626
FXUS65 KTFX 191703
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1103 AM MDT Thu Sep 19 2024

...Updated Aviation Section...



.SYNOPSIS...

A few showers linger this morning across north-central Montana
before drier conditions and seasonable temperatures develop
across the area this afternoon. Temperatures cool slightly for
Friday and Saturday, though mainly dry conditions are expected
through the weekend with just some showers moving east along the
Canadian border on Friday. Another weak weather system moves
through the area Monday before a warmer and drier weather pattern
develops next week.

&&

.Update...

Morning update has been published, with the main adjustment being
to linger low chance PoPs (15% to 20%) PoPs across portions of
Central and North Central Montana into the afternoon hours today.
These showers are not expected to produce much in the way of
additional rainfall, mainly a couple hundreths of an inch.
Otherwise the remainder of the forecast remains on track, with
fog/low cloud cover within the valleys of Southwest and Central
Montana persisting through the late morning before gradually
dissipating. The Areal Flood Advisory, which is set to expire at
1200PM MDT, is being evaluated for the need of a temporal
extension; however, early indications are that despite record
breaking rainfall across this area from September 17-18th most
locations are already see water levels receding. - Moldan

&&

.AVIATION...
19/18Z TAF Period

VFR conditions will prevail during this TAF period with mostly few
to scattered clouds at all terminals excluding the KWYS terminal.
There are MVFR cielings at the KWYS terminal and cielings will lift
by 19/20Z. At all terminals except for the KHLN terminal there will
be gusty winds after 20/00Z through most of the rest of the TAF
period. At the KCTB terminal there will be gusty winds during all of
this TAF period. Winds will gust the most at the KCTB, KGTF, KHVR,
and KLWT terminals. Friday morning there is a 20% chance for fog to
form at the KWYS terminal. There will be mountain wave turbulence
across North-central and Central Montana from 20/12Z through the end
of the TAF period. -IG

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

&&

.HYDROLOGY...

Little additional rainfall is expected this morning but some
minor flooding from the recent heavy rainfall may persist before
more noticeable improvement develops today. The flood advisory
has been cancelled for Cascade and Meagher counties, where stream
gauges indicate the elevated flows have passed, but the advisory
contiues for Chouteau, Hill, Blaine, Judith Basin and Fergus
counties, where heaviest rainfall totals were observed and minor
flooding impacts, including standing water in low-lying areas and
surface water hazards near some roads could linger through this
morning. Hoenisch

&&

.PREV DISCUSSION...
/ISSUED 505 AM MDT Thu Sep 19 2024/

A few showers continue to track across north-central MT early
this morning within a corridor of lower level (850MB) convergence
from eastern Glacier county southeast through Judith Basin
county. Lingering showers and cloud-cover will gradually diminish
through the morning period as the storm system that brought
significant precipitation to the area yesterday continues to move
out of southeast SK. By this afternoon, mainly dry but somewhat
breezy conditions are expected across the area with seasonable
temperatures.

A progressive weather pattern develops through Monday with
a series of lower amplitude troughs in the upper level flow moving
east across western Canada. The first trough and its associated
low at the surface already move east across southern AB tonight
with a cooler airmass sliding south in its wake across north-
central tomorrow, expanding into southwest MT Saturday. Breezy
west winds this evening and overnight on the plains will shift to
the north and northwest on Friday with a few showers possible
near Glacier NP and along the US/Canadian border but most areas
will remain dry. While afternoon temperatures are only slightly
below seasonal averages, the cooler airmass and clearing skies
later Friday night and again Saturday night will allow
temperatures to fall to the 30s at many locations and bring the
risk of frost to some areas. Dry and warmer conditions develop
Sunday as upper level ridging transits the area before breezy
conditions develop with the arrival of the next upper level wave
Sunday night and Monday.

There is some uncertainty still with precipitation associated
with the wave moving through the area Sunday night and Monday, but
this is a fast moving system with current probabilities around
20-30% for showers on Monday. Medium range model ensembles seem
to be in reasonable agreement in the depiction of upper level
ridging building across the western US by the middle of next week,
likely resulting in a return to near and above average temperatures.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  73  48  69  39 /  10   0  10  30
CTB  71  45  62  35 /  10  10  50  40
HLN  74  48  72  40 /  10   0   0  10
BZN  71  42  72  35 /  10   0  10  10
WYS  60  31  63  27 /  10  10  10  20
DLN  68  41  69  34 /   0  10   0   0
HVR  72  47  66  38 /  10  10  20  30
LWT  66  45  66  35 /  20  10  10  20

&&

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

$$

http://www.weather.gov/greatfalls