Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 240151
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
751 PM MDT Mon Oct 23 2017

.UPDATE...

Only adjustment to the going forecast was to lower lows over the
plains. Winds have decreased significantly along the Rocky
Mountain Front under clear skies, allowing temperatures to fall
close to previously forecasted lows. Have therefore decreased
lows along the east slopes of the Rockies around 5 degrees or so.
The lighter winds will likely cool temperatures more than expected
over the eastern plains, so have lowered lows there about 3
degrees. The main cooling will occur through midnight, then
persistent wind will help temperatures plateau after midnight. The
remainder of the forecast appears to be in good shape.
Coulston

&&

.SYNOPSIS...
A brisk westerly flow aloft will reside over the region through
Wednesday. As a result temperatures will be seasonable today, but
then warm to the mid 60s for Tuesday and Wednesday. A fast moving
cold front will move southward through the region Wednesday
night, producing some rain and snow showers. The cold air will
not last long, as high pressure and warmer air return to the
region Friday.

&&

.AVIATION...
Updated 2310Z.

VFR conditions with only a few passing high clouds expected
through at least Tuesday. High pressure aloft over the western
United States will keep a fairly dry northwesterly flow aloft
over the forecast area. Gusty westerly winds will decrease across
much of the area through 02Z, except along the Rocky Mountain
Front. Breezy westerly winds will return to the plains after 15Z.
Gusts will mostly be in the 20 to 30 kt range, but gusts in
excess of 40 kt will be possible closer to the Rocky Mountain
Front. Coulston

&&

.FIRE WEATHER...

As mentioned in the main section of the discussion, relative
humidities will fall into the 15 to 25 percent range over the
plains of north central Montana ahead of a cold front. West winds
will increase to between 20 and 30 mph with gusts to 40 mph ahead
of the front Wednesday afternoon, then they will shift more
northerly and remain quite breezy for an hour or two behind the
front. The lowest humidity will be in central Montana (Cascade,
Chouteau, Fergus, Judith Basin, and Meagher Counties), so have
issued a Fire Weather Watch for those areas for late Wednesday
morning into early Wednesday evening. Humidity should recover
quickly behind the front as winds decrease Wednesday evening.

&&

.PREV DISCUSSION...
/ISSUED 510 PM MDT Mon Oct 23 2017/

Tonight through Wednesday...A couple nice days on tap to start
the week as breezy winds, clear skies, and warming temperatures
dominate Central Montana. The main concern continues to be winds
and dry conditions Wednesday afternoon. With relative humidity
dropping into the upper teens, gusty winds, and a frontal
passage, a fire weather watch has been issued for portions of
Central Montana for Wednesday afternoon and early evening. There
is also the potential for high wind highlights on Wednesday along
the front range of the Rockies and adjacent plains.

Wednesday night through Monday...A period of upslope enhanced
rain and mountain snow will move from north to south Wednesday
night, along with a rather strong cold front. Moisture appears
rather limited with this system, so precipitation totals should
range only from around 0.05 to 0.25 inches. Rain is expected to
change to snow down to lower elevations, with low temperatures
dropping into the upper 20s early Thursday. However,
precipitation rates still look to decline by the time the change
to snow occurs. Therefore, snow totals are expected to range from
around a trace at lower elevations to several inches at higher
elevations over the Rocky Mountains and the Central MT ranges.
Fair but cool weather prevails on Thursday with a northerly flow
aloft. Dry and milder conditions are expected Friday through the
weekend, influenced by an anomalously strong ridge aloft over the
western U.S. Next week Monday may turn somewhat cooler and
unsettled as a shortwave trough and accompanying Canadian cold
front advance southeastward over the region. However, models
differ on the amplitude (i.e. strength) of the shortwave and how
much moisture will reside ahead of the front. Thus, forecast
confidence for next week Monday is low. PN/Jaszka

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  64  48  66 /   0   0   0  20
CTB  34  62  43  61 /   0   0   0  30
HLN  35  62  37  67 /   0   0   0   0
BZN  32  61  32  68 /   0   0   0   0
WEY  25  52  23  53 /   0   0   0   0
DLN  33  61  34  65 /   0   0   0   0
HVR  32  61  39  65 /   0   0   0  10
LWT  31  64  42  68 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Wednesday morning through Wednesday
evening Central and Eastern Lewis and Clark National Forest
Areas...Chouteau and Fergus Counties.

&&

$$

weather.gov/greatfalls



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