698
FXUS65 KTFX 200227
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
827 PM MDT Fri Jul 19 2024

.UPDATE...

Satellite imagery this evening shows that much of the afternoon
cumulus field has dissipated, leaving clear (but hazy) skies
across most of the area. There is some lingering instability and
isolated convective cloud-development ongoing across primarily
Beaverhead county in SW MT as well as from areas near Glacier Park
south along the Rocky Mountain Front, where the risk of an
isolated shower or weak thunderstorm continues through around
midnight. Did make some minor adjustments to pop/weather grids to
give mention (~15% chance) of isolated showers/thunderstorms in
the above mentioned areas through the rest of this evening, while
the overall forecast remains on track. Hoenisch

&&

.SYNOPSIS...

Above normal temperatures and dry conditions continue through the
middle of next week.

&&

.AVIATION...
20/00Z TAF Period

VFR conditions prevail through the TAF period with mainly terrain-
based cumulus dissipating later this evening and redeveloping
Saturday afternoon. An isolated high-based shower cannot be ruled
out through early this evening where some of the stronger cumulus
development was occurring late this afternoon, primarily across
southwest MT near the ID border. Hoenisch

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

&&

.PREV DISCUSSION...
/ISSUED 530 PM MDT Fri Jul 19 2024/

The overall hot and dry weather pattern continues with a large
scale upper level ridge positioned over the interior west. Water
vapor satellite imagery and numerical model analyses reveal a weak
shortwave aloft drifting through Southeast Montana. Meanwhile,
another weak wave is forecast to move through the top of the
ridge, passing over the Canadian Rockies into Eastern Montana on a
northerly flow on Saturday. Available moisture remains limited,
so the only changes from this shortwave on Saturday will be a
10-20 percent chance of an isolated afternoon shower or
thunderstorm, mainly focused over the Glacier Park, and Snowy
Mountain (Lewistown)regions. Gusty winds and a couple lightning
strikes would be the primary concern resulting from any such
thunderstorm Saturday afternoon. A thermal trough in the surface
pressure field over the interior west will help to create an
easterly breeze over our region, noted only in the afternoon hours
with deep layer mixing. -PN

Sunday through Wednesday...ensemble clusters continue to favor
strong upper level ridging residing over much of the Western CONUS,
with longwave troughing over the Pacific Northwest and western
seaboard of Canada. This upper level ridge will help maintain well
above normal temperatures and overall dry conditions across
Southwest through North Central Montana through the period.

Thursday through next Friday...ensemble clusters favor the breakdown
of the upper level ridge over the Northern Rockies as a longwave
trough slides east from the western seaboard. Leading mode of
uncertainty through the period will be the position and/or timing
of the longwave trough, which will ultimately impact how long the
above normal temperatures last across Southwest through North
Central Montana. None-the-less, ensemble model guidance does support
a brief and slight "cool down" towards the end of the work week as
upper level heights fall, but this may only result in daytime highs
reaching the mid- to upper 80s vs the preceding 90s to near 100
degrees. Additionally, as the ridge breaks down, expect southwest
to west winds to increase. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  61  93  61  92 /   0   0   0   0
CTB  57  93  58  91 /  10   0   0   0
HLN  63  97  62  96 /   0  10   0   0
BZN  57  93  56  92 /   0  10   0   0
WYS  44  83  42  83 /   0  10   0  10
DLN  54  88  52  88 /  10   0   0   0
HVR  62  94  62  94 /   0  10   0  10
LWT  57  87  56  86 /   0  20  10  10

&&

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

$$

http://www.weather.gov/greatfalls