Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
994 FXUS65 KBYZ 182030 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 230 PM MDT Sun Aug 18 2024 .DISCUSSION... Through Monday night... Showers and thunderstorms will wind down this evening into overnight. Skies could be pretty hazy tomorrow morning through early afternoon as upper level smoke moves in from the south. There is a surprising amount of uncertainty in the high temperature forecast tomorrow considering we are under upper ridging. A deeper look indicates this uncertainty is mainly being driven by the Canadian Ensemble which is forecasting temperatures about 5 degrees cooler than other ensemble systems. It is unclear why this system is forecasting cooler temperatures. The most likely scenario is for temperatures to be in the high 80s to mid 90s across the region tomorrow. Monday, PWAT values will be over 1 inch for locations east of Billings which is approaching 200% above normal for this time of year. This is caused by high pressure to our east wrapping southerly/southeasterly winds into the region. This will act to advect in Gulf moisture with some locations near the Dakotas border having a 40% chance of getting dewpoint over 65 degrees. Models are hinting at a low level jet of 25-35kts developing Monday evening helping to provide a more favorable shear environment for storms that are able to get going. This will also act to better sustain storms through the overnight. A stronger upper wave tomorrow will bring lift to our eastern areas allowing storms to tap into the more favorable environment in our eastern areas. CAPE will be in the 1,000-2,000J/kg range which is anomalously high with ECMWF EFI tables depicting values of 0.8-0.9. Looking at the latest HREF run, storms will get going around 1PM tomorrow afternoon across the east and west. The most favorable area will be from Sheridan County to the north and east where the HREF is showing large paintball clusters and multiple helicity tracks. One potential limiting factor will be weak shear values around 25kts in the afternoon when storms are forming. The shear does strengthen to around 35-40kts later in the evening however, which combined with the low level jet could help prolong storms. Looking at soundings, high based storms producing strong winds appear to be the main threat. Soundings are more moist than what we have seen recently bringing about the possibility for more rainfall from these storms. Hail will be a secondary threat as high freezing levels will make it difficult to produce large hail, though severe hail from some of the stronger storms can`t be ruled out. Torgerson Tuesday through Sunday... Model solutions are in good agreement on the large-scale pattern through Friday and then diverge for next weekend. Tuesday will be hot under 500 mb southwesterly flow with isolated showers and thunderstorms (20% chance) over the western mountains and locations north and northwest of Billings. A cold front probably will cross the area Wednesday morning with low-level winds switching to northwesterly then northeasterly. These winds will bring in modestly cooler air for Wednesday. Our area will still be under southwesterly flow at 500 mb with a disturbance moving through in the afternoon. The disturbance should facilitate development of isolated-scattered showers and thunderstorms mainly in the mountains and areas north of the MT/WY border Wednesday afternoon-evening. Wind shear looks strong, over 40 kt, but CAPE is on the low side...so not expecting severe thunderstorms at this point but will monitor. Thursday should be dry for much of the area as 500 mb shortwave ridging moves into the area. Friday could be active as the 500 mb ridge moves eastward out of MT and a 500 mb trough moves eastward over the western US. It will be hot and breezy with another round of isolated-scattered showers and thunderstorms (20-40% chance) in the afternoon- evening. Could have fire weather concerns on Friday. As mentioned earlier, next weekend has a lot of forecast uncertainty with some model 500 mb clusters showing troughing dominating our weather with cooler conditions and a chance of showers/storms and other clusters showing ridging dominating with warmer and drier conditions. In accord with this data, NBM has a 20-40% chance of showers and thunderstorms Saturday afternoon- evening and a 20% chance of showers/storms Sunday afternoon- evening. Stay tuned for forecast updates as we go through the week. High temperatures will generally be in the 80s and 90s Tuesday and Wednesday then 80s Thursday and 80s and 90s Friday. For Saturday and Sunday, NBM shows considerable uncertainty in the high temperature forecast with the 10th to 90th percentile at Billings ranging from the 70s to the 90s. RMS && .AVIATION... VFR will prevail through the TAF period. Through this evening, scattered showers and thunderstorms will occur mainly west of KBIL, though there is a low chance that they could reach near KBIL/KSHR/K00U. Storms today could produce erratic, strong wind gusts to 50 kt. In addition, southeasterly surface winds will strengthen over southeast MT after 02z Monday to about 15-20 kt gusting to 25-35 kt, persisting into the daylight hours Monday. Isolated-scattered showers and thunderstorms will then be over much of the area on Monday. Storms could produce strong wind gusts to 50 kt and large hail on Monday. Localized MVFR is possible under storms. RMS && .PRELIMINARY POINT TEMP/POPS... Mon Tue Wed Thu Fri Sat Sun ----------------------------------------------------------- BIL 066/093 062/095 060/089 058/086 060/093 060/088 056/081 03/T 20/U 01/U 20/U 01/U 21/B 22/W LVM 058/090 055/089 052/085 048/084 052/088 053/079 048/076 14/T 21/U 12/T 20/U 12/T 23/T 32/T HDN 066/094 059/097 059/092 056/088 059/094 058/090 053/083 13/T 20/U 00/U 20/U 00/U 11/U 22/W MLS 066/092 064/094 065/091 061/086 064/094 064/090 058/082 03/T 40/U 10/U 31/U 11/U 11/U 22/W 4BQ 064/092 064/096 066/093 060/089 065/094 065/092 057/084 04/T 30/U 00/U 20/U 10/U 11/U 21/U BHK 061/087 062/092 063/092 059/085 059/090 062/090 055/081 03/N 51/U 01/U 31/U 11/U 11/U 11/U SHR 062/091 057/095 059/093 055/087 058/092 058/089 051/082 04/T 20/U 00/U 10/U 00/U 11/U 21/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings