Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
638 FXUS65 KBYZ 050914 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 314 AM MDT Sun May 5 2024 .DISCUSSION... Today through Tomorrow Morning... .KEY MESSAGES... - Main threat today will be elevated fire conditions for locations from Sheridan County up through Rosebud County. - Cold front moves in this evening bringing chance of precipitation through the overnight hours. Strong southerly winds ahead of the upper low will bring strong warm air advection to much of the region. Temperatures will be 10-20 degrees above average for the plains bringing low 70s to low 80s for most. Winds will breezy in the 20s kts for locations from Sheridan up to Rosebud Counties and locations to the east in the morning and early afternoon. Winds will pick up after around 21Z today as temperatures rise and erase an elevated inversion. 850mb - 700mb lapse rates of greater than 8C/km will lead to efficient mix down raising wind gusts into the 30s and 40s mph. On the high end, locations in Sheridan and Fallon County have a 50% chance of seeing a wind gust over 50 mph. With abnormally high temperatures, RH values have a 40-70% chance of getting below 20% from Sheridan up through Carter Counties. This combined with the strong winds mentioned earlier will lead to localized fire concerns. Ongoing greenup is still patchy leading to relatively little fire concerns for areas that have already greened up and fire concerns for places that haven`t. Given the patchy greenup and the fact that the lowest RH values and strongest winds don`t look to be co-located, we have held off on issuing any fire products at this time. As we move toward tonight into Monday morning, a cold front will move across the area switching winds to westerly. Winds in the east will slowly die down during the overnight but winds in the west will be increasing. The cold front will bring pressure rises and a >70% chance of getting a wind gust over 40mph for western gap areas such as Big Timber and Harlowton. The strong winds throughout the day Monday will be covered in the long term discussion. Pops were lowered for this evening into tomorrow morning as the NBM had widespread precipitation chances that were not seen in various long and short range models that were looked at. The Beartooth/Absaroka mountains will be the fist to see precipitation under upper southwest flow by about 18Z. Precipitation chances will then spread across the region with 50-60% chances in the western CWA and 20-30% chances for the plains. Torgerson Monday through Saturday... Model solutions of 500 mb pattern for incoming storm system continue to be in general agreement. The system is currently forecast to come across Wyoming Monday as an open wave but strengthen and close off over the western ND/SD border area by Monday evening. After that the models differ as the GFS drifts the system west Tuesday while the EC keeps it near stationary. This difference is key as resultant precipitation will be very sensitive to the exact placement of the upper low due to close proximity to us and its dynamic nature...with the EC stationary solution much wetter for our CWA and the GFS "dry" slotting much of our CWA Tuesday. The ensembles all then gradually shift the system east/southeast through the remainder of the week. At this time we are using a blended approach to the forecast, but leaning toward the EC per the NBM data. Northwest flow persists over the area late in the work week which may result in unsettled showers (20-30% PoPs) and just a gradual warming trend to normal temps by Saturday. So there remains considerable uncertainty in overall precipitation and placement. So lets talk about what we do know...all solutions tend to target our eastern zones with substantial precipitation Monday/Monday night with probability of 50-75% of >0.50 liquid just in the Monday/Tuesday time frame (eastern border counties the highest). Western areas may miss out on best dynamics early in the week and also get downsloped by strong w/nw winds Monday afternoon through Tuesday evening limiting overall precipitation. Wednesday into Thursday has good potential for widespread precipitation over the entire CWA as the upper low gradually shifts east/southeast and phases with additional energy from the west. There remains potential for considerable wet snow accumulation in the high country as well this week with most areas above 7500 ft with a 40-65% chance of over a foot of snowfall through the week. We also know we will have an extended period of strong winds...mainly Monday afternoon through Tuesday evening...but blustery conditions with rain will be present through Wednesday night or Thursday. The corridor of strongest winds has shifted over the last 24 hrs from Rosebud to Carter County...to focus on portions of our western and central zones from Wheatland to Southern Big Horn County. This weather scenario does not fit our usual conceptual model of widespread high winds (=>60 mph gusts), but NBM guidance is hitting it hard (though we know it is often hot in some areas). With timing, placement and strength all jumping around...even a watch is hard to nail down. We will continue to message a long duration of strong winds across the region by other means for now. Snow levels drop from 9500 feet to around 5500 feet Monday and generally remain there or above that level through the week. For the mountains the wind fields support significant snow mainly on west to south facing aspects through Tuesday. Beyond that winds should turn more northerly bringing a better chance for north facing slopes to get in on the snow Wednesday and Thursday. Winter Storm Watch for the northern Bighorn mountains (Monday thru Tuesday morning) is in place to match up with RIW`s watch. As mentioned above, forcing for snow in the Bighorns will be mainly on west facing slopes, and although snow totals during that time are mainly 4-9 inches, the potential for blowing snow (winds 30-45 mph) could produce very limited visibility at times Monday into Tuesday. Busy weather week ahead...please keep tabs on the latest forecasts. BT && .AVIATION... Rain showers will begin to make their way into the region impacting KLVM by 21Z before spreading scattered showers through the area in the overnight. Locations west of Billings will generally have 30-40 Pops while locations to the east will have 20-30 Pops. Winds will gust into the 20s and 30s kts with the strongest gusts occuring after 21Z. This will mainly impact KSHR, KBHK, and KMLS. Torgerson && .PRELIMINARY POINT TEMP/POPS... Tdy Mon Tue Wed Thu Fri Sat ------------------------------------------------------- BIL 072 046/057 043/054 042/049 041/057 042/064 041/072 3/R 55/R 32/O 58/R 88/R 43/R 11/U LVM 064 039/053 036/049 037/047 037/051 036/061 037/069 5/T 76/R 23/R 78/O 76/R 22/R 01/U HDN 077 046/057 042/057 039/048 040/059 041/066 039/073 2/B 77/R 43/R 69/R 98/R 43/R 11/U MLS 080 049/057 040/051 037/050 040/061 043/065 041/071 2/R 69/T 85/R 89/R 87/R 32/R 11/U 4BQ 080 047/057 040/053 037/047 039/057 042/062 041/070 1/N 69/T 73/R 58/R 87/R 43/R 11/U BHK 074 049/060 036/051 034/050 037/059 038/063 038/068 0/N 69/T 86/R 78/R 76/R 22/R 11/U SHR 077 042/054 037/056 037/049 035/053 038/061 036/069 1/N 77/R 33/R 58/R 88/R 54/R 11/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...Winter Storm Watch in effect from Monday morning through Tuesday morning FOR ZONE 198. && $$ weather.gov/billings