Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 280528
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1028 PM MST Tue Jan 27 2015

.UPDATE...
Updated forecast is out. Really no big changes to the evening
forecast. Pops where increased over far Southwest MT...mainly
south of a Big Sky to Dillon line...where an area of light snow
continues to push northward. Overall an inch or two is expected
tonight over the mountain passes...with a bit more in the
mountains around Big Sky/West Yellowstone. There will be a chance
for showers later tonight as far north as the Helena and Kings
Hill area...but precip amounts are expected to be light on the
northern fringes of this system. No highlights at this time.
Otherwise mainly cloudy skies expected over the rest of the region
tonight...with generally above normal overnight lows expected. The
rest of the forecast is on track. Brusda

&&

.AVIATION...
UPDATED 0527Z.
A high pressure ridge over the western US is keeping most of Central
Montana warm and dry. A weak shortwave moving across Southwest
Montana will bring a chance of MVFR cigs south of a KDLN to KBZN
line during the night. Vsbys may also be reduced due to snow mainly
at higher elevations. A cold front will cross the Canadian border
early Wednesday morning and bring a chance of MVFR cigs across
Central Montana. Elsewhere VFR conditions will prevail through
Wednesday.

&&

.PREV DISCUSSION...
/ISSUED 443 PM MST Tue Jan 27 2015/

Tonight through Thursday...Satellite imagery showing moisture
plume just getting into southwest Montana. Snow will develop over
the southwest but amounts do not look to be significant. Winter
Weather Desk analysis agrees with snow amounts of 1 to 2 inches in
the valleys with 3 to 5 inches in the mountains. The associated
shortwave moves rapidly across the area and this will also help
limit accumulation amounts. The snow gradually ends by afternoon
as high pressure begins to build back in over the area. Dry
conditions return on Thursday. Cooler air will move across the
area Wednesday as a weak Canadian cold front pushes through.
Temperatures, however, will remain above seasonal averages
Wednesday and Thursday.

Thursday night through Monday...Models are in agreement in
forecasting a return to colder and snowier conditions over the
weekend. The period will start off quiet with dry conditions and
relatively light downslope winds over the plains. A cold air mass
will spread southeast Friday night into Saturday and will be
accompanied by snow. The ECMWF model run is faster with the cold
air mass and snow than the GFS model run. Temperatures on the order
of 40 degrees in the early evening on Friday will fall to the
upper teens to lower 20s by early Saturday morning with
temperatures not recovering to freezing except over far southwest
Montana Saturday afternoon. Snow accumulations could range from 1
to 3 inches. Then another surge of cold air and snow will spread
south Sunday and Sunday night with the ECMWF model run again
faster than the GFS model run with the snow and cold. This latter
surge could bring an additional 1 to 3 inches of snow
accumulation. Note that timing of the snow and snow accumulations
will likely change over the course of the next few days. The
previous run of the GFS model started to moderate temperatures and
go drier early next week but the very latest run of the GFS is
more in line with the ECMWF which keeps most of the area in cold
air with periods of light snow. Blank

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  38  47  29  44 /  10  10   0   0
CTB  36  46  26  44 /  10  10   0   0
HLN  31  46  24  41 /  10  10   0  10
BZN  29  44  23  40 /  70  30  10  10
WEY  29  38  20  34 / 100  50  10  10
DLN  34  49  27  44 /  90  20  10  10
HVR  33  43  25  41 /  10  10   0   0
LWT  34  40  23  42 /  10  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

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