827
FXUS65 KTFX 262022
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
222 PM MDT Sun May 26 2024

.SYNOPSIS...

Showers and isolated thunderstorms associated with a weather
disturbance moving east along the Canadian border will diminish
this evening as the disturbance exits the area. Winds diminish
tonight as high pressure builds across the Northern Rockies and
brings dry conditions with warming temperatures through Tuesday.
The next weather system moves into the region Tuesday night and
Wednesday with a risk for some strong Thunderstorms Tuesday
evening and Wednesday along with cooler temperatures for the
second half of the work week.

&&

.DISCUSSION...

A compact shortwave disturbance will continue to track east
across the Hi-line/Canadian border region this afternoon with
numerous showers and a few isolated thunderstorms in its vicinity
but only isolated showers further south across the central and
southwest MT mountains. These should diminish fairly quickly this
evening as the disturbance moves off to the the east with clearing
skies across most areas overnight as upper level ridging builds
across the Northern Rockies. Gusty west winds across much of the
area this afternoon will decrease tonight as well, beginning early
this evening across southwest MT with a more gradual decrease
through the overnight period further north across the Plains.

The upper level ridge axis shifts east across the State Monday
and Tuesday for a mainly dry period with temperatures climbing
above seasonal averages Monday and likely to the warmest levels so
far this season on Tuesday.

Probability of Max Temperatures 80F or Warmer Tuesday:

Cut Bank    80%
Havre       90%
Great Falls 90%
Lewistown   45%
Helena      95%
Bozeman     90%
Dillon      30%

By late Tuesday, southwest flow aloft behind the departing upper
level ridge will begin to import moisture into the region ahead of a
cold front associated with the next upper level trough moving into
the Northwest US. The cold front and upper level trough continue
east across north-central and southwest MT Tuesday night through
Wednesday with cooler and windy conditions likely across the area by
Wednesday afternoon. Thunderstorm development is likely across
Idaho and western MT late Tuesday afternoon ahead of the cold front,
translating east of the continental divide Tuesday evening. There is
a marginal (5%) risk for severe thunderstorms Tuesday evening across
western portions of north-central and much of central/SW MT with
primary threat being strong winds. There is some spread among models
in the timing of the cold front however, which will be key to the
risk of strong to severe thunderstorms late Tuesday and potentially
again on Wednesday for eastern portions of central and southwest MT.
Hoenisch

Thursday through next Sunday... On Thursday the upper-level trough
remains in place over North-central, Central, and Southwestern
Montana. Showers and thunderstorms are possible across the area on
Thursday. The thunderstorms will not be severe. On Thursday there is
a 20 - 40% chance for locations across North-central, Central, and
Southwestern Montana receiving a tenth of an inch of rain (total
liquid for mountain locations) or more. On Thursday for the
mountains of North-central, Central and Southwestern Montana there
is 40 - 60% chance for receiving a tenth of an inch of snow or more.
On Friday clusters indicate that an upper-level trough remains in
place over North-central, Central, and Southwestern Montana which
will keep unsettled weather in place for the area on Friday. On
Saturday two clusters (66% of ensemble members) have an upper-level
ridge in place over North-central, Central, and Southwestern
Montana. The other two clusters (44% of ensemble members) have the
upper-level trough remain in place over the area on Saturday. This
indicates uncertainty in the weather for Saturday at this time. Next
Sunday three clusters (80% of ensemble members) have an upper-level
ridge over North-central, Central, and Southwestern Montana. Next
Sunday one cluster (20% of ensemble members) has the upper-level
trough remaining over the area. This indicates that by Sunday the
weather pattern will most likely change to have warm and calm
weather for North-central, Central, and Southwestern Montana. -IG

&&

.AVIATION...
26/18Z TAF Period

VFR conditions are expected to prevail through the TAF period.

Windy conditions will be the immediate concern across all terminals
for the first half of the TAF period. The highest gusts up to 40 kts
are expected at KCTB with both KGTF and KHVR having gusts as high as
35 kts possible. Winds are expected to decrease after 27/04Z as the
shortwave trough exits the region.

The only other concern will be a minor chance for thunderstorms in
the vicinity of KHVR between 26/22Z and 27/03Z. Gusty and erratic
winds may accompany stronger showers and there is a slight chance of
pea-sized hail along portions of the hi-line east of KHVR this
afternoon.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  40  72  45  82 /   0   0   0  10
CTB  39  69  42  79 /   0   0   0  10
HLN  43  75  48  84 /   0   0   0  20
BZN  36  70  41  80 /   0   0   0  10
WYS  30  64  33  71 /  10   0   0   0
DLN  37  71  42  78 /   0   0   0  10
HVR  43  73  44  83 /  30   0   0   0
LWT  37  66  42  77 /   0   0   0   0

&&

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

$$

http://www.weather.gov/greatfalls