Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 220928
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
328 AM MDT Fri Sep 22 2017

.SHORT TERM...valid for Tdy and Sat...

Upper low is centered over southwest Idaho early this morning.
Analysis indicated strong isentropic lift across our
central/western CWA combined with divergence at 250MB producing
a wide band of precipitation across... Webcams are showing
periods of heavy snow in the high country, which is confirmed by
the snotels. This should continue as steep lapse rates over SW
Montana are progged to persist. The DOT site indicates snowfall
from Roscoe to Red Lodge and Bearcreek. Thus, things are panning
out as advertised and current highlights all look good at this
point.

The one issue we have to look at is if we should expand the
advisory area. Strong deep upslope into the Livingston area along
with strong dynamics aloft has led to a change over to snow
pretty early overnight at the Livingston airport. Models show road
surface temps hanging in the 40s, but observations indicate it is
much lower around 34 degrees. So would not be surprised to see
snow stick or conditions turn at least slushy. We will add
Livingston and Northern Park zones to the winter advisory list
that goes through noon today. Looking for 1-3 inches...mainly on
natural surfaces. Strong dynamics also affecting the stretch from
Reed Point to Rapelje and into Lavina. Snow was already reported
in Rapelje by midnight and webcams show snow sticking good at
Reedpoint. Therefore, will also throw Stillwater and Golden Valley
into the advisory list.

Models generally extend main band of precipitation across the
central and western zones this morning and leave it there until
tonight when it finally drives back out east into the plains as
best forcing aloft shifts slightly east. Another strong lobe
rotates around the upper low Saturday/Saturday Night but is
progged to affect primarily the southern and eastern sections of
the CWA. In the meantime the western zones will remain chilly with
some areas of light precipitation. BT

.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...

Upper level low will be in place over southern Wyoming Sunday
morning...helping to increase rain chances over southeastern
Montana. This upper level low will weaken and move northeast
through Tuesday morning giving much of southeastern Montana a
chance for rain Sunday through Monday night. The greatest chances
for rain are on Sunday morning and Monday afternoon as upper
disturbances move over SE MT during those times. Rainfall amounts
during the Sunday morning through Monday night time period look
light, in the range of 0.1 to 0.3 inches over SE MT.

Northwest flow aloft takes over briefly on Tuesday and Wednesday
which will give some of the mountains and nearby lower elevations
a chance for afternoon rain/snow showers.

After Wednesday a ridge of high pressure begins to establish
itself across much of Montana, which should allow drier
conditions and a warming trend in temperatures to continue
through the weekend. High temperatures start out in the lower 50s
on Sunday with the upper 60s to near 70 degrees possible by the
weekend. Dobbs/RMS

&&

.AVIATION...


MVFR to LIFR conditions are expected this morning over south
central MT in rain and snow. The snow is occurring west of KBIL,
affecting K6S0 and KLVM. The precipitation should taper to
scattered showers during the midday hours today. CIGs look to
improve only to MVFR though due to low-level east/northeast winds
keeping a cloud deck in place. KSHR could have MVFR CIGs this
afternoon. Mountains will be obscured today. RMS
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-------------------------------------------------------
BIL 044 037/049 039/051 039/056 040/061 043/063 043/065
    8/R 53/W    33/W    31/B    11/B    11/B    11/U
LVM 040 031/048 031/050 032/055 035/057 037/060 036/064
    9/O 42/W    22/W    31/B    12/W    21/B    11/U
HDN 048 039/052 039/052 038/057 037/063 041/064 040/067
    3/R 64/W    43/W    32/W    11/B    11/B    11/U
MLS 052 040/051 040/053 039/055 038/061 041/064 041/066
    2/R 35/W    54/W    32/W    21/B    11/B    11/U
4BQ 054 040/047 040/049 038/049 036/059 039/062 039/063
    2/R 47/W    75/W    33/W    21/B    11/B    11/U
BHK 052 040/050 041/051 038/052 038/058 038/062 040/063
    2/R 36/W    65/W    23/W    31/B    01/B    11/U
SHR 051 036/045 035/046 034/050 033/058 037/060 036/063
    3/R 57/W    55/W    43/W    21/B    11/B    11/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Weather Advisory in effect until noon MDT today FOR
      ZONES 34-40>42-56-65-66.
     Winter Storm Warning in effect until 6 AM MDT Saturday FOR
      ZONES 67-68.
WY...None.

&&

$$
weather.gov/billings


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