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FXUS65 KBYZ 030849 AFDBYZ

Area Forecast Discussion National Weather Service Billings MT 249 AM MDT Fri May 3 2024

DISCUSSION

Tonight through Saturday night...

Today southeast Montana will still be under the influence of a 500mb trough keeping temperatures on the cool side in the 50s F for most. Cyclonic flow on the back side of the low will keep some precipitation chances (20%) and clouds across much of the area today. Any precipitation is expected to remain light with NBM showing most of the region having a <10% chance of getting 0.10 inches of precipitation. Isobars will have a decent gradient on the back side of the low bringing some breezy conditions during the day as well. These breezy conditions will hold of until late morning/early afternoon when low level lapse rates get steep enough to mix down higher level winds. Most of the region will see a 40-60% chance of seeing a wind gust over 40mph during the day Friday. Due to the reliance on mix down, winds will die down pretty quickly in the evening with the loss of surface heating.

Saturday will see a change in pattern with a shortwave ridge making its way into the region bringing warmer temperatures and clear skies. Most of the region will see temperatures in the 60s F with clear skies. Saturday will see winds switch from northwest to southerly as an upper level low starts to impact the region. Winds will be strongest from the Wyoming border of Carbon County up through Wheatland County where there is a 60-80% chance of seeing a wind gust >40mph. Upper level ridging will keep things dry on Saturday. Torgerson

Sunday through Thursday...

Models are in good agreement that a strong upper low over the Nevada vicinity Sunday will push through Wyoming on Monday and settle into the Dakotas by midweek. While the exact track and details of how it all unfolds is still in question, cluster analysis indicates high confidence that our region will see below normal temps, quite windy conditions at times and possibly significant precipitation. Lower elevations will see primarily rain but elevations above 6500 ft could see substantial wet snowfall.

Sunday will likely be a transition day with pre-frontal warming pushing temps above normal with cooler, windy and possibly wet conditions then taking over Sunday night through at least midweek.
The EFI (Extreme Forecast Index) currently points to our eastern counties with 70-80% chance of seeing significant precipitation compared to climatology (40-60% chance of >0.50 precip) as a potentially powerful trowal feature sets up. Our western mountains have up to a 75% chance of greater than six inches of snowfall during this time as well.

This dynamic low will likely generate plenty of wind across portions of our CWA, including strong southeast winds on our eastern borders Sunday, southwest winds in our foothills by Sunday evening, and peaking with strong northwest winds across the entire region Tuesday. Gusts over 40 mph are likely (>75%) for most areas Tuesday afternoon, with the corridor from northern Rosebud to Carter County possibly seeing gusts up to 50 mph (probability 50-70%).

After temps in the 70s to lower 80s Sunday ahead of the front, we will see highs in the 50s to lower 60s Monday, and cooling to the 40s and 50s by Wednesday. By Thursday the models suggest the upper low will slowly drift east, but we may see lingering bands of precipitation across our east with temps mainly in the 50s.

Impacts: While our high country may see heavy wet snow at times, the main impacts we are concerned about are the harsh combination of wind and rain for people caught outside and especially for young livestock. Make sure to stay up to date with the latest forecast for your location as details emerge. BT

AVIATION

Today will be cloudy with ceilings in the 4-5,000 foot range.
Scattered rain showers will bring a 20% chance of precipitation to most of southeast Montana. Locations such as KSHR, KMLS, and KBHK will see northwest winds gust into the 20s kts during the afternoon before winds die down during the overnight. Torgerson

PRELIMINARY POINT TEMP/POPS

Tdy Sat Sun Mon Tue Wed Thu ------------------------------------------------------- BIL 052 031/066 042/074 046/057 043/057 042/054 041/058 1/E 00/U 02/R 46/R 44/R 56/R 56/R LVM 051 028/064 042/066 040/052 037/051 035/050 036/053 1/B 00/B 16/T 78/R 35/O 57/O 56/O HDN 053 027/069 040/079 046/058 042/057 039/053 038/059 2/O 00/U 02/R 37/R 55/R 56/R 66/R MLS 050 028/064 042/081 051/063 042/053 037/052 040/060 1/B 00/U 01/N 38/T 66/R 67/R 65/R 4BQ 051 028/066 043/080 050/060 040/054 038/050 037/057 1/B 00/U 01/N 47/T 65/R 56/R 55/R BHK 048 026/061 038/074 049/063 037/052 034/050 036/057 1/N 00/U 01/N 47/T 77/R 66/R 55/R SHR 050 026/066 038/077 042/055 039/056 037/052 036/054 2/O 00/U 02/R 38/T 55/R 56/R 56/R

BYZ WATCHES/WARNINGS/ADVISORIES
MT...None.
WY...None.

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