Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 211558
AFDGGW

Area Forecast Discussion
National Weather Service GLASGOW MT
858 AM MST Tue Feb 21 2017

.SHORT TERM...for northeast Montana...today through Thu...

Updated the forecast grids blending them with the latest model
guidance. They seemed to lower the snow amounts a bit with the
snow tonight, the other changes seemed to be minor in comparison.

Update has been issued. TFJ

Previous Discussion...
Models have trended much wetter with the cold front this afternoon
and tonight along with overrunning precipitation north of the
front on Wednesday.

Shortwave ridge will move to the east this morning and turn the
flow aloft to SW ahead of an upper trough that will move inland
from the Pacific tonight and Wednesday. This will bring a cold
front south across the forecast area this afternoon and evening
and reaches the Montana/Wyoming border late tonight. Shortwave
troughs on the SW flow aloft moves across Northeast Montana today
and tonight. This will bring some moisture into the forecast area
today for some rain showers which will be south of the Missouri
River this morning and spread north this afternoon.

The cold front drops south across the region this afternoon and
evening with a band of overrunning precipitation north of the
front. Temperatures will cool enough this evening to change the
rain to snow and areas north of the Missouri River will likely
see some accumulating snow late tonight which will spread to south
of the river Wednesday morning. Snow amounts between tonight and
Wednesday morning appear to be between one and three inches at
this point. Will hold off on issuing an advisory at this point
although one may be needed late tonight and Wednesday if the
current snow forecast hold true. The Yellowstone Valley will
likely see less snow as temperatures may stay warm enough for rain
tonight and Wednesday.

The front will move far enough to the south by Wednesday
afternoon that the snow will diminish in most areas. However, the
Little Rocky Mountains of SW Phillips County and possibly Central
Phillips County will maintain an upslope wind which combined with
weak waves in the northern stream of a split flow aloft could
continue to have accumulating snow into Thursday. Given the
possibility of 5 to 8 inches of snow in this area, will issue a
Winter Storm Watch for Central and Southern Phillips County late
tonight through Thursday. The main upper trough in the southern
stream remains far enough south that the main snow band from that
system will remain well to the south. However, shortwaves in the
northern stream will give most of the forecast area chances for
light snow Wednesday Night and Thursday. Forrester

.LONG TERM...Thu night through Tue...
The long range period begins Thursday night into Friday with
departing storm system. However, a broad upper level trough will
remain centered across the region for much of the second half of
the week. This will maintain relatively cold temperatures and at
least some chances for light snow due to the upper level forcing
for ascent.

Current 00z model runs show that the trough eventually pushes out
of the area while an upper level ridge develops over the northern
Rockies. Expect drier weather conditions to result though 500mb
heights still low enough to drive high temperatures mainly below
freezing. Maliawco

&&

.AVIATION...

An upper-level trough off the Pacific Coast is sending moisture
into the Pacific Northwest this morning, including Northeast
Montana. A frontal boundary will initiate rain showers this
morning and this afternoon.

Expect lowering ceilings later today as rain approaches from
south to north. Rain is expected to change to snow by 06z over
the terminal areas, except for KGDV where temperatures will
remain warm enough for mainly rain. Reduced visibility in
precipitation as well as lowering stratus may result in MVFR and
IFR conditions tonight.

Winds: Light west to southwest today at 5 to 10 kts, becoming
northerly tonight.

Templer


&&

.HYDROLOGY...

Ice is in the process of breaking up on the Yellowstone River in
the Glendive area overnight. Since the Yellowstone River has broke
up in Prairie County, will cancel the Flood Watch there.

An ice jam at the Highway 24 bridge over the Milk River
downstream of Glasgow continues to remain in place this morning
with the water flowing through the ice for now. The Milk River is
slowing rising with the river at 22.4 feet or around 2.4 feet
below flood stage. The Milk River is also slowly rising in the
Nashua area with the river level around 16.1 feet and is about 4
feet below flood stage today. Flooding concerns continue across
the area as a result of ice jams occurring from recent warm
temperatures.

The Big Muddy river in Sheridan County near Antelope has edged
upward to 10.95 feet which is just over 1 foot below flood stage.

The Frenchman Creek near the Canadian border in northern Phillips
County has risen past flood stage and was at 12.52 feet at 230 AM.
A flood warning warning remains in effect for the drainage from
the international border to the confluence with the Milk River.

The Beaver Creek near Saco (Guston Coulee) crested around 10.3
feet yesterday and continues to come down early this morning.

The Poplar River has also risen to 11 feet early this morning and
is approaching action stage.

Colder temperatures starting Wednesday will slow the snow melt
although warmer water could break up more ice, keeping ice jam
concerns elevated through most of this week.

A flood watch continues for Dawson and Richland Counties along
the Yellowstone River for ice jam flooding through Wednesday
afternoon.

A flood watch continues for Sheridan County for the Big Muddy
River through Wednesday afternoon.

A flood watch continues for Valley County for areas along the
Milk River downstream of Hinsdale to the confluence with the
Missouri River through Wednesday afternoon.


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from this evening through Thursday afternoon
for Central and Southeast Phillips...Southwest Phillips.

Flood Watch through Wednesday afternoon for Central and Southern
Valley...Dawson...Richland...Sheridan.

&&

$$

weather.gov/glasgow


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