Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 151708

Area Forecast Discussion
National Weather Service Great Falls MT
1108 AM MDT Sun Oct 15 2017

...Updated Aviation Discussion...


Updated winds and temperatures for today and tonight, with no
significant changes from the previous thinking. Will begin to
consider wind highlights for Tuesday for this afternoon`s
forecast package given continued good model agreement with
incoming 12z models. CC



High pressure at the surface and aloft over the western United
States will maintain dry conditions with warming temperatures
through Tuesday before a series of Pacific weather systems move
rapidly east across the region later this week. Gusty west winds
will continue across portions of north central Montana today through
Monday with increasing winds in all areas Monday night and Tuesday.
Strong winds are possible across portions of north central Montana
Tuesday and at times again later this week into next weekend in
association with individual Pacific weather systems moving across
the region.


Updated 1708Z.

VFR conditions will persist across north-central and southwest
Montana through tonight under a dry/stable W/NW flow aloft. Moderate
west winds continue across western portions of north central MT
today where gusts of 30-40 kts are likely to continue at the KCTB
terminal with gusts to 25 kts at locations further south and east.
Winds increase again later tonight with a subtle frontal passage
across western portions of north central MT with gusts 30-40kts or
possibly a bit higher along and adjacent to the Rocky Mtn Front as
well as the KCTB terminal. CC/Hoenisch


/ISSUED 515 AM MDT Sun Oct 15 2017/

Today through Tuesday...Low amplitude upper level ridge across the
western US remains in place with flow aloft gradually turning from
NW to westerly today as heights continue to gradually rise. More
significant warming is expected this afternoon in response to
stronger warm advection in westerly flow in the lower to mid levels
with additional warming occurring Monday and Tuesday. Little change
in wind speeds aloft today, though the surface pressure gradient
across the Rockies weakens slightly in response to weakening of the
surface high west of the divide, resulting in continued breezy to
windy conditions across much of north central MT, though wind
speeds/gusts should be slightly lower than yesterday. Ridge begins
to flatten slightly tonight with a wind max at 700MB around 50kts
passing across the Rocky Mtn Front region tonight, providing a
chance for a period of gusts of 50kts or more there tonight. Overall
winds aloft gradually increase across much of the area Monday and
Monday night as the upper ridge flattens further. Upper level trough
moving into BC Tuesday will further increase winds aloft as the
upper level jet sags SE along the US/Canadian border. This in
combination with deepening surface low pressure across AB will bring
favorable chances for more widespread strong winds across western/NW
portions of the forecast area on Tuesday, initially for areas along
and adjacent to the Rocky Mtn front, but likely to spread east as
the day progresses. Hoenisch

Tuesday night through Sunday...Overall pattern will continue to
suggest well above-normal temperatures to persist through mid-week
with a progressive zonal pattern set up aloft across the state.
Expect a quick moving shortwave trough and surface cold front to
swing through early Wednesday which will likely bump temperatures
down a tad, but not by much with temperatures still generally
remaining above normal during the day on Wednesday. Additionally,
the big story will be continued widespread strong winds which will
likely last even into the overnight hours on Wednesday and into
Thursday. We begin to see a slight transition in the upper air
pattern beginning on Thursday as a stronger longwave trough sets up
across the west coast. With southwesterly unidirectional flow aloft
downstream of the trough, expect downsloping to aid in much warmer
temperatures, as hinted by the latest model trends the past few
days. Otherwise, it will remain dry for most areas through late
Thursday. By Friday, another quick moving, yet stronger cold front
is forecast to push across the state followed by cooler
temperatures. Latest model guidance still suggests showers
increasing in coverage following the frontal passage across the area
late Friday and into early Saturday. Timing on any cooler air and
associated precipitation will need to be watched as we get into
Saturday morning, with the potential for rain and/or snow,
especially across higher elevations of southern Montana. By the
weekend, expect any lingering precipitation to quickly exit leaving
behind periods of sun and clouds with temperatures slowly moderating
into Sunday. KLG


GTF  62  46  68  48 /   0   0   0   0
CTB  58  41  65  43 /   0   0   0   0
HLN  61  36  67  39 /   0   0   0   0
BZN  61  33  66  35 /   0   0   0   0
WEY  48  22  52  24 /   0   0   0   0
DLN  55  30  62  33 /   0   0   0   0
HVR  61  39  67  42 /   0   0   0   0
LWT  60  40  67  42 /   0   0   0   0



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