Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 250501

Area Forecast Discussion
National Weather Service Great Falls MT
1100 PM MDT Sun Sep 24 2017



One final day of well below normal high temperatures is in store
for Southwest and North Central Montana today, before temperatures
moderate into the upcoming work week. A few isolated afternoon
showers are possible over the Little Belt and Snowy Mountains and
in the West Yellowstone area, but otherwise most locations will
enjoy partly to mostly sunny skies today.


Very minor changes required tonight, mainly to increase
cloud cover in some locations through the remainder of this
evening. Skies are still expected to clear out by midnight. Also,
removed some isolated PoPs over the Little Belt Mountains as
clouds have moved out of this area. Temperatures and winds appear
to be on-track so made no changes to these forecast elements.
Region is still on-track to see increasing temperatures and dry
conditions through the upcoming week. mpj


Updated 0500Z.

VFR conditions will continue for the most part across the forecast
area through the next 24 to 36 hours. Skies will remain mostly clear
through 18Z under a northwest flow aloft, but patchy MVFR level fog
and low clouds are possible between 10Z and 17Z in the valleys of
southwest Montana. Mid and high level cloudiness will then increase
from the northwest after 18Z with the potential for mountain showers
increasing after 21Z. However, the showers will likely not impact
the terminals. Winds will also remain fairly light.


/ISSUED 453 PM MDT Sun Sep 24 2017/

Rest of today through Tuesday...The upper level trough over the
western US will begin to edge eastward over the next couple of days,
but it won`t be a quick process. As it pushes east, a NW flow will
develop aloft, allowing some low/mid level moisture to advect into
the area. While there does not appear to be any significant lifting
mechanism, steep lapse rates, increasing moisture, and an upslope
flow should allow a few showers to develop, especially over and
downwind of the mountains. Any precip amounts will be light. The
clouds will keep temps in check through Tuesday before milder air
arrives by mid-week. It will be cool overnight as well, but the
increasing cloudcover should keep temps from falling too low, even
in the typically colder valleys. The clouds should also tend to
limit fog development, especially Monday night. MARTIN

Tuesday night through Sunday...We begin to see a clear transition in
the synoptic pattern as we get into the middle of the upcoming week.
Large, highly amplified ridging returns to the Pac NW while the
lingering longwave trough responsible for the previous days cool
and wet weather finally pulls off to the NE. This will lead to the
big story, moderating temperatures. Highs on Wednesday will likely
return to near normal for many with highs reaching the mid to upper
60`s across the Plains, while the mountains stay cooler. But by
Thursday and Friday, the aforementioned ridge across the Pac NW will
slowly transition eastward, which is reflected by steadily
increasing height anomalies per the latest ensemble model forecast.
This supports a continued warming trend through the rest of the week
ahead with highs easily reaching the lower to mid 70`s across the
Plains. Long-range models have started showing increasing trends in
confidence over the idea that the ridge will eventually break down
by next weekend. This will be followed by a slow downward trend in
temperatures back to near normal, with isolated rain chances
returning into Sunday. Overall, the upcoming weather pattern
continues to suggest no extreme cold/winter weather concerns for the
next 7-10 days. KLG


GTF  35  61  41  64 /   0  10  20  10
CTB  34  63  40  64 /   0  10  10  10
HLN  34  60  41  63 /   0  10  10  10
BZN  30  56  36  60 /  10  10  10  10
WEY  26  49  27  53 /  10  10  10  10
DLN  31  54  33  57 /   0   0  10  10
HVR  34  64  40  68 /   0   0  10  10
LWT  33  58  38  62 /   0  10  10  20



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