Area Forecast Discussion
Issued by NWS Billings, MT
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Issued by NWS Billings, MT
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-- Discussion containing changed information from previous version are highlighted. --337 FXUS65 KBYZ 290911 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 311 AM MDT Wed May 29 2024 .DISCUSSION...-- Changed Discussion --Today through Thursday night... Current 500 mb analysis is showing troughing over the Pacific NW with the low off the coast of BC Canada. Current radar has isolated showers over our west with Hi-Res models continuing those isolated chances through the morning as far east as Rosebud county. Went ahead and put in a small chance (15%) for rain for this aforementioned time and locations. As shortwave troughing moves east through central MT, an associated cold front will bring showers and thunderstorms (potentially a few severe). The Storm Prediction Center has Fallon and Carter county in a slight risk (2/5) with the remainder of the CWA in a marginal risk (1/5). The main threat outlined is strong winds with secondary threats being hail and heavy rain. Expected timing on this front today is late morning to noon (Livingston up to Harlowton), reaching Billings around 1-4 pm MDT. 0-6 km mean wind suggests storms associated with the front will generally track northeast through the evening. SSE low level flow will advect in warm air and moisture ahead of the front giving way to PWATs of 0.7-1 inch across the region (highest in the east). This will result in the highest uniform instability out east with MUCAPE values up to 2000 J/kg, and values to the west generally around 500-1500 J/kg with locally higher values possible. 0-6 km shear values will be highest in the western and central zones (50-60 kts) suggesting storms have a better likelihood of being sustained/long track. For the far east counties, CAMs are showing convection developing ahead of the front mid afternoon, generally tracking in a NNE direction. The main front will bring additional thunderstorms to the east later in the evening. Shear values out east will be less, but sufficient enough to sustain storms (30-40 kts). With above normal atmospheric moisture and strong forcing, the environment is supportive for heavy rain under any thunderstorm. The chance for at least an inch of rain generally exists Billings and east (10-40%). As for snowfall, snow levels will drop to around 6000 ft by Thursday morning. The highest peaks have a likely chance of getting at least 6-8 inches of snow. Thursday, energy associated with the low will remain over northern MT and provide low PoPs (less than 20%) over the northern parts of the CWA. Westerly flow creating downsloping and lower moisture will prevent anything noteworthy. High temperatures today will be in the low 80s out east, generally decreasing to the 70s and 60s to the west. Thursday, temps will cool down to the 60s for the region. TS Friday through Tuesday... A progressive pattern is expected to persist Friday thru next Tuesday. Heights will be rising on Friday but a final weak shortwave on southern periphery of upper low to our north should be enough for a slight (20%) chance of showers and t-storms in our far east. In fact, models hint at a bit of theta-e return into far southeast MT prior to the wave`s passage, giving some confidence for the low pops in this area. Friday night thru Saturday morning will be dry underneath flat ridging, but the next weak Pacific wave will bring our next chance of showers and t-storms from west to east Saturday afternoon thru Sunday (there may actually be two PV maxes during this time). After a brief dry period Sunday night into Monday the next potentially stronger Pacific wave will bring the next dose of showers and t-storms Monday afternoon thru Tuesday...but by this time the model spread increases substantially with regard to the strength of the trof. Overall, due to the progressive flow, do not see a severe risk on the convective days, though next Monday could be a day to watch. Temperatures will remain more-or-less seasonable. The warmest days (mid 70s to lower 80s) will be the pre-frontal days Saturday and Monday...the latter of which could be warmer if the upstream trof is more amplified. Look for highs in the upper 60s and 70s on the other days. Looking further ahead, ensemble agreement is actually pretty good in showing higher heights across the northern Rockies for the latter half of next week. Depending on the exact location of the ridge, we could see some hotter days (see CPC`s 6-10 and 8-14 day outlooks), but a ridge axis to our west would keep our area prone to backdoor cooling periods even with the high heights. JKL-- End Changed Discussion --&& .AVIATION...-- Changed Discussion --Approaching upper level disturbance and Pacific cold front will bring showers and thunderstorms to the region this afternoon and evening, with activity expected to begin as early as midday in the west. All TAF sites are at risk of seeing a thunderstorm (or two) along with local MVFR/IFR in brief heavy rain and erratic wind gusts of 35+ knots. A few storms could be severe and produce large hail and strong wind gusts, especially east of KBIL. Thunderstorm potential will decrease from west to east in the evening but some showers will linger overnight. Mountains may be occasionally obscured in rain/snow showers tonight. TS POTENTIAL TIMES TODAY: KBIL: 19-04Z KLVM: 17-03Z KMLS: 22-06Z KSHR: 20-04Z JKL-- End Changed Discussion --&& .PRELIMINARY POINT TEMP/POPS...-- Changed Discussion --Tdy Thu Fri Sat Sun Mon Tue ------------------------------------------------------- BIL 074 045/063 043/070 046/079 053/075 053/081 056/075 9/T 92/W 00/U 00/B 24/T 12/T 42/T LVM 066 038/060 037/069 040/079 048/071 049/078 050/071 +/T 71/N 00/U 01/B 25/T 13/T 43/T HDN 077 045/064 041/071 043/082 051/076 051/083 054/075 7/T 92/W 00/U 00/U 23/T 11/B 42/T MLS 082 048/064 041/070 045/081 054/077 053/082 056/076 4/T 82/W 01/U 00/U 23/T 11/B 32/T 4BQ 084 048/063 042/071 045/081 054/077 054/083 057/076 4/T 91/B 11/U 00/U 12/T 11/B 32/T BHK 082 046/064 039/069 042/080 051/077 051/081 053/074 5/T 81/N 02/T 00/U 13/T 21/B 32/T SHR 080 041/062 038/070 040/081 049/075 049/083 052/076 7/T 82/W 11/U 00/U 13/T 11/B 32/T-- End Changed Discussion --&& .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings