Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221621

Area Forecast Discussion
National Weather Service Great Falls MT
921 AM MST Mon Jan 22 2018


No significant changes to previous forecast in the update this
morning with minor adjustments based on current observed trends.
Weak shortwave passing through the region today will bring snow
showers to the mountains as well as portions of SW MT with valley
accumulations generally less than an inch while some SW MT Mtn
ranges pick up 1 to 3 inches of snow. Drying behind the lead piece
of shortwave energy is already working into NW portions of the
forecast area this morning and should expand across much of
N-central MT this afternoon. Surface low pressure in southern AB
will begin departing to the east today but moderate pressure
gradient extending across N-central MT will maintain breezy to
locally windy conditions. Hoenisch



Continued progressive westerly flow aloft will bring a series of
weak weather disturbances through the region this week. Periods of
light snow can be expected in the mountains with valleys and
plains remaining mostly dry. Temperatures will remain near or
slightly above seasonal averages through much of this week.


Updated 1148Z.

An upper level disturbance will spread snow over the mountains of
the Continental Divide and areas of light snow across portions of
Southwestern Montana today. Periods of IFR/MVFR conditions can be
expected at affected terminals in Southwest Montana, including KBZN,
KEKS and KDLN but mountains will remain obscured. Remainder of the
forecast area will see mainly VFR conditions, increased cloud cover,
and breezy/gusty winds. Conditions will improve from west to east
after 00Z Tuesday. mpj


/ISSUED 448 AM MST Mon Jan 22 2018/

Today through Wednesday..A weak shortwave will bring widespread
snow and areas of blowing snow to the high mountains along the
Continental Divide today with periods of light snow also expected
across Southwest Montana. Snow accumulations are still expected to
remain less than one inch for the southwest valleys, but 2 to 4
inches can be expected in the mountains. Only minor snow-related
impacts are expected, mainly at pass level, so a winter weather
advisory will not be issued. In the north, surface winds will
increase and become gusty along the Rocky Mountain Front and over
the adjacent plains as surface low pressure develops in southern
and central Alberta, then departs eastward with a weak Pacific
cold front sweeping through the forecast area. The upper level
shortwave continues moving eastward overnight with ridging aloft
developing for mostly dry and breezy conditions over the plains
Tuesday through Wednesday. However, westerly flow aloft will
continue to bring Pacific moisture inland for persistent
orographic snows over the northern Continental Divide Temperatures
will remain near or slightly above seasonal averages on Tuesday
but Wednesday will see the warmest temperatures for the upcoming
week as thickness values increase substantially. mpj/PN

Wednesday night through Monday...Medium range models continue to
show a broad upper level trough moving inland across the western
USA, then continuing eastward through the Northern Rockies
Wednesday night through Friday. Bulk of associated energy and
precipitation is still expected to remain mostly south of
Montana, but abundant Pacific moisture entrained in the upper
trough will bring widespread precipitation to Western Montana,
the mountains of the Continental Divide and much of Southwest
Montana. Additionally, unsettled conditions due to lower pressure
aloft will allow a chance for some light precipitation to move
out over the plains at times during this period. On Thursday,
models indicate that a moderately strong surface cold front will
sweep through the region leaving a cooler airmass and unsettled
condtions in place Friday and Saturday. Models are now showing
strong and fast westerly flow aloft with anti-cyclonic curvature
Saturday night before a weak ridge develops Sunday night through
Monday. This strongly progressive pattern will continue to bring
more of the same weather to the region... dry and windy over the
plains while the western mountains continue to see light high
mountain snows. mpj


GTF  38  25  36  28 /  10   0   0   0
CTB  38  21  33  22 /  10   0   0  10
HLN  32  12  29  14 /  30  10   0  10
BZN  26  10  28  14 /  50  20   0   0
WEY  22   5  23  12 /  70  40  20  30
DLN  28  15  29  19 /  40  10   0  10
HVR  37  18  27  14 /   0   0   0  10
LWT  36  19  32  20 /  20   0   0   0



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