502
FXUS65 KTFX 121126 CCA
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
530 AM MDT Sun May 12 2024

.SYNOPSIS...

Above normal temperatures will continue through Monday across all
of the Northern Rockies, with increasing westerly winds on Monday
as a Pacific front sweeps eastward across the region. This front
will also bring more widespread chances for showers and even a few
thunderstorms on Monday afternoon and evening, with better
chances for rain on Tuesday across portions of the region.

&&

.DISCUSSION...

Today through Monday...above normal temperatures will prevail
throughout the period, with temperatures ranging from the 70s to low
80s across lower elevations. Morning showers over eastern portions
of North Central Montana will gradually depart to the east through
the mid-morning hours today, with additional showers and even a few
thunderstorms developing this afternoon along and northeast of a
Kings Hill Pass, to Great Falls, to Sweet Grass line. With "drier"
air in the low to mid-levels (i.e. inverted-V soundings) this
afternoon and evening, any initial shower or thunderstorm will be
capable of producing gusty and erratic winds. By tonight a shortwave
and associated Pacific front will begin to move from over the
Pacific Northwest and towards the Northern Rockies. This shortwave
and Pacific front will then move over/across the Northern Rockies
during the afternoon/evening hours on Monday, leading to additional
chances for showers and thunderstorms across all of Southwest
through North Central Montana. In addition to increasing
precipitation chances, westerly surface winds will be on the
increase across all of Southwest through North Central Montana with
and behind the passage of the Pacific front. While probabilistic
data does not support the threat for High Winds on Monday
afternoon/evening, wind gusts of between 30-40kts will be common
across most locations.

Tuesday...ensemble clusters all favor a secondary shortwave diving
southeast over the Northern Rockies through Tuesday night, with some
uncertainty in the amplitude of the shortwave as it digs from
Western Montana/Idaho towards the Central Rockies. NBM probabilistic
gives areas along and southeast of a Cut Bank to Lewistown line, and
northeast of a Butte to West Yellowstone line, a 40-80% chance for
24hr (12z Tuesday to 12z Wednesday) precipitation amounts to
exceeding 0.10", with generally between a 20-50% chance for amounts
to exceed 0.25". While this precipitation will be beneficial for
many lower elevations, the rain falling on top an already rotting
snowpack across Central Montana mountains will lead to additional
runoff into area creeks and streams. High temperatures on Tuesday in
wake of Monday`s Pacific front will fall back below normal after
several days of above normal temperatures, with readings in the 60s
across lower elevations.

Wednesday through next Sunday...an active and unsettled pattern is
expected through the remainder of the work week and into the
upcoming weekend as quasi zonal to northwesterly flow develops over
the Northern Rockies through much of the period. While the multi-
model ensemble mean favors this pattern there is still a degree of
uncertainty with respect to the amplitude of the ridge over the
Eastern Pacific and trough over the center of the CONUS/Canada,
especially from Thursday onwards, which will have a big impact on
how warm/cool temperatures end up being across Southwest through
North Central Montana over this timeframe. Daily chances for showers
and thunderstorms will be favored across the entire CWA within this
quasi zonal to northwesterly flow regime; however, daily
precipitation values will largely remain below 0.10" where
precipitation is observed. - Moldan

&&

.AVIATION...
12/12Z TAF Period

VFR and MVFR conditions are expected today, as some smoke from
Canadian wildfires pushes into North Central Montana. Smoke will be
most noticeable along the US 2 corridor, with KCTB and KHVR being the
most impacted with periods of visibility at or below 3SM at times.
KLWT and KGTF will see some reductions, but should remain VFR for
the most part. Watch for a few TSRA around KLWT this afternoon,
otherwise expect dry conditions today. Ludwig

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

&&

.HYDROLOGY...

The Flood Warning for Clear Creek has been cancelled as water
levels have finally fallen below minor flood stage as of early
this (Sunday) morning. Water levels on Clear Creek will continue
to slowly fall to below action stage through Monday afternoon.

The Flood Watch for the Bears Paw Mountains has also been
cancelled this morning given no recent reports of flooding across
the watch area. With this being said, the Big Sandy Creek gage near
Havre (which is outside of the Bears Paw Mountain zone) was
approaching Action Stage as of this morning. We will continue to
monitor this gage through the remainder of the morning and act
accordingly should water levels rise further through Action Stage
towards Minor Flood Stage. - Moldan

The flood watch continues for the mountain ranges of Central
Montana. No new flood impacts have been reported over the past
12-24 hours. This is good news, as this means the runoff is
coming off slowly or the runoff is soaking into the ground. In
either case, if this trend continues, this flood watch could also
be cancelled early. Brusda/Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  78  49  78  49 /  20  10  20  40
CTB  78  48  77  47 /  10  10  30  60
HLN  80  49  78  49 /   0   0  20  20
BZN  76  45  74  42 /   0  10  40  30
WYS  68  36  64  34 /  10  20  70  40
DLN  75  46  72  42 /   0  10  30  20
HVR  75  49  78  50 /  20  50  40  50
LWT  70  46  72  47 /  40  50  30  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday morning for Cascade County below
5000ft-Fergus County below 4500ft-Judith Basin County and Judith
Gap-Little Belt and Highwood Mountains-Meagher County Valleys-
Snowy and Judith Mountains-Western and Central Chouteau County.

&&

$$

http://www.weather.gov/greatfalls