588 FXUS65 KBYZ 220350 AFDBYZ Area Forecast Discussion...Updated National Weather Service Billings MT 950 PM MDT Sat Jul 21 2018 .UPDATE... Updated forecast to adjust precipitation chances for current diminishing trend. Convective cold pool has become the defacto cold front this evening as surface pressure rises now extend from the leading edge all the way northwest into Canada. Synoptic cool air and pressure rises should arrive in the area in the early morning hours with a noticeable increase in northwest winds that will continue through the day Sunday, especially over eastern zones. With convection diminishing over central zones expect the gusty cold pool winds to diminish as well and don't anticipate any additional strong wind gusts given current trends. Peak wind gust from Molt this evening was measured at 68 mph on a personal weather station. This was the gust that prompted the warning for Yellowstone county, supported by WSR88D wind profiles showing 50 to 60kt winds within 500 feet of the surface moving into the Billings area. Strongest gust at the Billings airport was 50 mph while our office saw 41 mph. Appears the core of the strongest winds this evening moved west to east just to the north of Billings and Billings Heights before diminishing as it outran the parent storm. Winds also gusted to 50 mph in Alzada earlier in the day with severe storms over Carter county, along with reports of 1 and 1.25 inch diameter hail. Outside of the increased northwest winds with the cold front, the rest of the night looks pretty quiet weather-wise. Chambers && .SHORT TERM...valid for Sun and Mon... Ridge axis was shifting east into the Dakotas this afternoon as an upper trough and associated cold front approached the region. At the same time, a surface trough over the area was moving east, with southeasterly winds across eastern areas transporting 60 plus degree dewpoint temperatures into the area. Isolated to scattered showers and thunderstorms will move through portions of the area late this afternoon and evening, with a few strong to severe storms developing east of a Miles City to Broadus line later this afternoon and evening where an area of convergence exists. With modest instability and decent deep layer shear over the far east, large hail and damaging winds are possible there. Convection decreases in coverage later this evening with the aforementioned cold front moving through the area overnight bringing a wind shift to the northwest and north. Cooler and dry conditions can be expected on Sunday with gusty northwest winds continuing over mainly eastern areas behind the front. Dry conditions look to persist through most of Monday with a slight chance of a shower or thunderstorm over the Bighorn Mountains and far southeastern areas Monday evening/night with a weak disturbance moving overhead. Highs in the 80s can be expected on Sunday and Monday with low temperatures in the 50s to 60s tonight, with upper 40s to 50s both Sunday night and Monday night. STP .LONG TERM...valid for Tue...Wed...Thu...Fri...Sat... Only minor changes for the extended forecast this afternoon, as pattern remains consistent from previous runs, with good agreement in GFS and ECMWF models. Overall, expect temps to be mainly seasonal, or slightly below average, and mainly dry. There will be some increasing shower potential by mid week, but still only isolated to scattered activity. Zonal flow will persist to start the day Tuesday, but will slowly shift to northwesterly flow, as the upper trof shifts eastward across southern Canada. Meanwhile, an upper level ridge builds into the Great Basin, toward northern Idaho, deepening northwest flow over Montana for Wednesday onward. Multiple shortwaves and increasing Pacific moisture will allow for an increasing chance of showers and thunderstorms from mid week into the weekend. At this time, convection continues to appears isolated to scattered in nature. Any storms are not expected to be terribly strong, with low CAPE and PWAT values generally below three quarters of an inch. As for temps, expect highs to be fairly cool compared to recent days, with persistent Northwest flow aloft and mainly east to northeasterly flow at the surface. AAG && .AVIATION... An isolated thunderstorms is possible before 06Z east of Billings, otherwise expect dry conditions. VFR conditions will prevail. A cold front will bring additional gusty northwest winds to the area overnight into the morning. Low level wind shear can be expected for locations east of Billings tonight. Chambers/Reimer && .PRELIMINARY POINT TEMP/POPS... Sun Mon Tue Wed Thu Fri Sat ----------------------------------------------------------- BIL 062/083 057/087 060/083 058/080 057/081 058/082 058/083 21/U 00/U 11/U 01/B 22/T 33/T 31/U LVM 050/082 048/086 051/083 051/080 050/080 050/080 050/082 00/U 00/U 11/U 12/T 22/T 33/T 31/U HDN 062/084 055/089 059/084 058/082 056/083 057/084 057/086 21/U 00/U 11/B 01/B 22/T 33/T 31/B MLS 066/084 055/086 060/084 057/080 056/081 058/083 058/085 21/N 00/U 10/U 01/B 22/T 33/T 31/B 4BQ 066/085 056/087 060/086 057/081 058/081 057/082 058/085 11/N 00/U 11/U 01/B 22/T 33/T 31/B BHK 063/082 052/082 057/083 053/078 053/077 054/080 055/082 22/W 00/U 20/U 00/U 22/T 22/T 20/B SHR 059/083 053/087 055/084 055/080 053/080 053/081 053/082 21/N 01/U 21/B 22/T 23/T 34/T 43/T && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Red Flag Warning in effect until midnight MDT tonight FOR ZONE 117. WY...None. && $$ weather.gov/billings