980
FXUS65 KTFX 170848
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
248 AM MDT Fri May 17 2024

.SYNOPSIS...

A gusty day is in store for the region as a Pacific cold front
progresses eastward this morning and early afternoon. Cooler
temperatures will be the theme this weekend into next week, with
opportunities for precipitation most days.

&&

.DISCUSSION...

Through Tonight... Zonal flow aloft largely persists through today,
though a wave pivoting through a larger scale trough will, with the
help of a developing surface low across southern SK, propel a
Pacific cold front through the Northern Rockies this morning into
early afternoon. Temperatures this morning will be on the mild side,
but fail to rise too much before the Pacific front arrives, allowing
temperatures to stagnate or fall slightly through the afternoon.
Forecast soundings support wind gusts in the 40-55 mph range
today, with only isolated instances of stronger gusts approaching
60 mph away from the Rocky Mountain Front (Where the chances are
moderate today). Given a lack of high confidence for more than a
few isolated synoptically driven wind gusts 50 kts or greater, I
have opted to forego any High Wind Warnings at this time. A
complicating factor will be any showers that form where winds
aloft are on the stronger side. Given respectable inverted-V
soundings, decaying showers will be able to produce a bit more
momentum transfer to the surface compared to mixing alone.
Confidence in a timing or location of this is quite low, which
will necessitate monitoring of trends through the day today. Winds
will slowly diminish heading into tonight.

Aside from winds, zonal flow aloft will also bring snow to the high
terrain of the Rocky Mountain Front. Although impacts don`t look
to occur at or below pass level, those recreating should be aware
of forecast conditions.

This weekend... Large scale upper troughing will remain in place
across SW Canada and the far northern portions of the NW CONUS this
weekend, resulting in largely zonal flow aloft, with shortwaves
pivoting across the region at times. The end result is for
unsettled conditions remaining. Temperatures will be on the cooler
side, with opportunities for showers and perhaps a few
thunderstorms.

Sunday looks to be the day more favored for showers and
thunderstorms, as a robust shortwave pivots through the broad
troughing. Confidence in timing is not yet high, but the chance for
a tenth of an inch of precipitation Sunday into Sunday night is
largely greater than 50% across the region.

Next Week... Ensembles favor a continuation of unsettled conditions
heading into next week as large scale troughing remains in place
across much of the Pacific NW and Northern Rockies. Although
confidence is high that unsettled conditions will remain, specifics
with respect to timing and magnitude of any precipitation is murky
at best at this point. -AM

&&

.AVIATION...
18/06Z TAF Period

Note: The NWS Great Falls Office manages the following TAFs: KCTB,
KHVR, KGTF, KLWT, KHLN, KBZN, KEKS and KWYS.

All airfields begin this TAF period in VFR conditions. Beginning at,
17/19Z, KCTB, KHVR and KLWT fall into predominant MVFR conditions
due to light rain showers and low ceiling (KCTB). The TAFs for all
of our airfields include PROB30 groups that bring each airfield into
MVFR conditions in rain or rain/snow (KLWT) and, in some cases, with
low ceiling. These PROB30 groups begin as early as 17/15Z. Mountain
obscuration is forecast. Generally, widespread strong gusty westerly
winds are forecast throughout this period. Mountain wave is
forecast. Areas of virga, and all of the associated hazards to
aviation flight ops, should be expected. Some isolated thunderstorm
activity is forecast to occur across portions of north central,
central and southwest Montana, Friday afternoon/evening. As of this
time, thunderstorm is not forecast to occur within the ten mile
aerodrome of our airfields.
- Fogleman

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  39  64  40 /  30  30   0  20
CTB  54  35  59  34 /  60  40  20  10
HLN  62  38  67  41 /  20  10   0  20
BZN  65  30  66  39 /  40  10   0  20
WYS  61  25  58  35 /  20  10   0  10
DLN  62  29  66  37 /  10   0   0  10
HVR  62  38  64  38 /  40  90  10  10
LWT  60  36  60  38 /  50  20   0  20

&&

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

$$

http://www.weather.gov/greatfalls