Area Forecast Discussion
Issued by NWS Great Falls, 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 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS65 KTFX 151549

Area Forecast Discussion
National Weather Service Great Falls MT
849 AM MST Sun Jan 15 2017


A weak disturbance aloft is producing high clouds over the
Northern Rockies (a Chinook Arch) and gusty downslope winds along
the Rocky Mountain Front. Expect Southwest Valley temperature
inversions to hold today. Forecast remains in good shape overall.
Made minor updates to match sky and wind to observed trends, and
to lower today`s high temperatures a few degrees in Southwest
valleys. PN


Updated 1150z.
Overall, VFR conditions will prevail over the region, but valley
smog/haze is trapped in the Helena valley reducing the visibility.
Expect poor visibility in the Helena valley through tonight. Gusty
west winds are also expected along the front range of the Rockies
through the period. Brusda


/ISSUED 450 AM MST Sun Jan 15 2017/
Today through Tuesday...An upper level ridge will be over the
region today, resulting in quiet conditions and sunny skies. It
will continue to be windy along the front range of the Rockies and
across Central MT from Great Falls to Lewistown. With light winds
in the valleys of Southwest MT and north of Highway 2 in the
Havre area, expect another cold day and cold night tonight, with
temperatures well below guidance. On Monday, an upper level
disturbance will move southward through the region, but with limited
moisture, no precipitation is expected during the day, with a few
passing light showers at night. Temperatures are likely to remain
below guidance in the valleys of Southwest MT during the day on
Monday. However, on Monday night, increasing cloud cover should
prevent temperatures from falling too much. Thus on Tuesday, as
stronger winds aloft move into the region, combined with some
mixing, most locations should break the inversions. Additionally, a
high wind watch is in effect for the Rocky Mountain Front/Cut Bank
area from late Monday night through Tuesday wind
speeds could reach warning criteria in this region. The chances for
precipitation also increase throughout the day, especially over
the Rocky Mountain Front. Brusda

Tuesday Night through Sunday...The period starts with an upper level
ridge over much of the western US with a broad upper level trough
over the Pacific. By Thursday, this trough will move into the
western US as the ridge shifts east. From late in the week through
next weekend, the models generally agree on a broad trough remaining
across the western US. Locally, this translates to generally dry
and, at times, windy conditions across the plains. For the SW
valleys and western/southwestern Mountains, it will likely be a bit
more active. Temp-wise, a general moderating trend is expected
through mid-week, followed by a gradual cooldown heading into the
end of the week. A few quick summary notes below:

*Wind: the strong winds developing in the short term period will
likely continue on through at least Wednesday morning across
central Montana. For now, the High Wind Watch will only go
through Tuesday, however based on the latest model guidance, it
is likely that this will need to be extended through at least
Tuesday night in later shifts. But, since Tuesday night/Wednesday
is still 3-4 days away, we`ll hold off on going this far with
the watch as the models may still come in lower in later runs.
That said, if the current models are correct, the potential
exists for 60-80+ mph wind gusts along the Rocky Mtn Front and
40-60 mph gusts across parts of the plains Tuesday

*Precip: quite the surge of moisture will move in off the Pacific
through mid-week as a potential atmospheric river event sets up
briefly. This will favor the western and southwestern mountains
until the jet stream shifts south by Thursday. I raised pops some
in the mountains given the setup. For central MT, downsloping
still looks to limit precip, but given the seasonally high
moisture, I wouldn`t be surprised if a few showers make it out of
the mountains.

*Temps: 700mb temp anomalies of 2-3 std deviations plus a
downsloping W/SW wind should allow much, if not all, of central
Montana to see above normal highs for a change...a January thaw,
if you will. CIPS analog guidance even suggests a few locations
may approach or exceed 50 degrees by mid-week before cooler air
moves in late in the week. Temps are trickier across SW MT. The
current forecast assumes the current inversions will be able to
break with some wind and rising 1000-500mb thickness values, but
temps may end up cooler longer if the inversions remain stronger
longer. Martin


GTF  32  18  36  33 /   0   0   0  20
CTB  37  16  37  30 /   0   0   0  10
HLN   7  -3  20  15 /   0   0   0  10
BZN   8  -7  23  11 /   0   0   0  10
WEY   6 -19  21  -1 /   0   0   0  10
DLN  31   4  27  15 /   0   0   0  10
HVR  19  11  29  22 /   0   0   0  10
LWT  30  14  35  26 /   0   0   0  10


High Wind Watch from late Monday night through Tuesday afternoon
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.


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