Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250233
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
833 PM MDT Thu Sep 24 2020

.UPDATE...

Winds are decreasing in the wake of the strong cold front that
moved through the area late this afternoon and evening. A few
showers are possible over portions of the area overnight as ascent
from an associated shortwave moves overhead. With the decreasing
winds and increasing relative humidity, have gone ahead and
cancelled the Red Flag Warning across the area. Have updated pops,
winds, and sky cover to current trends. The previous forecast
discussion and an updated aviation discussion are below. STP

&&

.DISCUSSION...

Tonight through Saturday Night...

Red Flag conditions being met at several locations so far as
mixing ahead of front has temps in the 80s and Rh in the teens.
Winds are gusting in the 40s in the foothills and 20-30 mph over
some areas on the plains. Frontal passage from the north is still
pegged for later this afternoon through mid evening. Frontal
timing looks to be around 2-4pm from Livingston to Roundup, 3-5pm
Miles City to Billings to Red Lodge, 6-8pm for Sheridan to Baker
to Alzada. A band of post-frontal showers may develop thanks to
favorable upper dynamics, but lower levels are quite dry so we do
not expect much wetting rain. Winds will back off after sunset but
remain brisk in the foothills.

Friday will see temperatures around 70 with much less wind over
the plains. We may still see breezy to brisk west winds in the
foothills. Scattered showers are possible by late afternoon over
the mountains, spreading into the plains Friday night into
Saturday thanks to mid to upper jet forcing and good mid level
moisture advection.

We are becoming a little more concerned regarding winds Friday
night into Saturday. The foothills will certainly see strong winds
gusting to 45+ mph from Livingston to Big Timber. Model proggs
are also showing a 700mb wind max of 60kts sliding over our
central zones (including Billings) around 9 AM Saturday. Soundings
suggest decent mixing at that time which could tap into those
stronger winds. Therefore, we have raised our wind speed forecast
for Saturday across the plains and will initiate stronger
messaging regarding this wind episode. These could impact outdoor
activities and driving high profile vehicles. Temps will only be
in the lower 70s Saturday with RH in the 20s, so fire weather
concerns are elevated, but not screaming red flag for now. BT

Sunday through Thursday...

Unsettled weather can be expected to continue into Sunday as a
strong jet stream remains over the forecast area. A few
disturbance in the northwest flow, will provide diminishing shower
potential across the region. Windy conditions are also expected
to continue through much of the day Sunday, with gusts of 25 to 35
mph common, and higher gusts along the eastern Montana border.
Meanwhile, a quite amplified ridge of high pressure is building in
the Pacific Northwest.

The ridge over the Pacific Northwest shifts east toward the CWA
on Monday. This results in strong northerly flow aloft over the
region. This pattern is progged to remain in place through the
rest of the period. At this time, flow looks quite dry, so no
precip is expected. Models seem to keep a backdoor front hanging
around the eastern portions of Montana, resulting in a bit of a
temperature gradient from west to east. At this point there is
about a 10 to 15 degree difference between western zones
(Livingston to Billings) and eastern zones (Miles City to the
eastern Montana border, with highs in the 60s along the eastern
Montana border. Gilstad

&&

.AVIATION...

Cold front has pushed through the entire area and W-NW winds are
decreasing most places. Expect gusts of 25-35 kts at K6S0 and KHWQ
through the evening...then 15-25 kts overnight. SW-W winds will
increase again along the western foothills by Friday afternoon.
Gusts could approach 40 kts at KLVM after 22z.

Otherwise, VFR will prevail tonight and Friday, with some mid
level clouds possibly yielding a few light rain showers tonight.
Mountains may be occasionally obscured.

JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 051/073 053/067 045/064 045/076 047/069 043/068 041/072
    20/B    22/W    22/W    00/U    11/U    00/U    00/U
LVM 042/072 045/064 036/063 040/075 043/073 038/072 038/076
    21/N    43/W    22/W    00/N    11/U    00/U    00/U
HDN 049/074 051/067 041/064 040/075 044/069 040/067 037/071
    20/B    22/W    22/W    10/U    11/B    10/U    00/U
MLS 049/073 051/067 043/063 040/072 045/066 039/063 036/067
    20/U    22/W    22/W    11/B    11/B    11/U    00/U
4BQ 049/074 051/067 042/062 039/072 046/066 039/062 036/067
    10/B    23/W    12/W    11/U    11/U    11/U    00/U
BHK 048/072 049/065 040/061 038/069 041/062 036/059 033/063
    20/B    21/N    22/W    11/N    11/N    11/U    00/U
SHR 044/075 047/068 037/062 036/074 043/068 038/066 036/071
    10/B    13/W    23/W    11/U    21/U    11/U    00/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Red Flag Warning in effect until 9 PM MDT this evening FOR
      ZONE 117.
WY...None.

&&

$$
weather.gov/billings


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