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000
FXUS65 KTFX 110044
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
544 PM MST Tue Dec 10 2013

.UPDATE...

Early update to forecast this evening as temps have fallen quickly
over western portions of north central MT where partial clearing
has occurred. T/Td spreads are also very small across these same
areas, which includes Great Falls, and have added the mention of
patchy fog this evening. By midnight, expect pressure gradients to
favor south to southwest surface winds along the east slopes of
the Rockies and adjacent plains which will allow temps to rise
later tonight. Hoenisch

&&

.AVIATION...
UPDATED 2340Z.
A weakening upper-level trof currently making it way through central
MT is bringing widespread cloud cover, with mix of VFR/MVFR
ceilings.  There is also some -SN with the trof, primarily in the
area from KGTF south to KBZN and east to KLWT.  Expect snow to
steadily dissipate and all stations return to VFR conditions by
02-03Z.  The only weather items of note for the overnight period
will be patchy fog vcnty KHVR/KLWT/KBZN and wind gusts increasing to
around 25 kts at KCTB by early Wed morning.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED 430 PM MST Tue Dec 10 2013/
Tonight through Thursday...Models indicate a relatively quiet
period of weather. The weather disturbance aloft responsible for
Tuesdays snow will be moving into eastern Montana Tuesday evening
so lingering snow will be ending. An upper ridge from off the
Pacific Northwest coast and extending north will move inland
Wednesday and weaken as it moves into Montana on Thursday. About
the only threat for snow from Wednesday into Thursday will be over
the mountains of the Rocky Mountain Front. There will be however
an increase in moisture across the north Thursday night and have
expanded the area with a slight chance of snow a little. The
approaching upper ridge will result in a warming trend with highs
likely reaching the 35 to 45 degree range over the east slopes on
Thursday. The main weather concern during the period will be the
threat for high winds for the Rocky Mountain Front later Wednesday
night into Thursday evening. Westerly flow aloft will be
increasing over that area and other factors should also contribute
to an increased threat of high winds. For now confidence is not
high enough to go with a high wind warning so will keep the
highlight as a high wind watch for now. Blank

Thursday night though Monday...An upper level low pressure
shortwave will move through the Pacific Northwest Thursday night
and cross the Northern Rockies by early morning Friday. This will
bring in increased chance of precipitation across central Montana
Thursday night and Friday, and some accumulations at higher
elevations could be significant. The shortwave will also keep the
surface lee trof in place and the resulting brisk winds across the
Rockies and adjacent plains. High pressure will rebuild aloft
again by late Friday although several weak disturbances will be
moving through the northwest flow aloft. This will keep the air
mass unsettled with at least a chance of precip in most areas. A
low pressure trof in Alberta will rotate across eastern Montana
Saturday. Most of the dynamics will remain to the east however the
chance of precip will increase once again and an associated cold
front will drop south and bring cooler temps across mainly the
northern and central zones. By Saturday night, another shortwave
will cross the Pacific Northwest and increase the threat of
precipitation again. The models disagree somewhat on temps with
the GFS being cooler than the ECMWF. This system will also develop
a strong low pressure trof along the lee of the Rockies. Strong
and gusty winds should develop across the Rockies and adjacent
plains although at this point the models have not been consistent.
Unsettled northwest flow aloft will continue through the end of
the period and a chance of precip and breezy conditions will
continue. Temperatures will not vary too much from normals,
dropping slightly below early in the period and rising back to
near or slightly above normals by Sunday. Zelzer

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF   2  33  23  42 /  20   0  10  10
CTB   0  31  21  38 /  10   0  10  10
HLN   7  28  15  35 /  10   0  10  10
BZN  -1  24   7  34 /  20   0  10   0
WEY -14  17  -3  26 /  30  10  10  10
DLN   1  25   8  33 /  10   0  10   0
HVR  -8  25  13  32 /  10  10  10  10
LWT   3  34  19  44 /  40  10  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH from Wednesday evening through Thursday evening
Northern Rocky Mountain Front...Southern Rocky Mountain Front.

FLOOD ADVISORY until further notice for the Gallatin River near
Gallatin Gateway.

&&

$$


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