Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
332 FXUS65 KBYZ 111920 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 120 PM MDT Sat May 11 2024 .DISCUSSION... Through Sunday Night... Satellite imagery shows one weak shortwave dropping from southern SK into ND, and another upstream moving from BC into central AB, all within a dry NW flow aloft. Temps today are responding to the existing ridge and downslope warming, as it is already mid 60s to mid 70s at noon. Some cumulus are beginning to form in Wheatland County. Current mesoanalysis shows a region of 850-925mb frontogenesis from Musselshell into northern Stillwater, and this is fairly consistent w/ where latest high res models show weak convection developing by ~21z. Low level convergence axis will drift southward and eastward in the late afternoon and evening as winds shift to the NW-N...so any weak convection capable of producing isolated light showers/sprinkles/virga should do likewise over the next several hours. Forecast has this covered well for now, but will need to watch...LIs are near zero as of 18z. Do not see much risk of thunder but elevated surface moisture from recent precipitation may allow for a bit more instability than currently thinking. Aforementioned shortwave to our northeast is really not a factor other than being associated with the wind shift. Diurnal activity, whatever it turns out to be, will diminish w/ sunset, but the next upstream wave (which is a bit stronger) will approach from the NW late tonight bringing a low risk (20%) of showers in our north by sunrise Sunday. Models show showalter indices near zero and this gives a little confidence that there will be a few showers around. Sunday, modest ascent from the shortwave should yield isolated showers in our northeast in the morning. As winds veer to the N then E, diurnal instability should be greater by tomorrow afternoon, especially in our central parts as our east sees a bit of post-frontal drying and our far west has drier/mixed westerly winds. So looks like a 20-30% chance of showers/t-storms Sunday afternoon and early evening (highest pops east of Livingston and west of Forsyth/Lame Deer). Storms will stay on the weak side but the risk of lightning is greater tomorrow than today. Late Sunday night should turn dry as upper level ridge reasserts itself ahead of the next stronger trof set to arrive late Monday. Temps will remain above normal, though highs tomorrow will likely be a bit cooler tomorrow than today over the east half of our forecast area. JKL Monday through Friday... Into Monday, ridging will begin to breakdown as shortwave troughing approaches MT. Ensembles are differing on the exact timing of the frontal passage whether it be Monday afternoon or late Monday evening. The GFS is giving our region SB-CAPE values of around 500-1000 J/kg with 0-6 km shear values of 25-40 kts. If timing were to be in the afternoon/early evening hours, this instability and a sufficient push of moisture would have the potential to produce some thunderstorms. Cooler and wet weather will continue into Tuesday from the frontal passage with chances for precip generally around 60-70% with an 80% chance for the mountains. Most areas across the region have about a 40-50% chance of getting at least a quarter inch of rain with the mountains at a 70-80% chance for snow water equivalent Monday through Tuesday night. For the second half of the week, clusters are varying greatly in the mid level pattern for the remainder of the period. With this uncertainty, the NBM generally keeps PoPs at 30% or less Wed- Fri. For Friday, ensembles are hinting at the potential for another round of unsettled weather. High temperatures will be in the 60s and 70s for the period. TS && .AVIATION... VFR will prevail over the next 24 hours with mostly light winds. Expect scattered cumulus clouds late this afternoon and evening, some of which could produce isolated light showers, sprinkles or virga. Any of this activity could produce surface wind gusts to 20kts. By late tonight and early Sunday, more isolated showers are expected to spread in from the north, then by afternoon look for scattered showers and a few t-storms. Again, VFR will prevail Sunday, but convection has the potential to produce erratic surface wind gusts to 30kts. JKL && .PRELIMINARY POINT TEMP/POPS... Sun Mon Tue Wed Thu Fri Sat ----------------------------------------------------------- BIL 050/074 049/077 050/066 046/069 048/074 048/070 045/067 13/T 26/T 47/T 32/T 23/T 32/T 23/W LVM 046/077 048/074 045/065 043/068 045/072 045/069 041/065 12/W 16/T 37/T 32/W 24/T 22/T 23/W HDN 046/075 044/078 049/068 045/070 045/075 046/072 043/068 12/T 15/T 57/T 32/T 23/T 32/W 23/W MLS 048/073 045/079 050/067 045/069 047/075 048/070 046/066 12/W 02/T 54/T 22/T 22/W 31/U 22/W 4BQ 048/074 044/079 050/066 045/067 045/074 047/071 044/067 12/T 02/T 55/T 32/T 12/W 31/U 22/W BHK 046/072 043/076 048/066 042/067 043/072 044/069 042/064 12/W 12/T 54/T 22/W 12/W 31/U 22/W SHR 044/074 044/076 045/066 042/065 041/073 044/072 042/066 14/T 25/T 57/T 53/T 22/T 32/T 23/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings