Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 201939

Area Forecast Discussion
National Weather Service Billings MT
1239 PM MST Fri Jan 20 2017


Another update this morning to cancel the Freezing Rain Advisory.
Air and road surface temps have risen above freezing in most no additional freezing precip is expected...even
though light drizzle is possible in many areas. That
said...refreezing of wet roadways will be a concern tonight.

Made several other adjustment to forecast to better reflect
current conditions. Most significant change was reduction in pops
to reflect drizzle (or flurries east) rather than measurable rain
or snow. Also warmed up western zones a bit more...Livingston had
already surpassed forecast high...and Billings is quickly
approaching forecast high...but left the east as inherited. AAG


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

Band of precipitation affecting our CWA this morning is situated
north to south, generally from the Big Horns to Musselshell and
Northern Rosebud Counties. We have not had any reports so far
other than light rain or drizzle within this band. Temps in the
east and even at Sheridan dropped well below freezing, but as
clouds moved in readings have risen dramatically preventing
freezing precipitation from depositing on sidewalks or streets.
For instance, Sheridan was down to 25 degrees, but warmed to 37
degrees as clouds moved in. Temps are much colder a little east of
the cloud cover (teens to lower 20s), so there is a risk of seeing
some freezing precipitation right on the edge of the precipitation
band before temps warm up. However, the warm layer aloft is
shallow on progged soundings. So its possible rain changes to snow
over much of the CWA by sunrise. Bottom line, we do not feel the
need for any type of winter weather advisory this morning, but our
media partners may want to mention the possibility of isolated
slick roads and bridges.

The precipitation is slowly working east and downslope flow off
the higher terrain appears to be quickly drying out our western
zones. So have lowered PoP`s in the west for the morning and
afternoon. The band of precipitation is linked to the 500 MB
jet and associated differential vorticity. Much of this forcing
weakens later today as jet maximum slides north, but some
remaining low level upslope and convergence may have precipitation
linger in the east into the evening.

Saturday, 500 MB ridging occurs over our region ahead of the next
approaching trough. Wind fields look weak so there will not be
much mixing. Temperatures will be around normal. Some Pacific moisture
moves into the mountains as the upper winds back to the southwest.
So some low PoP`s for the west facing slopes seems appropriate for
Saturday night. BT

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

Large upper trof pushes into the west coast over the weekend. As
southern stream of the jet enhances over the southwestern part of
the country a lobe of low pressure develops over Wyoming and
pushes eastward into the Dakotas. Although the upper-level pattern
is agreed upon fairly well by the GFS and ECMWF, the qpf pattern
is quite different. ECMWF keeps precip confined mainly to extreme
southern Montana and Wyoming with most of the snow south of
Billings. GFS is much more bullish with upslope flow bringing
several inces of snow into Billings. For now have gone with a
blended solution, which brings an inch or so up to south central
Montana with several inches in northern Wyoming and southern
Montana. Snow tapers of Tuesday as amplified ridging begins to
move in from the west. Expecting generally dry conditions through
the end of the week with temps near to slightly below climo. Walsh



VFR conditions will prevail from Billings west today. To the east
an area of MVFR to local IFR conditions exists this morning with
areas of snow and light rain/freezing rain. This area will slowly
diminish through early afternoon as it drifts eastward. Freezing
Rain may impact KSHR and KMLS through mid day, with just a very
slight chance of it making it into KBHK before it dissipates. By
mid afternoon expect VFR conditions all areas. Chambers



    Tdy Sat     Sun     Mon     Tue     Wed     Thu
BIL 041 018/032 021/032 016/027 016/026 012/024 012/026
    1/M 10/U    01/B    12/S    53/S    22/S    11/U
LVM 045 014/036 022/039 018/034 012/028 009/027 010/028
    1/B 11/B    21/B    24/S    42/S    22/S    11/B
HDN 038 011/029 009/030 006/025 010/024 004/022 003/024
    1/M 10/U    01/B    11/B    54/S    22/S    21/U
MLS 037 019/030 014/028 006/023 009/022 007/021 005/022
    1/M 21/E    01/U    11/B    33/S    22/S    21/B
4BQ 037 016/032 014/032 005/027 009/025 006/023 005/025
    2/W 31/B    00/U    11/B    54/S    22/S    21/B
BHK 033 021/031 014/027 005/024 010/022 008/021 006/022
    1/M 22/J    21/B    11/B    32/S    22/S    21/E
SHR 036 010/032 009/033 008/029 009/024 003/023 003/026
    2/J 20/U    01/B    12/S    75/S    22/S    21/B




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