Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 190949
AFDTFX

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

.SYNOPSIS...

A fast west to southwesterly flow continues across the region
with mild temperatures and breezy to windy conditions expected
this afternoon. The next in a series of Pacific weather systems
moves onshore tonight with a cold front moving east across the
area Friday. Showers will accompany the front on Friday along with
shift to west winds and cooling temperatures. Cooler but
continued breezy to windy conditions are likely through Monday.

&&

.DISCUSSION...

Today through Saturday...Upper trough approaching the west coast
today amplifies some with flow aloft backing to more southwesterly
over the Northern Rockies and MT by this afternoon. Southwest
flow aloft and already mild temperatures to start this morning
will allow afternoon temperatures to warm well into the 70s for
most lower elevation areas this afternoon. Backing flow aloft and
decreasing stability at ridgetop levels will make conditions less
favorable for mountain wave enhanced winds along the northern
Rocky Mtn front this morning and expect gusts there to gradually
subside below high wind criteria early this morning. Afternoon
mixing will support the transport of moderate southwest flow aloft
to the surface across much of the area later today with
widespread gusts to 25-35kts. Pacific trough and front moves
onshore late tonight and progress east across north-central and
southwest MT Friday. Showers increase along the continental divide
Friday morning and accompany the frontal passage across southwest
Montana Friday afternoon with a few showers also possible as the
front moves east across north-central MT Friday afternoon. Winds
shift to westerly and become gusty following the frontal passage
Friday with temperatures cooling back to the 50s and 60s at lower
elevations. Snow levels lower to around 5000-6000 feet behind the
front with some potential for snow showers at pass levels late
Friday afternoon and evening before precipitation decreases Friday
night. Cooler but continued breezy to windy conditions are
expected Saturday as a period of drier westerly flow aloft shifts
across the region. Hoenisch

Saturday night through Thursday...The weather pattern will continue
to quickly evolve through the upcoming weekend as the longwave
trough pushes east, leaving behind a quasi-zonal flow aloft. While
normally this would yield benign or near-seasonal weather
conditions, this will not be the case. To the southwest, a strong
upper-level ridge will develop which will lead to steepening
heights/increasing upper-level flow along the northern Rockies. This
will transition into yet another high wind event during the day on
Sunday for most of the CWA, especially along the Rocky Mountain
Front, east across the Plains. While the exact magnitude and of the
event remains uncertain this far out, maximum wind gusts will have
no problem peaking again 35-45mph across the Plains, with the
potential for higher gusts above 50-55mph along ridgetops. Expect
these numbers to be fine tuned as we get closer to the upcoming
weekend. With the upper-level flow set in place, expect gusty
winds to persist into the overnight hours Sunday night and to a
lesser extent into Monday. We will see another cold front swing
through during the day on Monday as a weak disturbance rides the
progressive westerly to northwesterly flow aloft. There may be
enough moisture around to squeeze out a few showers along northern
areas, but coverage will be limited. Temperatures will drop off
again for afternoon highs on Monday thanks to the passing front,
and a developing PacNW surface high draining in cooler air from
the northwest. Much of the same will be expected on Tuesday as the
surface high drifts east across Montana. The good news is with
this surface high in place, winds are not expected to be a
problem. Wednesday, another cold front will dive south from
southern Canada. GFS and ECMWF solutions currently are not in
agreement on timing, which will have a big impact on how warm we
get for afternoon highs on Wednesday. At this time, regardless of
frontal speed, it is likely SW low-level flow will support
adequate downsloping, enough for a relatively warm day before the
front knocks temperatures down yet again Wednesday night. Looking
even further out Thursday and beyond, the pattern stays relatively
inactive with a NW flow in place, temperatures should remain near
seasonal average while staying relatively dry. KLG

&&

.AVIATION...
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

&&

.FIRE WEATHER...

Gusty southwest winds will develop this afternoon as
moderate southwest flow aloft mixes down to the surface. Mild and
dry conditions have continued overnight across much of the plains of
north central MT with further warming and drying this afternoon
creating critical fire weather conditions in grassland fuels.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  75  48  60  36 /   0   0  30  10
CTB  68  40  55  33 /   0  10  10  10
HLN  73  42  54  34 /   0   0  40  10
BZN  74  41  60  30 /   0   0  60  40
WEY  60  30  46  23 /   0   0  70  70
DLN  71  41  52  27 /   0   0  40  10
HVR  75  43  63  36 /   0   0  20  20
LWT  75  45  63  33 /   0   0  40  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
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.

&&

$$

weather.gov/greatfalls


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