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
894
FXUS65 KTFX 172158
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
258 PM MST Tue Jan 17 2017

.DISCUSSION...

Tonight through Thursday...Seasonally mild temperatures and strong
southwest winds will prevail across North-central Montana tonight
through Wednesday. 700 mb winds peak near 60kts over the Northern
Rockies early Wednesday, but models indicate a stable surface
layer will inhibit mixing to the surface. Will continue to monitor
as we expect winds to remain near, but below high-wind criteria.
The valley temperature inversions held once again today for the
southwest, causing persistent air quality concerns. Expect one
more cold night, then cooler temperatures aloft will weaken the
inversion and allow some moderating temperatures in most, but
possibly not all of the southwest valley locations. Pacific
moisture advances up to the west side of the Continental Divide,
producing only a narrow range of snowfall mainly over backcountry
areas through the day on Wednesday. A broad synoptic scale trough
crosses the western U.S. on Thursday. Most of the energy with this
system will split into the central Rockies, spreading chances for
light snow across southwest MT on Thursday. PN


Thursday night through Tuesday...Medium range models continue to be
in good agreement for much of the forecast period but solutions
gradually diverge early next week. Period starts off with a closed
low off the Washington coast merging with a weak trough over the
Great Basin to form a broad upper level trough over the entire
western USA with above normal temperatures across north central
portions of the state returning to more seasonable averages. Core of
energy associated with the upper trough should remain well south of
Montana but occasional disturbances being ejected from the main
trough will bring some chance for precipitation to southwest Montana
and the western mountains. However, expect only a slight chance for
light rain and snow showers across the north central plains. Main
portion of the upper trough drops into the Desert Southwest and
progresses into the southern Great Plains over the weekend.
Shortwave ridging behind this trough will probably remain too weak
to significantly affect temperatures and weather in Montana but
another broad upper trough is expected to develop over the west
coast by early next week. GFS progresses this feature steadily
eastward but the ECMWF holds the trough axis back along the
California coast for an extra 24 hours before beginning eastward
progression. As a result, the ECMWF puts additional precipitation in
southwest Montana on Tuesday while the GFS remains generally dry.
mpj

&&

.AVIATION...
Updated 1745Z.
Overall VFR conditions should prevail at most terminals through the
period. However...some haze could reduce visibility at times in
Helena...mostly this morning and again Wednesday morning. A Chinook
arch over the region this morning will give way to more widespread
clouds over the Rocky Mountain Front with some passes obscured by
12z Wed. Expect gusty winds as well...mostly over the northern
Plains...with some low level wind shear possible towards 06z this
evening. Cassell

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  35  47  35  44 /   0  10   0  10
CTB  31  46  31  43 /   0  10   0  10
HLN  10  35  19  34 /   0  10   0  20
BZN   6  36  18  38 /   0  10   0  10
WEY -23  23  14  30 /   0  20  30  30
DLN   7  33  22  35 /   0  10  10  30
HVR  30  46  29  42 /   0   0   0  10
LWT  30  47  30  44 /   0  10   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/greatfalls



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