Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 191015
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
315 AM MST Sun Nov 19 2017

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

Strong western winds will dominate the weather concerns for the
first part of the short term. Attention will then turn to a cold
frontal passage Monday night and the potential for snowfall. First
to the winds.

Wind Advisory criteria has already been hit several times at
Livingston and Nye. See no reason why this will not continue
today, with winds increasing in strength tonight. Current surface
pressure gradient from Idaho Falls to Lewistown was 14mb. GFS
increases this to 17mb overnight, as a 110kt jet max moves across
southern Canada. Guidance and local tools suggest the possibility
of wind gusts approaching Warning criteria (75mph) tonight and
Monday morning. Bumped wind gusts to 70mph within the existing
Advisory and will let the day crew take a closer look at possibly
upgrading to a Warning, given a couple more model runs.

Will need to keep a close eye on Warning winds developing at Big
Timber too. 700mb increase to 60kts toward Monday morning from Big
Timber to Harlowton. Surface pressure gradient does not look
orientated quite right for High Wind type of winds there, plus the
time of day is not climatologically consistent with the strongest
winds typically. Local guidance tools approach a trigger point
late Monday morning. Will raise winds there to just below Warning
criteria and see how the models handle this today.

A cold front will advance toward the area Monday and this will
decrease the wind gradient over the west. Highlight may have to be
extended into the afternoon, depending on timing of the front, as
the front has slowed down. This front will drive into central
zones and set up a band of precipitation, (rain changing to snow),
along and east of the boundary. The GFS has driven the boundary a
little farther west, allowing for Billings to be right in the
heart of the precipitation band. Have raised PoPs to high
scattered for this event. A mild couple of days ahead of the
front, may limit snow accumulations within the band, but could see
a quick inch or two. The mountains will see a steady stream of
moisture again, this time on the west and northwest slopes, for
several inches of snowfall Monday into Tuesday. Moisture feed
should provide 3 to 6 inches of snowfall in the high country. TWH

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

Once again only minor changes to the extended forecast
period, with models in reasonably good agreement, and continuing
with consistent message of mainly dry extended period.

Tuesday appears to be the coolest day, following of the extended
as a Canadian surface high drops into the Dakotas giving us
cooler east winds. Expanded coverage and increased POPs into
Tuesday, as expect to see upslope flow into foothills, and some
degree of overrunning across a fairly large chunk of west and
central zones. This should result in light snow or mixed precip,
in most locations. Expect a pretty good thermal gradient across
the region form west to east, with temps around 50 in the west,
and lower 30s east.

Expect temperatures back into the 60s for Wednesday and Thursday as
ridge settles in with increased downslope gradients. Record highs
(lower- mid 60s) on the 23rd are possible, but records for
Thanksgiving Day will be tougher. Expect mainly dry conditions
through this period for the lower elevations. Isold to Sct showers
will continue to be possible in high terrain, as mean flow brings
Pacific moisture into mountains. Enhanced winds are once again a
concern along our western foothills from Tuesday night through
Thursday, with Advisory strength speeds possible at Livingston and
Nye.

Our next shot at precip if a shortwave crossing the region
Thursday night and Friday. The shortwave will bring some cooler
air into the region, but airmass appears to stay warm enough for
mainly rain showers at lower elevations, with a few inches of snow
for area mountains. This system exits Friday night, with ridging
building back in for Saturday, and a return of slightly above
normal temps and mainly dry conditions, at least for lower
elevations. AAG

&&

.AVIATION...

VFR conditions will prevail over the next 24 hours. Expect
breezy conditions across much of southern MT, especially around
KLVM and the foothills with wind gusts 40-50 kts through the day,
and increasing this evening and overnight, with gusts in excess of
60 knot possible. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Mon     Tue     Wed     Thu     Fri     Sat
-------------------------------------------------------
BIL 051 035/051 026/043 038/062 042/062 042/055 033/050
    0/N 03/W    54/W    21/N    11/B    22/W    12/W
LVM 050 037/048 032/050 042/059 042/059 043/052 030/048
    0/N 04/W    54/W    21/N    11/N    23/W    22/W
HDN 054 030/052 024/043 032/061 038/064 038/057 030/051
    0/U 03/W    54/W    11/N    11/B    22/W    12/W
MLS 053 028/051 018/033 028/058 036/061 039/053 028/047
    0/U 02/W    32/J    12/W    00/B    12/W    11/B
4BQ 057 029/055 022/039 031/061 039/063 039/056 031/050
    0/U 02/W    52/J    01/N    00/B    12/W    21/B
BHK 052 026/055 011/030 021/056 032/058 036/053 025/045
    0/U 01/N    11/U    02/W    11/B    12/W    11/B
SHR 055 026/055 025/046 033/062 036/064 036/056 029/051
    0/U 02/W    33/W    11/B    00/B    12/W    22/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Wind Advisory in effect until noon MST Monday FOR ZONES
      65-66.
WY...None.

&&

$$
weather.gov/billings



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