Area Forecast Discussion
Issued by NWS Great Falls, MT

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249
FXUS65 KTFX 161101
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 AM MDT Mon Oct 16 2017

Updated Aviation Discussion

.SYNOPSIS...

A westerly flow aloft across the Northern Rockies and Montana will
maintain dry, mild and breezy conditions across the region today
with increasing winds tonight through Tuesday. Strong winds are
possible across much of north central Montana late tonight through
Tuesday evening as a weather disturbance moves across western
Canada. Windy conditions are likely to continue through much of
this week and into the weekend as a series of fast moving Pacific
weather systems track east along the Canadian border.

&&

.DISCUSSION...

Today through Wednesday...Fast westerly flow aloft continues
across the region today around a flattening upper level ridge
centered over the SW US. Surface pressure gradient across the
Rockies will continue to support locally strong winds along areas
immediately adjacent to the Northern Rocky Mtn front today with
afternoon mixing bringing an increase in winds, though not as
strong, to much of north central MT again this afternoon. Upper
trough moves into BC tonight with band of strong flow aloft
sagging south to areas along the AB border by Tuesday morning.
This will support increasing winds tonight for much of north
central MT with gusts in excess of 50-60 kts developing along the
Rocky Mtn front and Glacier county by Tuesday morning as a
critical level (favorable wind profile with low level maximum near
ridgetops) increases along the northern Rocky Mtn Front through
Tuesday morning. Band of strongest winds aloft sags further S and
E into N-central MT Tuesday while a surface trough in AB deepens
ahead of the upper trough moving across BC. Upper level trough
emerges in AB Tuesday night with surface low and cold front moving
quickly east off the Rockies with a trailing portion of the front
sweeping SE across N-central MT Tuesday night. Strong winds
initially along the Rocky Mtn front Tuesday morning will likely
spread east into adjacent western portions of n-central MT early
Tuesday afternoon with potential increasing for a period of strong
winds to extend further east across much of the remainder of
n-central MT Tuesday afternoon and evening. Strongest wind gusts
along the Rocky Mtn Front are likely to occur Tuesday afternoon
and may exceed 80 mph locally in areas favorable for enhanced
winds. Further east, wind gusts of 60-70 mph are most likely to
occur late Tuesday afternoon and early evening. Winds aloft
diminish slightly late Tuesday night and Wednesday, maintaining
windy conditions across the forecast area, however the surface
pressure gradient relaxes across the region as the surface trough
moves east into central Canada. Hoenisch

Wednesday night through Monday...The overall windy and warm pattern
will persist well into the overnight hours Wednesday night as strong
upper-level winds continue aloft. However, things begin to change on
Thursday with the development of a west coast longwave trough. This
will allow for a progressive southwesterly flow to transition aloft
across the area. The effect will be much warmer temperatures during
the day on Thursday due to downsloping/chinook winds, which has been
reflected well by model trends the past few days. Another note will
be the overnight lows Thursday and Friday morning, as temperatures
wont drop too far given persistent nocturnal gusty winds and
downsloping. It is possible that some locations could reach near-
record warmest overnight low temperatures for those dates with many
only seeing lows in the upper 40`s to lower 50`s across the Plains.
During the day on Friday, a quick moving cold front will swing
through the CWA leaving behind slightly cooler temperatures, as well
as increasing light rain showers. As cooler air filters in behind
the passing cold front Friday afternoon, some higher elevations in
south central and southwestern MT may end up with some accumulating
snow through late Friday night. By Saturday, any early morning
lingering rain or mountain snow showers will quickly exit to the
east leaving behind moderating temperatures and intervals of sun and
clouds. The long range pattern does suggest the development of a
reinforcing strong ridge across SW US. As heights progressively
increase/steepen in this response, model guidance appears to support
a developing strong zonal jet right across the northwestern US. This
may introduce the next potential strong wind event at some point
Saturday and into Sunday followed by a trend in near to above normal
temperatures into early next week. KLG

&&

.AVIATION...
Updated 1100Z.

Area remains under a dry and stable westerly flow aloft with VFR
conditions prevailing with scattered to broken high level cloud-
cover streaming over the Northern Rockies. Breezy west winds on the
plains will increase again this afternoon with gusts 25-35kts across
most n-central MT terminals while gusts 35-45 kts continue along and
adjacent to the Rocky Mtn Front. Wind speeds will increase further
this evening across n-central MT with gusts in excess of 50kts
possible along and adjacent to the Rocky Mtn front after 06z
Tuesday. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  68  48  71  45 /   0   0   0  10
CTB  64  44  66  37 /   0   0   0  10
HLN  67  40  72  46 /   0   0   0  10
BZN  65  35  72  40 /   0   0   0   0
WEY  52  25  54  28 /   0   0   0   0
DLN  62  33  67  38 /   0   0   0   0
HVR  68  44  72  37 /   0   0   0  10
LWT  67  42  71  41 /   0   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Tuesday afternoon through Tuesday evening
Cascade...Central and Southern Lewis and Clark...Chouteau...
Eastern Pondera...Eastern Teton...Hill...Judith Basin...
Liberty...Toole.

High Wind Watch from late tonight through Tuesday evening
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

&&

$$

weather.gov/greatfalls



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