Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 311559
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
959 AM MDT Fri Oct 31 2014

.UPDATE...
Satellite imagery this morning shows a significant amount of
cloud-cover spreading north into the region in SW flow ahead of a
deep upper level trough just off the W-Coast. Cloud-cover will
likely keep most areas from reaching record warm temperatures this
afternoon, but a few areas may still approach records or at least
values 15-20 degrees above seasonal averages. Temperatures this
morning vary quite a bit, especially across north-central MT,
where locations exposed to S/SW winds are in the 50s  while many
river valley locations are still in the 30s. Expect this to even
out over the next few hrs as afternoon warming flushes out these
pockets of cooler air. Hoenisch

&&

.AVIATION...
UPDATED 1124Z.
A high pressure ridge will continue to keep the air mass warm and
dry today. A deep low pressure trof over the Eastern Pacific will
move over the West Coast by midnight tonight and mid-high level
cloudiness will increase across Central Montana. Local MVFR vsbys
due to fog are possible near KCTB until 14z this morning. Otherwise,
VFR conditions will prevail through the next 24 hours.

&&

.PREV DISCUSSION...
/ISSUED 525 AM MDT Fri Oct 31 2014/
Today through Sunday...An upper level high pressure ridge is just
east of the zones this morning and our next weather system, a
deep low pressure trof, is over the Eastern Pacific. This leaves
the zones underneath southwest flow aloft. The air mass will
remain quite warm and some locations will see near record temps
today. Cooler air will push into the zones Saturday morning from
the north with showers developing over the Northern Rockies. The
low pressure trof from the Eastern Pacific will dig well south into
Northern California by early Saturday and move north to Southern
Idaho by late Saturday. Very weak instability will develop over
Southwest Montana Saturday afternoon and an isolated thunderstorm
is possible. Coverage will be low and will not mention in the
grids. The northward movement of the low pressure center will
bring widespread precipitating across Central Montana Saturday
night and Sunday. By late Sunday, the low pressure center will
move north over the Hiline. Precipitation will diminish from the
south and west Sunday but continue across the northeast zones.
Snow amounts of 3 to 5 inches are expected across much of the
plains with 5 to 10 inches possible at higher elevations. The
current winter storm watch will be continued. Temperatures will
continue well above normals today but tend downwards Saturday as
the cold front moves through the zones. Temperatures will drop to
below normals Sunday.

Sunday Night through Friday...With the weekend storm exiting the
area to the east Sunday night, snow showers will decrease from west
to east across the area. A more progressive westerly flow aloft will
then develop for the workweek, providing a more windy pattern with
precipitation mostly falling in the mountains with passing
disturbances. Models are in good agreement with bringing a shortwave
trough through the area Monday night into Tuesday. As mentioned, the
best chance for precipitation will remain in the mountains,
especially along the Rocky Mountain Front, while potentially strong
west winds spread out over the North Central Montana plains. High
Wind highlights may be needed, especially along the Rocky Mountain
Front. A weak upper level high pressure ridge will build into the
area on Wednesday, bringing the possibility of locally strong winds
to the Rocky Mountain Front once again. Moisture will move through
this weak ridging, which will bring a chance of showers to the
mountains and a lesser chance of showers to the plains. Another
shortwave trough will move through the area on Thursday, again
bringing the potential for strong winds to the Rocky Mountain Front.
However, the GFS (yes) and ECMWF (no) models do not agree on this,
so there is some uncertainty here. The chance for showers will
increase in the wake of this disturbance Thursday night into Friday
as the flow aloft shifts more northwesterly. Temperatures will be
about 5 degrees below normal to begin the week, but they will warm
to between 5 and 10 degrees above normal for Monday night through
Friday due to the persistent westerly downsloping winds.
Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  69  40  54  33 /   0   0  10 100
CTB  62  34  46  29 /   0   0  40 100
HLN  67  39  57  39 /   0   0  40 100
BZN  66  34  62  33 /   0   0  30  90
WEY  55  26  52  25 /   0   0  50  90
DLN  66  38  59  36 /   0   0  40  90
HVR  58  33  56  33 /   0   0  10  90
LWT  68  40  63  34 /   0   0  10  90

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH from Saturday evening through Sunday evening
Beaverhead...Broadwater...Cascade...Central and Southern Lewis
and Clark...Chouteau...Eastern Glacier...Eastern Pondera...
Eastern Teton...Gallatin...Hill...Jefferson...Judith Basin...
Liberty...Madison...Meagher...Northern Rocky Mountain Front...
Southern Rocky Mountain Front...Toole.

&&

$$

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