Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
155 FXUS65 KBYZ 052052 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 252 PM MDT Sun May 5 2024 .DISCUSSION... This afternoon through Monday night... Models have come into good agreement with the synoptic pattern through Monday night. EC/GFS/Canadian now have similar tracks with the upper low moving from the ID/NV line this afternoon, across southern Wyoming tonight, and curving north east into NW SD by late Monday. While that is the track of the upper low, a trof extending north of that energy moves west to east across the forecast area tonight becoming stationary over SE Montana on Monday. Westerly winds build in behind this upper trof tonight as a cold front moves through the area, also becoming stationary somewhere over far SE MT tomorrow, and staying in the vicinity into Tuesday. The upper and surface trofs combined with the main low spinning northward into the area will set the stage for a significant precipitation event (1 inch +) for the eastern third of the forecast area (Rosebud county east) through Monday evening. Downslope winds are finally being acknowledged in the models with much lower precipitation totals showing for the next 36 hours from Billings west. Will see scattered showers tonight into early tomorrow before westerly winds kick in tomorrow morning. An isolated thunderstorm is possible just about anywhere from this afternoon through late tonight, with gusty winds and small hail/graupel the main threat. Models continue to advertise strong winds over the western half of the forecast area, as well as down into the Bighorn foothills, for Monday. Will issue a High Wind Warning along and west of a Ryegate to Sheridan Wyoming line for Monday into Monday night to cover these areas where probabilities for gusts over 55mph is above 60 percent. As far as snowfall goes totals trended down over the western mountains due to the track of the low staying further south and east than previous runs. As a result will see less than 6 inches of snow for the Beartooth/Crazy mountains, though strong wind gusts will still make conditions difficult for those working on the Beartooth Pass. Will issue a winter weather advisory for the Bighorn mountains where around 5 to 8 inches of snow is expected to fall from early Monday morning into the early evening hours. Winds will be strong at times in this area as well, so those planning to head up to the Bighorns should be prepared for snow and strong wind gusts. Chambers Tuesday through Saturday... Model solutions continue to have consistency issues but are in closer agreement than yesterday. The Canadian/EC solutions hold the upper low in the NW SD/SW ND vicinity through early Wednesday before kicker energy arrives from the northwest and pushes the energy eastwards leaving a north to east flow over the area aloft into Friday. The GFS yesterday was pivoting the upper low well into Canada and then curving it southward over NC MT before kicking it eastward. The latest GFS solutions still go further west with the energy than the Canadian/EC do, but is much further south and in line with the latitude of the other models. The differences in the two solutions still causes disagreement with strength of the surface winds on Tuesday into Wednesday and placement/strength/and latency of precipitation. Thus confidence in particulars is low to moderate with this extended forecast. NBM continues to show strong winds across a good portion of the forecast area Tuesday into Wednesday on the back of consistently strong EC ensemble wind forecasts. There is a corridor of strongest winds from Harlowton to Sheridan once again, along with an area along the northern tier of counties from Custer to Baker and then south into Carter. Added a High Wind Watch for the southern wind corridor where probabilities for over 55 mph winds was above 60 percent. Held off on the other areas as progs were right around 50 percent at this time. This is likely due to the further west GFS solution which would put the upper low around Roundup, limiting the stronger winds from there eastward. Will continue to monitor areas further east for strong wind highlites as the models get better consistency. Precipitation over central and western zones looks to ramp up for Tuesday night into Thursday as winds turn more northerly and possibly northeasterly for a time allowing upslope and isentropic ascent to increase and killing most of the downslope drying that accompanied the first half of this system. Half an inch to over an inch of precipitation is forecast for central and western zones during this period, and this solution has been pretty consistent over the past several days. That said a track change to the core of the upper low, or the kicker wave arriving in too vigorous a manner could cut those precipitation amounts down some, so stay tuned. The current forecasts all show near to above warning type snow accumulations from Tuesday night into Thursday, with almost 2 feet progged in the highest elevations of the Bighorn mountains. Still a bit too much uncertainty and a bit far out for a Winter Storm watch for these areas, but will probably need one as we get closer to the heaviest snowfall period. Snow levels have trended lower going into Tuesday night, such that a dusting of snow is possible down to 4000 feet or so. Will need to keep an eye on foothills locations down to 4500 feet for impactful accumulations that may need an advisory Tuesday night into Wednesday morning. Snow levels increase Wednesday night so for now do not expect any lower elevation snow impacts for that period. As the upper storm system moves east of the area expect improving conditions going into Friday, with ridging build in from the west. Chambers && .AVIATION... Breezy winds at most terminals will decrease this evening. Before sunset, storms and rain showers have a small chance to bring a brief, erratic wind gust to all areas. A cold front will pass through overnight, shifting winds to the west. Winds will then increase throughout the morning, and widespread rain will occur for terminals east of KBIL. Mountains will be obscured due to snow. Vertz && .PRELIMINARY POINT TEMP/POPS... Mon Tue Wed Thu Fri Sat Sun ----------------------------------------------------------- BIL 046/057 042/055 039/049 040/059 041/067 043/076 048/077 56/R 13/R 69/R 86/R 22/R 00/U 12/T LVM 039/053 034/049 033/045 036/055 035/065 038/073 043/074 46/R 14/O 78/O 74/R 11/B 01/U 12/R HDN 046/057 041/057 038/049 039/061 040/068 040/077 045/078 58/R 44/O 79/R 86/R 32/R 00/U 11/U MLS 049/057 040/054 037/053 041/062 042/067 042/075 046/076 49/T 86/R 78/R 65/R 21/B 00/U 11/U 4BQ 047/057 039/055 036/049 039/059 041/064 040/073 045/075 59/T 75/R 67/R 76/T 32/R 00/U 11/U BHK 049/060 036/051 034/052 038/061 039/065 039/072 043/072 49/T 97/R 67/R 64/R 12/R 00/U 00/U SHR 042/054 037/056 034/046 035/055 037/063 037/072 042/074 68/T 33/R 58/O 87/T 33/R 11/U 12/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...High Wind Watch in effect from Tuesday morning through late Tuesday night FOR ZONES 29-34-42-57-138-170-173-235. High Wind Warning in effect from 10 AM Monday to midnight MDT Monday night FOR ZONES 34-42-138-170-235. High Wind Warning in effect from 10 AM Monday to 6 AM MDT Wednesday FOR ZONES 63-65-66-141-172-228. WY...High Wind Watch in effect from Tuesday morning through late Tuesday night FOR ZONE 199. High Wind Warning in effect from 10 AM Monday to midnight MDT Monday night FOR ZONE 199. Winter Weather Advisory in effect from midnight tonight to midnight MDT Monday night FOR ZONE 198. && $$ weather.gov/billings