Billings forecast discussion

Discussion

Rest of Today through Wednesday...

Warm and dry conditions this afternoon with periods of clouds pushing through from southwest to northeast. Afternoon temperatures will be well into the mid 70s with a few locations close to 80 degrees by 4pm.

Storm System late tonight through Saturday morning...Changes from the recent warm and dry pattern begin late tonight as an upper level low over the Great Basin pushes this direction throwing increased moisture over the area, and a Canadian trof slides in from the northwest bringing colder air and additional upper level support for precipitation. The good news is models have consolidated their thinking over the past 24 hours and the forecast has stabilized, so no big changes with this forecast package.

Expect showers, and possibly an isolated thunderstorm, to build into southwest mountain/foothills zones overnight and into the sunrise period. Main front will push into northwest zones around noon with a good deal of wind (gusts 30-45 mph with a few lower 50s here and there) behind it thanks to 2-3mb/hr pressure rises behind the front. The strongest winds are expected from mid afternoon through late Friday night. Precipitation will fill in along and behind the front with high chances for the western 2/3 of the area through Friday evening. Eastern zones still look to get left out of significant precipitation with this system, but there is still a 15-30% chance for a shower/thunderstorm late afternoon into the evening hours. Overall, the bulk of precipitation will be done by midnight Friday night with chances diminishing through sunrise as the upper level energy splits north and south of the area leaving just some lingering gusty winds and much cooler temperatures for Saturday.

Rainfall forecast shows the probability for a quarter inch or more in the 30 to 50 percent range west of a Roundup to Hardin line, with 60-100 percent west of a Ryegate to Big Timber line and into the Western mountains. From Rosebud county east the probabilities for a tenth of an inch of precipitation are under 20 percent, and near zero for most of Carter and Fallon counties.

No significant changes to the snowfall forecast this afternoon. Still looking at a dusting in the western foothills with 4 to 8 inches in the Beartooth/Absaroka/Crazy mountains, and 4 inches or less for the Bighorn and Pryor mountains. Snow levels fall to under 4kft after 3am Friday night, so there could be a few flakes mixed in across the lower elevations down to 3200ft as precipitation is tapering off early Saturday morning, but do not expect any impactful snowfall (>1 in) outside of the western foothills above around 5kft.

Will issue a Winter Weather Advisory for the Judith Gap zone for late Friday afternoon through 6am Saturday. Strong northerly winds will combine with snowfall there (2 inches or less) to make travel difficult along US-191 from Harlowton up through Judith Gap. Heaviest snow will be in the 8pm through 2am range and wind gusts 40-55 mph will create poor visibility in blowing snow. Roads will be mainly slushy overnight, but some slick snow covered spots can be expected especially over the higher hills along this route.

Fire Weather...Ahead of the front over NC WY/SE MT south- southwest winds gusting 30 to 40 mph will develop and persist until the front arrives early evening. Post frontal winds will shift to the northwest with gusts to 45 mph through the early morning hours. Afternoon temperatures in this area will range from 75 to 85 degrees (20-30 degrees above normal), in the record high temperature range for the day. RH values will drop into the 15-25% range as well. So, this sets up as a critical weather scenario for grass fire danger from Sheridan county east along the MT/WY state line. Will issue a Red Flag Warning for Friday afternoon through 9pm Friday evening for the Sheridan foothills and a good portion of SE Montana to cover this scenario.

Storm system dissipates Saturday afternoon for a seasonally cool and breezy afternoon.

The next concern is another upper low moving northeast from the Great Basin and clipping SE Montana late Sunday into Monday. Models are steadily ramping up precipitation chances (20-40%) for this area. Right on the heals of the Great Basin system, a stronger and more organized Pacific system pushes into the area from the west for Tuesday and Wednesday with more widespread 30-50% precipitation chances. Lates model runs are tapping some colder air with this system by Wednesday along with better upslope flow into north facing mountains/foothills than previously advertised, so precipitation chances could continue to rise with this system going forward, and may see chances for lower elevation snowfall mix in too. As mentioned yesterday there is still considerable uncertainty with the forecast for next week so stay tuned to the forecast as details get ironed out going forward. Chambers

Aviation

Rain/snow showers are expected to move into the region around 12-15Z Friday with snow levels around 9,000 ft, dropping to 6,000 ft in the evening. Breezy prefrontal winds are forecast to begin late morning across northern WY and southeast MT. Mountain wave activity is possible across the Bighorn foothills which could lead to periodic gusty and erratic winds at KSHR mid day Friday. Gusty frontal winds 30-45kts, becoming west to northwest, are expected across the region beginning late morning, lasting well into the evening. Mountain obscurations are expected through the day Friday. TS

Preliminary Point Temp/Pops

    Fri     Sat     Sun     Mon     Tue     Wed     Thu     
-----------------------------------------------------------
BIL 051/069 035/050 031/051 031/051 033/053 034/049 031/049
    06/R    80/U    00/U    00/B    12/W    32/W    11/B
LVM 046/058 024/047 023/050 025/052 027/054 027/049 025/051
    09/R    90/U    00/U    00/B    24/W    42/J    11/B
HDN 050/074 030/053 025/055 028/055 030/055 029/050 025/052
    16/R    90/U    00/U    01/B    13/W    32/W    11/B
MLS 050/076 035/048 029/053 032/050 032/052 031/046 028/049
    02/R    60/U    00/U    11/B    11/B    32/W    10/B
4BQ 053/081 035/048 031/051 033/050 034/056 034/048 030/052
    02/R    30/U    01/B    11/B    12/W    31/U    10/B
BHK 051/083 030/047 024/050 026/046 026/051 027/046 024/049
    01/N    20/N    00/U    22/W    21/B    32/W    10/B
SHR 050/077 027/050 025/053 027/055 030/057 029/052 026/054
    02/R    40/U    01/U    11/U    12/W    31/U    11/B

Byz Watches/Warnings/Advisories

MT...Winter Weather Advisory in effect from 3 PM Friday to 6 AM MDT Saturday FOR ZONE 63. Red Flag Warning in effect from noon to 9 PM MDT Friday FOR ZONES 131-133. WY...Red Flag Warning in effect from noon to 9 PM MDT Friday FOR ZONE 274.

weather.gov/billings