Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
981 FXUS65 KBYZ 192113 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 313 PM MDT Sun May 19 2024 .DISCUSSION... Through Tuesday night... The ongoing light to moderate rain showers this afternoon will decrease through the evening hours today. So far, there has been no lightning in our area, but we still can`t rule out a rumble of thunder this afternoon. Overall, the showers will remain benign. By tonight, dry conditions will persist before another more robust weather system brings precipitation chances back to the region Monday through Tuesday. This next system will mainly impact the western and southern foothills, as well as the Beartooth/Absaroka and Bighorn Mountains. While rain is expected over the lower elevations, the previously mentioned mountains could see heavy snow above 7000 feet. Those working to clear the Beartooth Highway or with travel plans along US-14 through the Bighorn Mountains Monday through Tuesday should pay close attention to the forecast. Monday will start out dry with temperatures warming into the 50s to lower 60s. By late morning, chances of precipitation will increase west and south of Billings as a trough digs south into Idaho and eventually Wyoming. By Monday afternoon and evening, chances of precipitation will spread east through Billings (40-90% chance, highest over the mountains), however, areas from Miles City to Baker look to remain dry (less than 10% chance of precipitation). As we get into Tuesday, the chance of precipitation will remain mainly over the southern mountains and foothills (50-95% chance, highest over the mountains). By Tuesday evening and night, the upper trough will move east and precipitation will come to an end. As far as precipitation and snowfall amounts go for the Monday through Tuesday event, some uncertainty remains. There continues to be a disconnect between the deterministic forecast values and their respective probabilities. At this time, the probabilities are much lower than the associated deterministic values. With that said, the NBM probabilities for 0.25 or more inches of liquid (rain or melted snow) is high over the Beartooth/Absaroka and Bighorn Mountains, as well as their respective foothills (70-90%). These probabilities drop quickly as you move north and east over the lower elevations with Billings having a 40% chance and Miles City having a 10% chance. With snow levels hovering around 7000 feet for this event, snow is expected in the higher elevations of the mountains. Probabilities remain moderate for 10 or more inches of snow in the Beartooth/Absaroka and Bighorn Mountains, however, the deterministic values suggests 8-14 inches over the higher terrain. With these amounts and the ongoing work to clear the Beartooth Highway, we have gone ahead and issued a Winter Storm Watch for the Beartooth/Absaroka Mountains covering the period from 12PM MDT Monday through 12PM MDT Tuesday. Heavy snow looks likely for the Bighorn Mountains too, but decided to wait on any products as the impactful snow does not get started until Monday evening and night there. Arends Wednesday through Sunday... The extended forecast still was looking quite active, especially for the Wednesday through Friday time frame. The pattern shaping up supports a very good chance of rainfall, with below seasonal temperatures. Wednesday through early Friday: An upper low pulls into the Great Basin Wednesday afternoon, spreading energy and moisture into the west for an increasing chance of showers. As this upper low moves across northern Wyoming, this will spread the increasing chance of showers across central and southeast zones Wednesday night through Thursday night. The chance of precipitation will be 30-50% Wednesday afternoon and night west and central. The chance increases to 50-80% for the entire area Thursday into Thursday night as the system swings across northern Wyoming (which is a really good position for precipitation). Chance of 0.25 inches through the period was 50-70%, with 35-55% chance of 0.50 inches. Another aspect to keep our eye on is snow potential for the higher elevations. Snow amounts were falling in the 6-12 inch category, with a 40% chance of amounts above 10 inches. Friday afternoon through Sunday: The mid week system moves east and small scale ridging pulls in for a brief period of drying Friday afternoon through early Saturday. The flow opens up to the southwest as the next upper system drops into the Great Basin and brings up more energy and lift and another increasing chance of showers Saturday afternoon through Sunday. At this time, the focus for highest precipitation chances (30-50%) is over western and central zones (including the mountains and foothills). The bulk of the heaviest rainfall (over an inch in some cases) is currently progged over northern Montana with this system. Will have to watch this closely, as ensemble trends have been to drag some of the higher rain amounts farther south with each passing run. Temperatures: Below seasonal readings in the 60s will be across the entire area Wednesday through Friday, with the warmest day (mid to upper 60s) being Wendesday. The weekend looks slightly warmer, with highs around 70 degrees. TWH && .AVIATION... Showers will be present over western and central sections of southern Montana (impacting KLVM and KBIL) with light to moderate rainfall and occasional MVFR conditions. These showers will become less numerous by late afternoon and early evening. Gusty north to northwest winds (gusts to 25kts) will be over the area through the afternoon, with decreasing winds this evening. Overnight will have mid level clouds gradually decreasing toward Monday morning. The mountains will be obscured this afternoon into early evening. TWH && .PRELIMINARY POINT TEMP/POPS... Mon Tue Wed Thu Fri Sat Sun ----------------------------------------------------------- BIL 038/060 042/062 042/068 045/057 041/062 043/071 048/069 15/T 45/T 13/W 58/T 64/T 13/W 35/T LVM 035/055 036/060 037/062 040/051 036/060 040/068 041/064 28/T 46/T 16/T 79/T 64/T 14/T 46/T HDN 036/062 041/062 037/071 043/061 039/063 040/073 047/072 14/R 35/R 12/W 47/T 74/T 22/W 34/W MLS 037/063 042/064 042/070 045/063 040/061 041/072 047/070 11/B 12/R 11/B 26/T 64/W 21/B 23/W 4BQ 039/060 044/061 040/070 045/067 040/060 041/072 047/072 12/R 24/R 21/U 25/W 64/W 21/B 23/W BHK 036/063 040/064 038/070 042/065 038/059 038/070 045/071 11/B 12/R 11/U 25/W 64/W 21/B 23/W SHR 036/057 039/055 033/068 040/062 036/059 038/070 044/069 17/T 78/T 32/W 26/T 64/W 22/W 34/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Watch in effect from Monday afternoon through Tuesday morning FOR ZONE 67. WY...None. && $$ weather.gov/billings