National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KTFX 060500
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1100 PM MDT Wed May 5 2021

...UPDATED AVIATION SECTION...

.SYNOPSIS...
Skies clear overnight. Warm, dry, and breezy conditions can be
expected for Thursday, with many locations observing afternoon highs
well into the 70s. Rain showers and a few thunderstorms are expected
Friday with a passing cold front. Areas of steady rain then develop
later Friday and continue overnight into Saturday. Snow levels drop
below 5000 feet by Saturday morning. Cool weather continues with
periods of rain and mountain snow through early next week.

&&

.UPDATE...
Updated forecast is out. Overall current forecast is on track.
Only adjustment this evening was to sky cover, as high clouds
increase from the northwest. Showers/thunderstorms have moved
eastward into eastern MT, and we should remain dry in our area for
the rest of today and most of Thursday.

Looking ahead, main concerns are the cold front Friday, resulting
in the potential for a few strong storms and brief heavy
rainfall. There is the potential a squall line could move over the
Bridger burn area, and a flash flood watch might be needed for
that burn area. With the main front pushing eastward Friday night,
then we will have to see how the wrap around precipitation
develops later on Saturday/into Sunday. Still several different
solutions on precipitation amounts from Saturday afternoon thru
Sunday, from very light amounts to over an inch in some areas,
with snow possible at times at all elevations as well. Brusda

&&

.AVIATION...
1100 PM MDT Wed May 5 2021 (06/06Z TAF period)

VFR conditions will continue over north central and southwest
Montana through at least the next 24 hours. A high pressure ridge
will move over the area with scattered to broken high level
cloudiness. Winds will mostly remain light, but southerly winds
could gust to 25 kt in some areas between 18Z and 00Z. -Coulston

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

&&

.PREV DISCUSSION...
/ISSUED 545 PM MDT Wed May 5 2021/
Satellite imagery reveals low level moisture wrapping around an
upper level low presently located near Medicine Hat, Alberta.
Scattered showers and thunderstorms are ongoing across portions of
Eastern Montana, with only a few scattered light rain showers
occurring under the weakly unstable northwesterly flow across
North-central Montana. Model guidance indicates the upstream ridge
to our west will advance eastward overnight into Thursday,
providing mostly clear skies across the region except for high
clouds streaming over the ridge. Minimum relative humidity values
Thursday afternoon will likely drop near, to below 20 percent, as
south to southeasterly breezes gust up to 25 mph at times in the
afternoon. The fair weather ridge moves away to the east on
Thursday night, setting the stage for a period of cooler and
wetter weather through the weekend ahead.

Friday...A deep Pacific trough and attendant cold front
approaches, which will usher in an increasingly moist and unstable
southwesterly flow aloft to the forecast area. This will lead to
cooler temperatures and a good chance for widespread showers and
some thunderstorm development for most areas. The timing of the
frontal passage will play a key role in determining thunderstorm
strength and coverage, as will the extent of high and middle level
cloudiness streaming ahead of the system. Ensemble guidance
suggests that precipitable water values may rise as high as 3 to 4
standard deviations above climatology, which could add a threat
for brief heavy downpours in addition to gusty winds and small
hail. By Friday evening the thunderstorm threat diminishes as
showers and general rains become more prevalent. Widespread
Rainfall amounts of .25 to 1 inch are possible Friday and Friday
night, with the heaviest activity over the southeastern two thirds
of the CWA. Area rivers and streams will be monitored as will
fire scars, including the Bridger Foothills scar. Snow levels
begin drop Friday night as colder air filters in behind the cold
front and snow will begin falling over mountain areas. However
impacts should remain above pass level.

Saturday and Sunday...Forecast guidance generally agrees with the
low pressure center of the trough remaining quasi-stationary over
the region, producing periods of rain and mountain snow through
Monday. However, details in position and strength of the low
remain unresolved. Confidence for this period is low to moderate
for timing and location of precipitation, but still expect an
unsettled overall showery and cool weekend, with impacts likely
for outdoor recreation due to periodic mountain snow and ongoing
cool wet conditions.

Monday through next Wednesday...Another round of showers is
likely on Monday as the aforementioned trough continues to exert
an influence on the region`s weather. Temperatures will remain
below average, with highs mostly in the 40s and 50s and lows in
the 30s. By Tuesday, the trough finally begins to lift out of the
area but an unsettled west to northwest flow aloft will likely
keep temperatures slightly below average, along with a day to day
slight chance for showers. -RCG/PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  36  74  46  65 /   0   0  10  70
CTB  35  69  43  60 /   0   0   0  40
HLN  39  79  49  66 /   0   0  10  80
BZN  33  77  43  70 /   0   0  10  90
WYS  23  70  32  66 /   0   0   0  60
DLN  35  77  46  66 /   0   0  10  80
HVR  34  70  46  68 /   0   0   0  50
LWT  33  69  43  67 /   0   0   0  60

&&

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

&&

$$

http://www.weather.gov/greatfalls