National Weather Service National Headquarters

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

000
FXUS65 KTFX 292000
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
200 PM MDT Mon May 29 2023

.SYNOPSIS...

Isolated to numerous showers and thunderstorms are continue
across much of North-central, Central, and Southwest Montana;
however, precipitation with any shower or thunderstorm will be
brief and limited to a few hundredths of an inch. Tuesday and
Wednesday will be on the drier side, though a few isolated
showers remain possible, becoming more widespread toward the
latter end of the week. Afternoon temperatures trend above
seasonal averages today.

&&

.DISCUSSION...

Rest of Today through Tuesday...Zonal flow across the Treasure State
comes to an end as an upper-level trough from the Gulf of Alaska
deepens southward parallel to the Pacific Northwest within the next
couple days. This will shift the westerly flow aloft to a more
southwesterly flow, indicative of more showers and possible
thunderstorms later this week. Below the zonal flow, expect isolated
to numerous showers and thunderstorms to develop during the
afternoon hours, predominately across Southwest Montana, but showers
may develop across portions of North-central Montana as well.
Generally light precipitation is expected from these showers,
amounting to a few hundredths of an inch; however, localized heavy
rainfall remains possible with these storms with precipitation
amounts upwards of 0.25" cannot be ruled out. That being said,
latest probabilistic guidance limits this to Southwest Montana,
where the most robust cells are likely to develop, with only a 25-
30% probability of occurrence. Tuesday will be very similar, with
shower and thunderstorm development mainly across Southwest
Montana. All in all, much like the past week, a rinse, lather, and
repeat approach can be taken for the next several days with
regards to showers and thunderstorms.

WPC continues to place North-central, Central, and Southwest Montana
in a Marginal Risk for Excessive Rainfall, meaning there`s a 5%
probability of low-lying areas and areas of poor drainage to
experience flooding opportunities. However, by the latter end of the
week, that increases to a Slight Risk, or a 15% probability, meaning
in addition to low-lying areas, areas of flooding are more likely,
and something to keep watch on as the week progresses.

Afternoon temperatures continue to trend slightly warmer than
seasonal averages, with many locations above 70 degrees and some
locations in North-central Montana exceeding 80 degrees. CPC
continues to depict a 60 to 80% likely above normal through the
first week of June. - Pierce

Wednesday through next Monday...both cluster and deterministic
guidance depict longwave troughing developing across the Western
CONUS to begin the period and persisting through the first half of
the upcoming weekend, with embedded shortwaves lifting east
northeast and over the Northern Rockies and High Plains. This
southwest flow pattern will help to transport anomalously (1.5 to
2.5 standard deviations) high PWATs northeastward and across the
Northern Rockies over this timeframe, leading to the potential for
widespread rain/showers and thunderstorms across Southwest through
North Central Montana from Wednesday through Saturday. ECMWF EFI QPF
values even begin to approach 0.8 (across eastern portions of
Southwest through North Central) from Thursday evening through
Friday evening, suggesting the potential for some instances of
excessive rainfall. While some uncertainty does begin to arise from
late Thursday onwards on the position and/or timing of the longwave
trough over the Eastern Pacific and western seaboard, confidence
remains high in daily chances for precipitation across Southwest
through North Central Montana for much of the timeframe, with above
normal temperatures on Wednesday falling back to or slightly below
normal for the remainder of the work week and through the weekend. -
Moldan

&&

.AVIATION...
1145 AM MDT Mon May 29 2023 (29/18Z TAF Period)

Expect mainly VFR conditions today as a quieter weather pattern
develops over the area. Main concern will be a few isolated SHRA,
especially along the MT-ID border. Any showers will die off
overnight, and some fog may redevelop near KWYS. Ludwig

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  78  51  76 /  10  10  10  70
CTB  47  78  47  78 /  10   0   0  40
HLN  52  78  54  78 /  10  30  30  80
BZN  46  76  47  75 /  30  50  30  70
WYS  36  67  35  70 /  40  80  40  50
DLN  45  73  46  72 /  40  60  50  70
HVR  53  81  52  83 /  40   0   0  50
LWT  49  74  51  75 /  30  30  20  70

&&

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

$$

http://www.weather.gov/greatfalls