Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 060436
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
936 PM MST Tue Dec 5 2017

.UPDATE...

Minor tweaks to cloud cover and min temperatures for latest
trends. Increased winds along the Bighorn foothills where it looks
like gusts in the 35 to 50 mph range will continue through most of
the night. Otherwise forecast remains in good shape. Chambers

&&

.SHORT TERM...valid for Wed and Thu...

Satellite imagery shows a shortwave moving into northeast MT in
northerly flow aloft. Upstream radar imagery shows a convective
area of snow associated with this wave, in a region of steep mid
level lapse rates. Winds in our cwa have been quite strong today,
as expected, and gusts reached 58-60 mph at Rock Springs and Miles
City earlier this afternoon.

Core of strongest boundary layer winds passed through our eastern
cwa around 18-21z. This is consistent with our observed gusts, and
do not expect gusts to get this high for the remainder of the
afternoon, with the possible exception of a convective gust
associated with the aforementioned precip to our north. Winds in
our west near Big Timber and Harlowton have begun to decrease. So,
will not issue any additional wind highlights, and have cancelled
the warning for our west. Nonetheless, winds will remain quite
gusty through the remainder of the day, and tonight even with some
surface stabilizing.

Snow will increase over our east with passage of shortwave by this
evening, followed by a backing Canadian front late tonight into
Wednesday. All of this will be associated with steep low level
lapse rates that extend into the dendritic layer across our far
east. For these reasons have extended the winter weather advisory
for Fallon/Carter through Wednesday afternoon, with expectation of
another 1-2 inches of snow along with persistent gusty NW winds
and travel impacts due to areas of blowing and drifting snow.
Areas to the west through Rosebud County will also pick up some
light snow later tonight and Wednesday as cold front and low level
baroclinicity shift in that direction over time. Precip will
finally taper off by Wednesday evening as cyclonic flow aloft
exits and heights begin to build from the west. Dry weather will
follow through Thursday night.

Winds on Wednesday will remain gusty but at speeds less than
today. Expect 30-45 mph mixed wind gusts tomorrow. Lee side
pressure gradients tighten along the foothills bringing increased
west winds again at Big Timber and Harlowton late Wednesday night
through Thursday. Gusts could reach 50 mph.

Temperatures will cool a bit tomorrow, with highs expected near
normal for early December. Look for highs back to the 40s to near
50 degrees for Thursday. It will remain coldest in our east.

JKL

.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...

Strong ridge of high pressure will control the much of the
extended forecast period. This will yield mostly dry and warm
conditions through the weekend and through much of next week. West
and northwest flow underneath this ridge will keep downslope
conditions prevalent across much of the region. Expect breezy
conditions along the foothills through much of the extended
forecast period as well. These breezy conditions will spread east
onto the Plains each afternoon as we mix into the these winds. By
Tuesday and Wednesday of next week, a few disturbances moving
southeast on the backside of the ridge could bring a chance for
cooler weather and snow showers in the Dakotas and along the
MT/ND/SD border. Locations further west such as Billings and the
Mountain foothills will likely be under the influence of the
downslope westerly winds so the dry and above normal temperatures
will likely continue. Dobbs

&&

.AVIATION...

VFR conditions will prevail for zones west of KMLS but a
disturbance dropping out of Canada tonight will bring snow showers
and MVFR cigs/vis to terminals and routes east of KMLS, including
KBHK. The stronger snow showers could temporarily bring IFR/LIFR
restrictions. Also be on the lookout for gusty 25 to 35 northwest
winds this evening causing areas of blowing/drifting snow. West of
KMLS, conditions will remain breezy through the period with wind
gusts generally around 20 to 35 kts...with the higher amounts
being along the foothills. Dobbs
&&

.PRELIMINARY POINT TEMP/POPS...

    Wed     Thu     Fri     Sat     Sun     Mon     Tue
-----------------------------------------------------------
BIL 026/038 026/048 035/054 033/052 031/049 029/048 031/050
    00/N    00/N    00/B    00/U    00/U    00/B    11/B
LVM 022/036 022/044 030/048 029/047 026/045 026/046 030/048
    00/N    00/N    00/N    00/N    00/N    01/B    11/N
HDN 026/036 020/046 028/052 028/052 025/049 025/048 025/048
    01/M    00/B    00/B    00/U    00/U    01/B    11/B
MLS 026/031 019/043 027/047 025/049 024/046 024/043 023/044
    34/S    01/B    01/B    00/U    00/U    12/W    11/B
4BQ 026/031 016/040 028/046 028/051 026/048 025/045 022/046
    16/S    11/E    01/B    00/U    00/U    02/W    11/B
BHK 023/026 012/037 023/040 021/045 022/043 022/038 019/039
    76/S    21/E    01/B    10/U    00/U    12/W    11/B
SHR 022/033 019/044 029/051 027/054 024/050 023/048 024/050
    01/M    11/N    00/B    00/U    00/U    00/B    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings



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