886
FXUS65 KTFX 110455
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1055 PM MDT Fri May 10 2024

.SYNOPSIS...

Upper level ridging will result in above average temperatures
across the region this weekend. Weak disturbances moving through the
ridge will result in isolated showers and perhaps a few
thunderstorms in the afternoon this weekend, mainly near terrain and
across North-central Montana. Flooding concerns will remain in areas
where significant snowmelt is occurring.

&&

.UPDATE...

No major changes were made to the going forecast with this update.

In space weather news, we`ve hit the G5 geomagnetic storm level
for the first time since October 2003. Aurora viewing across
north-central, central, and southwestern Montana is on track to
be spectacular this evening with the best chances expected between
sunset and 3 AM. High clouds are still unfortunately expected to
come down out of the north and hamper some viewing efforts
particularly along the hi-line. These clouds will start to move in
after 10 PM and make for partly cloudy skies by 3 AM across
portions of north-central Montana. The Space Weather Prediction
Center currently expects this geomagnetic storm to last through
much of the weekend. So in terms of cloud cover, Saturday night
into Sunday morning will be most cloudy across much of north-
central and central Montana with some clearing possible in
southwestern Montana. And Sunday night into Monday morning,
clouds will start to clear for north-central and central Montana
after midnight while southwestern Montana will deal with partly to
mostly cloudy skies through the night.

-thor

&&

.AVIATION...
1055 PM MDT Fri May 10 2024 (11/06Z TAF Period)

Outside of some passing upper level clouds, which will not restrict
mountain visibility, VFR conditions will prevail throughout the
1106/1206 TAF period. - Moldan

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

&&

.HYDROLOGY...
A Flood Warning remains in effect for Clear Creek in North Central
Montana through Saturday morning, with water levels expected to
slowly fall from minor flood stage to action stage over this
timeframe. Additionally, a Flood Watch remains in effect for the
nearby Bears Paw Mountains from this afternoon through the weekend
as warming temperatures and subsequent snowmelt runoff, and
remaining runoff from rainwater, could push creeks and streams out
of their banks.

Further south across the Island Ranges of Central Montana (i.e.
Highwood, Moccasin, Judith, Little Belt, and Snowy), increased
snowmelt and subsequent runoff into creeks and streams is expected
from Saturday through Monday as overnight temperatures and dewpoint
temperatures remain above freezing. This runoff could result in
waterways nearing bankful by Saturday night/Sunday morning. Hence,
a Flood Watch has been issued for the Little Belts eastward
toward the Lewistown area. - Moldan/AM

&&

.PREV DISCUSSION...
/ISSUED 535 PM MDT Fri May 10 2024/

Through Sunday... An upper level ridge will slowly shift eastward
from the west coast toward the central CONUS this weekend, allowing
for temperatures to climb back above average in most areas. Although
temperatures will warm at the surface, a relatively cool
northwesterly flow will be in place aloft. This will combine with a
weak disturbance to result in isolated to widely scattered showers
and thunderstorms, primarily across North-central Montana, late
Saturday evening into Sunday. Isolated afternoon showers will be
around near terrain this weekend, but the probability of these at
any one location is quite low at this point. -AM

Monday through Tuesday...Ensemble clusters are in relatively good
agreement with a shortwave within initially zonal flow, and an
associated Pacific front, digging east/southwest and over/across the
Northern Rockies during the period. High temperatures ahead of the
shortwave and Pacific front on Monday will once again warm well
above normal and into the 70s, but fall back below normal and into
the 60s on Tuesday. Surface winds will be on the increase through
the morning hours on Monday ahead of the aforementioned Pacific
front, becoming breezy and gusty during the afternoon and evening
hours on Monday. While the latest NBM probabilistic data does not
support high winds materializing over this timeframe; most lower
elevations across Southwest through North Central Montana have
between a 20-50% chance of seeing wind gusts in excess of 35kts.
Light precipitation is also expected to accompany and follow the
passage of the Pacific front Monday afternoon/night, lingering into
the day on Tuesday as the upper level disturbance digs into the
Central Rockies. While widespread, heavy precipitation is not
expected over this timeframe, NBM probabilistic data does support
between a 40-70% chance for QPF amounts to reach or exceed 0.10"
across most of Southwest through North Central Montana.

Wednesday through next Friday...ensemble clusters diverge
drastically throughout the period, with the main difference between
the clusters being the timing of shortwave ridging and troughing.
The multi-model ensemble favors a more zonal pattern, with
temperatures near normal and daily chances for showers. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  78  45  79 /   0   0  20  20
CTB  45  78  44  79 /   0  10  20  20
HLN  42  79  50  81 /   0   0   0   0
BZN  34  75  43  77 /   0   0   0  10
WYS  29  67  34  69 /   0  10   0  10
DLN  37  73  42  76 /   0   0   0   0
HVR  46  79  47  77 /   0   0  40  20
LWT  40  72  44  71 /   0   0  30  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for Bears Paw Mountains and
Southern Blaine.

Flood Watch from Saturday afternoon 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