Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 220448
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1050 PM MDT Tue Mar 21 2017

Updated Aviation Discussion.

.UPDATE...

Overnight lows were trended higher as has been the trend the last
day or so with the models. There remains some conditional threat
of freezing rain overnight especially over our far northeastern
areas especially in Hill and Blaine counties north of US Highway
2, and our far southwestern areas in the sheltered valleys of
Beaverhead County, but confidence is too low to issue any hazards
at this time. Will continue to monitor. Cassell

&&


.AVIATION...
Updated 0450z.

Complex forecast overnight throug the morning Wednesday, with rain
showers at times across the region. Some freezing rain can not also
be ruled out, especially far northeast areas as well as some
sheltered valleys of SW MT that do see some rain. However, any
widespread freezing rain threat is minimal. Fog has also become an
issue especially over south and eastern areas, and may spread north
and west across the Plains overnight. Otherwise, a series of
disturbances will move northeast over the region. A mix of flight
categories can be expected until 12z to 18z over the Plains, when
skies will mostly clear out and become VFR as gusty west to
southwest winds develops across the Rocky Mountains and spreads out
over the Plains. Cassell

&&

.PREV DISCUSSION...
/ISSUED 525 PM MDT Tue Mar 21 2017/

Tonight through Thursday...Low level moisture has lingered a lower
cloud deck and areas of fog across portions of the southwest
today. Until the next wave comes through...it looks like this may
continue into the evening. Some freezing fog/drizzle is still
possible at the pass levels as a result through this
evening...however...the high spring time sun angle should limit road
impacts. A few showers and perhaps an isolated thunderstorm is also
possible this evening ahead of the next wave...mainly across the
south and central. Thunderstorm potential is not looking as good as
earlier...as the more unstable air is in Idaho where full clearing
took place this afternoon. Still can`t rule out an isolated
thunderstorm until the sun sets. The next wave then lifts across the
region tonight into Wednesday morning. Abundant warm air along a
warm front could bring some interesting precip types. The high line
still looks to be the best shot of a wintry mix of freezing
rain...sleet...perhaps some rain...and little snow. Confidence is
getting moderate to high freezing precip will
occur...however...confidence in the impacts is still only moderate.
Will hold off on an advisory for now...but something to monitor
tonight. The remainder of the area will see at least a chance for
rain...with the mountains perhaps seeing some snow...and cooler
valleys getting into some freezing rain. A weak cold front then
pushes out the disturbance Wednesday afternoon ending precip across
much of the area...although a weakly unstable environment could
bring an isolated to scattered shower Wednesday afternoon. Upper low
then moves into the Wyoming area Wednesday night into Thursday.
Looking like this low has trended to south for us to see widespread
precip. An isolated to scattered shower across the southwest is all
we are expecting at this point. Temperatures will be on a warming
trend throughout the short term.
Winds may also become breezy Wednesday and Thursday. Anglin

Thursday night through Tuesday...An upper level ridge of high
pressure will build over the region for Thursday night and Friday.
Thus expect mostly dry conditions away from the Rocky Mountain
Front, along with comfortable spring time temperatures on Friday.
For the rest of the extended, the GFS/EC models differ on
timing/location of precipitation events. The GFS is wetter Saturday
afternoon through Sunday, while the EC is wetter Monday
afternoon/night. Thus confidence is low for now in terms of how wet
this weekend will be, especially across Southwest MT. By early next
week, both models bring in enough cold air, that snow could mix in
at all elevations from time to time, but especially at night/early
in the morning. Overall temperatures will be the warmest/well above
normal on Friday, then gradually cool to near/slightly above
seasonal normals over the weekend and into early next week. Brusda

300 PM Update.

River levels in Blaine and Hill Counties have all shown a slow
decrease over the past 24 hours, but it will take a little more time
to get all the water through the system. Lodge Creek in NE Hill
county remains well above flood stage, but Battle Creek has lowered
enough below flood stage to cancel the flood warning there. The Milk
River at Harlem has fallen to right near the flood stage level, but
additional lowering has been slow this afternoon. With reports of
lowland flooding in rural areas still existing along the Milk River
in the Harlem to Ft. Belknap vicinity, will continue the warning
there through tonight with more significant lowering of river levels
expected by Wednesday morning. In Beaverhead County, an ice jam is
causing flooding problems on the Big Hole River upstream of Wise
River. This is a very unpredictable problem/impact with latest river
observations in the vicinity still showing erratic effects from ice.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  41  63  36  58 /  20  20  10  10
CTB  34  56  32  51 /  50  40  10   0
HLN  38  62  35  56 /  30  20  10  10
BZN  38  60  33  53 /  50  40  10  20
WEY  32  43  28  43 /  70  50  20  40
DLN  36  56  32  53 /  50  30  10  20
HVR  32  63  34  58 /  20  20  10  10
LWT  34  62  34  52 /  30  20  10  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Ice Jam Flood Warning in effect until further notice for the Big
Hole River near Wise River in north-central Beaverhead County.

Flood Warning remains in effect until further notice for the Milk
River near Harlem in Blaine County.

Flood Warning remains in effect until further notice for Lodge
Creek near Havre in Hill County.

&&

$$

weather.gov/greatfalls


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