Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
074 FXUS65 KBYZ 190122 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 722 PM MDT Sat May 18 2024 .UPDATE... Satellite imagery shows cooling tops in our west in response to a weak shortwave moving from central ID into southcentral MT. There isn`t much instability, but mid level lapse rates are sufficiently steep (~8.5c/km) to allow for light showers to develop...and sure enough that is what local web cameras are showing along the western foothills. Tonight`s precip won`t amount to much, and the greater chance of precip is tomorrow when stronger wave arrives. There is also a low chance (20%) of showers in our east later tonight, per low level jet and mid level warm front, but the boundary layer is quite dry so not sure if we`ll see any precip in our east actually reach the ground. Mesoanalysis shows pwats of less than 0.40". Admittedly we should see pwats increase gradually thru the night so this bears watching. Forecast is in good shape and covers everything mentioned above. Have expanded pops in our west slightly this evening, and adjusted winds per current trends (e.g. easterly winds have reached Livingston as of 7pm). JKL && .DISCUSSION... Through Sunday night... The dry and mostly sunny skies this afternoon will give way to increasing clouds and precipitation chances this evening through Sunday as we remain in an active weather pattern. Any precipitation that falls will not be significant, with southeastern Montana potentially seeing no precipitation (60-75% chance for no accumulating precipitation through Sunday). The breezy winds ongoing today will decrease this evening as surface winds turn out of the southeast/east. This will allow better plains moisture to move into the region, increasing the moisture content in the air. This, paired with an approaching trough, will allow the chance of precipitation to return to the forecast, mainly Sunday. While most areas will remain dry through this evening, a low chance (25% or less) for light showers returns to areas west of Billings this evening. Any rain that occurs will be light with this round. By tonight into Sunday morning, better jet dynamics will move into our western areas allowing better precipitation chances to be introduced to the forecast for that area (15-55% chance). By Sunday afternoon, precipitation looks to spread east (15-30% chance). However, this precipitation looks to be lighter and more isolated as it moves out of the better forcing. With the precipitation Sunday, a rumble of thunder or two is possible, but the overall chance remains low with limited instability. Snow levels will hover around 7000 feet Sunday as well, so expect light snow in the mountains, mainly in the Absaroka/Beartooths (1-3 inches over the highest peaks). Overnight lows will be in the 40s tonight and 30s Sunday night. High temperatures Sunday will range from 50s west to upper 60s to 70 degF east. Arends Monday through Saturday... Pattern: Several upper disturbances will swing across the Northern Rockies through the week and this will carve out general troughing. This pattern will lead to several waves of precipitation chances and keep temperatures generally below seasonal averages. Details below. Monday and Tuesday: The first wave swings across the Great Basin and settles into southern and central Wyoming. This will bring upper diffluent flow to the forecast area for ascent, for an increasing chance of showers. The system will drop south and keep the highest chance of showers to the south, but there will still be a solid 40-60% chance of rainfall over western and central zones during the period. The most likely location for showers will be over western zones, and south of Billings (including the mountains and foothills). NBM probabilities give a 70% chance of 0.25 inches of rainfall over the mountains and foothills (including Livingston, Red Lodge and Sheridan) during this time, with a 35% chance at Billings. The system pulls away Tuesday night for potential drying. Tuesday night and Wednesday: Transitory ridging moves into the area. This looks to be the most likely period for drying. That being said, the next upper system drops into eastern Washington and Oregon and sends energy into the west Wednesday afternoon and evening, for another round of showers. Wednesday night through early Friday: The next upper low pulls out of eastern Washingto and Oregon and moves eastward across central Wyoming. The position of this low looks a little farther north and could potentially produce a better chance of showers. Going with a general 50-70% chance for this round. NBM probabilities have a 50-70% chance of 0.25 inches of rainfall for this second round of showers (highest over the mountains and foothills). The northward push of this low was keep the vast majority of the QPF north (totals exceeding a half into to an inch over northern Montana). Will have to watch this as the trend has been to sink this higher QPF south. Friday afternoon through Saturday: Small scale ridging builds back in for a period of drying. So overall, the pattern looks pretty unsettled with good potential for rainfall most days. Temperatures will be seasonal to a bit below (generally in the 60s). TWH && .AVIATION... VFR conditions will prevail over the next 24 hours as clouds increase from the west. The breezy conditions ongoing today will decrease this evening as precipitation chances increase around KLVM. By Sunday, expect isolated to scattered showers to spread across the area, best chance around and west of KBIL. With this, breezy northwest winds will occur Sunday with gusts in the 15 to 30 mph range. Expected periods of mountain obscurations beginning this evening, lasting through Sunday. Arends && .PRELIMINARY POINT TEMP/POPS... Sun Mon Tue Wed Thu Fri Sat ----------------------------------------------------------- BIL 043/060 038/061 043/061 042/068 045/059 042/062 043/068 15/W 35/W 45/W 14/T 57/T 55/W 35/T LVM 041/055 035/057 037/061 039/062 039/055 037/060 040/064 26/T 37/T 55/T 17/T 68/T 55/T 46/T HDN 041/064 036/062 041/062 039/070 044/063 040/063 040/070 12/W 34/W 44/T 13/W 56/T 54/W 34/T MLS 043/066 040/062 041/063 041/068 046/062 043/061 041/068 12/W 22/W 22/W 11/B 35/W 54/W 33/W 4BQ 042/069 041/060 044/060 040/068 044/065 043/060 041/068 01/B 23/W 44/W 11/B 24/T 53/W 33/T BHK 041/069 037/062 039/062 037/067 041/061 039/059 038/065 22/T 32/W 22/W 11/B 24/W 44/W 33/W SHR 040/066 037/057 038/055 035/066 039/061 038/060 038/068 02/W 36/W 77/T 22/T 36/T 54/W 34/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings