Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 020505
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 PM MDT Wed Oct 1 2014

UPDATED AVIATION SECTION

.UPDATE...
No significant changes to the forecast ahead of the frontal
passage. Have slightly changed some of the weather grids to better
align with temps and QPF across the area. Otherwise previous
forecast looks on track as latest satellite images show the cold
front south of Calgary. Suk

&&

.AVIATION...
UPDATED 0500Z.
Breezy west winds will continue across much of north central,
central and southwest Montana this evening ahead of an approaching
Canadian cold front. The front is currently just south of Lethbridge
(CYQL) and Medicine Hat (CYXH) and should reach the Hi-Line (KCTB
KHVR) around 07Z and central Montana (KGTF KLWT) between 10Z and
12Z. Behind the front, winds will become gusty (up to 30 kt) out of
the north with MVFR/IFR conditions in rain/snow following an hour or
two behind the front. The rain/snow mix with MVFR conditions reach
into the KHLN area, but only light showers with possible mountain
obscuration will reach KBZN. Conditions will improve from north to
south between 17Z and 22Z with VFR conditions and lighter northwest
winds prevailing most areas after 22Z.
Coulston

&&

.PREV DISCUSSION...
/ISSUED 720 PM MDT Wed Oct 1 2014/

Tonight through Friday...There is a slight chance of a shower this
afternoon in higher terrain as instability has increased with
diurnal heating. Otherwise, dry conditions are expected through
midnight. Breezy southwest winds will also persist. A fast-moving,
but strong shortwave trough coupled with an upper-level jet and
surface cold front will cross north-central Montana after
midnight. With ample lift along and behind the front, precipitation
and a cooler, Canadian airmass will accompany the frontal passage.
Snow levels will lower to the surface, which will lead to
precipitation type starting out as light rain, then transitioning to
a mix of rain and snow followed by a period of light snow. Forecast
models hint at enough lift and instability that there may be a period
between 6am and Noon Thursday that a heavier band of precipitation
develop, but there is uncertainty where this band will set up.
Within this band of heavier precip, a quick inch of snow
accumulation is possible, otherwise, dusting up to a half-inch of
snow accumulation is anticipated. In the mountains, particularly
along the Rocky Mountain Front and Little Belts, precip will be all
snow with accumulations of 1 to 3 inches, and isolated higher amounts
are possible. Impacts to travel are expected early Thursday morning
over Marias and Logan Pass, thus a Winter Weather Advisory remains
in effect. There may also be some travel concerns at Kings Hill Pass
and will monitor for possible additional winter weather highlights.
The cold front will be near the Canadian border around midnight,
Hi-Line around 3 AM MDT, Great Falls by 6 AM MDT. This front and
associated precipitation should stay along or just north of a line
from Helena to Bozeman, but a brief rain or snow shower is possible.
This system will quickly depart the area Thursday afternoon and
drier weather is in store for Friday. High temperatures on Thursday
will be well below seasonal averages, then return to near seasonal
averages by Friday as a ridge of high pressure builds back into the
region. MLV

Friday night through Wednesday...An upper level ridge of high
pressure will be over the region from Friday night into Monday.
As a result...mostly dry and mild conditions can be expected over
the region. There is a very small chance for an isolated shower
over the Rocky Mountain Front and north of Highway 2...but
confidence is quite low in the precip happening. It will be a bit
windy over the region Friday night into Saturday...and there is a
small potential for high wind highlights over the Rocky Mountain
Front. For Tuesday through Wednesday...the upper level ridge
begins to break down...and precipitation chances increase just a
bit over the northern portions of the region. Again...confidence
is low in determining when/where the light precipitation will
fall. Temperatures will be above normal on Tuesday...then fall a
few degrees for Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  37  45  30  60 /  50  90  10   0
CTB  35  44  29  61 / 100  60  10   0
HLN  40  50  31  63 /  10  60  10   0
BZN  33  52  27  58 /  10  30  20   0
WEY  23  48  20  53 /  10  10  10   0
DLN  32  55  29  61 /  10  10  10   0
HVR  39  49  26  58 /  50  30  10   0
LWT  37  44  29  58 /  20  90  10   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until Noon MDT Thursday Eastern
Glacier...Northern Rocky Mountain Front.

&&

$$

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