127
FXUS65 KTFX 071102
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
402 AM MST Thu Nov 7 2024

Aviation Section Updated.

.KEY MESSAGES...

 - Strong and gusty winds are expected along the Rocky Mountain
   through Friday, and then again on Monday.

 - Temperatures warm back above normal through the end of the work
   week, with temperatures remaining above normal through Monday.

 - Dry conditions are expected through Saturday morning, with
   generally light precipitation returning to the Continental
   Divide Saturday afternoon and persisting through Sunday night.

 - More widespread precipitation returns to the remaining
   mountains and to Southwest Montana from Monday through Tuesday.

&&

.DISCUSSION...
/Issued 312 AM MST Thu Nov 7 2024/

 - Meteorological Overview:

Broad, upper level ridging will largely persist across the Western
CONUS and Canada through Friday afternoon, with heights beneath the
ridge gradually falling thereafter through Monday as longwave
troughing moves across Northern Canada and helps to flatten and
suppress the ridge axis. A strong pressure gradient residing along the
Rocky Mountain Front through Friday beneath this ridge, due in part
to high pressure residing west of the Continental Divide and a
developing area of low pressure in lee of the Canadian Rockies, will
support strong winds along the immediate eastern slopes of the Rocky
Mountain Front with breezy and gusty winds expected elsewhere. This
upper level ridge/pseudo zonal flow pattern combined with the
downsloping winds will help temperatures to warm above normal
through the end of the work week across all locations, with
temperatures remaining above normal into the start of upcoming work
week before a longwave trough moves eastward and across the Northern
Rockies through the middle of the work week. This longwave trough
will bring a return for more widespread precipitation to Southwest
through North Central Montana, particularly to the mountains and
valleys of Southwest Montana, in addition to the threat for strong
winds to the Rocky Mountain Front. - Moldan

 - Forecast Confidence & Scenarios:

NBM probabilities for wind gusts in excess of 45 mph across the East
Glacier Park and Northern High Plains through today generally range
from a 50% to 70% chance, with a 20% to 30% chance for gusts to
exceed 55 mph across these same areas. Probabilities fall slightly
for the day on Friday along the Rocky Mountain Front, generally to a
30-50% chance and 5-20% chance for 45 mph and 55 mph respectively.
Breezy and gusty winds will persist through the weekend, with the
next threat for strong to potentially high winds returning on Monday
ahead of an eastward advancing Pacific front. Wind gusts on Monday
have 40-60% chance of exceeding 55 mph along the Rocky Mountain
Front and across the immediate eastern plains. With EFI values
throughout this windy pattern remaining below 0.5 and H850-H700
wind anomalies failing to exceed 1 standard deviation I am not
overly concerned that High Wind highlights will be needed on any
given day going forward into early next week. With that being said,
the surface pressure gradient of 6 mb to nearly 12 mb along the
Continental Divide through Friday combined with favorable thermal
profiles near ridgetops amongst modest mid-level flow does provide
the opportunity for wind gusts to over achieve beneath mountain wave
activity.

Ensemble clusters with respect to the approaching disturbance from
Monday through Tuesday are in fairly good agreement; however, there
does remain some uncertainty with the amplitude of the trough as it
digs southeast from the Gulf of Alaska towards the Great Basin and
Desert Southwest from Monday through Tuesday. This will ultimately
impact where and how much precipitation falls across the Northern
Rockies, with the current track favoring precipitation falling along
the Continental Divide and across areas south of the Montana Hwy 200
corridor. - Moldan

&&

.AVIATION...
07/12Z TAF Period

VFR conditions will prevail across all terminals during this TAF
period with few high-level clouds or clear skies due to an upper-
level ridge over North-central, Central, and Southwestern Montana.
Due to the upper-level ridge there will be light winds at all
terminals except for the KHVR, KCTB, and KGTF terminals. At the
KCTB, KGTF, and KHVR terminals there will be wind gusts up to
25kts from now until about 07/22Z. There is a 20% chance for fog
to form at the KBZN terminal from now through 07/15Z. Due to the
lack of probabilistic support this wasn`t included in the KBZN
TAF. Today until about 07/22Z there will be mountain wave
turbulence across North-central Montana. -IG

The KWYS TAF will not be issued until airport operations resume next
spring.

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  31  59  33 /   0   0   0   0
CTB  56  30  62  34 /   0   0   0   0
HLN  51  24  57  26 /   0   0   0   0
BZN  49  20  53  22 /   0   0   0   0
WYS  40   7  46   9 /  10   0   0   0
DLN  48  22  53  23 /   0   0   0   0
HVR  51  23  55  29 /   0   0   0   0
LWT  52  25  58  27 /   0   0   0   0

&&

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

$$
http://www.weather.gov/greatfalls