Drought in Montana, September 6 to 30, 2022

Area Forecast Discussion
National Weather Service Glasgow MT
845 PM MDT Mon Sep 5 2022

.DISCUSSION...

Evening Update:

Temperatures are falling and winds are diminishing around the
region, while relative humidity recoveries are just starting to
get underway. The Red Flag Warning has been canceled.

Previous Discussion:

Afternoon Update (2100Z): No major updates to the overall forecast
today in terms of what types of weather can be expected. With a
good amount of continuity between the last few cycles, confidence
has increased in critical fire weather and a concerning level of
heat impacts for Wednesday. Beyond mid-week, the large scale
pattern still breaks down and brings the region closer to normal
conditions for this time of year.

Cliff

PREVIOUS DISCUSSION:
Synoptic Setup: A large area of hot high pressure is bottled up
over the Intermountain West in the CONUS. A large pacific trough
has moved into the northern Canadian Prairie Provinces. Between
these two large airmasses lies zonal flow across northeast
Montana.

Today: Ridge has shifted to the east with a strong pressure
gradient forming across the northern zones under zonal flow
aloft. This should bring winds up in the north with enough
confidence to run a Red Flag Warning for these zones from noon to
9PM again.

Wildfire smoke across the area from the Pacific Northwest/Idaho
is also reducing visibility and generating a less than 10SM haze.
In some places the concentration has become high enough to lead
to health impacts for sensitive populations. This smoke is
expected to be pushed south and east today, but may return by
Tuesday and Wednesday.

Tonight to Wednesday night: Zonal flow gets pushed out with the
next incoming ridge. Tuesday may hit the lower 90s but 100s with
record max temperatures could easily return for Wednesday at the
peak of the ridge. There is also the potential for compressional
warming ahead of the incoming cold front overnight. The one thing
that may stop record temps is if smoke concentrations up wind
from central Idaho become high enough that a higher percent of
insolation is blocked out from hitting the surface. Confidence is
high enough to drop a Red Flag Warning for this day already, but
have held off to prevent confusion with the current Red Flag for
today.

Thursday onward: Ridge will get pushed out by southwest flow
aloft and an incoming Pacific trough. The cold front will be very
strong with a chance for showers and thunderstorms to occur along
it into the evening hours. Cold air advection behind the front
will likely lead to a Lake Wind Advisory. Though, model ensembles
are having difficulty defining the center and strength of the
trough afterwards that moves through over the next 2 days. There
are plenty of differences in the phase of the wave to warrant low
confidence in the forecast from here onward. To give an example
the forecast warmed 3 to 7 degrees 36 hours ago and has now cooled
that same 3 to 7 degrees over these periods from 12 hours ago
with a wide spread among ensemble members still in place. While a
cool down will hit, how strong it will be or how long it will
last is uncertain with disagreement among ensembles. GAH

GAH

&&

.AVIATION...

Updated: 2100Z

Expected Flight Category: VFR

Discussion: While some haze and patchy wildfire smoke will linger
over the area for the next couple of days, expect little cloud
cover and continued warm temperatures.

Winds: West to northwest winds of 10-20 kts this afternoon and
evening. Overnight winds should be back to light and variable for
most locations. On Tuesday, north winds of 5-15 kts are expected.

EQUIPMENT: While the KGDV visibility sensor is down, amendments
will be limited to clouds and wind for this terminal.

Cliff

&&

.FIRE WEATHER...

Conditions are lining up for another critical fire weather day on
Wednesday, with humidity bottoming out close to the single digits
of percent and winds in the teens of mph across the region.
Temperatures will also be quite hot, with mid 90s to mid 100s
region-wide, which will only enhance the fire risk for the day.
Once Wednesday is over, the large pattern shift will bring
increased humidity each day and lower temperatures, thus bringing
down the fire risk leading into next weekend.

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
&&

weather.gov/glasgow