Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 170426
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
926 PM MST Thu Nov 16 2017

.UPDATE...
We have made some significant changes to the forecast through
Friday regarding PoP`s. There has been a question as to where a
progged narrow band of precipitation would set up tomorrow
morning, and if it would be north of Billings, over Billings, or
south of Billings. Viewing the IR satellite trends it appears the
best forcing upstream is trending toward southern Montana and
northern Wyoming. The newest model data is also backing up this
idea, setting that narrow (possibly intense) precipitation band
south of Billings from the Beartooths to the Pryors/Big Horns
region.

Therefore, we have decreased PoP`s for tomorrow morning over the
northern two thirds of our CWA including the Billings
vicinity...and increased the PoP`s across the aforementioned
southern Montana and northern Wyoming region. This change means a
better chance of some wet/slick roads or bridges down around the
Big Horns and Sheridan area including the I-90 corridor from
Sheridan to Lodge Grass. We will change our weather story to
reflect this as well. In the meantime...we have also updated the
overnight PoP`s for current trends as good upper divergence on
500mb jet max plus instability is producing that narrow band from
Absarokee to Hysham and Terry...but focus is slowly switching to
the Big Horns region. BT

&&

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

It was a warm day across portions of the area as strong
downsloping winds and a mix of sun and clouds allowed some
locations to make it into the 60s. Colder air has been working
into the northwest zones late this afternoon as a cold front moves
through the area. Rain and snow showers will gradually spread
from the southwest mountains out onto the foothills and plains
this evening and overnight as frontogenesis provides a focus for
forcing. A mix of rain and snow showers is expected to transition
to snow showers overnight as a reinforcing shot of colder air
moves south and isentropic ascent from a strong jet max shifts
overhead. Still a lot of uncertainty in where this band of
isentropic ascent sets up, and a related band of snow. Snow
showers are expected to persist into Friday as pieces of vorticity
work through cyclonic flow over the area, gradually diminishing
from west to east through the afternoon and evening. Breezy west
to northwest winds can be expected on Friday as well, with winds
increasing in the gap prone areas Friday night as surface pressure
gradients tighten. Drier conditions return for Saturday with
breezy conditions continuing as high pressure builds into the
region. Strong winds persist in the gap areas for Saturday night
as well.

Additional snow accumulations of 8 to 14 inches are possible on
south and west facing slopes in the Absaroka/Beartooth mountains
through Friday, with significantly less amounts for north and east
facing slopes as southwest to westerly winds aloft downslope. As
for the Bighorn Mountains, amounts up to 6 inches look possible
through Friday. A few inches of snow are possible along the
foothills tonight into Friday morning, with a quick inch or two on
grassy surfaces for plains locations. Have not gone with any
advisories for foothills locations as these locations will be
downsloping for much of the system. Snowfall amounts for the
plains will be dictated by when exactly the rain changes over to
snow, as well as where does the snow band set up over the area.

High temperatures will range from the 30s to 40s for Friday and
Saturday, with lows tonight in the upper 20s to lower 30s, with
20s for lows Friday night and Saturday night. STP

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

Main theme for the extended forecast will be warm and breezy
conditions interrupted by a cold front Monday evening into
Tuesday morning.

Warm conditions anticipated Sunday afternoon, as well as
increasing winds through the day as strong downslope conditions
move into the region. Pressure falls east of the Rocky Mountain
front will tighten pressure gradients across the foothill regions
leading to strong winds Sunday night into Monday. A disturbance
moving east through southern Canada will sling a cold front
through the region on Monday afternoon which will bring a brief
pause to the warm and breezy conditions across the region. This
front will also bring a brief chance for snow showers across many
of our foothill locations and possibly in the plains.
Precipitation amounts don`t look to high for now so heavy
widespread snow is not anticipated.

Cool temperatures anticipated Tuesday afternoon but breezy
conditions and warmer temperatures back into the 50s are
anticipated Wednesday as the cool air retreats east and downslope
conditions move back into the forecast area. Some mountain snow is
possible Wednesday night into Thanksgiving, but expect little (if
any) snow to sneak into the Plains as of this update.

A warm Thanksgiving looks possible with temperatures in the mid to
upper 50s across much of southern Montana. Dobbs
&&

.AVIATION...

VFR will prevail over the area tonight into Friday morning.
However, expect conditions to decrease to IFR late tonight over
KSHR. MVFR to IFR conditions are expected Friday afternoon from
KLVM to KSHR, while VFR continues elsewhere. VFR will return to
the entire area Fri. evening. The Beartooth, Absaroka and NE
Bighorn mountains will be mostly obscured through Friday. There
will be areas of obscuration over the Crazys. Mountain obscuration
will decrease Fri. evening. Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 031/040 026/041 026/046 033/046 025/042 033/053 037/056
    44/W    10/B    00/B    02/W    21/B    11/B    11/B
LVM 028/035 023/037 025/043 036/045 028/044 039/052 040/053
    43/J    11/N    00/N    03/W    31/B    12/W    22/W
HDN 031/042 025/044 022/049 028/048 023/043 028/056 033/058
    55/W    10/B    00/B    01/E    11/B    11/B    11/B
MLS 030/043 025/042 023/048 028/047 018/035 024/052 031/055
    62/W    10/B    00/U    01/B    11/B    11/B    11/B
4BQ 031/042 026/042 023/051 028/050 021/041 027/054 033/057
    45/W    21/B    00/U    01/B    11/B    11/B    10/U
BHK 028/042 020/039 020/049 026/047 015/032 020/047 028/053
    32/W    11/B    00/U    01/B    11/B    11/B    10/B
SHR 029/041 021/043 020/052 025/052 023/045 027/056 030/057
    66/W    20/U    00/U    01/B    11/B    11/B    10/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until 5 PM MST Friday FOR ZONE
      67.
WY...None.

&&

$$
weather.gov/billings



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