Area Forecast Discussion
Issued by NWS Great Falls, MT

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000
FXUS65 KTFX 300000
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
600 PM MDT Sat Apr 29 2017

.DISCUSSION...

Tonight through Sunday night...Cumulus development continues this
afternoon across the forecast area with weak instability and
plenty of surface moisture available along with some forcing from
a weak shortwave aloft. Scattered to numerous showers have
developed over much of N-central MT with best, albeit weak,
instability focused over eastern portions of N-central MT, where
a few isolated thunderstorms cannot be ruled out through early
this evening. Shear is minimal however and short-lived/pulse type
convective cells will be the dominant theme. A weakening upper
level ridge progresses east across the forecast area tonight as
it is quickly flattened by an upstream Pacific upper level
trough/jet that moves east across the region on Sunday. Showers
and cumulus will diminish quickly this evening followed by
increasing cloudiness from the west later tonight. Deepening
surface low in southern AB Sunday will produce breezy west winds
across the forecast area with the upper level trough and embedded
shortwave energy in WNW flow aloft also triggering some showers.
Surface low in AB moves off to the east Sunday night with
additional shortwave energy dropping into N-central MT as flow
aloft turns more northwesterly. A surface frontal boundary may
accompany this energy as it moves southeast across N-central MT
Sunday night along with the potential for some showers with snow
levels lowering back down to around 4000 ft by early Monday
morning. Hoenisch

Monday through Saturday...Overall active weather to start the
upcoming work week...becoming warm and dry mid week...then some
uncertainty towards next weekend. Unsettled northwest flow will
be found Monday through Tuesday as a large upper low is found
across the Midwest...and a ridge of high pressure builds in the
Pacific Northwest. Monday`s activity looks to be scattered with
snow levels above 5000 feet. A weak disturbance in the northwest
flow may bring more widespread showers on Tuesday...with snow
levels possibly lowering to 4000 feet on Tuesday morning. More
instability and increased shear from a strong jet streak will
also be found Tuesday...creating perhaps some scattered
thunderstorms during the afternoon hours. We then see the long
awaited return of ridging on Wednesday...which now looks to
continue through the day Thursday. Warm temperatures and mainly
dry conditions are expected...with perhaps some breezy winds at
times. Most models indicate a cold front will move through at
some point on Friday...returning chances for showers to much of
the area. The weekend then becomes the most uncertain part of the
forecast. Most models develop some sort of large disturbance
across the western US coast. How it influences our weather
pattern by the weekend is still up for interpretation. For now it
is a monitor type situation...however...active weather may
continue through next weekend. Temperatures look to remain below
normal through Tuesday. Ridging and downsloping flow could then
return high temperatures in the 60s and perhaps 70s Wednesday and
Thursday. Friday into Saturday could even be near to above normal
temperatures. There is some concern warm temperatures combined
with melting of fresh mountain snow could bring some flooding
concerns by mid to late next week. Another item to keep a close
eye on in the long term. Anglin

&&

.AVIATION...
Updated 0000Z.

VFR conditions are expected at least through the day on Sunday,
but brief MVFR ceilings are possible with showers. The few showers
lingering over the eastern terminals (KHVR KLWT) should diminish
quickly through 02Z as the airmass stabilizes. Otherwise, mid and
high level cloudiness will increase overnight from the west ahead
of another disturbance in the westerly flow aloft. Showers will
also increase over the Western and Southwest Montana mountains
during this time, and some showers will spread out over the plains
between 09Z and 15Z. However, breezy westerly downslope winds will
limit showers along the east slopes of the Rockies (KCTB KGTF)
after that time, but better instability will continue showers and
possibly a few thunderstorms elsewhere. Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  59  35  55 /  10  30  20  30
CTB  37  56  35  53 /  10  20  30  30
HLN  40  59  36  57 /  10  20  10  20
BZN  33  57  33  55 /  10  40  20  20
WEY  24  46  25  44 /  10  30  40  20
DLN  35  55  31  54 /  10  30  30  10
HVR  36  63  38  58 /  20  20  30  20
LWT  33  56  35  52 /  20  50  30  20

&&

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

$$

weather.gov/greatfalls



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