Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 251133
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
430 AM MST Thu Dec 25 2014

AVIATION SECTION UPDATED

.DISCUSSION...
Thursday through Saturday...Snow has ended over much of Central
Montana but will continue this morning over Southwest Montana,
diminishing by this afternoon. Additional snow accumulation of 1
to 3 inches is possible over the Southwest Montana valleys with 3
to 6 inches over the mountains. The system moves out of the region
this evening but another weak trough looks to move into the region
Friday morning. A chance of some short lived light snow during the
day Friday is about all that will result. This feature quickly
passes over the region with a more substantial low pressure system
moving into the Pacific Northwest Saturday. Temperatures will
trend down through the next few days.

Saturday Night through Thursday...Forecast still on track for a
strong shortwave trof to plunge through southern
Alberta/Saskatchewan on Sat, crossing the US/Can border early Sun
morning. This system will combine its arctic air mass with a broad,
but somewhat diffuse plume of Pacific moisture, pushed into our
region by a second weaker trof along the PacNW Coast, to generate
widespread snow for Sun through Mon night. Initial estimates show
that lower elevation locations west and south of a Cut Bank-to-
Great Falls-to-Lewistown line could see snow totals of 3 to 6
inches, with mountain locations possibly receiving 8-12 inches
over the 48-hr period. Hiline counties east of that line will only
see totals of 2-3 inches. Accompanying the snow will be a sharp
drop in temperatures from Sunday through early Wed, with low temps
returning to the single digits and teens below zero over the
entire forecast area each morning during the first half of the
week. Forecast models are in good agreement that the Canadian trof
will push into the Great Basin and northern California by Wed,
allowing a strong high pressure ridge in the eastern Pacific to
build into the Northern Rockies. This will keep our region under
northerly flow aloft, with a few weak disturbances embedded in the
flow bringing scattered areas of snow to eastern portions of the
Hiline on Thurs, while rest of the region remains dry. The arctic
air mass should erode by Wed, allowing high temps to rebound back
into the mid-upper 20s on Wed and Thurs. Waranauskas

&&

.AVIATION...
UPDATED 1130Z.
Low pressure system, currently centered in southeast ID, continues
to push moisture north into MT, creating widespread MVFR and some
IFR ceilings, along with scattered areas of -SN.  Precipitation has
largely dissipated at local terminals except KBZN, so have removed
mention of precip for KCTB/KHVR/KGTF and lessened precip chances to
VCSH at KLWT/KHLN.  The system will make slow but steady progress
eastward through the day, with very gradual improvement back to
mostly VFR conditions from north to south this aftn.  Winds should
remain at/below 15 kts across the region today.
Waranauskas


&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  25  10  24  10 /   0  10  30   0
CTB  25  12  24  13 /   0  10  20   0
HLN  25   9  22   7 /  60  10  40  10
BZN  24  -1  19  -2 /  90  20  20   0
WEY  25  -2  20  -5 / 100  30  10  10
DLN  27   5  23   4 /  90  20  20  10
HVR  28  16  28  14 /   0  20  30   0
LWT  24   8  24   8 /  30  10  20   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

WINTER WEATHER ADVISORY until 5 PM MST this afternoon
Beaverhead...Broadwater...Gallatin...Jefferson...Madison...
Meagher.

&&

$$

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