Weather Service Report

FXUS65 KTFX 250429

Area Forecast Discussion
National Weather Service Great Falls MT
1030 PM MDT Mon Oct 24 2016


Tonight...Moisture and scattered showers, and a thunderstorm or
two, are continuing to move across the lower portions of
Southwest Montana. These will diminish as the evening continues.
Updated to freshen POPs and WX. Zelzer


.AVIATION...Updated 0430Z.

Moist, southwest flow aloft ahead of a low pressure trof over the
Eastern Pacific will continue through Tuesday. A weak disturbances
in the flow aloft will keep a chance of showers over mainly
Southwest Montana. This includes KEKS, KBZN, and areas to the south
of these locations. Local MVFR conditions are possible near showers
and thunderstorms. Elsewhere, VFR conditions are expected through
the next 24 hours.


/ISSUED 528 PM MDT Mon Oct 24 2016/

Tonight through Wednesday...Disturbances ejecting from an upper
level low pressure trough will keep a good chance of showers in
the mountain areas through this period, but lower elevations
should remain dry. A weakly unstable and diffluent southwest flow
aloft will continue showers along and south of a Dillon to Bozeman
line through this evening, with a few thunderstorms possible
through early evening. The main shortwave trough will then
approach the Idaho Panhandle after midnight, bringing an
increasing chance of showers to Northwest Montana to the
Continental Divide. As this shortwave moves east along the Hi-Line
on Tuesday, showers will continue in the mountain areas, but
westerly downslope winds will increase over the plains, keeping
them dry. Wind gusts will be in the 35 to 45 mph range along the
Rocky Mountain Front, with 25 to 35 mph gusts expected elsewhere
across North Central Montana. A high pressure ridge will then
rebuild over the area Tuesday night into Wednesday, which will
keep much of the area dry with lighter but still breezy westerly
winds. However, moisture and weak energy riding over the ridge
will bring a good chance of showers to the mountain areas along and
west of the Continental Divide once again on Wednesday. Temperatures
will remain a few degrees above normal, with highs mostly in
the mid 50s to lower 60s and lows in the 30s to lower 40s.

Wednesday Night through Monday...

AFTERNOON UPDATE: A few tweaks worth noting for this afternoon's
publish, although not much has changed synoptically...please see
previous discussion for further break down of the weather pattern
details. Models now coming together for the end of this week.
Stronger winds should keep precip confined to just the Rocky
Mountain Front on Thursday...while breezy winds prevail across
the remainder of the forecast area. GFS and Euro in pretty good
agreement for Friday through Saturday...pushing rain from
southwest to northeast across the CWA. Raised pops to indicate
higher confidence with this feature. Snow levels still remain at
the highest peaks...mainly above 8000 feet. Other change worth
noting is the next disturbance for Sunday through Monday. Models
starting to come together that precip will spread across the
southwest Sunday afternoon/evening...then spread north and east
Sunday night through Halloween. Thus raised pops for this time
period as well. Models do indicate that some heavy rain is
possible at times. Snow levels also remain confined to the higher
elevation with this system. End timing of this precip remains a
little GFS is more progressive and ends from north
to south Monday evening...where the Euro lingers through Monday
evening. Kept at least slight chances through Monday evening to
account for uncertainty. Anglin

PREVIOUS FORECAST DISCUSSION: The extended period begins with a
broad upper level ridge axis centered over the Rocky Mountain
west. Fair and mild weather prevails for Thursday under this
ridge. The ridge axis flattens and shifts east on Thursday as an
Alberta Clipper system skirts along the international border.
Rain showers will be possible over the mountains and the north-
central plains as this system quickly moves through on Thursday
evening. A shortwave ridge amplifies along or just west of the
Continental Divide on Friday. Rain chances increase over
Southwest Montana Friday evening as a moist system is drawn up
through California into the eastern Pacific trough. The 00Z ECMWF
solution presents a rather wet outcome as this wave moves over
the Northern Rockies on Saturday morning. In contrast, the GFS
and ensemble mean solutions weaken the wave while it lifts north
into the Canadian Rockies. A model blend is adequate to support
widespread Chance POPs for this system on Saturday. Snow levels
remain above 8000 feet. The western ridge amplifies once again on
Sunday, followed by another round of Pacific moisture on Monday.
Temperatures remain near to above average through the period. PN


GTF  44  62  42  60 /  10  10  10  10 
CTB  39  55  36  54 /  10  30   0  20 
HLN  41  62  38  62 /  30  10  10  20 
BZN  42  61  40  63 /  30  10  20  10 
WEY  34  49  33  53 /  60  30  20  10 
DLN  39  58  37  60 /  30  20  10  10 
HVR  38  62  36  57 /  10  10  10  10 
LWT  44  63  39  60 /  20  10  20  10 




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