Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290449
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
940 PM MDT Wed Jun 28 2017

Aviation section updated

.UPDATE...
Updated forecast is coming out. No major changes this evening.
Scattered light rain showers/thunderstorms continue to move
through the region. Main threat is some wind gusts around 40 mph
and hail up to 1/2 inch. Showers will continue overnight as the
upper level disturbance moves through. Expect showers to gradually
end during the day on Thursday from north to south during the
afternoon hours. Brusda

&&

.SYNOPSIS...

Scattered showers and thunderstorms will continue to impact
Southwest Montana this afternoon, some of which could be on the
strong side with gusty winds and hail. Showers and perhaps a
thunderstorm will linger through Thursday as a cold front sweeps
through the area. Drier air moves in on Friday. Much warmer
temperatures are likely over the weekend and into next week.

&&

.AVIATION...
Updated 0445Z.
An upper level disturbance will continue to move southward across
parts of western Montana overnight tonight. With this system, a
continued chance of showers will persist for central and
southwestern parts of the state. There may likely be a lull in any
activity in the mid to late morning hours before another round of
spotty showers and thunderstorms develop mainly along and south of
GTF to LWT. Any one stronger storm may produce gusty winds and
lightning at times before likely coming to an end by the evening
hours. KLG

&&

.PREV DISCUSSION...
/ISSUED 605 PM MDT Wed Jun 28 2017/

Rest of today through Friday...An upper level jet is pushing
through OR/ID ahead of the main upper low over Alberta. Lift
associated with this jet and the main upper low has allowed
scattered to numerous thunderstorms to develop across SW MT. Most
storms have remained sub-severe. However, a couple of storms
managed to develop stronger/more sustained cores, producing hail
and gusty winds. This area will continue to be the most unstable
over the next several hours and we will continue to closely
monitor storms as the move through there. Gusty winds and hail
will continue to be the primary threats. Although, any area that
sees multiple storms train over the same location could see some
heavier rainfall amounts (perhaps up to a half an inch or so).
Flash flood guidance is 1-3", though, and significant flooding is
not anticipated. Still, cannot rule out some ponding of water on
roadways and higher stream flows.

A cold front approaching Montana from the north will sweep south
through tonight. Models continue to insist on a decent amount of
low/mid level moisture in the wake of the front which should help
generate isolated to scattered showers overnight into Thursday. A
period of gusty winds may accompany the front as well, especially
along the Hiline. Drier air moves in Thursday night, putting an end
to most of the shower activity. MARTIN

Friday night through Tuesday night...a progressive upper level
pattern best describes the long term once again, with very quick
transient ridging and shortwaves moving across the Northern Rockies
and Northern High Plains. A quick moving shortwave will translate
from the Intermountain West Saturday morning and across the Northern
Rockies through the remainder of the day. This shortwave should
spark off scattered showers and thunderstorms off of the higher
terrain of North Central and Southwest Montana by the afternoon
hours on Saturday, with any shower/storm then moving from west to
east. Thunderstorms on Saturday are expected to be of the garden
variety type, with a few storms possibly producing some breezy winds
and small hail. Both GFS and EC guidance have continued to trend up
with high temperatures through Monday, so felt comfortable in
raising temperatures further. For the day on Monday, upper level
ridging will begin to break down, with H500 flow becoming southwest
to westerly. H850 temperatures will soar into the mid 20C to low
30C. This should translate to high temperatures in the mid 80s to
mid 90s across the CWA. These warm/hot temperatures, combined with
dry/breezy downsloping winds and low afternoon relative humidity
values, will lead to heightened fire weather concerns for the day on
Monday. Given the ongoing dry conditions across our far eastern
zones, am growing concerned about the potential for grassland fire
spread given the aforementioned weather conditions. Finally, an
early look at Independence Day reveals highs potentially being just
as warm as Monday, with continued dry and breezy winds. Am not as
confident in temperatures being as warm on Tuesday (with respect to
Monday) given a broad trough moving into the region. However, given
the expected breezy winds and antecedent dry conditions, fire
weather concerns will once again linger for the day on Tuesday. -
Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  49  69  48  78 /  30  30  10  10
CTB  47  68  47  77 /  30  30  10  10
HLN  53  71  50  81 /  20  30  10  10
BZN  46  69  44  77 /  20  30  10  10
WEY  37  62  35  70 /  30  30  10  10
DLN  44  67  45  76 /  40  40  10   0
HVR  52  71  46  79 /  20  20   0  10
LWT  47  67  44  74 /  20  30  10  10

&&

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

&&

$$

weather.gov/greatfalls


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