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Area forecast discussion 
National Weather Service Great Falls Montana
1040 am MDT Wednesday Sep 2 2015'

Updated aviation discussion


No significant changes needed for the morning update. Some short-
term guidance suggests an isolated shower or thunderstorm may
develop in the higher terrain of south-central Montana this
afternoon as the front approaches from the west. Opted to leave
out any mention for now due to limited moisture/instability. The
evolution of precipitation for tonight still looks good with
showers developing along the Rocky Mountain front...possibly
reaching the Cut Bank area overnight. Martin


... 1640z.

Expect generally VFR conditions and ceilings should mostly be above
15000 feet except for the northwest portion of the forecast area. In this
area rain is expected to develop over the mountains by midnight then
spread to the adjoining plains (kctb) after midnight. Clouds will
lower to 8000 to 10000 feet mean sea level in the rain with ceilings possibly
lowering to MVFR over the plains and mountains becoming obscured.
Confidence in forecast winds is lower than average. Blank


Fire weather...
the red flag warning for today has been expanded to include
central Montana as well as southwest Montana. The red flag now includes
fire zones 115 and 117 and 118.

Little change in conditions expected for today as broad southwest
flow aloft keeps the region warm and dry with breezy daytime
winds. A Pacific weather system in Washington and British Columbia
will make slow eastward progress. Leading edge of showers from
this system may reach the Rocky Mountain front by this evening, but
main moisture plume will not arrive until Thursday. Best chance for
rain will be along the Rocky Mountain front east to the Little Belt
Mountains with wetting rains looking more likely in that area.
Precipitation will be more spotty with only light amounts (less
than 0.1 inch) for locations east and north of the little belts on
Thursday. Waranauskas/suk


Previous discussion...
/issued 546 am MDT Wednesday Sep 2 2015/
Wednesday through Friday...Wednesday will be the last day of
dry...breezy...and above seasonal temperatures for a while as an
upper level low begins to move into the Pacific northwest and
slowly impacts the area. Precipitation will begin along the Rocky
Mountain front Wednesday evening...and should become more
widespread throughout the day Thursday. Rain will begin as
scattered showers with possible thunderstorms Thursday during the
daytime hours and should become more widespread especially over
the Rocky Mountain front and adjacent High Plains. Winds will
continue to remain breezy through this time period...especially
Friday. Increasing cloud cover and precipitation should create
cooler temperatures each day with most locations well below
seasonal averages Thursday and Friday. Moisture totals for the
first part of the storm system appear to range in the one quarter
to one inch range. Suk

Friday night through Wednesday...a deep upper level low
pressure trough will move over the Pacific northwest Friday night
and the associated cold front will move through central Montana.
Widespread precipitation will continue behind the front under
moist southwest flow aloft. With the cold air aloft crossing The
Rockies Saturday, the air mass should become slightly unstable,
especially across the southern half of the County Warning Area. The GFS and European model (ecmwf)
have become more similar...still differences in placement but the
timing lines up better. A closed low will be over southern Idaho
Saturday night and move over central Montana by middle-day Sunday.
The airmass will begin to dry as the system moves east Sunday
afternoon although a shortwave moving into the trough Sunday night
will keep the airmass moist and unsettled. This shortwave will
move east of the zones by late Monday and the chance of
precipitation will drop Monday night. The air mass will remain
quite dry through Tuesday but a shortwave will cross The Rockies
Tuesday night. With northwest flow aloft, this will bring some
increased chances of precipitation although cold front looks quite
weak. Temperatures will begin the period well below seasonal
averages before rising back to near normals Sunday. Zelzer


Preliminary point temps/pops...
gtf 82 50 65 46 / 0 20 60 70
ctb 74 45 60 42 / 10 80 90 60
hln 84 48 68 45 / 0 10 60 70
bzn 87 48 76 45 / 0 10 20 40
wey 77 40 70 34 / 0 10 10 20
dln 81 48 73 43 / 0 10 40 40
hvr 86 50 71 49 / 0 20 20 50
lwt 88 48 69 44 / 0 10 20 30


Tfx watches/warnings/advisories...
red flag warning until 9 PM MDT this evening for mtz115-117-118.




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