Wildfire in Montana, August 4 to 9, 2022

Area Forecast Discussion
National Weather Service Great Falls MT
1043 PM MDT Wed Aug 3 2022

...Aviation Section Updated...

.SYNOPSIS...

Hot, dry, and windy conditions will continue across the Northern
Rockies through Thursday. Isolated to scattered showers and
thunderstorms will be possible over far southwest Montana
adjacent to the Idaho border today, with better coverage of
showers and storms further north and east across southwest and
central Montana Thursday.

&&

.UPDATE...

Main adjustment to the forecast was done to Southwest Montana.
Only very isolated showers/thunderstorms developed along the Idaho
border this evening; the only one that seems to remain will further
weaken and move east out of the West Yellowstone area through 10 pm.
However, with yesterday's rain, and any possible rain this evening,
the evening dewpoint of around 45 degrees there may translate into
areas of fog later tonight, as temperatures are expected to fall
into that range. Otherwise, what little cloud cover there is as of
825 pm should mostly diminish by midnight.

Increasing mid level winds with a passing disturbance are still on
tap for Thursday, so will leave the High Wind and Fire Weather
highlights as is for now. There is also a potential for strong to
possibly severe storms in Southwest Montana Thursday afternoon and
evening with the passage of the disturbance, with the main hazard
being strong gusty winds due to a continued warm and dry airmass
near the surface.
-Coulston

&&

.AVIATION...
1043 PM MDT Wed Aug 3 2022 (04/06Z TAF period)

VFR conditions are predominately expected throughout the 0406/0506
TAF period; however, there is a chance that patchy fog develops in
the Hebgen and West Yellowstone valleys near sunrise on Thursday,
bringing CIGS/VIS below VFR. Any fog, if it does develop, is
expected to burn off between 13-15z. Otherwise, scattered to
numerous showers and thunderstorms are expected to develop over
Southwest Montana/Northeast Idaho between 15-18z, lifting to the
northeast over eastern portions of Central and North Central Montana
through 00-06z Friday. Can't rule a brief period of MVFR conditions
beneath the stronger showers/storms, with the main impact to
terminal operations being gusty and erratic winds. Westerly surface
winds will also be on the increase, especially over the plains of
Central and North Central Montana from Thursday afternoon and
through the early evening hours. Mountain wave turbulence is likely
along the Rocky Mountain Front for much of the day on Thursday. -
Moldan

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

&&

.FIRE WEATHER...

A Red Flag Warning remains in effect until 9 PM Thursday across
all TFX fire weather zones. Windy, dry, and warm conditions are
expected each afternoon through Thursday evening, which in
combination with receptive fuels, would make any fire starts
difficult to put out. Cooler temperatures and lighter winds are
expected Friday and Saturday.

Upper ridging builds back over the area this weekend into Monday,
but models appear in good agreement with a ridge breakdown
sometime around the middle of next week as an upper trough moves
into the Pacific Northwest, with timing ranging from as early as
Tuesday to as late as Thursday of next week. This is a known fire
weather watchout for winds and thunderstorm activity in the
Northern Rockies region. Stay tuned.

&&

.PREV DISCUSSION...
/ISSUED 605 PM MDT Wed Aug 3 2022/

Rest of this Afternoon through Thursday night...

Flat ridging over the state will begin to push east as as a
large- scale upper trough with attendant mid-level jet streak
approaches the Northern Rockies from the northwest by Thursday
morning. This feature resembles a typical wintertime upper trough
and jet streak, but for the first week of August this is an
anomalous feature. The result will be high winds and extreme fire
danger developing Thursday morning along the Rocky Mountain Front,
and then expanding northeast across northwestern parts of north-
central Montana Thursday afternoon into early evening. For this
reason all fire weather zones remain under a Red Flag Warning
through Thursday evening. Finally, monsoonal moisture rotating
around the H500 high over the Great Basin/Desert Southwest and
across portions of the Northern Rockies is expected to lead to
isolated to scattered shower/thunderstorm chances today (mainly
over extreme Southwest Montana adjacent to the Idaho border) and
into the overnight hours tonight, with scattered to numerous
showers/thunderstorms expected on Thursday over Southwest and
eastern portions of Central and North Central Montana. Primary
concern with any shower/storm will be the potential for gusty and
erratic wind gusts given inverted-v profiles. SPC has issued a
Marginal Risk for parts of our southwest and central Montana
zones for Thursday afternoon and early evening.

Friday through next Wednesday...

High temperatures are expected to cool to near or below normal
for Friday and Saturday across the Northern Rockies in wake of a
Pacific cold front. In addition, winds will be significantly
lighter (especially on Saturday) and afternoon relative humidity
values higher (generally 15-30%). Showers and thunderstorms will
also be possible on Friday and Saturday, mainly southeast of a
Havre-Great Falls-Lincoln line, with the best coverage of showers
and thunderstorms over eastern portions of Southwest Montana (i.e.
Bozeman, Ennis, and West Yellowstone Areas). Upper level ridging
begins to build back in over the Western United States and Canada
on Sunday, amplifying into early next week. This will once again
bring a return of hot conditions to all of Southwest through North
Central Montana, with widespread readings in the 90s to low 100s.
Though there are timing issues, about 90 percent of ensemble
model members do break the ridge down at least somewhat toward
the middle of next week, which may bring renewed fire weather
concerns. -CC/Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  95  52  81 /   0  10  10  10
CTB  58  83  48  73 /   0   0   0  10
HLN  61  96  57  86 /   0  20  20  20
BZN  56  95  55  86 /  10  40  40  40
WYS  44  81  47  73 /  20  40  50  70
DLN  53  88  52  83 /   0  40  20  40
HVR  63  95  53  79 /   0  10  10   0
LWT  57  93  54  79 /   0  40  40  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT Thursday Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Gallatin National Forest...Helena and Townsend Ranger
Districts of the Helena National Forest...Hill and Blaine
Counties...Lincoln Ranger District of the Helena National Forest.

High Wind Warning from noon to 9 PM MDT Thursday Eastern
Glacier...Eastern Pondera...Liberty...Toole.

Red Flag Warning until 9 PM MDT Thursday Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Lewis and Clark
National Forest Rocky Mountain District-Rocky Mountain Front.

Red Flag Warning from noon to 9 PM MDT Thursday
Deerlodge/Western Beaverhead National Forest...Eastern
Beaverhead National Forest.

High Wind Warning from 6 AM to 9 PM MDT Thursday Northern Rocky
Mountain Front...Southern Rocky Mountain Front.

&&

http://www.weather.gov/greatfalls