Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
939 FXUS65 KBYZ 120758 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 158 AM MDT Mon Aug 12 2024 .DISCUSSION... Through Tuesday... Satellite imagery shows a low amplitude ridge over the northern Rockies and upstream weak PacNW troffing. As anticipated, clearing and light easterly surface winds has allowed fog to develop in parts of Carter and Fallon County (where up to 1" of rain fell on Sunday). Baker airport has seen visibility as low as 1/4SM. The fog is localized at this time and will monitor its coverage over the next several hours. Morning commuters near Baker & Ekalaka, and possibly as far west as Miles City & Broadus, should plan for areas of reduced visibility until ~9am. As the ridge axis slides east today we will see warmer air spread northward, giving us the warmest day in nearly a week (seasonable highs in the mid 80s to lower 90s most places). Weak shortwave emerging from the northern great basin will combine with modest diurnal instability to produce scattered t-storms over the west half of our cwa from mid afternoon through around sunset. Moisture/instability will be fairly limited and storms will be high-based, but there is potential for erratic wind gusts with any of today`s storms. Stay alert if you have outdoor plans late today. A few light showers may linger til closer to midnight east of the foothills, otherwise tonight will be dry. A stronger shortwave (currently located off the PacNW coast) will traverse the SW flow aloft and provide a more notable period of synoptic scale ascent Tuesday afternoon & evening. Convective elements are stronger tomorrow. Pwats are expected to rise to near an inch, and with temps again in the 80s to lower 90s this will yield greater instability (500-800 j/kg of sbcape in our west, but an axis of 1000-1500 j/kg east of Custer & Powder River Counties where moisture will be deepest east of surface trof). Chances of thunderstorms will be greater (30-70%) tomorrow afternoon and evening, with potential for heavy rain, gusty winds and hail. Severe risk would be greater w/ higher bulk shear (500mb winds progged at 20kts or less), but nonetheless some strong storms are a definite possibility. The latest Day2 outlook from SPC highlights our region for a marginal risk of severe t-storms. The far east would seem to have the greatest risk, with the favored time being after 00z. Skies will remain hazy due to lofted wildfire smoke originating from the western U.S. JKL Tuesday night through Monday... A shortwave crosses the area Tuesday night through Wednesday. This feature will drag a cold front through the area Tue. night. Strong 850-700 mb frontogenesis was forecast over the E Tue. evening on the GFS, but not so much on the ECMWF. Best Q-vector convergence also varies between the models. MLCAPEs around 1000 J/kg in the far E, move out on Wednesday. Bulk Effective Shear was 30 kt Tue. evening. Highest CWASP values for the period were over the NE Tue. evening. PWAT`s were 1-1.25 inches from KBIL E Tue. night and Wed., and decrease Wed. night. NBM PoPs Tue. evening were highest across the far E, northern tier and areas W of KBIL at 50-60%. PoPs were in the 30s and 40s elsewhere. Scattered PoPs continue across the N late Tue. night. See no reason to deviate from these PoPs given uncertainty in the location of the best forcing. PoPs increase again Wed. afternoon, with the highest PoPs W of KBIL. Precipitation chances decrease Wed. night. Given the above, strong storms are possible Tue. evening over the E and heavy rainfall with storms from KBIL E through Wednesday is possible due to high PWAT`s. Wednesday will be cooler behind the front with highs from the upper 70s W to the mid 80s E. Clusters had a ridge of varying strengths over the region on Thursday. Upper ridge or SW flow will be over the area Friday through Sunday with disagreement due to the timing of the next Pacific trough. This continued on Monday with one cluster bringing the northern part of the trough over the area and the other clusters having SW flow or ridging. There will be chances of showers and thunderstorms each afternoon and evening, except the forecast will be mostly dry on the weekend and on Monday. Below normal temps continue on Thursday with a warmup to around normal temps for the rest of the period. Arthur && .AVIATION... Areas of fog, locally dense w/ VLIFR visibility, will impact the east from KMLS to KBHK until ~15z this morning. Poorest visibility should be close to the Dakotas border. Otherwise, VFR will prevail across the region through early afternoon. Wildfire smoke will continue to reduce slant range visibility at times. By mid afternoon, look for scattered showers and t-storms to develop over the Beartooth-Absarokas and spread over the west half of our forecast area into the evening. Storms may produce erratic surface winds and local MVFR until around sunset. VFR will prevail overnight. POTENTIAL TS TIMES TODAY: KBIL 22-03Z KLVM 19-02Z KMLS NONE KSHR 22-03Z JKL && .PRELIMINARY POINT TEMP/POPS... Tdy Tue Wed Thu Fri Sat Sun ------------------------------------------------------- BIL 089 060/087 059/083 057/083 058/087 057/088 059/089 2/T 23/T 44/T 22/T 23/T 21/U 11/U LVM 086 050/082 050/078 048/082 050/083 049/087 051/087 3/T 36/T 66/T 23/T 35/T 21/U 11/U HDN 091 056/089 057/084 055/083 055/088 054/089 057/091 1/U 23/T 44/T 22/T 13/T 21/U 11/U MLS 086 061/091 062/085 060/083 058/086 059/088 062/089 0/U 12/T 43/T 22/T 13/T 21/U 11/U 4BQ 086 059/091 062/084 059/082 057/087 057/090 060/090 0/U 12/T 33/T 22/T 13/T 21/U 01/U BHK 082 056/089 059/085 056/082 054/084 055/085 057/087 0/U 12/T 64/T 22/T 12/T 21/U 11/U SHR 089 052/090 055/081 052/080 051/087 052/088 055/088 2/T 23/T 35/T 33/T 23/T 11/U 01/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings