156 FXUS65 KBYZ 302316 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 516 PM MDT Sun Apr 30 2017 .UPDATE... Shower activity progressing eastward a little faster than forecast so updated to increase shower chances over central zones this evening. Have not seen any lightning so far and with clouds starting to limit heating along with the time of day have pulled thunderstorms from the forecast. Chambers && .SHORT TERM...valid for Mon and Tue... Satellite imagery indicates models progged speed of vorticity moving across us today is pretty good. Looks like the main forcing reaches Billings by 6 pm, pushing further east thereafter. We already have showers in the west. Some thunder is possible as the main forcing sweeps through late today and early this evening. SSEO and other data suggest scattered precipitation as short wave moves through. Pressure rises look a bit stronger than what progs showed yesterday. Lapse rates look steep and may mix down 35 kts of flow. So peak gusts with stronger cells/showers to 40-45 mph still looks reasonable. The activity pushes off to the southeast overnight. Monday through Tuesday remains pretty unsettled with below normal afternoon highs. FLow aloft NW and tends to remain unstable, especially out along the MT/Dakota border region. As a result, we are looking for scattered to isolated showers Monday, with some thunder possible over the eastern section. Another short wave tracks over our region in the NW flow Tuesday which should increase coverage and intensity of showers. Embedded thunder is possible for most locations Tuesday based on instability indices. BT .LONG TERM...valid for Wed...Thu...Fri...Sat...Sun... No major changes were needed for the extended but I did need to adjust temperatures upwards for the weekend as the trend in model guidance towards next week is leaning towards a longer period of above normal temperatures. A ridge axis of high pressure will be centered to the west of the region on Wednesday with low-flow turning westerly through the day. The downslope flow, combined with warmer mid-level temps and ample sunshine, will que the warm up that should last through next weekend. Rain chances will also be near zero through the end of week with an absence of significant moisture across the region. Temperatures on Wednesday will be in the mid to upper 60s and then will warm into the low to mid 80s by Saturday afternoon. There are some hydrologic concerns associated with this warm-up, those will be detailed below. The ridge axis will shift into eastern Montana over the weekend. While warm conditions will be in place, the upper-level flow will turn more southerly bringing better moisture, and upper-level support for showers and thunderstorms across the region. Model guidance diverges quickly into the following week, but we should see temperatures cool off from the much above average weekend temperatures. Dobbs ...HYDROLOGICAL CONCERNS... As temperatures warm through next week, hydrologic concerns will increase as we start to increase the high elevation snow melt across the region. Above freezing temperatures will extended past mountain top levels from Friday morning into at least Sunday afternoon. With warm temperatures extending for long hours, (including overnight hours) we're expecting some rises on area rivers. Currently too early to speculate how much increase we'll see, and exactly when the snow melt will show up on area streams, but folks with plans on area rivers and streams, and those with interests on the river, should pay attention to the river forecasts as get we closer to next weekend. The primary period of concern for river and stream increases will be from Thursday May 4 through Monday May 8. The highest levels will likely be observed over the weekend. Dobbs && .AVIATION... Increasing clouds were noted across the region ahead of an approaching disturbance. VFR conditions will prevail through most of the TAF outside occasional periods of MVFR in showers that move through the region this afternoon and evening. Expect occasional mountain obscurations through the afternoon and evening. Shower chances will reduce later tonight as the front pushes out of the region. VFR conditions will continue behind the front. Dobbs && .PRELIMINARY POINT TEMP/POPS... Mon Tue Wed Thu Fri Sat Sun ----------------------------------------------------------- BIL 040/057 040/056 039/067 045/076 049/080 050/081 048/072 42/W 45/T 20/U 00/U 00/U 12/T 23/T LVM 034/054 034/054 033/064 041/073 044/076 045/074 043/069 32/W 45/T 20/U 00/U 01/U 12/T 24/T HDN 040/059 040/057 038/067 043/077 046/081 048/083 047/075 42/T 35/T 30/U 00/B 00/U 12/T 23/T MLS 043/060 040/059 039/066 044/076 050/081 051/084 051/077 32/T 13/T 21/U 00/U 00/U 11/U 22/T 4BQ 041/057 038/056 037/063 041/074 047/079 050/083 049/077 32/T 24/T 21/B 00/U 00/U 11/U 22/T BHK 039/056 034/057 035/061 036/071 044/075 046/077 046/074 34/T 13/T 21/B 00/U 00/U 00/U 12/T SHR 036/052 036/051 035/060 039/071 041/077 043/077 042/071 32/W 34/T 31/U 00/B 00/U 12/T 23/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings