685
FXUS65 KTFX 130526
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1125 PM MDT Fri Jul 12 2024

UPDATED AVIATION SECTION

.SYNOPSIS...
Expect hot, dry and windy conditions return on Saturday, with the
warm temperatures continuing into Sunday. Additionally, isolated
afternoon and evening thunderstorm activity is forecast for
Saturday in the Havre and Harlem areas.

&&

.UPDATE...
Updated forecast is out. Main adjustment was to add some
thunderstorms to Southwest MT for areas south of I-90 and east of
Dillon. Just general thunderstorms expected, with some storms
producing wind gusts near 30 mph. Most storms will exit our CWA by
Midnight. Otherwise, a windy, hot and dry day is expected over
Southwest MT. Thus the Red Flag Warning will continue. Further
north, there is a chance for a severe storm in the Havre/Harlem
area with the potential supercell that could develop towards
Saturday evening as storms move southeast out of Canada into
North Central MT. Hopefully the storm will not be as strong as the
isolated supercell in the Glasgow area this evening. We will also
have to keep an eye on far Southwest MT on Saturday evening for
the potential of a few storms, especially right near the MT/ID
border. Brusda

&&

.AVIATION...
13/06Z TAF Period

VFR conditions mainly with passing areas of mid-level cloudiness in
a generally dry westerly flow aloft will continue through at least
14/06Z across North Central (KCTB, KHVR), Central (KLWT, KGTF,
KHLN), and Southwest (KBZN, KEKS, KWYS) Montana. However, smoke from
wildfires in the Pacific Northwest will cause hazy conditions across
Southwest Montana, mainly reducing slantwise visibility on approach.
Similar conditions are possible at KHLN due to a wildfire within the
immediate vicinity. Also, temperatures warming into the 90s after
18Z will cause density altitude issues.

A disturbance moving over North Central Montana may bring a
thunderstorm or two to the KHVR terminal area and areas east between
18Z and 00Z, but the current probability for something directly
impacting the terminal is 20 percent, so have left mention out of
the TAF for now. There is a similar probability for a thunderstorm
to impact the KWYS terminal between 18Z and 00Z, so have also kept
mention out of its TAF as well. However, the hot dry air at the
surface will keep precipitation from any storms from reaching the
ground, so indirect impacts from any nearby storm development could
possibly include strong erratic wind gusts.
-Coulston

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

&&

.FIRE WEATHER...
Very warm to hot temperatures and low humidity 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 leads to more widespread gusty westerly
winds, especially across the central Montana fire districts where
deepest mixing is expected. A Red Flag Warning is valid from
Saturday at 2 PM through Saturday and midnight for Fire Weather
Zones 117 and 118.
- RCG/Fogleman

&&

.PREV DISCUSSION...
/ISSUED 300 PM MDT Fri Jul 12 2024/

Today, a cold front entering our region from the north, brings a
northerly wind shift and some relatively cooler temperatures to
the region. Sufficient atmospheric instability exists to allow for
some isolated afternoon and evening thunderstorms. An upper level
trof removes mass from the dominant upper level ridge, favoring a
tighter upper level height gradient with some gusty surface winds
at times, for the weekend ahead. Considering tomorrow`s hot, dry
and windy conditions, a Red Flag Warning has been issued for
portions of central and southwest Montana, valid from tomorrow
afternoon through tomorrow evening. For the most current Fire
Weather Discussion, please, scroll down toward the bottom of this
document.
 - Fogleman

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  58  95  58  94 /   0   0   0   0
CTB  55  90  55  88 /   0   0   0   0
HLN  60 100  61  98 /   0   0   0   0
BZN  55  97  58  96 /  20  10   0   0
WYS  44  87  47  85 /  20  20  10  10
DLN  54  94  57  91 /  10   0   0  10
HVR  60  93  59  91 /   0  20   0   0
LWT  57  91  57  89 /  10  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 2 PM Saturday to midnight MDT Saturday
night for Central and Eastern Lewis and Clark National Forest
Areas.

Red Flag Warning from 2 PM Saturday to midnight MDT Saturday
night for Helena and Townsend Ranger Districts of the Helena
National Forest.

&&

$$

http://www.weather.gov/greatfalls