U 00/U 4BQ 031/037 024/037 022/046 030/042 024/041 025/049 026/049 35/S 10/B 00/E 01/B 00/B 00/U 00/U BHK 027/035 016/033 015/041 021/036 016/037 020/045 023/043 67/S 10/U 00/B 00/B 00/B 00/U 00/U SHR 024/039 022/038 018/048 027/043 022/041 020/050 025/051 23/S 40/B 00/E 12/O 21/B 00/U 00/U

BYZ WATCHES/WARNINGS/ADVISORIES
MT...Winter Weather Advisory in effect from 5 AM to 5 PM MST Friday FOR ZONES 33-37.
WY...None.

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