Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 072337
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
430 PM MST Wed Dec 7 2016

AVIATION SECTION UPDATED

.DISCUSSION...

Tonight through Thursday...High pressure aloft will gradually
build northeast into the forecast area during the period. This
will shift the cyclonic northwest flow aloft to a more
anticyclonic westerly flow, which will help clear skies
overnight. As a result, temperatures will fall to their coldest
levels in at least a year, as lows generally fall into the -10F to
-20F. Some mountain valleys with higher snowpack will likely fall
to around -30F. However, the northerly winds across North Central
Montana have generally fallen below 10 mph, so have cancelled the
Wind Chill Advisory. Moisture will gradually increase as the high
pressure ridge builds into the area, bringing mainly high clouds
to the area on Thursday, but a few snow showers will likely move
into the Southwest Montana/Northeast Idaho border area. Warmer air
will start to move into Southwest Montana, pushing highs into the
10 to 15 above range, while cold air will keep highs across North
Central Montana in the single digits above and below zero.
Coulston

Thursday night through Saturday night...A series of Pacific upper
level jet and shortwave impulses will move across the region this
period with bulk of the energy moving near or just south of the
forecast area. First in this series is a weakening wave that
tracks east across SW MT Friday morning. Expect light snow to
spread east across central and southern portions of the forecast
area Thursday night with snow diminishing from west to east as
the wave exists on Friday. As this wave is weakening, higher
precipitation amounts will be found over southern and sw portions
of the forecast area where 1- 3 inches of snow are possible from
roughly Helena south with locally higher amounts up to 4 inches
near the ID border. A second and somewhat stronger wave moves
across the region Friday night through Saturday morning, brining
a second more widespread round of light snow. Much of the
forecast area will see 1-3 inches of additional snow from this
feature with areas near the ID border again seeing the highest
amounts of 3 to 5 inches. Will issue a winter weather advisory to
highlight arrival of snow in SW portions of the forecast area
Thursday evening and beginning over central portions of the
forecast area late Thursday night, though steadier snow
accumulations in northern areas may not occur until the Friday
night wave arrives. Hoenisch

Sunday through Wednesday...The northwest flow aloft will be quite
unsettled and snow showers will remain in the forecast through the
middle of next week. A shortwave in Alberta will move southeast
Sunday towards the Dakotas. This will will not bring much change
in the chance for precipitation but it will bring another cold
front across the Canadian border. Temperatures Sunday will again
struggle to move above zero across the Hiline and above single
digits across the central zones. Currently, the coldest air is
forecast to slide east of the zones...but a slight change in
position would cause very cold temperatures over the eastern
zones. Zelzer

&&

.AVIATION...Updated 2330Z.
VFR conditions expected overnight and through Thurs as weak high
pressure ridging moves into central MT. Current area of mid-level
ceilings (5000-6000 ft) over KGTF/KHLN/KBZN will persist into this
evening then gradually scatter out tonight while other local
terminals will see mostly clear skies. Winds across the region will
be light and variable tonight.
Waranauskas

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF -16   0  -5   5 /  10  10  70  50
CTB -20  -3 -10  -4 /  10  10  50  50
HLN -12  11   6  26 /  10  10  80  40
BZN -12  13  11  30 /  10  10  80  40
WEY -30  12   8  28 /  10  20  80  70
DLN -10  16  13  34 /  10  10  80  30
HVR -15   0  -6   2 /  10  10  20  50
LWT -17   4  -3   9 /  10  10  50  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM Thursday to 5 PM MST Saturday
Broadwater...Cascade...Central and Southern Lewis and Clark...
Fergus...Jefferson...Judith Basin...Meagher.

Winter Weather Advisory from 5 PM Thursday to 5 PM MST Saturday
Beaverhead...Gallatin...Madison.

&&

$$

weather.gov/greatfalls



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