Area Forecast Discussion
Issued by NWS Great Falls, MT

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000
FXUS65 KTFX 260011
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
610 PM MDT Fri May 25 2018

.SYNOPSIS...

Shower and thunderstorm activity will increase late this afternoon
and evening...with the best chances coming across the west and
southwest...possibly moving into central and northern portions
overnight. Expect continued warm temperatures on Saturday with
scattered to numerous showers and a chance for strong to severe
thunderstorms. Unsettled conditions and warm temperatures will
continue through the holiday weekend.

&&

.DISCUSSION...

Tonight through Memorial Day...Ridge of high pressure continues
moving eastward through the region tonight with a weak warm
front lifting from south to north late this afternoon and evening.
Weak instability and shear along this front will trigger isolated
to scattered showers and thunderstorms through early evening,
mainly across the west and southwest. Showers and thunderstorms
will lift northeastward across central and northern portions of
the forecast area overnight. Active weather is expected Saturday
afternoon and evening. Warming ahead of a cold front will bring
modest instability to the region. Large low pressure system then
pushes a cold front across the region...also providing some modest
shear. The result looks to be scattered showers and thunderstorms,
with a few strong to severe storms possible. Large hail and
strong winds will be the main threats from these storms. Those
with outdoor plans should keep an eye on the skies...and plan on
completing outdoor activities early. This large upper low then
lingers across the region on Sunday and again on Memorial Day. The
result will be near normal temperatures and chances for showers
and thunderstorms. Sunday the best activity might be across the
southern half of the CWA (Great Falls to Lewistown and
south)...while Monday looks to be more widespread as there is
slightly better instability everywhere. The outdoor enthusiasts
will have to monitor the latest forecasts during this active
weather. Anglin/mpj

Monday night through Friday...Long term period looks to remain
unsettled as multiple disturbances move through. Tuesday does see
weak ridging try to build over the region...however...lingering
instability and moisture could bring some scattered thunderstorms.
Sometime mid week a sharper cold front could move through bringing
the next best chance for widespread showers and thunderstorms.
This frontal boundary then looks to stall later in the week...and
moist southwest flow brings continues chances for showers and
thunderstorms to the region. Near normal temperatures look to
start the long term. These mention cold fronts could then cool
temperatures to near to even slightly below normal readings by
the end of the week. One other item worth monitoring for the long
term will be some 700 mb temperatures below freezing. This may
provide some chances for perhaps high elevation snow...although
most other areas will see all rain. Anglin

&&

.AVIATION...
Updated 0000Z.

Scattered IFR/MVFR in and around showers and thunderstorms that are
moving northeast across Central Montana. A few of these storms could
be strong with erratic, gusty winds and moderate rainfall. Expect
these storms to move out of the area overnight with only scattered
clouds after 12Z. Mostly cloudy and unsettled conditions expected to
redevelop Saturday afternoon. Scattered strong to severe
thunderstorms look to develop over Southwest Montana after 18Z,
spreading north and east after 20Z. Some storms could produce
erratic winds, heavy rainfall and hail.

&&

.HYDROLOGY...

Only change to hydrology highlights today was to (once again) push
back timing of the Flood Watch for the Sun River. Scattered to
numerous showers and thunderstorms are expected through the entire
Memorial Day weekend and any slow moving storms producing heavy
rain could cause minor to moderate local flooding. mpj

Current Highlights:

Flood Watch from Sunday morning through Thursday afternoon for
the Sun River in Cascade County.

Small stream flood advisory for Meagher County until 615 PM Friday.

Flood Warning in effect until 300 PM MDT Sunday for the Big Hole
River near Melrose in Beaverhead and Madison Counties.

Flood Warning in effect until 145 AM MDT Monday for the Jefferson
River near Three Forks.

Flood Warning in effect until 1000 PM MDT Saturday for the Missouri
River near Toston in Broadwater County.

Flood Warning in effect until 1015 PM MDT Saturday for the Gallatin
River near Logan.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  79  52  77 /  30  20  70  40
CTB  53  76  48  78 /  20  30  30  20
HLN  52  78  52  73 /  30  30  50  60
BZN  48  79  48  69 /  10  30  40  80
WEY  38  70  39  61 /  10  20  50  70
DLN  45  74  47  65 /  40  30  40  80
HVR  55  84  53  82 /  20  30  50  20
LWT  52  79  51  72 /  10  50  60  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

Flood Watch from Sunday morning through Thursday afternoon
Cascade.

Small stream flood advisory for Meagher County until 615 PM Friday.

Flood Warning in effect until 300 PM MDT Sunday for the Big Hole
River near Melrose in Beaverhead and Madison Counties.

Flood Warning in effect until 145 AM MDT Monday for the Jefferson
River near Three Forks.

Flood Warning in effect until 1000 PM MDT Saturday for the Missouri
River near Toston in Broadwater County.

Flood Warning in effect until 1015 PM MDT Saturday for the Gallatin
River near Logan.

&&

$$

http://www.weather.gov/greatfalls


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