Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 272121

Area Forecast Discussion
National Weather Service Billings MT
321 PM MDT Mon Mar 27 2017

.SHORT TERM...valid for Tue and Wed...

An upper trough was approaching the area to the west and was
generating scattered showers west of Billings. These showers will
become more numerous as the trough approaches. Raised PoPs for
tonight. Models have been robust on QPF amounts south of Billings
into Sheridan county through Tuesday morning for this event with
the GFS heaviest. Have maintained the Winter Weather Advisory for
the Bighorn mountains, with the heaviest snow being late tonight
through Tuesday morning. 850mb temperatures stay fairly warm
through the night, but do fall to around 1c along the foothills
late tonight. Rain could mix with some wet snow over the western
foothills. Kept accumulations down due to warm day today and the
lack of dynamic forcing, but should be able to put an inch,
possibly two, down at Red Lodge overnight.

The system works southeast through the day over south central
zones and Sheridan county, but the forcing gets held up over an
inverted surface trough over southeast Montanan during the day
Tuesday. Have raised PoPs Tuesday for the southeast, as the GFS
was producing around a half inch of rainfall over Carter county.
The rest of the area will dry out Tuesday afternoon.

Tuesday night and Wednesday will be a drying period for the
forecast area as low level downslope flow takes over. Temperatures
will be held in the mid 40s to mid 50s Tuesday, with clouds and
showers around, but will be allowed to modify into the 60s on
Wednesday with more sunshine. TWH

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

An active weather pattern will continue through the extended
period...especially during the beginning of the week.
Temperatures will generally be near or just above normal through
the week.

The big weather story of the extended period is a large upper
level low. This low will approach the western US Thursday and
then strengthen and dive towards the Four Corners region by
Friday afternoon. As this upper level low moves southeast Thursday
afternoon rain and heavy mountain snow will begin to overspread
the region as good upper level support forms an area of low
pressure over Wyoming. Rain and mountain snow amounts are highly
uncertain now given the fact the model differences in the strength
of the low pressure. The GFS is stronger with this low and with
the upper level support, so precipitation amounts are higher with
this solution. On the other hand the EC and Canadian solutions are
weaker with this low pressure and much further south with the
parent upper level low, so they are a little bit drier. Right now
the forecast calls for near an inch of precipitation in the
mountains (amounting to 8-12 inches of snow), and about 0.5 inches
of rain in the lower elevations. Foothills will see a mix of rain
and snow, with precipitation amounts nearing 0.75 inches. Forecast
precipitation amounts will change as the models come into better
agreement so be sure to stay up to date with the forecast.

While precipitation amounts vary, most model solutions are in
agreement that things will clear out overnight Friday with a nice
beginning to the weekend possible on Saturday. After that, model
solutions begin to quickly diverge so left rain chances in the
forecast on Sunday and Monday until model agreement improves.



A disturbance will work in tonight and produce an area of showers
over western locations (KLVM). These showers will spread into
central locations (KBIL/KSHR) overnight tonight and continue into
Tuesday morning. The heavier showers will lower conditions to MVFR
nearest the mountains and foothills. Some wet snow will mix in
with the rain over elevations above 4500 feet and cause local IFR
to LIFR conditions. The east (KMLS/KBHK) will remain VFR through
the night. The mountains will be obscured with areas of moderate
to heavy snow. TWH



    Tue     Wed     Thu     Fri     Sat     Sun     Mon
BIL 041/055 035/063 041/061 042/052 033/057 038/062 040/061
    66/W    10/B    13/R    65/R    21/U    11/B    12/W
LVM 032/054 029/060 038/055 034/049 029/057 035/061 036/058
    93/W    11/N    25/R    53/O    11/U    11/B    22/W
HDN 039/053 032/064 038/065 041/054 032/059 035/063 036/063
    56/W    10/B    13/R    55/R    31/B    10/B    12/W
MLS 041/056 036/064 040/068 044/054 035/058 037/064 040/064
    26/W    30/B    11/E    44/R    31/B    10/B    12/W
4BQ 041/050 035/062 038/067 042/054 035/055 036/062 039/064
    38/W    61/B    01/B    46/R    61/B    10/B    12/W
BHK 037/055 036/061 037/068 040/055 034/055 034/060 037/061
    26/W    71/B    01/B    35/R    51/B    10/B    02/W
SHR 035/046 030/058 034/062 038/051 032/055 033/060 035/061
    68/W    20/B    02/R    76/R    41/B    10/B    12/W


WY...Winter Weather Advisory in effect until 9 PM MDT Tuesday FOR
      ZONE 98.


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