Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 141617

Area Forecast Discussion...Updated
National Weather Service Billings MT
917 AM MST Thu Dec 14 2017


Forecast is on track this morning. A shortwave continues to drift
out into the Dakotas, with the precip moving out as well. Winds
will continue to breezy across the southeast into the afternoon as
the wave departs. Reimer


.SHORT TERM...valid for Tdy and Fri...

Be alert this morning for slick spots on roadways across SE MT/NE
Wy as well as in the Beartooth foothills.

Residual energy dropping through the northern plains will keep a
chance of snow showers in the forecast this morning for areas east
of a Forsyth to Sheridan Wyoming line. Could be some briefly heavy
snow bursts pushing visibility to around a mile at times, but any
accumulations from this activity will be light.  Its also going
to be a bit breezy for areas east of Billings this morning with
gusts up to 40 mph, diminishing in the afternoon. Conversely the
west starts off calm this morning, but will see winds increase
this afternoon into evening hours. Highs today range from the mid
40s central and west to the mid 30s east.

Winds continue to increase tonight over western foothills as
stronger cross terrain winds build in deepening lee-side troffing
along the front range. Winds should be pushing 50 mph by midnight
in the gap favored Livingston to Nye corridor, and likely touching
60 mph by sunrise. These gusty winds will keep temperatures mild
overnight from Billings west, while calmer wind areas across the
eastern plains drop toward 20 degrees.

Pre-frontal day on Friday and that means dry, windy and mild
conditions. This will be another heightened wildfire concern day
for areas from the foothills east toward a Forsyth to Sheridan
Wyoming line. Temperatures will push into the low to middle 50s
for highs. Will continue to see winds gusting around 60 mph in the
gap favored locations, with gusts in the 40 to 55 mph range from
Big Timber north to Harlowton. Some of these stronger gusts will
likely work east along the Yellowstone and Musselshell river
valleys toward Roundup and Billings too.

Cold front and precipitation arrive late evening over western
zones and sweep east across the region through the overnight
hours. This event is starting to resemble the system on Dec 3rd
(though colder so mainly snow) with lots of instability, dynamics
and wind, but possibly too much wind and instability from a
downslope direction limiting precipitation to a squall with the
front then little after that outside of a few orographic bands. As
with the Dec 3rd system the GFS is generating a good deal of
precipitation (0.50in) Friday night into Saturday for Billings and
the surrounding low elevations, while the NAM12 is a tenth or
less. Part of this discrepancy is the GFS turning winds NE for a
period which drops downslope from the equation for a time which is
not in the NAM. Local studies indicate leaning toward the higher
resolution CAM models and the NAM12 with these type systems, so
trending to the lower end of qpf and pops with this in mind. Dry
low level air will allow a quick wet bulb down to freezing with
this system so expect mainly snow once precipitation starts. Cant
rule out needing some foothills advisories for this system going
forward given current thinking, and more expansive advisories if
the GFS pans out. Chambers

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

The extended period looks to remain unsettled with above normal
temperatures to start before much below normal temperatures
arrive by the end of next week. A northwest flow aloft will be
over the forecast area Sunday into Tuesday. A disturbance will
move across the forecast area Monday night into Tuesday bringing
another chance for snow. A large upper low and trough will move
into the Pacific northwest Wednesday resulting in brief ridging
and a southwest flow aloft across the forecast area. As it moves
east late Wednesday into Thursday it will bring in much cooler air
along with increasing chances for snow. Models continue to bring
an arctic front along with continuing chances for snow into the
area Friday into next weekend. Highs will be in the lower 40s
Sunday through Wednesday with readings only in the 20s for highs
by Thursday. Hooley



Scattered snow showers near the Dakota borders will gradually
diminish by the afternoon. IFR to MVFR conditions with low cigs
and vsbys can be expected with the snow shower activity, with
conditions improving to VFR by the afternoon. Elsewhere, skies
will be partly to mostly sunny with VFR conditions prevailing.
Winds will increase along the western foothills this afternoon and
evening. STP



    Tdy Fri     Sat     Sun     Mon     Tue     Wed
BIL 044 030/054 031/036 020/042 029/045 026/044 029/044
    0/U 00/N    55/W    20/U    13/O    22/W    21/E
LVM 040 026/048 028/033 017/034 025/042 028/043 032/044
    0/U 00/N    67/W    21/B    23/O    22/W    22/W
HDN 043 026/055 031/038 020/041 027/046 025/043 026/047
    0/B 00/B    55/W    20/U    13/O    22/W    21/E
MLS 039 025/053 030/037 021/039 026/043 025/039 025/041
    1/B 00/B    43/J    10/U    12/O    11/B    21/E
4BQ 038 025/054 030/038 021/037 026/045 025/042 025/045
    2/J 00/B    45/W    10/U    03/O    21/B    11/B
BHK 035 022/049 028/035 019/037 026/041 023/038 023/041
    2/J 00/B    43/J    10/U    02/O    11/B    11/E
SHR 041 022/055 028/037 016/040 023/047 021/044 025/047
    1/N 00/U    57/W    31/U    12/R    22/W    21/B




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