Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 092340
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
440 PM MST Mon Dec 9 2013
AVIATION SECTION UPDATED
Tonight through Wednesday...A Canadian weather disturbance aloft
will move into central Montana Tuesday afternoon. Associated with
the disturbance a weak cold front will move south through much of
the forecast area during the day Tuesday. Moisture and lift
associated with disturbance will bring another round of snow to
the area late tonight through Tuesday. Expect up to a couple of
inches of snow for the lower elevations with up to 8 inches in the
higher mountains. Behind the weather disturbance the airmass will
become drier Tuesday night and snow should mostly end. Wednesday
an upper ridge will move into the Pacific Northwest and result in
warmer temperatures along with gusty southwest winds to the east
slopes of the Rocky Mountains. Do expect more snow and blowing
snow for the mountains of the Rocky Mountain Front but snow
amounts look relatively light. As for weather highlights will
continue the wind chill advisory for the higher elevations of far
southwest Montana into early Tuesday. Plan to let most of the
winter weather advisory for the central and northern zones expire
at 5 pm as winds and blowing snow should diminish. The exception
will be the Rocky Mountain Front and eastern Glacier County where
gusty westerly winds and blowing snow should continue until the
cold front mentioned above brings lighter northwest winds Tuesday
afternoon. Also westerly winds aloft will increase over the Rocky
Mountain Front Wednesday afternoon with a risk of high winds by
late afternoon. Blank
Wednesday night through Sunday...An upper level high pressure ridge
will be over the Pacific Northwest Wednesday night. Weak
disturbances will continue to move over the ridge and into Alberta.
This will keep surface low pressure along the lee of the Rockies and
brisk surface winds across the Northern Rockies and adjacent plains.
The best chance for precip will be over the Rockies but the west
flow should keep points east quite dry. A fast-moving shortwave will
approach the West Coast by late Thursday afternoon and approach the
Rockies by early Friday. This will increase the chance of snow over
the Rockies but most of the forecast area will continue dry. The
ridge will rebuild Friday night although several disturbances will
flatten the ridge and keep the air mass unsettled through Sunday.
Snow accumulations will generally only be significant over the
Rockies but winds will strengthen late Saturday and become strong
and gusty winds Saturday night. These strong winds could eventually
require high lights and will continue through Sunday. Temperatures
across the region will generally remain slightly above seasonal
normals through the period. Zelzer
Latest in series of weak trofs moving through northwest flow aloft
currently located across south-central and southwest MT. Moisture
associated with the trof is generating some spotty -SN and
occasional MVFR conditions vcnty KHVR/KLWT/KBZN which should last
only another hour or two. VFR conditions expected this evening with
ceilings generally at/above 5000 ft. Next trof in the flow will
cross US/Can border around 09Z and progress to south-southeast
tomorrow, bringing another round of -SN and ceilings that will be a
mix of VFR/MVFR. Could also see some occasional IFR conditions near
areas of moderate snow, primarily from late morning through
mid-afternoon. Wind speeds will gradually decrease this evening,
but will remain gusty from KGTF to KCTB, with gusts 25-30 kts.
he flood advisory for the Gallatin River near Gallatin Gateway
will continue until the threat from flooding has ended. Ice jams
can be very slow to break up...especially as cold air continues
to reside in the Gallatin Valley. There is the potential for this
highlight to continue for several days.
.PRELIMINARY POINT TEMPS/POPS...
GTF 8 21 4 33 / 20 70 10 10
CTB 7 19 3 33 / 30 50 10 10
HLN 9 24 7 28 / 20 60 10 10
BZN 4 21 -1 24 / 30 60 20 10
WEY -14 13 -12 19 / 40 60 30 10
DLN 1 20 0 25 / 10 30 10 0
HVR 5 16 -8 27 / 40 60 10 10
LWT 9 21 2 34 / 30 80 20 10
WINTER WEATHER ADVISORY until 5 PM MST this afternoon Blaine...
Cascade...Central and Southern Lewis and Clark...Chouteau...
Eastern Pondera...Eastern Teton...Fergus...Hill...Judith Basin...
WIND CHILL ADVISORY until 11 AM MST Tuesday FOR ELEVATIONS ABOVE
6000 FEET FOR Beaverhead...Gallatin...Madison.
WINTER WEATHER ADVISORY until 5 PM MST Tuesday Eastern Glacier...
Northern Rocky Mountain Front...Southern Rocky Mountain Front.