Area Forecast Discussion
Issued by NWS Great Falls, MT
FXUS65 KTFX 280549
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1035 PM MST Fri Feb 27 2015
AVIATION SECTION UPDATED
No significant changes to the forecast tonight as light upslope
snow continues to fall across parts of Central Montana.
Upper-level trough currently centered along US/Can border will
continue to push southward through MT tonight and tomorrow morning.
Expect mix of VFR/MVFR ceilings to persist thru the overnight
period, with 06Z TAFs backing off from the earlier forecast of more
widespread MVFR/IFR conditions and -SN ahead of the trough axis.
Will still see some scattered areas of snow flurries/-SN, but current
minimal precipitation coverage on radar and decreasing dewpoints at
KCTB/KHVR point to a drying airmass with less available moisture for
persistent snow. All TAF sites should be back to VFR by late
morning/midday Saturday as the trough exits into eastern MT/WY.
Northerly winds will remain light through tonight.
/ISSUED 445 PM MST Fri Feb 27 2015/
Tonight through Sunday...A couple of weather disturbances aloft will
be moving southeast through the forecast area later tonight and
Saturday. Ahead of them expect continued light snow along the east
slopes of the Rocky Mountains tonight and early Saturday morning due
primarily to upslope flow. For southwest Montana periods of snow
will be mainly over the mountains. As for snow accumulations the
lower elevations of the east slopes should get no more than an
inch while mountains from the Rocky Mountain Front to southwest
Montana could see up to 3 inches. Behind the disturbances clouds
will decrease from the north with skies finally becoming partly
cloudy over far southwest Montana by early Saturday evening.
Saturday night another weather disturbance aloft will clip the
area near and east of a Havre to Lewistown line. Models differ on
the associated moisture. Have decided to mention a slight chance
of snow showers only over the Little Rocky Mountains but there
could end up being a threat farther west. Sunday is expected to be
mostly sunny and not as cold as a weak upper ridge moves southeast
through Montana. Blank
Sunday night through Friday...Heights aloft will begin to drop again
Sunday night ahead of a shortwave trof moving through the northwest
flow aloft. Moisture ahead of this trof will move over the Northern
Rockies Monday and the associated cold front will cross the Canadian
border very early in the day. The cold front will move through
the zones during the day and move through the far southwest zones
by evening. Widespread snow will accompany this front and 1-4
inches of snow by Tuesday currently looks reasonable across the
plains and southwest valleys, and higher amounts in the mountains.
The trof will be moving east of the zones by late Tuesday. The
airmass will be drying and a cold surface airmass will allow for
very low overnight temps Tuesday night, mostly from 10 below to 20
below zero. A high pressure ridge will be building Wednesday
through Thursday. Several disturbances will move move through the
ridge in British Columbia and this will deepen the surface lee
trof along the Rockies and bring a period of brisk winds along the
slopes of the Rockies late Wednesday and Thursday. Other than the
winds, high pressure will generally remain aloft and keep the the
airmass dry and mild through Friday. Temperatures will drop well
below normals Monday night and Tuesday, and some dangerous wind
chill values will be possible. Temps will begin to trend upwards
Wednesday and reach near and above normals again Thursday.
.PRELIMINARY POINT TEMPS/POPS...
GTF 2 17 4 30 / 90 20 10 0
CTB 0 18 3 30 / 70 10 10 10
HLN 7 22 5 32 / 40 20 10 10
BZN 6 22 2 28 / 50 30 10 0
WEY -1 26 -13 31 / 40 30 10 10
DLN 7 23 2 30 / 40 30 10 10
HVR 0 20 3 28 / 10 10 10 10
LWT 1 17 2 28 / 30 20 10 10