Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 221538
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
930 AM MDT Wed Oct 22 2014

.UPDATE...
Other than scattered cloud cover along the Rocky Mtn Front and
portions of far southwest MT, skies are mostly clear across the
region this morning, thanks to a weak high pressure ridge over the
western half of the state.  Ridge is still forecast to makes it way
eastward through the day, keeping fair skies across our region.
High clouds will begin to increase from the west this evening as an
upper-level trof in eastern WA makes progress toward MT.  Going
forecast in good shape; just made a few tweaks to remove mention of
fog for the remainder of the morning around Bozeman (webcams there
showing clear conditions), decrease overall cloud coverage to match
current satellite imagery, and increased surface winds around
Browning/Heart Butte to match current observations there.
Waranauskas

&&


.DISCUSSION...
Today through Friday...The upper trough responsible for the recent
precipitation has moved into eastern Montana and as of 3 am there
were only a few lingering showers over north central Montana.
Expect these to end by around 6 am. As for the threat of
fog..there should be enough wind to prevent its formation this
morning with the exception of some of the valleys of southwest
Montana where winds are light. For today an upper ridge will move
into central Montana this afternoon and result in a good deal of
sunshine and no precipitation. For tonight into Thursday night
southwest flow aloft will increase along embedded moisture. Due to
downslope flow any precipitation should be confined to the western
mountains with also a small threat in the southwest valleys by
Thursday night. Snow levels will be relatively high so that
mountain passes should not see any snow.

High Wind situation...With the increasing southwest flow aloft
will have to watch the threat for high winds over the Rocky
Mountain Front this evening into Friday. Models are not in
particularly good agreement on the details of this flow. Models do
not indicate a strong stable layer above the mountains nor a
strong surface pressure gradient both of which would aid in high
wind development. Consequently do not have enough confidence to
issue any high wind highlights but there is enough of a threat
that the situation will need to be watched closely. Blank

Friday Night through Wednesday...Long term models in relatively good
agreement with larger features and timing, but showing some
differences in finer details. Period starts with an upper level high
pressure ridge covering much of the western U.S. with the next in
the series of low pressure troughs approaching from the west. Both
GFS and ECMWF show several small weather systems embedded in the
trough in a disorganized fashion though placement and strength of
these small systems varies between the models. At this time, the
trough is expected to push into central Montana late Saturday
afternoon or Saturday night, and may bring some precipitation,
mainly to the west and southwest mountains. With the current
progressive pattern, the trough moves off to the east fairly
quickly, and the high pressure barely has a chance to start
rebuilding Tuesday before the next area of low pressure sweeps in
Tuesday night. These back to back troughs are expected to bring in
some slightly colder air. Once again, could see some precipitation
with trough passages the middle of next week, but best chances
for this remain over the mountains.

&&

.AVIATION...
UPDATED 1134Z.
Mostly clear skies over area early in period as last of stratiform
precipitation exits to east and high pressure begins building.
Residual moisture from rain Tuesday and cool temperatures with calm
winds may allow development of fog is some southwest valleys early
in period, particularly at KBZN and KHLN. Conditions could drop down
to MVFR and possibly IFR in fog. Otherwise, expect VFR conditions.
Gusty winds expected across north-central Montana this afternoon,
with strongest winds near Rocky Mountains. Winds expected to
decrease near to after sunset.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  60  44  65  44 /   0  10  10  10
CTB  61  40  63  40 /   0  10  10  10
HLN  61  39  66  42 /   0  10  10  20
BZN  56  32  64  38 /  10   0  10  20
WEY  44  23  52  28 /  10   0  10  10
DLN  57  37  62  40 /   0  10  10  20
HVR  63  38  69  41 /  10   0  10  10
LWT  61  39  67  42 /  10  10  10  10

&&

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

$$

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