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Area forecast discussion 
National Weather Service Great Falls Montana
438 am MST Fri Dec 19 2014

Discussion...

Tonight through Sunday...a high pressure ridge will be over The
Rockies and moving over the zones during the day. To the west, a low
pressure trof will move over the West Coast during the day. Decent
dynamics develop as the trof crosses The Rockies although this will
be a fast-moving feature and little time for development of weather.
Best lift with this system will be Friday night over the southwest
zones. However, a chance for mixed snow and rain are expected
tonight over central and northern portions of the County Warning Area. Will include
some freezing rain in the grids after midnight as the surface
conditions cool. The upper level trof will move over the zones by
early Saturday and weak ridging will be in place to the west and
moving across the zones during the day. A strong jet at upper levels
will be over the Pacific northwest Saturday and spread east over the
zones Saturday night and Sunday. Mid-level winds will increase to
45+ kts Saturday night and Sunday. This will bring very strong winds
across The Rockies and adjacent plains. Some stability develops at
lower levels after midnight and the will bring the best chance for
strong winds spreading east. Currently, have some gusts above
58 mph over The Rockies but because of uncertainty will hold off on
statements. Some strong winds as well at higher elevations will also
occur across southwest Montana by Sunday and will have to be
monitored. Widespread precipitation will develop with the approach
of a shortwave associated with these strong winds Saturday night
and, once again, the chance of freezing rain will develop and will
be included in the grids after midnight into Sunday morning. Some
higher snow accumulations are expected at higher elevations in the
southwest zones but widespread heavy snow is not expected. Zelzer

Sunday night through Friday...a rather active weather pattern is
setting up for much of the region for next week. At this time...we
are not expecting significant snow storms...but rather several
accumulating snowfall events that will cause impacts for daily
commuters and travelers. Through much of the extended...the gfs13
and ec are in pretty good agreement. Temperatures will be near/a bit
above normal Monday and into Tuesday...but then begin to turn colder
Wednesday through Friday. For now I used a lower blend of the colder
models for temperatures...but temperatures could be several degrees
colder than currently forecasted should the snowpack become a bit
deeper than expected. Additionally...there is the potential for
another high wind event over portions of north central Montana on Tuesday.

In terms of precipitation...southwest Montana will continue to see
precipitation Sunday night and into Monday morning...with scattered
showers over north central Montana. The precipitation becomes fairly
light and scattered Monday night through Tuesday. Then a fairly
strong storm system will move through the region Wednesday afternoon
through Christmas day. At this time...it looks like central and
southwest Montana will see the brunt of this storm. At lower
elevations...there will be a swath of 3 to 5 inches of snow...with
around 8 to 10 inches in the mountains. It is too early to Pin-Point
the exact area that will see this heavier snowfall...but right now
that swath of heavier snow is forecasted along a Helena to Bozeman
line. This line of heavier snow could shift a bit over the next few
days as later model runs get a better handle on the storm track.
Brusda

&&

Aviation...
updated 1138z.
Weak high pressure will generally keep the airmass dry today. To the
west, a low pressure shortwave over the West Coast will approach The
Rockies by this evening and the chance of precipitation will
increase across central and southwest Montana...with the best
chances over southwest Montana. Local MVFR conditions are expected
tonight along with mountain obscuration. VFR conditions will prevail
Saturday.



Even though an upper-level ridge of high pressure will move over the
northern rockies tonight, Pacific moisture moving over the ridge
will keep scattered to broken cigs with mountain obscuration likely through
Friday. Taf locations will remain dry through Friday afternoon
before the next weather system moves into the area, however light
snow showers are expected over the mountains tonight and Friday.
Southwest winds will be less than 15 kts over the plains tonight as
the ridge continues to build, but southwest winds will increase at
kctb and kgtf again on Friday afternoon. Conditions will begin to
deteriorate from west to east on Friday afternoon and evening with
light snow developing at kbzn and khln by 02z Saturday. Have added
vcsh to khvr, kgtf and klwt by 04z Saturday. Mlv

&&

Preliminary point temps/pops...
gtf 42 28 40 34 / 10 30 10 20
ctb 40 26 36 29 / 10 20 0 20
hln 37 22 36 28 / 10 40 10 40
bzn 35 18 33 27 / 10 40 10 50
wey 33 20 32 27 / 50 50 40 70
dln 38 20 35 31 / 10 40 10 50
hvr 39 26 39 26 / 10 30 10 20
lwt 44 25 41 29 / 10 30 10 30

&&

Tfx watches/warnings/advisories...
none.
&&

$$

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