339
FXUS65 KTFX 101735
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1135 AM MDT Wed Jul 10 2024

...Aviation Section Updated...

.SYNOPSIS...

Hot temperatures persist across the region through the upcoming
week, but do look to fall a bit back closer to normal next week.
Isolated showers and thunderstorms look to be around over the next
week, mostly across Southwest Montana.

&&

.DISCUSSION...

Through Thursday night...The upper level ridge axis will be overhead
today, slumping/pivoting a bit eastward/southeastward for
Thursday. The result is for temperatures taking another step
warmer across the region today and continuing into tomorrow. Highs
largely look to fall in the upper 90s in most areas, but peak a
few degrees above 100 in spots that are prone to the hottest
temperatures. High resolution ensemble members show a non- zero
chance for showers or an isolated thunderstorm or two near the
Idaho border as well as across the plains today. Although low
probability, if a shower or thunderstorm does manage to form,
gusty winds would be a concern given a deeply mixed boundary
layer.

As flow aloft becomes more zonal, marginally cooler temperatures
look to work in aloft for Thursday. High resolution guidance is
keying in on showers and thunderstorm developing as a result of the
slightly improved lapse rates aloft, combined with a weak passing
wave within the more zonal flow. The concern would again be for
strong outflow winds from any shower or thunderstorm that does
manage to form. Given the deep, dry sub-cloud layer, not expecting
much in the way of precipitation from any showers or thunderstorms.

Friday into next week... Although upper level ridging looks to
continue to dominate across the west over the timeframe, there is
still a bit of uncertainty, especially for Friday across the plains.
Model consensus is for a slightly cooler, but more moist airmass to
drop south from Canada late Thursday night into Friday. Confidence
decreases in just how much moisture is pulled southward however,
which leaves quite a few questions with respect to any shower or
thunderstorm chances for the afternoon Friday. Less aggressive
guidance brings marginally higher dew points, and largely mixes them
out by early Friday afternoon. This leaves little in way of
instability but does result in a slightly cooler day across the
plains. More aggressive guidance brings considerably more moist air
southward within a slightly cooler airmass across the plains and
somewhat maintains the higher dew points through the day Friday.
Relatively warm temperatures aloft still bring questions as to how
much instability will be generated, and if it will even be
accessible by a surface-based parcel (Concerns for a capping
inversion at the top of the boundary layer). Regardless, the best
parameter space for instability looks to be near the Canadian border
and adjacent areas by Friday afternoon, with the caveat that a
capping inversion may inhibit convection altogether. For now I have
left the chance for any precipitation across the region Friday at
or below 10%.

Areas where confidence in the forecast is higher will be across the
valleys of Central and Southwest Montana. The hot temperatures will
stick around in these areas, with non-negligible opportunities for a
shower or isolated thunderstorm across Southwest Montana terrain
Friday.

Looking toward this weekend, the theme of hot will return/continue,
depending on where you are across the region. Opportunities for
mostly dry afternoon showers and isolated thunderstorms will
continue across Southwest Montana terrain.

Heading into next week, the upper level ridging overall looks to
persist, but moisture aloft rounding the western side of the ridge
does look to work its way toward the Northern Rockies. The main
takeaway is for more of the same: Above average temperatures and
daily opportunities for isolated showers and thunderstorms across
Southwest Montana. Fire weather concerns will be increasing through
the next week as drying of fuels occurs. Dry thunderstorms that form
over the next week will also start to raise concerns for lightning
starts. -AM

&&

.AVIATION...
10/18Z TAF Period

VFR conditions persist through the TAF period. The main concerns
will be a very low chance of a stray shower or thunderstorm this
afternoon. There may be some localized areas of reduced visibility
from wildfires. The heat will also bring density altitude concerns.
-Wilson

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

&&

.CLIMATE...

Temperatures today and Thursday are expected to reach near or match
record temperatures. The following table below shows locations where
the forecast temperature is within 3F, matches, or exceeds the
previous record high.

RECORD OR NEAR RECORD MAXIMUM TEMPERATURES FORECAST FOR JUL 10

LOCATION             FORECAST HIGH       RECORD HIGH
Boulder                  93                 96
Chester                  96                 98
Dillon                   93                 95
Helena                  100                102
Townsend                 96                 98
West Yellowstone         87                 90


RECORD OR NEAR RECORD MAXIMUM TEMPERATURES FORECAST FOR JUL 11

LOCATION             FORECAST HIGH       RECORD HIGH
Bozeman MSU              94                 96
Chester                  97                100
Conrad                   96                 99
Cut Bank                 95                 95
Great Falls              97                 99
Helena                  100                100
Stanford                 92                 94
Townsend                 95                 98


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  97  64  97  59 /   0   0  20   0
CTB  95  61  95  57 /   0   0   0   0
HLN 100  66 100  62 /   0   0  10  10
BZN  96  60  97  57 /   0   0  10  10
WYS  87  46  87  45 /   0   0  10  10
DLN  93  58  94  56 /   0   0  10  10
HVR  98  65 100  60 /   0   0   0  10
LWT  92  62  92  59 /  10  10  20  20

&&

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

$$

http://www.weather.gov/greatfalls