Area Forecast Discussion
Issued by NWS Great Falls, MT

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950
FXUS65 KTFX 202042
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
242 PM MDT WED JUL 20 2016

.DISCUSSION...

Tonight through Friday...Another weak disturbance is moving
across the zones this afternoon with the central zones becoming
unstable. Surface RHs are lower today than yesterday but isolated
thunderstorms are expected. Development will not be widespread and
the best chance for strong thunderstorms will be over Fergus
county. Brisk winds this afternoon have been a combination of
mixing and surface high pressure west of the Rockies. These will
diminish quickly during the evening. Water vapor pics show very
dry air moving into the region tonight. However, the extreme
southwest zones, and the Fergus county area, still develop weak
instability Thursday afternoon. Heights aloft will be falling
Thursday night as the low pressure over the West Coast approaches
the zones. As this shortwave crosses the region, good lift will
develop over the Hi- Line late Thursday night and Friday, and by
late Friday evening, this will shift to Southwest Montana and the
Northeast zones. The associated cold front will cross the Rockies
late Friday afternoon and spread east with cooler temperatures but
only the northwest zones will see temperatures drop back to
seasonal averages. Zelzer

Friday night through Wednesday...An upper level trof will be exiting
the region Friday night with mostly dry conditions and near normal
temperatures expected over the weekend. For early next week...an
upper level ridge will shift into the southwestern portions of the
U.S. At this time...the upper level ridge is not expected to be over
strong or greatly amplified northward into Montana. Thus only
slightly above normal temperatures are expected over the region for
the first half of next week. Initially...the chances for
thunderstorms early next week are quite low...because
timing/strength of any upper level disturbance moving through the
flow aloft is quite uncertain. However...the forecast model runs
during the day on Wednesday 7/20 are now hinting at the possibility
of isolated showers and thunderstorms over North Central Montana
along a temperature gradient boundary Tuesday through Wednesday.
Have therefore added a slight chance mention of showers/storms for
that period. Brusda/Coulston
&&

.AVIATION...UPDATED 1652Z.

The air mass will become unstable again this afternoon...most
unstable across central portions of the region including KHLN and
KLWT. Isolated thunderstorms are expected in this area. Gusty winds
to near 50 kts are possible near thunderstorms. VFR conditions will
prevail through the next 24 hours.
UPDATED 1050Z.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  90  57  87 /  10  10  20  20
CTB  48  86  52  79 /  10  10  20  50
HLN  59  93  61  88 /  20  10  10  10
BZN  51  93  54  91 /  10  10  10  10
WEY  43  82  49  79 /   0  10   0  10
DLN  49  90  54  86 /  10  10  10  10
HVR  53  90  58  87 /  10   0  20  30
LWT  54  88  59  88 /  30  10  10  20

&&

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

$$

weather.gov/greatfalls



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