Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 270445
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1045 PM MDT Mon Jun 26 2017

Aviation section updated

.UPDATE...
Updated forecast is out. First wave of showers/thunderstorms has
generally exited the eastern portions of the region. The second
wave is approaching the divide at 930 PM. This wave should move
across the region during the overnight hours. Wind gusts around
50 mph and lightning will be the main threat. A third wave of
precipitation will move eastward through the area on
Tuesday...mainly during the late morning early afternoon hours. A
few storms could be strong again on Tue afternoon. Temperatures
will not be as hot on Tue.

Looking ahead...the 00z WRF has a northerly flow with showers
continuing on Thursday...with afternoon highs only in the 60s over
North Central MT. Midnight shift will look at this closer. Brusda

&&

.SYNOPSIS...

A Pacific cool front will move through the region tonight. Expect
scattered showers and thunderstorms to accompany the cool front.
On Tuesday, afternoon temperatures will not be as hot as Monday
with scattered showers and thunderstorms continuing. Seasonable
temperatures and mostly dry conditions are expected on Wednesday.

&&

.AVIATION...
Updated 0445Z.
Scattered rain showers/isolated thunderstorms will continue its
eastward progression across the area through the overnight hours.
Expect brief periods of lower cloud ceilings and lower visibility in
any heavier downpour through the morning hours. There will likely be
a break in the rain activity by mid to late morning. However,
scattered shower and thunderstorms will be possible once again for
parts of Central and Southern Montana where again, brief periods of
lowered visibility and lower cloud ceilings will occur in any
heavier downpour. Expect this activity to continue through the
afternoon before most areas dry out by the late evening hours. KLG

&&

.FIRE WEATHER...
No fire weather highlights are currently in effect at this time.
Cooler and more moist air has moved into Hill and Blaine counties.
Thus the fire highlights have been allowed to expire. Brusda

&&

.PREV DISCUSSION...
/ISSUED 300 PM MDT Mon Jun 26 2017/

Rest of today through Wednesday...Latest satellite imagery shows a
convectively-induced wave moving into western Montana at this time
with a second, stronger s/w back to the west, moving onto the NRN
CA/OR coast. Still think this lead wave should provide enough lift
for isolated storms through this evening, especially along/east of
the I-15 corridor and latest radar imagery suggests this is
underway as of 225 pm. Gusty/damaging winds look to be the main
threat (ie. 45-65 mph). There may be a brief lull in t-storm
activity this evening in the wake of the first wave, but the
coverage of thunderstorms should increase again tonight
associated with the 2nd and stronger wave mentioned above. It
will likely remain unstable through the night, but a gradual
decrease in instability and a lack of better shear should limit
the threat for any severe weather overnight.

In the wake of tonight`s s/w, a cold front will drop south out of
Canada. The models are struggling with how unstable it will get
ahead of this front and this may largely depend on how much precip
falls tonight (ie. more precip could lead to more stable
conditions and vice-versa). Regardless, the threat of showers and
storms should continue through Tuesday afternoon. Of note, the
greatest instability/shear looks to be across far SW MT and is
where confidence is higher regarding the development of a few
stronger storms capable of gusty winds and hail. This same area
looks to be the focus on Wednesday as well. The overall severe
threat Tuesday and Wednesday looks somewhat lower due to a lack
of better shear. With the flow turning more northwesterly,
temperatures will trend much cooler Tuesday and Wednesday compared
to today. MARTIN

Wednesday Night through Sunday...An unsettled, northerly flow aloft
develops Wednesday night and Thursday associated with a closed upper
level low drifting through AB/SK. A cold front trailing behind this
system will lower temperatures into the low- to mid-70s on Thursday.
This pattern brings chances for scattered showers and thunderstorms,
although model guidance continues to differ on the timing and
spatial extent of this activity.  The latest forecast guidance has
slowed the departure of the upper low, with chances for isolated
light rain showers continuing Thursday night into Friday. Model
consensus suggests weak ridging through the weekend, providing
generally fair weather with temperatures near 80F and isolated
showers or thunderstorms possible. PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  76  50  77 /  20  30  10  10
CTB  60  75  47  75 /  30  20   0  10
HLN  60  78  51  78 /  20  20   0  10
BZN  55  74  46  75 /  20  60  10  20
WEY  50  63  38  66 /  30  60  30  40
DLN  54  73  46  73 /  30  30  30  10
HVR  61  79  52  81 /  30  20   0  10
LWT  59  74  48  75 /  30  30  20  10

&&

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

&&

$$

weather.gov/greatfalls


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