Area Forecast Discussion
Issued by NWS Billings, MT
Issued by NWS Billings, MT
860 FXUS65 KBYZ 160920 AFDBYZ Area Forecast Discussion National Weather Service Billings MT 320 AM MDT Mon Sep 16 2024 .DISCUSSION... Today through Tuesday night... Currently over our east, there are showers with a few embedded thunderstorms as a result of low level jet energy over the MT/Dakotas border. Showers are expected to lift north through the morning. For the big picture, a low currently moving into northern California is providing southerly flow over MT. As this low tracks northeast, energy will move into our west bringing an increased chance of showers and thunderstorms. CAMs are in good agreement with convection in the west, but are not as confident on development over the east. Instability looks more favorable for stronger storms over the east with values of around 750-1000 J/kg vs. the west at 500 J/kg or less. A few strong storms are possible, but no severe storms are expected at this time. Showers and thunderstorms will likely begin early to mid afternoon across the southwest mountains and foothills with the east seeing development late afternoon. As the low moves from the Great Basin into SW MT Tuesday, better forcing and increased chances for showers and thunderstorms will move into the region. Cyclonic flow will push a band of precipitation up from WY, generally increasing PoPs from west to east through the day. With strong synoptic level forcing in place as well as above average moisture (PWATs near an inch), a few strong thunderstorms are expected for much of south central and southeast MT. The HREF has highest MUCAPE values of up to 750 J/kg across the northern parts of the CWA where SPC has highlighted a slight risk (2/5) of severe thunderstorms with most the the remainder of the region in a marginal risk (1/5). The best timing for strong to severe thunderstorms is 1-9 pm Tuesday. With this same wave pushing up out of WY Tuesday evening, models are in good agreement of low level winds up to 45-50 mph over SE MT. Chances for getting a gust to 50 mph is around 20-50% across SE MT. Tuesday night, as snow levels drop down to around 9,500 ft, there is up to a 50% chance for an inch of snow along the Beartooth Pass with the highest peaks at a 70-80% chance. High temperatures will be in the 80s west to low 90s east Monday and 70s west to low 90s east Tuesday. Lows will generally be in the 40s and 50s across the region. TS Wednesday through Sunday... Confidence is high that a dynamic weather system will impact our region Wednesday & Wednesday night, w/ rain and strong winds, but there remains uncertainty regarding the exact track of the low. Of course, the track will have large impacts on where and how much precip will fall. A deep stacked low will lift slowly through eastern MT Wednesday then lift into southern SK Wednesday night. A period of strong ascent will impact our west while dry slotting will likely affect Sheridan County and our east. Models are in good agreement with this synoptic setup, but small deviations in the low`s track will affect the precip...and this uncertainty is seen clearly in all ensembles which continue to show large spread in QPF over this time period. Conceptually, heaviest precip should fall over the NW quadrant of our cwa, including the Crazy Mountains, while severe downsloping limits precip along the east side of the Beartooths. Furthermore, pwats will remain anomalously high thru Wednesday, near an inch, as plains moisture wraps around the low. Overall, there is a good chance of 1+ inches in the aforementioned favored areas, with a quarter inch or less across our southeast. Check below for the latest probabilities. SITE PROB 1"+ PROB 2"+ Billings 65% 20% Livingston 60% 15% Miles City 30% 5% Sheridan 5% 0% Judith Gap 90% 50% This is not a cold system but snow levels should fall to near 10kft, resulting in some snowfall over the high peaks of the Crazy & Beartooth-Absaroka Mountains. A heads up for those planning to travel the Beartooth Highway. Now wind. Developing strong downslope gradients w/ 700mb winds of 40-50 knots will result in strong westerly winds along our western foothills. There is a 75% chance of gusts to at least 50 mph from Livingston to Big Timber and Harlowton, while 45+ mph gusts are likely as far east as Musselshell & Yellowstone County. Ensembles show a very strong wind signal for Wednesday. The combination of rain & wind will make outdoor activities difficult for our west. The low will weaken as it exits to our northeast Thursday, which is a day that should exhibit drying and decreased winds. Much weaker troffing left behind over the great basin and possibly a weak Pacific shortwave will keep our weather somewhat unsettled and cool-ish Friday through the weekend, but any precip on these days should be spotty and light. One item to note: on previous days there appeared to be another strong trof arriving early next week, but recent models have trended toward weaker energy and higher heights...and overall faster Pacific flow. Cluster analyses show this trend being most probable to occur, but there is still the reduced possibility of a cooler/wetter trof by Sunday/Monday. Something to watch. JKL && .AVIATION... An area of showers w/ a few embedded thunderstorms over far southeast MT will exit by 12z this morning. Scattered showers & thunderstorms are expected this afternoon & evening, mainly west of KBIL. These storms could produce erratic wind gusts of 30-40 knots and brief MVFR. Mountains may be occasionally obscured. Otherwise, VFR will prevail across the region today and tonight. JKL && .PRELIMINARY POINT TEMP/POPS... Tdy Tue Wed Thu Fri Sat Sun ------------------------------------------------------- BIL 082 055/081 052/064 053/069 048/072 047/069 047/068 1/B 15/T 76/R 53/W 11/B 22/W 33/W LVM 082 047/071 045/060 044/066 040/071 039/068 041/066 3/T 48/T 87/R 65/W 12/T 22/W 34/W HDN 084 052/084 050/065 050/070 045/073 043/069 044/068 1/B 13/W 76/R 53/W 11/U 22/W 33/W MLS 090 057/089 054/065 053/068 047/070 045/066 046/066 0/U 11/U 86/R 53/W 11/B 22/W 32/W 4BQ 091 058/089 052/068 051/069 046/072 046/068 047/068 2/W 11/U 73/R 21/B 11/U 22/W 22/W BHK 089 056/091 051/070 049/068 045/072 043/069 043/069 2/W 11/U 74/R 22/W 11/B 22/W 22/W SHR 089 050/084 047/071 046/072 040/073 041/070 042/071 2/W 13/W 63/R 22/W 12/W 22/W 23/W && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...None. WY...None. && $$ weather.gov/billings