Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 081002
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
302 AM MST Fri Dec 8 2017

.SYNOPSIS...

High pressure centered west of the region will keep the weather
pattern stable and dry into early next week. Cold air trapped in
the southwest valleys will be slower to scour out, keeping
temperatures there below normal until at least this weekend.

&&

.DISCUSSION...

Today through Sunday...Persistence rules the forecast through the
weekend with a high-amplitude ridge parked over the west coast.
Temperature inversions will keep cold air trapped in southwest
valleys, possibly raising air quality concerns. Freezing fog has
not yet been observed this morning, but cannot be ruled out,
particularly in valleys having at least an inch of snow depth.
Forecast temperatures have been lowered below model guidance in
these colder valleys. In contrast, breezy southwest winds will
provide adequate mixing to maintain above average temperatures
across the North-central plains.

Monday through Friday...The western ridge weakens late Tuesday as
a minor shortwave traverses the northwest flow aloft. Models so
far indicate little to no precipitation with this fast moving
system. However, it is expected to produce stronger surface winds
and enough mixing to turn over the valley temperature inversions.
The ridge rebuilds after this wave passes, restoring the dry and
stable pattern with cold southwest valleys and breezy, mild
conditions for the north-central plains. Although details vary,
model solutions begin to break down the ridge just beyond the end
of the forecast period.

PN

&&

.AVIATION...
Updated 0520Z.

VFR conditions will continue across the forecast area through at
least the next 24 hours.

High pressure will remain anchored over the interior western U.S.
for mainly clear skies under a dry and stable northerly flow aloft.
some patchy fog cannot be ruled out in some SW MT valley locations
overnight, but is not anticipated to impact terminals. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  27  48  32 /   0   0   0   0
CTB  50  26  48  31 /   0   0   0   0
HLN  33  16  34  20 /   0   0   0   0
BZN  28  10  30  12 /   0   0   0   0
WEY  27   0  28   4 /   0   0   0   0
DLN  32  14  39  17 /   0   0   0   0
HVR  52  23  47  23 /   0   0   0   0
LWT  48  29  50  31 /   0   0   0   0

&&

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

$$

http://www.weather.gov/greatfalls



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