Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 221518
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
918 AM MDT Sun Apr 22 2018

.UPDATE...

Very minor tweaks to temperatures and cloud cover for today.
Otherwise forecast in very good shape heading into the storm
system for tonight and tomorrow. Afternoon package will
concentrate on this system and try to nail down snow accumulations
and qpf amounts. May need a few advisories for higher hills
southeast and mountain foothills based on going forecast. Will see
what the morning model runs have to say about that. Chambers

&&

.SHORT TERM...valid for Tdy and Mon...

Last evenings cool front produced little if any moisture across
our CWA and the cold advection was rather limited as well. The
only notable affect will be a prevailing easterly wind today which
will lead to somewhat cooler afternoon highs compared to
Saturday. Overall though, it should be another seasonally nice day
with just some high cloudiness.

In the meantime, a progressive short wave will be moving quickly
from the west coast into the inner northern Rockies. This system
is still progged to track right over our forecast area late
tonight through Monday. Timing is an issue with the EC a little
slower than the GFS, which is important as it affects how much
QPF would fall as snow for some locations. The EC has some support
in the NAM. Therefore, we slowed down the precipitation entering
our area (lowered PoPs in west for late afternoon), and lingered
it a little longer in the southeast Monday night.

There appears to be plenty of acute forcing directly over our
region and models have trended QPF upward a bit from recent model
cycles. The average of the GEFS Plumes are putting around 0.90
liquid over Billings. The tricky part this time of year are the
snow ratios and how much precipitation comes down as snow, and
then how much is able to accumulate on warmer surfaces and during
the daytime hours. We do not anticipate much accumulation on roads
in the lower elevations, but some slushy areas in the foothills
and Bozeman Pass is quite possible by Monday morning. A couple of
of inches of wet snow on natural terrain is expected from
Livingston and into the foothills. The mountains may see several
inches late tonight through Monday evening. We will let the next
shift get a better idea on timing and snow ratios with the next
few runs, but we may eventually need some winter weather
advisories in our western foothills. In addition, advisories may
be necessary from the Ashland Divide into the higher hills of
Carter County where a few inches of wet snow are possible Monday
night before the system exits to the east.

One more note, we did lower highs on Monday a bit due to
anticipated thick cloud cover and rain-cooled air. BT

.LONG TERM...valid for Tue...Wed...Thu...Fri...Sat...

A few lingering rain/snow showers possible in extreme
southeastern Montana at the beginning of the long term Tuesday
morning, but these will quickly dissipate through the morning as
the area of low pressure slides off to the east. Cool conditions
will remain in place through Tuesday afternoon but warmer
conditions will take over for the remainder of the week as a ridge
of high pressure takes hold over the western United States.
Expect temperatures in the 70s by the weekend.

As for precipitation trends, can`t rule out a few showers from
Roundup/Sheridan and westwards on Wednesday night into Thursday.
This is in response to a weak clipper moving throug the area.
Outside this clipper system, much of the period will be dry. By
the middle of the weekend, precipitation chances return to the
forecast area as better moisture works into the region from the
southeast. Dobbs

&&

.AVIATION...

VFR conditions and easterly flow will prevail through the region
through most of the TAF period. A disturbance will move in from
the west tonight into Monday which will bring increasing clouds
and widespread rain mixed with snow. MVFR/IFR conditions with
widespread mountain obscurations are anticipated to develop
overnight. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 064 037/041 029/055 034/065 038/063 042/073 042/072
    0/U 7+/O    30/U    00/U    21/U    00/U    01/U
LVM 064 035/040 023/055 031/068 033/065 036/070 037/069
    1/B 99/O    20/U    01/U    21/U    01/U    12/W
HDN 067 038/042 030/055 032/064 036/061 040/072 041/072
    0/U 5+/O    40/U    00/U    21/U    00/U    01/U
MLS 065 039/046 031/056 033/066 037/062 040/071 041/070
    0/B 38/O    40/U    00/U    10/U    00/U    00/U
4BQ 065 040/045 031/051 032/065 037/059 039/069 039/069
    0/U 28/O    71/B    00/U    11/U    00/U    00/U
BHK 062 037/044 031/053 031/063 036/056 037/067 039/066
    0/U 27/O    70/B    00/U    00/U    00/U    00/U
SHR 066 037/040 028/051 029/067 035/061 036/070 039/070
    0/U 27/O    51/B    00/U    21/U    00/U    11/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings


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