Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
155 FXUS65 KBYZ 162127 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 327 PM MDT Mon Sep 16 2024 .DISCUSSION... Today through Wednesday night... There is now better agreement that the upper low will travel through eastern and central Montana. Even with this better agreement in low track there is still uncertainty in precipitation amounts, and most importantly, where the highest amounts will fall. For example, even though our eastern areas are favored to receive the least amount of precipitation, 20% of models depict the heaviest precipitation amounts shifted with our central and eastern zones receiving the most precipitation. In conclusion, even though confidence in heavy precipitation has increased, there is still uncertainty in where the heaviest precipitation will fall and how much. Looking at the latest deterministic model runs, they have been consistent in showing the potential for dry slotting in our eastern zones early Tuesday. This will lead to the greatest precipitation chances being west of Billings in the morning and early afternoon hours. Wednesday will see precipitation chances all day across much of the area. Currently, from 6pm Tuesday through 6pm Thursday, the NBM is giving most of the region from Rosebud County and locations to the west a >50% chance of getting over an inch of precipitation. Locations to the east are likely going to be too close to the low and will see precipitation from frontal passage Tuesday evening followed by dry slotting. NBM is giving many of these eastern locations a 20-40% chance of receiving >0.5 inches of precipitation. ECMWF EFI tables for Wednesday indicate widespread values of 0.7-0.9 and a shift of tails of 2 indicating anomalously high precipitation for this time of year. These factors have led to the issuance of a level 1 of 4 risk for excessive rainfall exceeding flash flood criteria on Tuesday from Park County up through Musselshell county. On Wednesday a 1 of 4 risk has been issued for locations from Northern Park County up to Northwest Rosebud County. There will be a chance for severe storms tomorrow as the approaching trough creates strong lift. Soundings show decent dewpoint depressions bringing about the chance for strong winds (65mph) and hail (1 in). HREF is showing paintball reflectivity and helicity tracks in the afternoon and evening increasing confidence in convective activity. There is a level 1 and 2 of 5 for severe storms across the area tomorrow. The low pressure system will create a tight pressure gradient leading to strong (30kts) southerly winds Tuesday for Sheridan County and locations to the north and east from mid afternoon into the evening. As the low pressure system wraps around it will bring strong winds across the region Wednesday. The GFS is currently showing 700mb wind speeds near 50mph across much of the area leading to surface winds gusting into the 40s. These strong westerly winds may act to decrease precipitation totals in the foothills due to downsloping. There is increasing potential for snowfall on the Beartooth pass Tuesday evening through Wednesday. Currently there is a 50% chance for some parts of the pass to receive >than 2 inches of snowfall. Ensemble systems are showing the potential for a more significant snow event. Make sure to check the forecast if you have travel plans. As the upper level trough comes through it will drop temperatures significantly. Tomorrow, temperatures will vary greatly with low 70s in the west to low 90s in the east. These will drop 10-20 degrees for Wednesday with low 60s in the west and low 70s in the east. Torgerson Thursday through Monday... The low that should bring rain and wind earlier in the week will weaken as it exits to our northeast Thursday, which is a day that should exhibit drying and decreased winds. Much weaker troffing left behind over the great basin and possibly a weak Pacific shortwave will keep our weather somewhat unsettled and cool-ish Friday through the weekend, but any precip on these days should be spotty and light. One item to note: on previous days there appeared to be another strong trof arriving early next week, but recent models have trended toward weaker energy and higher heights...and overall faster Pacific flow. Cluster analyses show this trend being most probable to occur, but there is still the reduced possibility of a cooler/wetter trof by Sunday/Monday. Something to watch. JKL/RMS && .AVIATION... Scattered showers and thunderstorms are expected late this afternoon-evening, mainly west of KBIL, but isolated storms are possible from the Bighorns across southeast MT. These storms could produce erratic wind gusts of 30-40 knots and brief MVFR. Mountains may be occasionally obscured. Otherwise, VFR will prevail across the region tonight. On Tuesday, scattered showers and thunderstorms will develop from the west and south in the early afternoon then expand northeastward. Localized MVFR is possible in the heavier showers and thunderstorms. Additionally, south/southeast winds will increase on Tuesday near and east of KSHR and in far southeast MT to 10-20 kt, gusting to 20-30 kt. JKL/RMS && .PRELIMINARY POINT TEMP/POPS... Tue Wed Thu Fri Sat Sun Mon ----------------------------------------------------------- BIL 054/080 053/061 054/071 048/074 049/069 048/070 048/069 24/T 88/T 63/W 01/U 22/W 23/W 33/W LVM 047/072 046/058 045/068 042/072 041/070 041/068 040/069 28/T 98/W 63/W 12/W 22/W 33/T 33/W HDN 051/083 050/064 052/071 045/076 046/072 046/071 044/070 23/T 88/T 63/W 00/U 22/W 22/W 32/W MLS 056/088 054/066 054/068 047/074 048/069 047/068 046/067 31/B 87/W 63/W 01/U 22/W 22/W 32/W 4BQ 057/089 051/067 053/069 047/076 048/071 048/069 046/069 21/B 85/W 31/B 01/U 22/W 22/W 21/B BHK 055/090 052/073 050/069 045/075 046/072 044/070 043/070 31/B 74/W 31/N 01/U 22/W 22/W 22/W SHR 051/084 046/071 048/072 042/077 043/072 043/072 041/072 23/W 75/W 21/B 01/U 23/W 22/W 22/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings