Weather Service Report


580 
FXUS65 KTFX 261103
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
500 AM MDT SUN JUN 26 2016

Updated Aviation Discussion

.DISCUSSION...

Today through Tuesday...A westerly flow aloft will persist across
the region through early this week as an upper level ridge over the
SW US amplifies slightly while mainly weak shortwave energy moving
in from the Pacific across the NW US keeps the ridge somewhat
suppressed. Weak shortwave embedded within the westerly flow, noted
in satellite imagery early this morning over SE BC, will track east
along the US/Canadian border today. A few showers and perhaps an
isolated thunderstorm are possible mainly along and north of Hwy 2
this afternoon. Behind this, the ridge temporarily amplifies into
the Northern Rockies Monday before the next round of weak shortwave
energy, originating over the Eastern Pacific, moves into the region
Tuesday. Instability and moisture increase Tuesday afternoon for
widely scattered afternoon showers and thunderstorms, however flow
aloft and shear is relatively weak for limited organization to
convection. A gradual warming trend is expected through the next
several days with afternoon temperatures today near seasonal
averages, warming to above average Monday and Tuesday. Hoenisch

Tuesday night through Sunday...The models are in general
agreement in the medium range period, keeping an upper level ridge
over the western US through at least the end of the upcoming work
week. Of note, though, there has been a noticeable trend over the
last few days keeping the ridge from getting as amplified as the
models suggested a few days ago. And, by next weekend, there is a
bit more consistency regarding a possible breakdown of the ridge
as the upper level trough sitting off the west coast of North
America may begin to edge further inland. Temp-wise, this suggests
that temperatures this week may not get quite as warm as
originally forecast. It should be noted, however, that the models
have struggled some with forecasting the evolution of the trough
off the Pac NW coast late in the week which makes the forecast for
the July 4th weekend a lower confidence one at this time.

Beneath the ridge, it appears that a weak surface convergence zone
may setup in the lee of the Rockies from Canada to the Southern
Plains. Within this area, increasing instability and moisture
combined with the weak convergence should be enough to generate at
least isolated showers and storms most days. At this point, it is
too early to pinpoint which days may have a better coverage of
storms, so kept pops at slight chance / chance each afternoon /
evening for now. Very much a summer-time pattern. By the end of the
week, a Pacific front may sweep through the area, but this will
depend on whether or not the trough off the Pac NW coast can move
inland or not. If the trough doesn't move inland, then isolated
afternoon storms will likely be the norm going into the holiday
weekend. Despite the better agreement regarding the trough, the lack
of consistency still leads to a lower confidence forecast then and
opted to keep pops on the lower end over the weekend for now.
Regarding the strength of the storms from Wednesday on, there isn't
any significant severe weather signal on any day. But, a few strong
storms will be possible just about any day, especially across the
eastern half of the forecast area where the best instability/shear
may reside. Martin

&&

.AVIATION...UPDATED 1100Z.

A westerly flow aloft will persist over the region through the next
24 hrs with a weak weather disturbance moving east along the
US/Canadian border this afternoon. A few showers or thunderstorms
may develop near the KCTB/KHVR terminals late this morning through
this afternoon in association with the weak weather disturbance
while clear to partly cloudy conditions prevail elsewhere. Surface
winds will shift to northerly this afternoon but most locations
should remain at or below 10kts. Exception will be near any
thunderstorm activity that develops near the Canadian border where
local wind gusts to 30kts are possible along with brief MVFR
conditions. Otherwise VFR conditions prevail. Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  75  47  82  53 /   0   0  10  10 
CTB  71  46  78  50 /  20  10  10  10 
HLN  80  52  85  57 /   0   0  10  10 
BZN  81  46  86  50 /   0   0  10  10 
WEY  73  38  76  43 /   0   0  10  10 
DLN  79  46  85  51 /   0   0  10  10 
HVR  73  48  80  53 /  20  20  10  10 
LWT  73  48  80  53 /   0   0  10  10 

&&

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

$$

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