Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 180246
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
846 PM MDT Tue Oct 17 2017

.SYNOPSIS...
Strong winds will continue along the Rocky Mountain Front and
over North-Central Montana this evening as a low pressure system
moves east across Alberta. Warmer than average temperatures cool
slightly and winds taper some on Wednesday. An increase in winds
and temperatures is expected again Thursday as the next in a
series of fast moving Pacific weather systems moves across the
region.

&&

.UPDATE...Strong and gusty winds continue to lash central portions
of the state this evening. The High Wind Warning for this region
continues through midnight with no changes being made to winds,
wind gusts, or the existing hazard with this update. Earlier this
evening I extended the Red Flag Warning through 9 PM MDT to give
RH values a few more hours to recover above 20 percent. This trend
appears to be on-track so will allow the RFW to expire at 9 PM as
planned. With regard to other elements of the forecast, I have
made some minor changes to overnight lows and Wednesday afternoon
high temperatures. Have also made some increases to PoPs for the
remainder of tonight. However, this applies mainly to the
mountains near the Continental Divide so precipitation forecasts
for population centers remain unchanged. mpj

&&

.AVIATION...
Updated 2330Z

VFR and vigorous westerly flow aloft persist next 24-hours. Strong
and gusty southwesterly to westerly surface winds over North-Central
Montana will begin to subside overnight tonight, especially after
06Z/Wed, before increasing again toward 18Z/Wed. In Southwest
Montana, occasionally breezy surface winds are expected through this
evening and again Wednesday afternoon. However, KEKS will likely
have a breezy, southerly surface wind through the period. Areas of
LLWS, mountain wave activity, and turbulence are likely. Lastly,
occasional rain/snow showers are possible along the Continental
Divide.
Jaszka

&&

.FIRE WEATHER...
Latest observations and model runs continue to support widespread
RH values increasing above 20 percent by 9 PM MDT. As such, the
Red Flag Warning will be allowed to expire.

It will remain breezy with slightly higher humidity on Wednesday.
However, warm temperatures, low humidity, and strong winds are
once again expected on Thursday, especially over the eastern
portions of the region. Thus a fire weather watch has been issued
for a few zones on Thursday.

Note: An afternoon fire weather forecast will be issued through at
least Thursday for the Great Falls area. Brusda

&&

.PREV DISCUSSION...
/ISSUED 530 PM MDT Tue Oct 17 2017/
Tonight through Wednesday...Models continue to deepen a surface low
heading into AB/SK tonight, giving continued support for widespread
strong winds across much of North Central MT. Winds will peak and
begin to taper some later this evening with the passage of a dry
cold front. The potential for isolated gusts of 90-100 mph exists
for favored locations along the east slopes of the Northern Rocky
Mtn Front. Further south, winds should reach into the 50kt range
across the Central Montana plains, with Southwest Montana not seeing
anything overly strong, reaching into the 30kt range for a time.
Winds subside a bit Wednesday but increase again Wednesday night
into Thursday as the next Pacific trough reaches the region.
Temperatures will warm again into Thursday under SW flow aloft
with potential for another strong wind event on the horizon for
the end of the week.

Thursday night through Tuesday...By late week, we begin to see a
swift change in the weather pattern as a quick moving cold front
passes through the area on Friday. This will introduce increasing
clouds and spotty rain shower chances. Following the cold front
passage with be much cooler temperatures as afternoon highs will
range 15 to 25 degrees cooler than on Thursday. While the better
coverage of precipitation will likely be confided to central and
southwestern areas, some higher elevations in these areas may likely
see snowfall accumulations as freezing levels drop into Friday night
and Saturday morning.  This system will quickly depart Saturday
afternoon leaving behind clearing skies during the day with highs
remaining near average. However, by Sunday the upper air pattern
begins to change yet again thanks to the development of a strong
upper ridge across the southwestern US. The associated effect across
the northern Rockies will be the development of a strong upper-level
jet thanks to increasing/steepening heights aloft which will lead to
yet another potential high wind event beginning early Sunday and
lasting into the afternoon hours. While it is a bit early to get
specific with details, model guidance remains in good agreement that
another high wind event will bring widespread strong winds,
especially along the Divide and extending east into the Plains.
Since models have been struggling with wind gusts this far along in
the forecast, I have adjusted winds to reflect a more realistic
potential given the confidence of the upper-air pattern. Stay tuned
for updates. As we move into next week, the pattern is not expected
to change much with a progressively NW flow continuing on the
northern periphery of the west coast ridge. Temperatures wont warm
much because of this, but will likely range around to slightly above
normal while generally staying dry. KLG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  64  51  74 /   0   0   0   0
CTB  36  58  44  67 /   0  10  10   0
HLN  44  66  44  73 /   0   0   0   0
BZN  39  67  39  73 /   0   0   0   0
WEY  25  53  28  58 /   0   0   0   0
DLN  37  64  38  68 /   0   0   0   0
HVR  35  61  45  76 /   0   0  10   0
LWT  39  64  45  75 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until midnight MDT tonight Cascade...Central
and Southern Lewis and Clark...Chouteau...Eastern Pondera...
Eastern Teton...Hill...Judith Basin...Liberty...Toole.

Red Flag Warning until 9 PM MDT this evening Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Eastern Glacier/Toole/Central/Eastern
Pondera/Liberty...Hill and Blaine Counties...Lewis and Clark
National Forest Rocky Mountain District-Rocky Mountain Front.

Fire Weather Watch from Thursday morning through Thursday
evening Central and Eastern Lewis and Clark National Forest
Areas...Chouteau and Fergus Counties...Hill and Blaine Counties.

High Wind Warning until 4 AM MDT Wednesday Blaine...Fergus.

High Wind Watch from Wednesday evening through Thursday morning
Eastern Glacier...Northern Rocky Mountain Front...Southern Rocky
Mountain Front.

High Wind Warning until midnight MDT tonight Eastern Glacier...
Northern Rocky Mountain Front...Southern Rocky Mountain Front.

&&

$$

weather.gov/greatfalls



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