Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
FXUS65 KBYZ 221300

Area Forecast Discussion
National Weather Service Billings MT
600 AM MST Wed Feb 22 2017

.SHORT TERM...valid for Tdy and Thu...

Active and very interesting weather in store for us the next
couple days.

Water vapor imagery shows weak troffing over MT with strong jet
anchored well to our south in southern ID and WY. Upstream, main
feature of interest is a shortwave moving into northern CA, which
will impact our region tomorrow as it forms a weak closed low
while tracking thru WY. At the surface, a cold front is sagging
through northern MT and entering our N/NE parts. A mix of rain/
snow showers are spreading southward with this front.

Precipitation will be on the increase through the morning as front
backs into our cwa. Could see a local inch of snow accumulation
in our NE, but things get more interesting by this afternoon as
NW-SE oriented convergent band sets up along the front. Pretty
good low level instability will exist along this convergent axis,
perhaps up to 100 j/kg of cape, so expect a mix of rain/snow/
graupel with the low wet bulb temps. Best guess for this axis
would be downwind of the Belts/Snowies to Columbus/Billings and
Pryor/Fort Smith. It should be pointed out that the models have
had a difficult time with the speed of the front, with the best-
performing EC showing it to or west of Billings by 18Z. Impacts
could be felt during the late afternoon commute, with rapidly
changing wx conditions and local snow accumulation possible.

Front will push toward the southern foothills allowing for upslope
conditions to evolve this evening. As moisture/upslope flow
deepen through a lowering dendritic layer, expect snow to
intensify along the northeast aspects. This will include our
southern foothills but perhaps also the east side of the Crazies
depending on the boundary layer wind direction. Have raised pops
and snow amounts in all of these areas tonight. Aforementioned CA
wave will provide increasing synoptic ascent late tonight through
Thursday with trailing deformation extending through Thursday
night as this low moves east. Put it all together, and this should
be an extended period of snowfall for our southern upslope areas,
including Nye, Red Lodge, Pryor, Sheridan and Story. Have issued
a winter storm watch to cover the potential for significant
snowfall. Again, must stress that this system is not dynamic in
our region, and snowfall will be dependent on orographics and
instability. Further north snowfall will be lighter but with still
a little accumulation possible, depending on specific track of
upper low.

Temperatures the next two days will turn colder. Highs today
(upper 30s and 40s) will likely be felt in the morning as cold
front backs into our cwa. Look for temps mostly in the upper 20s
to mid 30s on Thursday.

Winter has returned.


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

The long term period will be fairly cool with below normal temps
as a broad trough will be entrenched across the Western US. The
primary disturbance in this broad trough will departing the region
Friday. In it`s wake, weak upper level flow and cold temperatures
aloft will make things somewhat unstable Friday and Saturday
afternoon. While widespread snow is not expected, the unstable
nature of this pattern will lead to pop up snow showers through
the afternoon and evening across the region.

A weak shortwave will cross the region on Saturday evening, and
this should reduce the snow shower chances on Sunday and Monday,
though cooler temperatures will still remain over the region.
Moving into the start of next week, another disturbance could move
into the region on Monday evening or Tuesday, so left a slight
chance of snow in the forecast for those days. Dobbs



Westerly and northwest winds will shift to north and
northeasterly by this afternoon as a cold front moves through the
region. Timing is difficult, but unstable conditions near and
behind the front could produce heavy snow showers bringing
occasional IFR/LIFR conditions and quick snow accumulations. The
main terminal impacted by this front will be KBIL with the best
timing estimate between 20-02z. KLVM will likely see VCSH through
the afternoon along with KMLS and KSHR. Mountain obscurations will
be widespread through the TAF period. Dobbs



    Tdy Thu     Fri     Sat     Sun     Mon     Tue
BIL 045 026/033 021/033 018/031 015/034 015/032 016/035
    6/W 65/J    43/J    22/J    11/B    12/S    22/S
LVM 041 018/030 016/028 011/026 010/029 013/032 015/033
    4/W 66/J    54/J    32/J    11/N    22/S    32/S
HDN 045 024/036 020/034 015/032 013/034 012/034 013/035
    6/W 65/J    43/J    22/J    11/B    11/B    22/S
MLS 040 025/037 021/035 019/033 017/035 016/034 017/035
    7/W 33/J    22/J    22/J    21/B    11/B    22/S
4BQ 046 025/036 019/033 017/033 015/034 014/038 018/036
    5/W 45/J    42/J    22/J    11/B    01/B    22/S
BHK 038 024/033 017/031 017/030 016/032 014/033 015/032
    7/W 32/J    21/E    22/J    21/B    01/B    22/S
SHR 045 023/030 018/028 012/029 008/029 009/035 013/032
    4/W 78/J    84/J    31/E    11/U    12/S    32/S


MT...Winter Storm Watch in effect from this evening through Friday
      morning FOR ZONES 38-56-66-67.
WY...Winter Storm Watch in effect from this evening through Friday
      morning FOR ZONES 98-99.


$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.