Billings, Montana

• Cool and damp for trick or treating tonight.
• Fog is likely tonight through Sunday morning. Prepare for reductions to visibility.
• High confidence for widespread precipitation Sunday through Monday. Snowfall in the Absaroka/Beartooths and Bighorns and rain across the lower elevations

- Windy conditions on Monday, gusts 20 to 40 mph. A few gusts of
  50 mph or higher in southeast Montana and northern Wyoming.

Rest of Today through Friday

Patchy fog will linger for portions of the forecast area through this afternoon, though areas and widespread fog are diminishing. When encountering any remaining fog, prepare for visibility reductions as low as 1 mile.

A weak upper wave has brought light showers to portions of southern Montana today. This activity will continue into the afternoon and move northeast. The chance for precipitation will diminish through the afternoon across most of the forecast area. One exception to this looks to be in and along the mountains and foothills west of Billings early this evening as another weak wave comes through. Though the chance for showers increases (up to a 30 percent chance) during trick or treat time out west, very little if any accumulations are forecast. As for the rest of the area, expect a cool and damp evening with temperatures in the 40sF between 5PM and 9PM MDT.

An upper low currently situated off the coast of Washington is forecast to dig into the Western U.S. tonight into Sunday. With this, our weather pattern will become more active by Sunday afternoon and last into the start of the week. Widespread precipitation is forecast in the Northern Rockies with promising accumulation amounts. Shower activity is forecast to begin increasing over southwest aspects of the Absaroka/Beartooths late tonight and early Sunday morning, before spreading across the plains through the afternoon. Expect precipitation to continue into Monday afternoon, though it will diminish from west to east.

For precipitation accumulations Sunday through Monday, totals range from 0.25" to over an inch of rain with the greatest accumulations over southeast Montana and portions of northern Wyoming. The latest probability for at least 0.5" of rain is 40 to 75% around and west of Billings (greatest near Billings and the mountains west of Billings. For locations west of Billings, the chance is 75 to 95%. The probability for at least 1 inch of precipitation is 50 to 75% for portions of southeastern Montana and the Bighorn Mountains. For locations including and south-west of Rosebud County (also including Sheridan County), the probability is 10-50% lowest west of Billings.

This does not look to be a very cold system, with high temperatures forecast in the 40s and 50sF Sunday and Monday. More importantly though, lower elevation snowfall will be hard to come by as Sunday night temperatures are forecast to remain above freezing across the lower elevations. Snow levels will drop as low as 5,500 feet by Monday morning though. North and west aspects of the Absaroka/Beartooths are forecast to collect up to 6 inches of snow tonight through Monday, locally greater amounts are possible for the higher elevations. As for the Bighorns, the latest forecast has 4 to 8 inches, with locally higher amounts possible.

In addition to all of the precipitation, a cold front is set to come through the region from the northwest late Sunday. This will bring widespread windy conditions on Monday, especially over southeast Montana and northern Wyoming. For much of the area, expect wind gusts in the 20s to 40 mph, while southeast MT and northern WY will see gusts in the 40s to low 50s mph. The probability for gusts of 50 mph or greater along the Dakotas border and for Sheridan County is 40 to 75 percent. The greatest chance for Sheridan County is shown to be closer to the Johnson County line. The addition of these winds to the Bighorn Mountains will make conditions much more difficult for anyone with plans in the high country.

Winds will diminish through Monday evening, as ridging rebuilds over the Northern Rockies. This will result in drier conditions and temperatures in the 50s to low 60sF for much of the week. A few isolated showers are possible in the mountains throughout the week, as some weak waves ripple through.

Matos

20z Discussion

Areas of MVFR to IFR conditions and full mountain obscuration are anticipated to continue through the entire period. Overnight tonight (after 04z) VLIFR conditions with low CIGs and VIS in FG are possible. The greatest likelihood of this occuring is at KBIL from 05z through 16z. Due to the transient nature of this fog, there will likely be frequent flight category changes through the entire forecast period. After 12z precipitation will move into the region and fill in from west to east. This will clear out the FG but keep conditions IFR. All precip at the terminals will fall as rain. WMR

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 035/048 041/053 034/058 033/054 033/056 036/058 037/057
    06/W    97/W    00/U    00/B    00/B    11/B    21/U
LVM 033/048 033/048 025/055 029/053 028/054 028/053 027/052
    26/W    +5/W    00/B    00/B    01/B    12/W    41/U
HDN 030/054 038/053 027/060 027/055 027/057 030/060 032/059
    04/W    99/W    10/U    00/B    00/B    11/B    31/U
MLS 037/056 042/050 031/056 031/052 031/054 034/056 035/055
    12/W    99/W    10/U    00/B    00/B    00/B    11/B
4BQ 036/061 042/047 031/055 031/053 031/056 034/056 036/053
    03/W    8+/W    30/U    00/B    00/B    11/B    22/W
BHK 037/059 040/051 028/053 029/052 027/054 030/055 031/051
    21/E    9+/W    30/U    00/B    00/B    01/B    11/B
SHR 030/054 033/046 025/059 028/057 027/057 029/058 030/056
    04/W    7+/W    10/U    00/B    00/U    11/U    32/W

MT

None.

WY

None.