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afdbyz

Area forecast discussion...updated
National Weather Service Billings Montana
848 PM MST Thu Nov 21 2019

Update...
just some minor tweaks to the forecast this evening. Westerly
winds are picking up a little bit from Billings to Livingston
the last hour. This will prevent temperatures from dropping much
through the night despite clear skies. Bt

&&

Short term...valid for Fri and Sat...

Satellite imagery shows high pressure anchored over southern
British Columbia/Alberta, with a cut off low over The Four Corners area. This
leaves US in a dry northerly flow aloft. A weak/splitting
shortwave along the British Columbia coast will move inland and pass to our
north tomorrow and tomorrow night. We will not see any
precipitation with this wave, but an associated cold front will
produce a breezy northwest wind beginning late Friday. In the meantime,
upper level ridging will introduce Lee side troffing and
increasing foothills winds tonight. Mid level flow will back
westerly and be more favorable for gap winds, but speeds at
mountain top level will not be very strong, and surface high
pressure is extending thru western Montana. As a result, pure gap flow
is not expected, and gusts should be limited to 35-50 mph at
Livingston, Nye, Big Timber and Harlowton...with a peak occurring
Friday morning. Arrival of pressure rises will reduce the winds by
early/mid afternoon. Jkl

Long term...valid for sun...Mon...Tue...Wed...Thu...

Main story this weekend will be wind, especially west of Billings.
Expect gusty winds in the Livingston-Nye-Big Timber-Harlowton-
Judith Gap areas on Saturday. Winds should strengthen in these
areas Saturday night as the sea-level pressure gradient increases
as low pressure tracks east/southeastward from southern Canada
into North Dakota. The strong winds should continue into Sunday
with gusts to around 60 mph possible as strong mid-level winds
move overhead, with the potential for these winds to be brought
down to the surface partially due to descending motion on the Lee
side of the crazy, Castle and belt mountains. Farther east, gusty
winds are expected Sunday over southeast Montana and north central WY,
but not anticipating gusts over 40-45 mph there due to lack of
mechanism to bring the stronger winds aloft down to the surface.
Given all of this, have issued a high wind watch for Livingston,
the beartooth foothills, and areas northward to Wheatland County
from Saturday night through Sunday. Please prepare for strong
Crosswinds if driving or hauling a high-profile vehicle or
trailer.

The winds over the weekend will also be downsloping winds, so the
air will be mild with high temperatures generally in the 50s. No
precipitation is expected on Saturday into Saturday night. Then
the chance of precipitation will increase on Sunday as an upper
air disturbance approaches the region from the northwest.

The upper air disturbance and associated weak surface cold front
will cross the area late Sunday afternoon/early evening and usher
in a cooler air mass. A few rain and snow showers are possible
with and behind the front. Unsettled conditions should continue
through the week as an upper trough digs over the western US. A
chance of snow exists each day next week. There is much
uncertainty with the forecast details, so please stay tuned for
updates. Temperatures look to trend downward into next week, with
highs in the 30s and 40s on Monday, then 30s on Tuesday, and 20s
and 30s on Wednesday and Thanksgiving. Rms



&&

Aviation...

High pressure aloft will bring VFR flight conditions across the
region through Friday. SW-west winds will increase along the western
foothills, with gusts of 30-40 kts at klvm by early tomorrow. Jkl

&&

Preliminary point temp/pops...

Fri Sat sun Mon Tue Wed Thu
-----------------------------------------------------------
bil 023/051 031/051 038/054 031/042 023/035 019/031 017/029
00/north 00/b 03/r 55/S 43/S 24/S 44/S
lvm 022/051 030/049 035/050 028/037 019/032 015/030 014/029
00/north 00/north 15/o 55/S 43/S 35/S 54/S
hdn 019/051 025/052 033/055 027/042 021/036 016/034 015/030
00/u 00/u 04/r 55/S 42/S 23/S 34/S
mls 021/048 027/049 034/053 028/041 021/036 017/033 017/031
00/u 00/u 03/r 32/S 22/S 13/S 34/S
4bq 018/048 026/050 033/053 028/040 021/035 016/035 018/034
00/u 00/u 03/r 33/S 22/S 12/S 33/S
bhk 018/046 025/047 032/050 026/039 020/034 015/032 016/032
00/u 00/u 01/north 11/b 12/S 13/S 33/S
shr 014/051 022/051 028/052 024/038 016/033 012/033 013/032
00/u 00/u 02/r 45/S 32/S 22/S 33/S

&&

Byz watches/warnings/advisories...
Montana...high wind watch in effect from Saturday evening through
Sunday afternoon for zones 63-65-66-141-172-228.
Wyoming...none.

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