542
FXUS65 KTFX 190238
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
838 PM MDT Sat May 18 2024

.UPDATE...

An upper level trough encompasses much of SW Canada extending
into the NW US with somewhat moist and unstable westerly flow
across the Northern Rockies and MT leading to the development of
widely scattered showers earlier today. These showers will
continue to decrease through the rest of this evening as the
atmosphere stabilizes. The next disturbance moving through the
upper level trough will arrive in western MT later tonight with an
area of more widespread precipitation developing over western
portions of central MT early Sunday morning. Incoming model
guidance supports this area of precipitation as more of a
frontogenetic feature (focused band of rain/mountain snow) that
propagates east across central MT from roughly Helena to Lewistown
Sunday morning before precipitation becomes more showery Sunday
afternoon. Hoenisch

&&

.SYNOPSIS...
Light rain showers will affect the Cut Bank and Havre areas
overnight tonight, while rain and snow showers become more
widespread on Sunday across Central and Southwest MT. Expect
showers early in the week, with a better chance for widespread
rain and mountain snow by the middle of the work week. Overall,
temperatures will generally be below normal across the area
through the upcoming week.

&&

.AVIATION...
19/00Z TAF Period

Area remains under a somewhat moist/unstable westerly flow aloft
with widely scattered showers tracking east across the northern tier
of the state while more isolated activity exists elsewhere early
this evening. These showers may affect KCTB and KHVR through 04z
with a brief period lower VFR (>3000ft) ceilings and some very
isolated lightning cannot be ruled out as well. Otherwise, VFR
conditions prevail through most of tonight, but mid-level clouds
increase with some increase in showers across portions of central
and southwest MT later tonight. A weather disturbance embedded
within the westerly flow moves into the region Sunday morning with
showers becoming more widespread across central and southwest MT.
While VFR conditions generally prevail, periods of MVFR conditions
and more widespread mountain obscuration can be expected on Sunday.
Surface winds decrease across much of the area tonight with a return
to west/northwesterly winds at most terminals by Sunday afternoon.
Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 555 PM MDT Sat May 18 2024/
Tonight through Sunday...Scattered light rain showers will affect
the Hi-line area tonight, with a rumble of thunder also possible.
On Sunday, the precipitation becomes a bit more widespread over
Central and Southwest MT. Snow levels will fall to about 3500 feet
on Sunday morning. Any snow accumulations will be in the mountain,
mostly above 7000 feet. Since most areas will receive less than 2
inches of snow, and the snowfall will occur during the day, no
winter highlights are planned for at this time. Afternoon
temperatures will continue the cooling trend on Sunday as well.

Monday and Tuesday...An upper level trof will be trying to develop
over MT early next week. This will result in unsettled conditions
and the chances for light showers to continue Mon/Tue.
Temperatures will warm a touch each day Mon/Tue.

Wednesday through Saturday...There is the potential for another
spring storm to affect a good portion of the CWA next Wed/Thu.
Some forecast models prog over 1 inch of QPF over the Southern
Rocky Mountain Front and Central Montana during this period.
However, the latest NBM only has a 20 percent chance of 1 inch of
rainfall in these areas. It does look like it will be cold enough
for snow as well, mostly above 6500 feet. Snow accumulations could
approach 10 inches or snow near the peaks, and a winter highlight
might be needed for portions of the CWA. As we go into Memorial
Day weekend next weekend, there is some uncertainty of how
widespread the precipitation will be, but it is looking likely
that showers will be affecting portions of the CWA next weekend.
Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  40  56  35  59 /  20  80  40  60
CTB  32  55  34  57 /  10  80  30  60
HLN  42  58  37  61 /  50  60  20  60
BZN  36  54  33  57 /  10  70  30  70
WYS  35  53  26  50 /  20  40  20  60
DLN  35  53  32  55 /  10  40  20  50
HVR  38  60  38  60 /  20  70  20  40
LWT  37  52  32  54 /  30  80  30  60

&&

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

$$

http://www.weather.gov/greatfalls