Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 190041

Area Forecast Discussion
National Weather Service Billings MT
641 PM MDT Tue Oct 18 2016

Quiet weather around the cwa early this evening. Water Vapor
imagery shows shortwave approaching from the west, and there
exists a band of showers approaching GTF-BTM-DLN. Forcing is still
a few hours from reaching our west, so have trimmed back evening
pops based on current radar/satellite trends. For Billings, the
evening should stay dry, with best chance of pcpn between 09-15z,
and feel that we will see some light showers w/ passage of mid
level front, especially as low level downslope winds are not
strong. For the mountains, expect a few inches of snow as the wave
passes, with plenty of instability helping the cause (700-500mb
lapse rates in excess of 7C/KM). Further east, a weak backdoor
front will allow for a shift to light NE winds. This is something
to watch as there is a large area of lower cigs associated with
the cooler airmass just to our northeast. Some lower clouds could
advect into MLS-BHK-Ekalaka late tonight. It is also possible that
fog forms where stratus does not, given dew points in the mid to
upper 30s. Latest HRRR runs have been suggestive of fog in our NE
late tonight. Have raised sky cover and added mention of patchy
fog to these areas after 09z. JKL


.SHORT TERM...valid for Wed and Thu...

The Pacific jet stream to our south is beginning to amplify as
ridging slowly builds up the Western US coast. As this trof pushes
southeast, showers will overspread the region from west to east
beginning tonight as jet-aided divergence crosses the forecast
area overhead. While most locations will see scattered rain
showers, a rain/snow mix possible in the hills above 4000ft and
north and west of Billings overnight. The high elevations above
6000ft in the Beartooths and Big Horns will see 4-6 inches of snow
through the morning with western facing slopes being the largest
recipients of snow. Cloudy conditions will persist through the
early afternoon before slowing clearing up from the west as the
ridge begins to take hold over the area on Wednesday. A few snow
showers could persist in the mountains until 6 pm but conditions
should quickly improve through the remainder of Wednesday night.

Winds will turn southwesterly over the forecast area on Thursday
morning and this will cue a warm up across the region. Weak
downslope conditions will move in and this will help temperatures
climb to around 60 across the forecast area. Lee-side troughing
along the Rocky-Mountain front will strengthen the pressure
gradient across Livingston which will bring an increase in the
winds through the afternoon. Held off on a wind advisory for now
but highlighted these wind concerns in the hazardous weather
outlook. Wind gusts up to 50 or 60 mph are possible late Thursday
afternoon. Currently it looks like these winds will begin to
decrease through Friday morning as the pressure gradient across
our western zones weakens. Dobbs

.LONG TERM...valid for Fri...Sat...Sun...Mon...Tue...

Upper-level ridging should dominate on Friday with dry and warm
weather. Gap winds near Livingston should decrease during the day
as the surface pressure gradient continues to relax.

Models bring a disturbance over central and northern MT on
Friday night. This disturbance could generate a few showers
mainly west and north of Billings.

Ridging should dominate again Saturday and Sunday. Ridge axis
looks to move east of the area early Monday, placing our area
under southwesterly flow aloft. Disturbances propagating in the
southwest flow can produce showers mainly over the mountains on
Monday and then extend to areas east of Billings on Tuesday. 700
mb flow looks southwesterly, which typically results in a local
drying effect near Billings due to downsloping.

Temperatures should be above normal Friday-Tuesday.  RMS/BT



VFR will prevail over the area tonight. Some showers are
beginning to develop western portions of the forecast area...but
stronger activity is expected to move in from the west yet this
evening, affecting KLVM by midnight. Showers will shift slowly
eastward overnight...reaching KBIL by early Wednesday morning.
This activity will produce localized MVFR conditions over the
lower elevations at times...with associated mountain obscurations
becoming common overnight. Patchy fog is also a concern in eastern
routes...including KMLS and the early morning hours
Wednesday. AAG



    Wed     Thu     Fri     Sat     Sun     Mon     Tue
BIL 040/054 034/060 043/067 045/063 042/065 043/064 044/063
    43/W    00/B    10/B    10/B    11/B    11/B    11/B
LVM 034/048 032/058 042/064 042/061 039/065 041/063 042/061
    62/W    00/N    11/N    21/B    11/N    12/W    22/W
HDN 037/055 032/062 039/069 043/064 040/066 041/066 042/065
    35/W    10/B    00/B    10/B    11/B    01/B    11/B
MLS 036/052 034/061 041/066 044/062 040/064 040/064 042/064
    12/W    10/U    10/B    11/B    11/U    01/B    12/W
4BQ 035/050 032/062 039/068 042/065 040/068 041/069 043/068
    14/W    10/U    00/B    00/B    11/U    01/B    12/W
BHK 032/049 031/059 037/064 041/061 037/063 038/063 040/063
    03/W    10/U    00/B    11/B    11/U    01/B    12/W
SHR 033/050 027/060 037/067 040/065 037/068 039/067 039/065
    35/W    10/B    10/B    00/U    11/B    01/B    11/B




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