Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 231127

Area Forecast Discussion
National Weather Service Great Falls MT
430 AM MST Mon Jan 23 2017

Updated Aviation Discussion


Today through Wednesday...Upper level trough continues to progress
inland and across the western US through the first half of this
week. Satellite imagery this morning shows a vigorous upper low
center drifting south off the OR coast with several pieces of
shortwave energy ejecting NE across the Great Basin and Northern
Rockies. Energy moving into western MT has spread light snow
across much of north-central MT overnight and this feature will
elongate and gradually weaken today over north central MT as moves
NE into a stalled upper level low located over the Canadian
Prairies. Light snow will continue through this morning across
much of N-central MT then diminish to snow showers and flurries by
tonight as the main upper level energy weakens but moist
northerly upslope flow continues in the lower levels. Fog has
mostly improved with the arrival of snow across most of north
central MT, though some areas of locally dense fog may continue
into early this morning over Fergus county. Total snow
accumulation in these areas of around an inch or two are expected
through this morning. While snow accumulations are relatively
light, light accumulations will make roadways slick for the Monday
morning commute. In addition, some areas of black ice deposited
by fog Sunday evening will be concealed by the light snow
accumulations, making roadways particularly hazardous in some
places and will issue a winter weather advisory for locations
where these conditions are possible this morning. Further south,
the stronger energy ejecting out of the coastal trough will track
east through southern ID and WY today with light snow accumulations
also expected for areas near the ID/WY border this afternoon and
evening. Tuesday and Wednesday, the area remains under a cyclonic
N/NW flow aloft as the upper trough shifts east into the central
CONUS. This will keep a small chance for snow showers or flurries,
primarily over the Mtns and along the N slopes of the central MT
Mtn Ranges. Temperatures will remain around 10 degrees below
climatological averages. Hoenisch

Wednesday night through Monday...Overall a generally quiet weather
pattern...with a slight warming expected for the extended
forecast. Northwest flow and a broad scale trough will be found
Wednesday night into Thursday across the region. This combined with
lingering moisture could bring a few flurries to light snow showers
across the region. Best chances look to be across the
southwest...however...anywhere that receives snow will see light
accumulations at best. A large ridge then builds into the region
Thursday night...diminishing chances for any snow. This mentioned
ridge then takes over for Friday through Saturday. Dry air under
this ridge will provide for mostly sunny skies and dry conditions.
Ridge starts to flatten on Sunday...possibly bringing some breezy
winds at times to the region...but continued dry conditons. A weak
disturbance and cold front look to push through on
Monday...however...moisture appears limited with this feature...and
mainly dry conditions...with some gusty winds are expected at this
time. And even though an isolated snow shower could be
possible...left out mention for now. Temperatures are expected to
start off below normal on Thursday into Friday. The mentioned ridge
then begins a warming trend on Saturday...and continues through
Monday...with highs in the 30s to low 40s possible for the lower
elevations. The one hindering factor for the warming trend will be
found across the valleys as light flow under the ridge could bring
back an inversion set up. This would mainly affect the southwest and
the Helena Valley for Friday and Saturday. Anglin


Updated 1130Z.

Weather disturbance in moist SW flow aloft will stall over N-central
MT this morning for widespread IFR conditions in light snow with
some areas of fog persisting as well through the early morning
period, particularly in the KLWT area. Slow improvement is expected
this afternoon though light snow showers and MVFR conditions will
likely persist through tonight at N-Central MT terminals. VFR
conditions will prevail across SW MT terminals this morning with
light snow and MVFR conditions developing there this afternoon and
evening. Hoenisch


GTF  27  13  24  12 /  90  70  40  10
CTB  24  11  23  11 / 100  50  30  10
HLN  23   7  20   6 /  40  40  30  20
BZN  26   6  19   2 /  30  50  40  20
WEY  25   2  18  -6 /  70  60  30  20
DLN  31  10  23   6 /  40  40  30  20
HVR  26  13  22   8 /  90  50  20  10
LWT  26  12  21  10 /  70  70  50  20


Winter Weather Advisory until 11 AM MST this morning Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.


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