Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 291756
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1150 AM MDT WED JUN 29 2016

AVIATION SECTION UPDATED

.UPDATE...
Latest satellite/radar imagery shows the small area of showers and
thunderstorms that were over Hill/Blaine counties earlier this
morning are exiting into Phillips County, with mostly clear skies
over the rest of central/southwest MT. So have removed any
mention of precip for remainder of the morning in our forecast
area. Still expecting isolated thunderstorms to develop again this
aftn/eve, mainly along the Rocky Mtn Front and over the central
and Hiline counties. One or two cells may become strong, producing
small hail and outflow winds gusting around 40-45 mph. Highs will
be in the upper 80s to around 90 degrees this aftn.
Waranauskas

&&

.AVIATION...
UPDATED 1750Z.

Westerly flow aloft with weak embedded disturbances will persist
over the region today. Scattered clouds are already developing over
local mountain ranges and will continue this aftn with isolated
-TSRA developing in some areas. Also expect thunderstorms to move
south-southeast out of Alberta and track toward KCTB/KHVR this
evening. Convective activity should dissipate overnight, but another
weak trough and moisture is forecast to move through southwest MT,
bringing scattered -SHRA vcnty KBZN/KHLN early Thurs morning.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED /

Today through Friday...Little change is expected to the large
scale pattern across the region through the next several days,
featuring a broad upper level ridge over the interior Western US,
which gradually decreases in amplitude through the remainder of
the week as a series of very weak shortwaves originating in both
the Eastern Pacific and Great Basin move through the upper level
ridge. Weak shortwave tracking ESE along the US/Canadian border
early this morning will continue to produce a few showers and
isolated thunderstorms through the morning period along the Hwy 2
corridor with some additional activity also developing over
eastern portions of central MT. This afternoon, the airmass
becomes moderately unstable again with additional very subtle
shortwave energy moving in from the west. Bulk wind shear values
(0-6km) generally range from 25-35kts across the region so an
isolated strong storm or two cannot be ruled out but overall
convection should be non-severe. Showers and thunderstorms will
decrease in coverage tonight, but mid level instability remains
remains high enough for a few showers and thunderstorms to linger
through the night once again. Similar conditions occur again on
Thursday with perhaps slightly more organized weak shortwave
energy across both north central MT originating to the west and SW
MT originating in the Great Basin. This may lead to somewhat
better coverage of afternoon/evening convection Thursday with
again most of being non-severe though a few stronger cells cannot
be ruled out. Friday appears to be mostly dry as little in the
way of shortwave activity is currently forecast to move across the
region until Friday evening, though daytime heating/instability
will maintain a small threat for afternoon thunderstorms across
the mtns. Temperatures will remain about 5-10 degrees above
seasonal averages through the remainder of the week. Hoenisch

Friday night through Wednesday...Overall, an unsettled westerly
flow will prevail through the period, with a cooler and possibly
wetter system arriving mid-week. A shortwave trough crossing the
Canadian Rockies Friday night will support isolated showers and
thunderstorms. Winds shift to westerly early Saturday as an
associated surface front brings slightly cooler temperatures for
the weekend. The westerly flow aloft continues to strengthen
Sunday through Tuesday, causing breezy conditions and isolated to
scattered showers and thunderstorms. At this time, Monday evening
weather for the 4th of July appears dry for most areas but with
westerly surface winds and isolated showers. A stronger, closed
upper level moves across southwest Canada Tuesday night and
Wednesday. This system will bring cooler temperatures with areas
of rain across portions of the forecast area. Models remain in
fairly close agreement through the period at synoptic scale,
although details in timing and position of smaller scale features
will continue to evolve. PN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  86  55  85  56 /  10  20  20  20
CTB  82  50  81  51 /  20  30  30  20
HLN  90  59  87  58 /  10  10  30  20
BZN  90  52  86  52 /  10  20  20  20
WEY  81  44  74  44 /  20  20  30  20
DLN  89  53  84  52 /  10  20  20  20
HVR  85  54  83  55 /  20  20  20  30
LWT  83  53  82  54 /  20  20  30  20

&&

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

$$

weather.gov/greatfalls



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