629
FXUS65 KTFX 120957
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
357 AM MDT Fri Jul 12 2024

.SYNOPSIS...

The extended period of very warm to hot and dry weather will
persist through the weekend into next week. Weak weather systems
will maintain breezy to windy conditions at times and there will
be a daily slight chance for shower and thunderstorm activity with
little to no rainfall.

&&

.DISCUSSION...

A weak cold front is approaching the Canadian border and will
slowly continue southward throughout the day and bring a northerly
wind shift and slightly cooler temperatures, most notably over
the plains. Passing shortwave disturbances will dampen the upper
level ridge some through Sunday, resulting in breezy to windy
conditions at times while moisture aloft combined with diurnal
instability maintains slight chances of mostly afternoon and
evening showers and thunderstorms. The primary thunderstorm
concerns will generally be gusty and erratic winds and a few
lightning strikes in the presence of little or no rainfall.

Saturday looks to be the most active day weatherwise with breezy
to windy and dry conditions expected for most locations. There
will also be a bit more instability and moisture for a few
stronger thunderstorms, mostly over Hill and Blaine Counties.
Forecast soundings are starting to show longer hodographs
favorable for at least a short opportunity for marginally severe
weather Saturday afternoon. Otherwise, the focus will mostly be on
the gusty winds and potential red flag conditions over Southwest
and portions of Central Montana where fuels are the driest and
fire activity is already being observed. Many of these locations
have over a 70% chance for 20 mph sustained winds and a 30 to 50%
chance for wind gusts over 40 mph. This in combination with
expected RHs in the lower teens continues to warrant the Fire
Weather Watch already in place. I continued to hold off on adding
fire zone 117 to the watch area with it looking to be a shorter
period of gusty winds and lower RHs, though this area will still
need to be monitored by upcoming shifts for any changes.

Winds diminish Saturday night before picking up once again on
Sunday as another shortwave moves from the northwest. While winds
will be on the gustier side throughout the entire forecast area,
winds don`t appear to be quite as strong for as long of a period
of time over the southwest and northern areas will see slightly
cooler temperatures and higher RHs move in by the afternoon hours.


Lighter winds are expected for much of next week as westerly flow
weakens and the ridge begins to slowly become more amplified.
Still weak perturbations moving within the ridge look to maintain
daily isolated shower and thunder activity. Temperatures will
mostly stay in the upper 80s and lower 90s until the end of the
week when peak amplification of the ridge pushes temperatures back
into the 90s to near 100 again. - RCG

&&

.AVIATION...
12/06Z TAF Period

VFR conditions will generally prevail across all terminals during
this TAF period; however, there will be periods of hazy conditions,
from regional wildfires, impacting slantwise visibility during
ascent and descent. A weak cold front crosses the Canadian border
around 12/12Z and then slowly moves southward during the day on
Friday with a northerly wind shift being the most noticeable impact.
Another round of isolated shower and thunderstorm activity is
expected Friday afternoon and evening, mostly along and south of
I90. - RCG

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

&&

.FIRE WEATHER...

Very warm to hot temperatures and low humidity will continue to
rapidly dry fuels and increase fire danger across the area with
several fire weather concerns over the next several days. In
addition to the heat and dryness, localized gusty and erratic
winds are possible near any high-based showers and isolated
thunderstorms along with occasional lightning strikes.

On Saturday the combination of deep afternoon mixing and stronger
westerly flow aloft may lead to more widespread gusty westerly
winds, especially across the Central Montana fire districts where
deepest mixing is expected. A Fire Weather Watch remains in effect
Saturday afternoon and early evening for fire weather zone 118.
- RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  90  59  95  58 /   0   0   0   0
CTB  85  56  90  55 /   0   0  10   0
HLN  98  62 100  61 /   0  10   0   0
BZN  96  56  97  58 /  10  20   0   0
WYS  86  44  87  47 /  20  20  10   0
DLN  93  54  94  57 /  10  20   0   0
HVR  91  60  93  59 /  20  10  20   0
LWT  87  58  91  57 /   0  10  20   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday afternoon through Saturday
evening for Helena and Townsend Ranger Districts of the Helena
National Forest.

&&

$$

http://www.weather.gov/greatfalls