Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 262136
Area Forecast Discussion
National Weather Service Great Falls MT
236 PM MST Sun Feb 26 2017
Tonight through Tuesday...A shortwave trough over southern BC, the
Pac NW, and vicinity this afternoon should cross our CWA from west
to east between mid-morning and early evening on Monday. As
predominantly cyclonic flow aloft occurs, another shortwave trough
should advance eastward across our CWA during the day on Tuesday. At
the surface, a cold front has stalled along the Big/Little Belts and
Big Snowy Mountains. This front is expected to remain nearly-stationary
across this area through much of Monday morning. By late Monday
morning, the front should begin advancing slowly northward as a
warm front due to weak low-level WAA ahead of the first shortwave
trough. By late Monday evening, southerly to southwesterly flow is
expected region-wide behind this weak warm front. On Tuesday, a
Pacific cold front is expected to cross the CWA as the second
aforementioned shortwave does the same thing, causing
predominantly southerly surface winds to veer to westerly.
The above pattern will support periods of light snow across the CWA,
especially the rest of today into Monday. However, brief periods of
moderate to heavy snow are possible tonight into Monday morning
along and near the stalled front across the central third of our
forecast area. Here, snowfall rates may occasionally reach a half
inch to 1 inch per hour within a narrow band or bands due to
enhanced lift along the front extending through the dendritic snow
growth zone, where abundant moisture is also expected. Thus,
efficient snow production and higher snowfall rates are not out of
the question. Tough to say where exactly the heaviest and most
persistent snow will occur, but Great Falls, Helena, and Lewistown
may experience some heavier snow showers. In addition, periods of
moderate snow are expected along eastern aspects of the Rocky
Mountain Front, along/just north of the Continental Divide in far-
southern Southwest MT, and along the Bridgers due to upslope
flow. Thus, winter weather advisories remain in effect for much of
the CWA the rest of today into Monday. Please see our statements
for additional details, including expected additional snow
Later Monday into Tuesday, more snow showers are expected,
especially along the Continental Divide and along the higher terrain
of Central and Southwest MT. Elsewhere, much less precipitation is
expected due to developing downslope flow. Below-normal
temperatures will prevail during the period.
Tuesday night through Sunday...Period begins with a fast NW flow
aloft over the region. Surface low develops east of the Rockies in
AB Tues night and quickly moves SE across eastern MT on Wed.
Increasing winds Tuesday night through early Wednesday with strong
winds possible along the east slopes of the Rockies. Enough snow-
cover will probably be present for potential blowing/drifting snow
issues across western portions of north-central MT, particularly
where winds will be strongest along the Northern Rocky Mtn Front.
Fast W/NW flow aloft continues through the rest of the upcoming week
with next stronger shortwave moving east along the MT/AB border
Friday night. Models continue to advertise favorable pattern for
widespread strong winds in association with this feature
Friday/Friday night but have backed off some with the strength of the
low emerging east of the Rockies on the Canadian Prairies as well as
overall wind speeds aloft. Temperatures will gradually warm through
the later part of the upcoming week before cooling again next
Flight conditions continue to deteriorate from north to south today
with widespread IFR/MVFR and areas LIFR conditions due to light
snow, low clouds and fog in north central and central Montana.
MVFR/VFR conditions in southwest Montana not expected to deteriorate
significantly until the weather system spreads southward overnight.
Conditions are expected to gradually improve Monday morning.
.PRELIMINARY POINT TEMPS/POPS...
GTF 7 22 14 29 / 70 50 20 10
CTB 3 18 7 23 / 60 40 20 20
HLN 10 23 11 27 / 70 50 20 20
BZN 14 25 10 26 / 30 20 30 30
WEY 11 22 4 19 / 70 60 60 60
DLN 12 26 11 25 / 20 10 20 20
HVR 9 22 13 28 / 50 30 20 20
LWT 10 21 10 28 / 80 60 20 20
Winter Weather Advisory until 11 AM MST Monday Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Jefferson...Judith Basin...Meagher counties.
Winter Weather Advisory until 5 PM MST Monday for Southern
Winter Weather Advisory until 5 PM MST Monday For the Bridger
Range in Northern Gallatin County.
Winter Weather Advisory until 11 AM MST Monday Northern Rocky
Mountain Front...Southern Rocky Mountain Front.