Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Billings Montana
921 PM MST Thursday Dec 12 2013
no significant updates for tonight. We did add some low probability of precipitation for
our central zones...including Yellowstone County...for tomorrow.
Back door cold front will be sliding into our forecast area
tomorrow and with weak upper trough moving across we may see
enough lift and convergence to squeeze out some flurries or light
Current Wind Advisory for foothills in good shape. 700mb cold
front moving across western Montana should effectively disrupt
vertical profile to reduce the higher winds later tonight. Bt
Short term...valid for Friday and Sat...
A progressive pattern will dominate the short term portion of the
forecast. Shortwave ridging over the forecast area today will
give way to shortwave troughing on Friday...which will swing a
back door cold front into the forecast area. The most sensible
impact from this front will be across central and eastern zones as
850 mb temperatures crash to 5 to 10 c below zero. The effect will
be less sensible for the western zones as the airmass will just
glance our region. Rising heights on Saturday will swing slightly
warmer air back across the forecast area.
Precipitation chances remain scattered at best through this period
as the shortwaves bring disjointed periods of moisture and lift
across the forecast area. Downslope winds will also play a role in
keeping western and central zones mainly dry through this period.
However...mountain locations will pick up snow showers through
The main threat that develops on Saturday through the weekend will
be an extended period of gap winds for the Livingston and Nye
areas. Very cold temperatures in Yellowstone Park will combine
with falling surface pressures along the Canadian Front Range to
create a tight pressure gradient across the area. Models are
persistent in developing about a 20 mb difference between Lewistown
and Idaho Falls with nearly 60 knots at 700 mb. Given these values
and the very cold air in the Yellowstone Park...expect the
potential for High Wind Warning criteria winds. Thus have issued a
high wind watch starting Saturday morning through Monday
afternoon. With the two periods of strongest wind possibly being
Sunday morning and Monday morning.
Long term...valid for sun...Mon...Tue...Wed...Thu...
The main concern for the extended period is the potential return
of more Arctic air by middle to late next week.
Before getting to the potential late period Arctic...will first
mention the difficult temperature forecast for both this coming
Sunday and Monday. These two days will most likely be the warmest
the area has seen in a while. Which of these two days will be
warmer is the tricky part. The determining factors will be
drainage winds from the Big Horn basin and snow cover. There is a
good chance a lot of the top layers of snow will melt off over the
next several days. A thinner layer will help bring temperatures up
sooner. Either way...both days will surely see middle 40s for highs
across most of the region. Very strong...near warning criteria...winds
in the Livingston...Nye and beartooth foothills will also work to
keep temperatures up.
The 300 mb jetstream will bring northwesterly flow to the region
for most of the period. This will start to change by late
Wednesday night...as the jet carves out a positively tilted
longwave trough covering most of the western US.
The best potential for accumulating snowfall will probably be
Wednesday night into Thursday with the approach of the trough from
the west. Too early to say how much snow may accumulate...so
further model runs will aid in helping to zero in on potential amounts.
Extended models still vary on the timing for the potential Arctic
air mass late this week. Whichever solution comes to fruition...it
appears this round of cold air will not be as long lived or quite
as cold as the previous one from last week. While this is still
near the very end of the period...it is something that should be
mentioned and planned for. Singer
Gusty southwest winds will continue overnight in klvm and along
the beartooth foothills...with gusts 45 to 50 knots. Winds will
continue through Friday. VFR conditions should prevail at all
terminals overnight. Scattered snow showers will develop over area
mountains and near foothills early Friday morning. Some isolated
snow showers are also possible across the plains...impacting kbil
in the moving and proceeding eastward throughout the day. Localized
MVFR to IFR conditions will be possible in heavier snow. Expect
increasing mountain obscuration through the night and Friday
Preliminary point temp/pops...
Friday Sat sun Monday Tuesday Wednesday Thursday
bil 025/035 023/040 031/044 029/044 021/034 023/030 013/019
02/j 11/north 11/north 11/north 11/b 22/j 43/j
lvm 022/035 021/040 029/046 027/038 020/035 024/034 009/019
12/j 22/west 21/north 11/north 21/north 22/j 34/j
hdn 020/032 020/038 028/046 027/043 019/035 017/031 013/019
02/j 11/east 11/north 11/b 11/b 12/j 43/j
mls 013/022 012/030 023/042 025/043 016/030 013/024 010/010
11/east 22/j 11/b 12/j 11/b 12/j 43/j
4bq 013/028 013/034 025/043 025/043 017/032 016/029 010/014
02/j 11/east 21/b 01/b 11/b 12/j 44/j
bhk 009/020 006/024 018/040 023/039 014/027 013/024 008/009
12/j 22/j 22/j 12/j 10/b 12/j 33/j
shr 018/034 018/039 025/044 025/041 018/034 016/035 012/016
02/j 11/east 11/b 11/b 11/b 22/j 34/j
Montana...Wind Advisory in effect until 8 am MST Friday for zones
High wind watch in effect from late Friday night through
Monday afternoon for zones 65-66.