Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 200919
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
319 AM MDT Thu Apr 20 2017

.SHORT TERM...valid for Tdy and Fri...

Not many changes to the forecast with this package. Some patchy
fog is still possible through mid morning, mainly from Rosebud
County east. Otherwise, today will be dry for much of the area. As
divergence moves in over the western mountains ahead of the next
trough, precip chances will be on the increase this afternoon. The
forcing will push east this evening, spreading precip as far east
as Billings and Sheridan. This forcing will linger over the
central zones which will setup a band of heavier precip along the
western foothills through Billings and down to Sheridan. The
Beartooth/Absaroka foothills could see some light snow accumulations
and possibly some light slush on roadways, but impacts should be
minimal.

The Bighorn Mountains especially will see some high QPF amounts.
With snow levels dropping from around 7000 feet down to 5500
feet, this is going to produce some significant snow
accumulations. While the snow ratios will not be especially high,
the amount of moisture in the atmosphere will end up producing 8
to 12 inches in the mountains with some locally higher amounts
possible. Given that the models have been consistent with the QPF,
have gone with a Winter Weather Advisory for the northeast
Bighorn Mountains from midnight Friday through 6 AM Saturday. One
thing that will be limiting the impacts with this system will be
the time of year. With the higher sun angle, the road will likely
only be slush covered not fully snowpacked.

Through the day Friday and overnight into Saturday the trough
will slowly push east. Precip will slowly decrease from west to
east coming to an end Saturday morning. Reimer

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

The extended forecast still appears to be fairly active after the
weekend with a chance for rain about every other day.

A departing upper air disturbance could produce a few showers
over portions of south central and southeast MT and north central
WY on Saturday morning. By Saturday afternoon, upper ridging is
expected to build over the region, which should end any shower
activity. The upper ridge should slide east on Sunday, making way
for an upper trough to move eastward and bring a chance of
showers to areas west of Billings in the morning...then expand
eastward to Billings and southeast MT by Sunday night. Models
differ on the details of the upper trough...as the GFS shows a
more amplified trough with higher precipitation amounts, and the
ECMWF shows a flatter trough with lighter precipitation amounts.
Models do agree on shower activity across the area Sunday night.

For Monday-Thursday, models agree on the idea of disturbances
propagating eastward over the region...bringing periods of shower
activity to the area. A more organized storm system with
widespread rainfall is possible later in the week, but confidence
in the timing and track is low at this time.

High temperatures should be near 60 on Saturday...climb into the
60s on Sunday...then settle to the 50s for early next week under
clouds and rain showers. RMS/Reimer

&&

.AVIATION...

VFR conditions will prevail across most of the region through the
TAF period. Patchy fog is possible over southeast MT this
morning. Showers should develop from west to east
Thursday night...bringing MVFR conditions to KLVM overnight.
Beartooth/Absaroka Mountains will be obscured late this afternoon
into the overnight. Bighorn Mountains should become obscured
toward Friday morning. RMS/Reimer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 065 044/051 038/059 041/067 042/056 038/056 039/057
    1/U 67/W    62/W    02/W    43/W    33/W    33/W
LVM 058 037/048 031/059 038/062 037/055 034/055 035/056
    5/W 77/W    51/B    13/W    43/W    45/W    44/W
HDN 066 043/057 039/060 039/069 042/057 038/058 039/059
    0/U 46/W    62/W    01/B    33/W    23/W    33/W
MLS 062 042/062 042/061 042/069 044/054 037/053 038/058
    0/U 12/W    42/W    01/B    34/W    22/W    23/W
4BQ 061 042/059 039/060 040/069 043/055 035/054 038/057
    0/U 13/W    32/W    00/B    34/W    23/W    34/W
BHK 057 039/060 037/061 037/065 040/050 032/050 033/054
    0/U 01/B    11/B    01/B    35/W    22/W    23/W
SHR 062 039/050 037/056 037/065 040/054 036/053 036/055
    2/U 67/W    73/W    01/B    33/W    24/W    33/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...Winter Weather Advisory in effect from midnight tonight to 6
      AM MDT Saturday FOR ZONE 98.

&&

$$
weather.gov/billings


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