Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 280306

Area Forecast Discussion...Updated
National Weather Service Billings MT
906 PM MDT Thu Apr 27 2017


Convective precipitation band continues from Roundup through
Billings and south into the Pryor mountains this evening producing
periods of heavy rain. Upslope into the Beartooth front is also
producing rain and snow from Red Lodge to Big Timber. Isentropic
ascent can be found from Treasure county south into Sheridan
county where snow is coming down above 3500 feet. All of these
processes are expected to continue through the night in about the
same locations, though the isentropic lift may push a bit further
northwest toward Billings overnight. Adjusted precipitation
chances just a bit for current radar and 00z model trends, but
this didn`t change the character of the forecast much. As
temperatures cool into the 30s will see mix of rain and snow work
down into the valleys. Could see some light accumulations on
grassy surfaces in the Valleys, with a couple of inches in the
foothills. More significant snow will continue in the Bighorn and
Pryor mountains and foothills where going Winter Storm Warnings
are unchanged. Webcams on I-90 south of Crow Agency through
Sheridan county show poor visibility and roads becoming slush/snow
covered. Higher elevation cameras showing snowpacked roads at this
time. This system isn`t going to be quick to clear so expect
additional periods of rain/snow tomorrow, ending tomorrow night.


.SHORT TERM...valid for Fri and Sat...

Lots of energy dropping into the central Rockies cutting out a
powerful upper trough across our region. This pattern has created
an inverted surface trough from SE Wyoming to north central
Montana cutting right through our CWA. This will continue to be
the focus for precipitation, and over the Big Horns region will
be aided by deep northeasterly upslope flow in the 825-400 mb

Currently, accumulations are being muted by the warmth of the
day, but once the sun sets and dynamic cooling kicks in even
stronger we should see the snowfall pile up much more efficiently.
We are still looking for around a foot or more of snowfall in the
Big Horns with generally lesser amounts in the foothills and
about 4-6 inches around the city of Sheridan. The precipitation
will likely continue through Friday morning before it begins to
taper slowly down. Much of the precipitation will be over by
Friday evening as wind fields in the lower levels turn more

Other areas may see a couple of inches of wet snow overnight into
Friday...mainly over higher hills south of Billings and possibly
over N/NE facing slopes in the foothills of the Beartooths,
Crazies and Belts...and possibly in the Bull Mountains. Roads are
expected to generally remain just wet at lower elevations, so we
do not plan to issue any advisories at this time.

For Saturday, the upper low will dive further south. However, its
quasi-axis will still need to drift over our area and could lead
to a few rain or snow showers. The higher terrain has the best
shot of anything measurable. We certainly do not expect much if
any impacts on Saturday as temps try to warm up to the 55 degree
mark in many locations. BT

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

Not much change needed to the extended period which will feature a
NNW flow aloft with energy in the flow, until the end of the
period when an upper ridge will build into the area.

Jet energy will dive SE through the region for most of the period.
On Sunday, models showed a surface low moving SE from S. Canada
and it`s attendant cold front moving through the area. The front
will spread isolated to scattered showers across the area through
Sun. night, as well as windy conditions. Showers with afternoon
thunderstorms will continue on Monday due to the energy aloft.
Windy conditions will continue as well behind the cold front. More
showers will continue Mon. night and Tuesday with the energy
aloft. Thunderstorms are possible Tue. afternoon. The showers
will decrease Tue. night.

Anticyclonic flow ahead of the ridge will move in on Wednesday
with drier conditions, and Thursday looked dry under the ridge.
Temperatures will be around normal for much of the period, except
for Thursday, when highs will approach 70 in many areas. Arthur



Rain and snow will affect areas from Roundup to KBIL to KSHR
tonight, with the heaviest precipitation expected from KBIL to
KSHR. Scattered rain/snow showers will affect much of the
remainder of the area. Expect MVFR/IFR conditions in the rain and
snow with IFR to LIFR conditions around KSHR. The Bighorn
Mountains will be obscured, while areas of obscuration will affect
the other mountains. These conditions will persist through Friday
morning, with conditions slowly improving Friday afternoon.



    Fri     Sat     Sun     Mon     Tue     Wed     Thu
BIL 036/047 035/055 037/060 041/057 039/056 039/063 042/068
    +7/O    32/W    22/W    32/W    34/T    32/W    11/B
LVM 031/046 027/053 033/056 036/055 035/055 034/062 038/065
    56/O    22/W    23/W    33/W    33/T    32/W    21/B
HDN 035/050 034/056 035/062 040/058 038/058 038/063 040/069
    +7/O    22/W    22/W    33/W    34/W    32/W    11/B
MLS 034/054 035/058 036/062 042/058 039/058 039/062 041/068
    22/O    11/B    01/B    23/T    23/W    22/W    11/B
4BQ 033/051 031/056 032/061 040/057 037/055 037/060 039/066
    43/O    11/E    01/U    33/T    24/W    22/W    11/B
BHK 027/052 029/057 032/060 037/056 035/055 034/057 036/062
    10/B    01/B    01/U    33/T    23/W    21/B    11/B
SHR 031/041 028/049 029/055 037/052 035/052 035/057 036/063
    +9/O    32/W    11/B    33/W    34/W    32/W    11/B


MT...Winter Storm Warning in effect until midnight MDT Friday
      night FOR ZONE 38.
WY...Winter Storm Warning in effect until midnight MDT Friday
      night FOR ZONES 98-99.


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