Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 190618

Area Forecast Discussion
National Weather Service Great Falls MT
1218 AM MDT Thu Oct 19 2017


Quick update to include a High wind warning issued for the
Northern Rocky Mtn Front, where gusts in excess of 75mph are being
reported at several stations along the immediate east slopes.
Strong winds aloft and favorable conditions for mountain wave
induced winds will continue through tonight then abate Thursday
morning. Hoenisch



Breezy west to southwest winds will increase late today and tonight
across North Central Montana with windy and warmer conditions
returning Thursday. Dry and windy conditions will raise fire
concerns across Central Montana Thursday. The next front moves
across the region with showers across Southwest Montana Friday,
cooler temperatures, and windy conditions through Sunday.


Updated 0500Z.

West-Southwest flow aloft gradually backs to Southwesterly over the
next 24 hrs with VFR conditions prevailing under scattered to
broken high cloud-cover. Surface wind gusts increase to around 40kts
in the KCTB vicinity by around 12z and somewhat higher along the
Rocky Mtn front. Southwest winds increase across all areas Thursday
afternoon with gusts to 30kts likely across most of the plains as
well as some SW MT valleys, including the Madison valley and KEKS
terminal. Hoenisch



Breezy west winds this afternoon will continue into Thursday.
Additionally, afternoon temperatures will warm into the mid/upper
70s with humidity falling into the low teens over the eastern
portions of the region. Thus a Red Flag Warning is in effect for
this region. More seasonable temperatures and slightly higher
humidity move back into the region on Friday. However, it will
remain windy most days from Friday through early next week.


/ISSUED 844 PM MDT Wed Oct 18 2017/

Moist and strong southwest flow aloft will persist across the
region tonight. As such, the windy conditions will continue across
North Central Montana but models are still indicating that even
the strongest winds should remain below high wind criteria.
Combination of downslope winds and cloud cover aloft will also
prevent temperatures from falling too far. Finally, while
orographic lift will bring widespread precipitation to northern
portions of the Continental Divide, the strong downslope winds
will prevent and showers from moving out over the plains. The
current forecast package has a very good handle on all these
variables and, at this time, it appears that no update will be
required this evening. mpj

/ISSUED 502 PM MDT Wed Oct 18 2017/

Tonight through Friday...Transient high pressure exits the region
today with the next upper trough moving from the Gulf of AK toward
the BC coast. Winds aloft will increase from the SW again later
today and tonight. Gusty SW winds will persist across North-Central
MT during the period with the strongest winds along the Rocky Mtn
Front. Southwesterly flow aloft allows for temperatures to surge
back to well above average Thursday as well. The upper level trough
moves inland Thursday night and Friday with a surface front moving
east across the forecast area by Friday afternoon. Precipitation
will increase along areas near the Continental Divide Friday with
showers also possible across Southwest Montana. Temperatures cool
about 10 to 15 degrees for Friday and Saturday.

Friday night through Wednesday...Look for spotty, light showers to
persist following the passage of the cold front through the
overnight hours Friday night and into Saturday. As colder air
filters in from the north, temperatures will likely continue to
drop, along with freezing-levels leading to the potential for
accumulating snow for higher elevations of south-central and
southwestern MT, especially along the Madison, Bridger and Gallatin
Ranges. This system will quickly depart early Saturday leaving
behind clearing skies with cool afternoon highs. However, by
Saturday night clouds will begin to increase from the west as
another quick moving system swings across just north of the
MT/Canadian Border. Behind this system, models continue to
confidently illustrate the development of a strong jet aloft, which
will push eastward across the Northern Rockies into the early hours
on Sunday. This will likely yield yet another high wind event across
most of the CWA beginning Sunday morning, with the peak of the event
being in the afternoon hours. Given forecast H7 wind speeds ranging
between 55-75kts across the Plains, and even higher along the Rocky
Mountain Front, strong winds aloft will have no trouble transferring
to the surface via sufficient boundary layer mixing. Having said all
of that, I have adjusted forecast wind speeds reflect a more
realistic possibility of high winds following the jet aloft, timed
with the best diurnal mixing in the afternoon hours. Looking at the
synoptic pattern as we get into next week, long-range models have
persistently been advertising the development of a re-enforcing
ridge across the Southern Pacific coastline, which will reflect
increasing heights across the majority of the western US. As strong
ridging amplifies along the entire west coast, this will transition
the upper-level flow more from the northwest and aid in the
development of a dominant surface high across the northern Rockies.
This will likely keep temperatures near, to slightly above normal
while staying dry through the middle part of next week. KLG

GTF  48  58  36  54 /   0  40  10  10
CTB  42  55  33  51 /   0  10  10  10
HLN  43  55  35  55 /   0  40  20  10
BZN  43  58  30  51 /   0  70  40  10
WEY  33  48  22  38 /   0  70  50  20
DLN  42  51  28  47 /   0  60  30  10
HVR  43  62  35  56 /   0  20  10  10
LWT  45  59  33  51 /   0  40  20  10


Red Flag Warning from 11 AM this morning to 7 PM MDT this
evening Central and Eastern Lewis and Clark National Forest
Areas...Chouteau and Fergus Counties...Hill and Blaine Counties.

High Wind Warning until 9 AM MDT this morning Northern Rocky
Mountain Front.


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