Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 022350
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
450 PM MST Mon Mar 2 2015
UPDATED AVIATION SECTION
Tonight through Wednesday...Canadian cold front continues to sweep
southward this afternoon. So far, snow amounts do not appear to be
measuring up to what models have been indicating. Most of this is
due to snowmelt on warm pavement but snowflake morphology appears
to be small conglomerations which are not adding up as well as large
dendritic flakes would. Also, snowfall at KCTB has been off and on
and radar imagery appears to already be showing precipitation
echoes diminishing from north to south. Forecast for this evening
calls for the main band of precipitation to move into southwest
Montana leaving only chance pops over the northern third of my
forecast area. However, overall conditions behind the front
remain generally windy, and colder temperatures are finally moving
south of the Canadian border. Wet roads are still expected to
freeze up overnight and wind chills will likely drop to near or
below advisory level. As such, I am continuing the Winter Weather
Advisory through the night, but would expect that if snow
completely tapers off in the north that subsequent shifts will end
the advisory early and/or transition to wind chill highlights.
Tonight and Tuesday night will be cold with lows expected to be
near or below zero. Tuesday afternoon highs will only climb into
the single digits above zero in the north and into the teens in
the south. Cloud cover will begin to break up on Tuesday leaving
mostly clear to partly cloudy conditions in place overnight.
Wednesday will see a transition back to more seasonable conditions
as the high pressure system moves off to the southeast and
pressure falls east of the Continental Divide allow downslope
winds to return to the region. Wednesday temperatures will climb
back into the 20s and 30s with partly cloudy skies, although some
models suggest that the return of westerly winds could cause a
Chinook Arch to develop just east of the Rockies. mpj
Wednesday Night through Monday...Extended forecast period currently
looking mostly uneventful, with broad ridge of high pressure over
the western states and Pacific coast bringing dry conditions and
warming temperatures. With the center of the ridge only moving from
the coast to the Great Basin area during this period, Montana will
be under persistent northwesterly flow aloft, with most of the
available moisture being deflected more into eastern parts of the
state. Latest forecast models are in good agreement overall, with a
slight exception Fri aftn to midday Sat. The GEM, GFS and ECMWF all
depict some variation of a shortwave trof crossing through the top
of the ridge at that time, but only the EC shows a more developed
low pressure system with widespread light snow occurring mainly Fri
night. Have kept a mention of scattered snow showers for the Rocky
Mtn Front and the central/southwest mtn ranges to cover the EC`s
solution but have little/no snow for the lower elevations. May see
windy conditions as well for the central and Hiline counties on
Thurs and Sat as leeside surface trofs develop, creating favorable
pressure gradients for stronger winds. Finally, after warming back
into the low-mid 40s on Thurs, temps don`t change much each day,
perhaps making it to the upper 40s to around 50 degrees for the
Cold front will continue to push toward southwest Montana through
the evening. Light snow and gusty northerly winds will also continue
behind the front. Snow will taper off across the north after 02z.
MVFR/IFR conditions prevail due to low ceilings, snow, and blowing
snow. Mountains obscured.
.PRELIMINARY POINT TEMPS/POPS...
GTF -4 10 -5 28 / 80 10 0 0
CTB -6 9 -7 28 / 30 0 0 0
HLN 3 17 0 32 / 100 20 0 0
BZN 1 16 -5 28 / 100 40 0 0
WEY -4 15 -19 24 / 80 50 0 10
DLN 1 19 -4 33 / 100 20 10 0
HVR -4 9 -9 25 / 30 10 0 0
LWT -5 8 -8 25 / 90 20 10 0
WINTER WEATHER ADVISORY until 11 AM MST Tuesday Beaverhead...
WINTER WEATHER ADVISORY until 5 AM MST Tuesday Cascade...Central
and Southern Lewis and Clark...Chouteau...Eastern Teton...
Fergus...Judith Basin...Southern Rocky Mountain Front.
WINTER WEATHER ADVISORY until 5 AM MST Tuesday Eastern Glacier...
Eastern Pondera...Northern Rocky Mountain Front...Toole.