Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 161657

Area Forecast Discussion...Updated
National Weather Service Billings MT
957 AM MST Thu Nov 16 2017


Cloud cover from an approaching storm system was streaming over
the area with snow showers affecting the southwest mountains this
morning. Precipitation will begin to make it off the mountains
late this afternoon and evening as a cold front moves through the
area. Have adjusted temperatures and pops to current trends. Will
let the Wind Advisory for the Beartooth Foothills expire as
planned at 11 AM MST as surface pressure gradients will continue
to weaken into the afternoon diminishing the gap winds. The rest
of the forecast remains on track and the previous forecast
discussion is below. STP


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

Wind Advisory for the Beartooth foothills remains in place until
noon. Issued a Winter Storm Warning for the Beartooth/Absaroka
mountains through Friday afternoon.

Ridge of high pressure over the central U.S. is shifting east as a
storm system moves into the Pacific NW. A strong Jet stream is
pouring copious moisture into the area on SW flow aloft, bringing
significant snow to the southwest mountains. Areas around Cooke
City should see 12 to 16 inches of additional snow from this
moisture feed over the next 36 hours. Low to mid level moisture
will get wrung out by the mountains today leaving just cloudy
skies and breezy to windy conditions across the plains. While the
radar will continue to show returns, outside of maybe a few
sprinkles this activity should remain aloft.

As colder air aloft shifts into the area this afternoon should see
instability increase along the foothills which will end the high
end gap wind threat for the Livingston to Nye area, but will
continue with gusty mix-down winds for hills and foothills across
the area. These downslope winds should boost temperatures into the
45 to 55 degree range this afternoon, though cloud cover may hold
a few areas just under the max heating potential from the models.

Cold front moves into the area quickly from the northwest around 6
pm and shoots through the forecast area before midnight.
Precipitation chances will increase across the area through the
night behind the front. Stronger jet energy arrives after 3am
which will bring the best precipitation chances to the area
through mid day Friday, with lessening pops for the afternoon and
evening hours from west to east.

The Pacific nature of this system will limit snow accumulations
across the lower elevations so only looking at an inch or two on
grassy surfaces on the high end for elevations below 4500 feet.
For the foothills the downslope winds will be a limiting factor on
north and east facing slopes. For now have accumulations late
tonight through Friday below advisory criteria.

Winds on Friday afternoon could be pretty gusty, especially in
higher exposed locations across the plains. Increased gusts to
over 40 mph in some plains locations Friday afternoon into the
evening hours. Chambers

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

Relatively minor changes to the extended forecast this morning,
with models in relatively poor agreement for the bulk of the
extended period. Upper ridging dominates the pattern Saturday and
Sunday, with dry and mild conditions. Expect strong gap flow
winds near Livingston Saturday and Sunday as a surface high builds
over eastern ID and a lee trof develops over eastern MT.

On Monday, a weak shortwave trof approaches the region from the
west. Best chances for precip will be in the high terrain, with
downslope flow limiting shower potential across lower elevations.
That said, cannot rule out some showers making it off the
mountains. Have expanded coverage of slight POPs into lower

After Monday, operational model solutions diverge with the GFS
showing a cooler and wetter pattern and the ECMWF resuming the
upper ridging and dry, mild weather over the Northern Rockies.
The operational ECMWF has ensemble support from the GFS and
ECMWF, so continued to lean that direction, at least for temps.
That said, have introduced more widespread slight POPs in a nod
toward more active GFS. These increased POPs are in large part due
to approaching Thanksgiving Holiday and expected increased
travel. Would rather err on the side of caution, than have no
mention of potential precip.

High temperatures should generally be in the 40 to low 50s
Saturday through Thursday. AAG



Gusty W to SW surface winds at KLVM will continue through much of
the day, with gusts around 40 kts. A cold front moving S across
the region this evening, will cut off the S winds, and shift
winds to the N over most of the area. Mountain obscurations will
increase through the day. Otherwise, mainly VFR conditions will
prevail today, with areas of MVFR conditions behind FROPA this
evening. AAG



    Tdy Fri     Sat     Sun     Mon     Tue     Wed
BIL 053 031/041 026/044 026/048 032/047 028/044 032/053
    3/W 66/W    00/N    00/N    02/W    22/W    01/B
LVM 051 028/037 022/040 024/045 031/045 030/044 033/051
    4/W 66/J    11/N    00/N    02/W    23/W    11/B
HDN 057 031/042 025/046 022/051 027/050 026/045 027/054
    2/W 66/W    10/B    00/B    01/B    22/J    01/B
MLS 055 030/045 024/045 023/050 027/047 022/037 024/050
    2/W 42/W    10/B    00/U    01/B    11/B    21/B
4BQ 059 031/042 025/044 023/052 028/050 025/043 027/053
    2/W 56/W    30/N    00/U    01/B    11/B    11/B
BHK 053 028/043 019/040 020/051 026/047 018/033 021/048
    2/W 33/W    20/U    00/U    01/B    11/B    21/B
SHR 057 029/040 020/045 021/052 025/051 025/046 026/055
    1/B 44/W    20/U    00/B    01/B    11/B    01/B


MT...Wind Advisory in effect until 11 AM MST this morning FOR ZONE
     Winter Storm Warning in effect until 5 PM MST Friday FOR ZONE


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