Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 190951
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
251 AM MST Mon Feb 19 2018

.SYNOPSIS...

A cold upper level low pressure system in place over the western
United States will maintain cloudy and very cold conditions
across the northern Rockies and Montana with generally light snow
decreasing to flurries through this afternoon. Very cold
temperatures continue though Tuesday with a slow moderation of
temperatures expected mid to late this week. Most areas will
remain below normal for temperatures with mostly dry conditions
through the week.

&&

.DISCUSSION...

Today through Tuesday....Deep upper trough continues to slowly
drift east across western Montana toward the central part of the
state. As it does so, weak shortwaves continue to eject from the
base of the trough across our area, resulting in widespread light
snow. This trough will finally exit the region to our east
tonight, with a very cold air mass remaining over north-central
and southwest Montana as high pressure settles over our area.
A wind chill continues over our entire forecast area until 11 am
this morning, with another very cold night tonight possibly
resulting in additional advisories tonight, though winds will be
quite marginal. Some slight moderation in temperatures (primarily
single digits to teens above zero) begins to occur Tuesday as a
weak lee trough develops east of the Northern Rockies. CC

Tuesday Night through Sunday...A deep, positively-tilted low
pressure trough will remain over the western and central United
States through this period, keeping the forecast area generally
under a northwesterly flow aloft. A series of disturbances will
move through this flow, bringing a chance of snow mainly to the
western and southwest Montana mountains with mainly breezy
westerly downslope winds over the plains. These winds should help
bring a gradual warming to the area, but temperatures will only
warm from around 20 degrees below normal for Tuesday
night/Wednesday to around 5 to 10 degrees below normal by Saturday
night/Sunday. The strongest disturbance is forecast to move south
along the Pacific coast, which will focus the best precipitation
there. However, the greatest chance for (what is currently
forecast to be) light snow over the entire forecast area will be
next weekend, as a relatively strong disturbance moves northwest
to southeast over Montana.
Coulston

&&

.AVIATION...
Updated 0948Z.

There are no changes in thinking from the previous forecast.

An upper level low pressure trough drifting east across our area
today will result in continued MVFR/IFR conditions with light snow
and patchy fog. Gradual improvement to VFR conditions will occur
primarily after 18z from the northwest as snow ends and clouds
thin. Breezy north winds will continue to gradually diminish
through the day. Temperatures will drop near or below -20F
overnight tonight at all terminals. CC

&&

.HYDROLOGY...

An Areal Flood Warning remains in effect until further notice for
the area just north of Townsend in central Broadwater County.
Continued cold temperatures have kept the ice jam in place there
over the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  -3 -19  11 -12 /  50  20  10  10
CTB  -1 -19  13 -13 /  30  10  10  20
HLN   1 -18  10 -10 /  40  20  10  10
BZN   1 -20   7 -12 /  50  20  10  10
WEY  10 -26   8 -17 /  70  20  20  30
DLN   3 -16   9  -8 /  30  20  10  10
HVR  -2 -21   4 -16 /  40  20  10  20
LWT  -1 -19   8 -13 /  60  30  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST early this morning
Beaverhead...Broadwater...Gallatin...Jefferson...Madison.

Wind Chill Advisory until 11 AM MST this morning Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Jefferson...Judith Basin...Liberty...Meagher...
Northern Rocky Mountain Front...Southern Rocky Mountain Front...
Toole.

Wind Chill Advisory until 11 AM MST this morning Beaverhead...
Gallatin...Madison.

Ice Jam Flood Warning continues until 915 PM MST for the Missouri
River near Townsend in central Broadwater County.

&&

$$

http://www.weather.gov/greatfalls



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