Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
990 FXUS65 KBYZ 180251 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 851 PM MDT Wed Jul 17 2024 .UPDATE... Updated forecast for latest model trends. Cluster of thunderstorms northwest of Billings is riding a well defined cold poole southeastward, but low level thermodynamics are becoming unfavorable with sunset. Its possible that this activity will root itself above the surface inversion and continue its southeastward course into Billings over the next hour or two, but its most likely going to weaken and fall apart before it gets to Billings. Once this convection dissipates expect clearing skies and light winds overnight into tomorrow morning. Another round of convection is on tap for tomorrow. This round will have the potential for stronger, possibly severe, wind gusts. Chambers && .DISCUSSION... Through Thursday Night... Satellite imagery shows a ridge axis over central MT and an upstream weak low over western WA/OR. As expected, we are beginning to see convection develop over the mountains with lightning noted south of Cooke City and Sheridan as of 1pm. There is nothing yet over the Crazies or Snowies, but as the ridge axis migrates to the east and the air mass moistens a bit more this should begin to happen over the next few hours (especially given upslope SE winds from the surface to 700mb). Overall, convection between now and about 10pm will be weak but may produce erratic surface winds to about 40 mph. Greatest potential is near the mountains/foothills but some activity may spread eastward to include Roundup & Billings this evening. High res models have been fairly consistent in this regard. Late tonight and Thursday morning will be dry, then by afternoon we begin to see the effects of the approaching Pacific low. The low will crest the ridge and not induce height falls, and flow aloft will remain quite weak, but the ascent along with a bit moister air mass (pwats ~0.90") will result in a much greater potential (30-50% probability) for thunderstorms tomorrow afternoon and evening across the region. HREF shows only a modest signal for convective winds, but forecast soundings are somewhat indicative of wet microbursts and so gusty outflow winds will need to be watched. Wind shear will be too low and mid levels too warm for a risk of anything but wind and localized downpours. As the PV anomaly tracks from north central thru southeast MT, the chance of showers & thunderstorms will persist over our east thru tomorrow night. Regarding fire weather, the increased lightning activity on Thursday may be problematic given our drying fuels, but the storms will be wet and there is a reasonable expectation of localized wetting rains...including during the nighttime hours in southeast MT. Temps of course will remain warmer than normal. Look for highs Thursday in the 90s most places but a few notorious hot spots could touch 100F as 700mb temps rise to near +14C. JKL Friday through Wednesday... Upper ridge axis will be over W. MT on Friday, while NW flow brings shortwave energy SSE through the eastern part of the forecast area. In addition...other shortwaves will move through the remainder of the area, while monsoonal moisture continues over the region. PWAT`s will be just over an inch in the far E. Thus there is a 20% chance of showers and thunderstorms in the morning from KMLS E and SE. Chances for showers and thunderstorms will increase from Rosebud County E in the afternoon with highest chances on the MT/Dakotas border at 40 to 50%. Southern mountains will have 30-40% PoPs and there will be slight chances (20%) over KSHR and over areas near the western mountains. Low PoPs linger in the evening over the SW mountains and far SE MT. The best chances for 0.25 inches or higher of rainfall through Fri. evening will be E and SE of KMLS in the teens to around 20%. Region will be under upper ridging Saturday through Tuesday with continued monsoonal moisture over the area. Expect 20-30% chances for showers and thunderstorms over the SW mountains and the NE Bighorns for the weekend each afternoon. Low afternoon/evening chances continue over the SW mountains through Tuesday. Models showed a trough approaching the area from the W on Wednesday with low PoPs over the western mountains spreading into adjacent areas including KLVM, K6S0 and Judith Gap. Mean 700 mb temp was 16 degs C which could cap lower elevation convection, but this was way out in time in the forecast period, so will continue to watch model trends. As for temperatures, highs will be in the upper 80s to low/mid 90s Fri. through Monday, then in the 90s on Tuesday and in the 90s to around 100 on Wednesday. There was a 30-50% chance of reaching 100 degrees in the river valleys on Wed. and this area included KBIL, KMLS and KSHR. KMLS will be close to record temps if this scenario plays out. Arthur && .AVIATION... A cluster of storms may make it into Billings by 10pm, but most likely will dissipate before arrival. Brief MVFR conditions and gusts to 40 mph can be expected near this activity. Expect clearing skies and light winds for the rest of the night once current storms dissipate. Smoke and haze will continue to reside over the forecast area, with slant range visibility impacts possible at times. Chambers && .PRELIMINARY POINT TEMP/POPS... Thu Fri Sat Sun Mon Tue Wed ----------------------------------------------------------- BIL 063/097 064/094 065/093 063/091 062/093 063/095 064/099 22/T 41/U 11/U 01/U 00/U 00/U 01/U LVM 056/094 054/094 057/093 055/091 055/091 054/095 057/097 13/T 22/T 11/U 01/U 01/U 01/U 12/T HDN 061/099 062/095 062/093 060/092 059/093 059/097 060/100 22/T 41/U 11/U 11/U 00/U 00/U 00/U MLS 064/096 068/091 063/090 064/089 064/090 064/094 066/097 00/U 43/T 11/U 11/U 00/U 00/U 00/U 4BQ 064/097 066/092 063/089 061/087 061/090 063/094 064/097 00/U 33/T 10/U 01/U 00/U 00/U 00/U BHK 059/094 063/088 060/087 058/086 059/088 059/092 060/094 00/U 44/T 11/U 11/U 10/U 00/U 00/U SHR 058/098 059/093 057/090 056/087 055/090 056/093 058/095 22/T 22/T 11/U 11/U 01/U 00/U 01/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings