Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 300246

Area Forecast Discussion...Updated
National Weather Service Billings MT
846 PM MDT Wed Mar 29 2017

Radar showing increasing light shower activity areas west of
Billings and webcams showing accumulating snow has begun in Cooke
City. Current timing of the precip well handled by forecast and no
updates will be sent. borsum


.SHORT TERM...valid for Thu and Fri...

Dynamic upper trough moving into the area from the west will
impact the weather the next couple of days. Flow aloft will back
tonight and allow deeper mid level moisture and shortwave energy
to ride into western zones and the Beartooth/Absaroka mountains.
Models have come in line in spreading strong ascent into western
and central zones late tonight and early Thursday courtesy of
coupled jets. Have raised PoPs to likely and higher from basically
Billings westward for this time frame. The time of strongest
ascent looks to be Thursday morning, with showers tapering off a
bit Thursday afternoon as jet energy slips away. West and
southwest facing slopes of the mountains will get a quick shot of
accumulating snowfall. This snowfall will likely spill over to the
northern facing slopes late tonight as the jet forces ascent
everywhere. Have decided to upgrade the Winter Storm Watch for the
Beartooth/Absaroka mountains to a warning for late tonight
through Friday evening. The strongest upslope ascent will take
place Thursday afternoon through early Friday, so the mountains
should to get a couple of shots of snow impacting various slope
aspects through the event.

The flow turns deeply upslope Thursday and continues through
early Friday. There is quite a difference in QPF amounts for the
western and upslope locations for Thursday afternoon through
Friday when comparing the GFS to the ECMWF. The GFS produces over
an inch of QPF over these locations and this was consistent with
the NAM and Canadian model. The GFS ensembles took a big jump up
in rainfall totals with the 12z run as well. The ECMWF was the odd
model out here and thus leaned heavier on the GFS and WPC
guidance for QPF totals. Have also decided to upgrade the Winter
Storm Watch to a warning for the Bighorn mountains but will start
the warning there at 12z. Mountains were looking at 10 to 16
inches of snow by the time the system is done. Rain looks to
linger into Friday afternoon as the models try to cool the lower
layers. System still looks too warm for heavy snow accumulation
concerns over the foothills, but do think some wet snow will mix
Thursday night and Friday morning for some light accumulations.
Will have to watch this closely as Red Lodge has a tendency to
"overachieve" sometimes with these Spring systems. TWH

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

The weekend will be mostly quiet and warm across the region with
high temperatures in the upper 50s and lower 60s. Rain chances
will be near zero on Saturday as a weak ridge of high pressure
sits over the region. An active weather pattern will quickly
return the the region on Sunday evening as a shortwave moves into
the northwestern US. Mountain snowfall, isolated rain showers, and
increasing clouds will move in later in day Sunday ahead of this

there is good agreement that this shortwave will then strengthen
as it passes over Wyoming on Monday so precipitation chances for
Monday and Tuesday were increased. An associated area of low
pressure will also form at the surface near central Wyoming on
Monday. With good support aloft, and strong north and
northeasterly flow in the lower levels, widespread precipitation
will develop through the day on Monday should this model solution
hold forecast. Some solutions indicate the area of low pressure
could form further south; these solutions would reduce
precipitation amounts across the region. This system also looks
colder than the last few to cross our region so cannot rule out
snow with this system on Monday night. Too early to speculate
on exact precipitation totals but amounts ranging from 0.25-0.75
inches are possible.

The area of low pressure pushes out of the region Tuesday
afternoon with quieter conditions moving in for next Wednesday.
Looking towards the end of next week, a progressive weather
pattern looks continue. Dobbs


VFR conditions continue under increasingly cloudy skies as a
disturbance moves in from the west. MVFR cigs will overspread KBIL
and KLVM after 10z as rain showers, and occasional MVFR vis move
in. Mountains obscurations will be widespread. MVFR restrictions
should persist through Thursday outside any brief improvements to
VFR between rain showers. KSHR will see MVFR restrictions later
Thursday afternoon (after 18z), and KMLS around 00z.  AAG/Dobbs



    Thu     Fri     Sat     Sun     Mon     Tue     Wed
BIL 043/055 041/051 035/061 042/061 040/048 035/049 033/056
    27/W    76/R    20/U    01/B    55/R    63/O    11/B
LVM 042/051 034/049 029/059 036/056 033/046 030/047 030/055
    58/W    84/O    10/U    13/R    54/O    32/O    11/B
HDN 037/060 040/052 035/063 039/064 037/051 035/050 032/058
    16/W    76/R    40/B    01/B    45/R    53/O    11/B
MLS 040/061 042/055 037/062 042/065 040/054 038/052 033/057
    04/W    54/R    30/B    01/B    44/R    53/R    11/B
4BQ 039/064 041/053 037/059 039/063 039/055 037/048 030/053
    03/W    65/R    31/B    01/B    34/R    75/R    21/B
BHK 037/063 040/054 038/060 038/064 037/053 036/049 031/054
    02/W    42/R    31/B    01/B    25/R    65/O    31/B
SHR 034/059 038/048 032/057 034/060 036/050 033/045 029/054
    04/W    87/R    61/B    01/B    45/R    64/O    11/B


MT...Winter Storm Warning in effect from midnight tonight to
      midnight MDT Friday night FOR ZONE 67.
WY...Winter Storm Warning in effect from 6 AM Thursday to 6 AM MDT
      Saturday FOR ZONE 98.


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