Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
016 FXUS65 KBYZ 130722 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 122 AM MDT Tue Aug 13 2024 .DISCUSSION... Today through Wednesday night... A line of showers was pushing through SE MT early this morning ahead of an eastward moving low-level trough. Kept a slight chance of a shower or thunderstorm in NE Fallon County through 15Z to account for any lingering activity. Forecast area will be under SW flow today with jet divergence aloft and a decent shortwave moving into the western zones by 21Z. This wave will cross the area through tonight and another wave will follow it for Wednesday. Wave will push a cold front through the area tonight. Low-level ESE flow continues from KBIL E today, bringing in high PWAT`s of 1-1.25 inches. MLCAPEs are progged to climb to 1000-1500 J/kg over the E with 2000 J/kg MUCAPE forecast along the MT/Dakotas border. Bulk Effective Shear will be around 30 kt over eastern areas as well. Steep mid level lapse rates are forecast over the area today and tonight. Looking at soundings across the area, profiles suggested a wet microburst potential given moist mid/upper levels and an inverted-v below the moisture. In addition, DCAPE was 1000-1500 J/kg E of KLVM this afternoon and evening. Above factors supported strong, gusty wind potential with any thunderstorms. As for hail, lapse rates are steep, but freezing levels are high, between 10,000-11,000` AGL over most of the area. With best CAPEs being over the E, best chances for hail would be in the E. That said, a Marginal Risk from SPC was across the entire area for strong gusty winds. Have added the winds and mention of heavy rainfall to the forecast for the afternoon and evening. Precipitation chances will increase from W to E from late this morning through this evening. PoP`s were 30-60%, highest W and N of KBIL. Precipitation will linger in the E overnight. Highs today will range from the lower 80s W to around 90 from KBIL E. Probabilities for reaching at least 90 degrees were 30-60% today, but drop to near zero for Wed. behind the cold front. On Wednesday, the next wave moves through the area with chances for showers and thunderstorms through the day, highest in the afternoon W of KBIL. The high CAPEs in the E will shift E out of the area during the day. No significant shear is forecast and PWAT`s will slowly decrease through Wed. night. In general, not expecting any strong storms for Wednesday. Precipitation will taper off from W to E Wed. night. It will be much cooler Wed. with high temps in the upper 70s W to the mid 80s E. Not expecting surface smoke over the area through Wed. night, but there will be areas of haze. Arthur Thursday through Monday... We should see a brief period of ridging on Thursday, between shortwaves, but there may be enough lingering energy in our east in the morning and ascent from the west associated with the next wave to make the ridge mostly a non-player in our weather. If Thursday proves to be mostly dry, the next shortwave should bring some showers and t-storms to our west by Thursday evening and night. There is model uncertainty here, as the EC takes a large component of the PV and undercuts the ridge...an interesting but outlying solution amongst the current models. In any event, the greater chances (30-60%) of showers and wet t-storms will be Friday into Friday night per this next wave. Temperatures will be seasonable to slightly cooler than normal Thursday & Friday. There is high confidence for building heights next weekend as a low cuts off along the Pacific coast. Monsoon moisture will need to recover (it will be displaced east of the 4-corners Wed-Fri), so these may turn out to be dry & warmer days for us. At most, slight chances of weak diurnal convection for the mountains. Temps should climb to the upper 80s and lower 90s most places. By Monday, the monsoonal flow should allow for increasing chances (20-30%) of high-based but wet thunderstorms. Temps should remain on the warm side w/ highs in the upper 80s and lower 90s. One thing to monitor is tropical activity in the western Pacific. There is a tropical storm (Ampil) south of Japan that is currently strengthening. Over the next week it will lift northward and become extratropical, potentially reaching the Aleutians and causing height rises into AK, and resultant downstream troffing somewhere in western Canada. If we are to be impacted by Ampil it won`t be until the latter half of next week, but it is something to watch over the coming days. JKL && .AVIATION... Lingering showers east of KMLS will exit MT by 10z. Scattered showers and thunderstorms will impact the region this afternoon & evening, beginning as early as 18z over the Beartooth-Absarokas and spreading to the NE-E thereafter. All TAF sites are at risk of seeing a TS (see times below), and there may be multiple rounds. Storms could produce strong/erratic wind gusts, small hail and locally heavy rain capable of dropping flight categories to MVFR- IFR. Expect mountain tops to be occasionally obscured. Wildfire smoke will continue to reduce slant range visibility at times. POTENTIAL TS TIMES TODAY: KBIL 20-05Z KLVM 18-03Z KMLS 00-07Z KSHR 20-04Z JKL && .PRELIMINARY POINT TEMP/POPS... Tdy Wed Thu Fri Sat Sun Mon ------------------------------------------------------- BIL 089 059/083 058/084 059/087 057/087 059/090 061/092 3/T 55/T 22/T 24/T 21/U 11/U 11/U LVM 083 049/079 048/082 050/082 049/086 052/087 054/089 6/T 66/T 23/T 56/T 22/T 11/U 12/T HDN 091 057/083 056/085 057/088 054/088 055/091 059/092 2/T 54/T 22/T 24/T 21/U 10/U 11/U MLS 090 064/083 060/084 059/087 059/088 061/089 062/090 0/U 53/T 32/T 13/T 22/T 11/U 11/U 4BQ 090 064/083 059/084 056/087 057/089 059/091 060/091 1/B 43/T 32/T 13/T 21/U 11/U 11/U BHK 089 060/084 056/084 054/085 056/086 056/087 057/087 2/T 55/T 22/T 02/T 22/T 11/U 11/U SHR 090 055/081 052/083 052/087 052/088 054/090 056/090 2/T 45/T 33/T 24/T 21/U 01/U 11/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings