Area Forecast Discussion
Issued by NWS Great Falls, MT

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000
FXUS65 KTFX 190300
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
900 PM MDT Thu Sep 18 2014

.UPDATE...

There a few showers and thunderstorms lingering across southwest
Montana this evening as an upper-level trough continues to move
across the region. These showers should dissipate by midnight. No
severe weather is expected, however some storms may contain gusty
winds up to 40 mph & frequent lightning. Mainly dry conditions are
expected for the rest of tonight and have lowered pops slightly
across the plains and valleys but kept a chance pops in the
mountains. Areas of smoke from wildfires over the Pacific
Northwest will continue to impact the area as well. The remainder
of the forecast is on track so made no further changes. MLV

&&

.AVIATION...
UPDATED 2340Z.
Isolated showers and thunderstorms have ended across the area as the
axis of an upper level disturbance moves through. Gusty surface
winds will decrease after sunset but will increase again after 15z.
VFR conditions prevail.

&&

.PREV DISCUSSION...
/ISSUED 540 PM MDT Thu Sep 18 2014/

Tonight through Saturday...A weak upper level trough and
associated surface cold front will sweep through Montana
overnight. Isolated to scattered showers and thunderstorms will
mainly impact Southwest Montana and southern sections of Central
Montana this evening with breezy to windy conditions expected for
much of the forecast area. Windy conditions persist through the day
on Friday, especially along the Rocky Mountain Front, but do not
expect that high wind criteria will be reached. Temperatures are
expected to be cooler than those of today, and as the mid and
upper level winds shift to a more westerly direction behind the
system, the widespread smoke that has moved into the area should
clear out. Breezy conditions are expected to diminish Friday
night as an upper level ridge begins to build over the western
USA. This ridge will usher in mostly clear skies with seasonable
temperatures and light winds on Saturday. mpj

Saturday night through Thursday...High pressure will be building
over the region Saturday night and the ridge will be over Central
Montana by Sunday. Moisture will begin to move north underneath the
ridge but convection will remain south of the zones. The ridge will
begin to move east of the zones Monday and a shortwave will
approach the Rockies. The air mass will remain very dry and only the
extreme southwest should see any convection. Moisture will slowly
increase across the region Monday night and Tuesday and by Wednesday
afternoon a low pressure trof over the Eastern Pacific will be
approaching the West Coast. The GFS is faster with this feature and
has it moved over the West Coast by 00z Thu. The ECMWF, slower, has
it hanging back over 135W. The GFS solution would bring moist,
unsettled flow aloft across the zones Thursday night and Friday, It
would also create an unstable air mass with showers and
thunderstorms likely lasting into the night as the trof continues to
approach the Rockies. However, with the ECMWF keeping the trof west,
and the GEM more in line with the ECMWF as well, will keep pops near
climo and wait for the models to come more into agreement.
Temperatures will remain well above normals through the period
although the GFS solution would bring significant cooling on
Thursday. Will keep more moderate temps due to the disagreement in
the models. Zelzer

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  75  46  73 /  10  10   0   0
CTB  47  72  42  72 /  10  10   0   0
HLN  51  76  47  77 /  20  10   0   0
BZN  45  74  42  74 /  20  10   0   0
WEY  37  68  33  71 /  50  20  10   0
DLN  47  74  43  75 /  20  10   0   0
HVR  53  78  48  74 /  20  10   0   0
LWT  52  74  47  72 /  20  10  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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