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025
FXUS65 KBYZ 230217
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
817 PM MDT Sun Oct 22 2017

.UPDATE...

Updated forecast to extend High Wind Warning for Sweet Grass and
Wheatland counties until Midnight. Continue to see gusts around 60
mph in the Judith Gap and Harlowton areas. Strong gusts likely
continue lee of the Crazy mountains around Melville as well.
Strongest pressure rises are working through western zones now.
Should see winds taper off of Warning levels there over the next
few hours. Further east these strong pressure rises combined with
increased subsidence aloft should bring a few 60+mph gusts into
Central and Eastern zones through late tonight, and down into
Sheridan county through the early morning hours. Chambers

&&

.SHORT TERM...valid for Mon and Tue...

Lets talk wind.

So far the strongest official winds in the gap locations include
a 69 mph at the Livingston airport. Unofficially we had somewhat
stronger comparable gust in the Nye area. Winds in this area are
backing off mainly to advisory level as we become more of a mixed
environment than a stable true gap scenario and the pressure
gradient slowly weakens. So the period of strongest winds in the
gap locations has passed. Look for winds to slowly decrease into
the evening there.

Further north and east, from Big Timber to Harlowton, we have seen
gusts from 50 to 56 mph. The strongest 700mb winds are currently
going across this area, so we could yet see something higher. As
such, the areas downstream to the east such as Roundup and
Billings still have a chance of seeing higher winds as well
through the mid to late afternoon. Thus, we will continue the high
wind warnings for these areas.

We do have two issues to deal with for this package. One, do we
upgrade the high wind watch for Big Horn and Sheridan Counties?
Second, do we issue a wind highlight for Custer, Fallon and Carter
Counties?

As far as the high wind watch over Big Horn and Sheridan
Counties...on one hand we have some good pressure rises moving in
behind a front tonight (1.6 mb /hr), and we have some patchy 50 kt
winds at 850 mb progged overnight in this area. On the other hand,
those pressure rises are not quite strong enough for us to think
high wind criteria, and the timing of potential winds is after
dark which is not climatologically favorable. We have decided to
ride the watch for now and monitor pressure rises upstream to see
how much punch we get out of the front overnight. Highest winds
will probably occur in Sheridan between 11 pm and 3 am. Future
shifts will monitor conditions.

As for Custer, Fallon and Carter...Current observations (2 pm)
have Miles City and Baker at 50 and 54 mph respectively. The
strongest winds at 850 MB do not reach this area until after 6 pm
which is not ideal, but the low level lapse rates do remain pretty
high (7 C/km) through the evening. There is also some cold air
advection which helps the case for stronger wind. Will go ahead
and expand our high wind warnings to this area from this afternoon
through midnight.

Otherwise, expect snow showers with a little accumulation over the
mountains, and some brief rain showers along baroclinic zone for
the lower elevations mainly this evening. Dry weather will then
prevail late tonight through Tuesday as ridge builds back in from
the west. NW winds will remain gusty in our east on Monday, with
35-50 mph gusts expected. Cooler tomorrow with 50s for highs. BT

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

Ahead of a strong low pressure system diving south from Canada we
will have a pre-frontal warm up on Wednesday with highs making it
into the mid 70s. Pressure falls over northeastern MT and
northern Dakotas will enhance wind speeds across the region,
especially over the western foothills and gap areas on Wednesday.
Cold front pushes through in the evening bringing rain/snow mix
and minor snow accumulations to the lower elevations into
Thursday. Temperatures have trended a bit warmer with this system
and a little less precip is expected. Best locations for precip
will be in the Mountains, and north facing foothills.

Chances of rain and snow showers will decrease from NW to SE
during Thursday. Much cooler temperatures expected behind the
front on Thursday and Friday with highs in the mid 40s.
Slight warming trend as we head into next weekend but we remain
under northerly flow through the end of the forecast period.
Models have trended toward a drier solution in the extended with
almost no precip chances as a ridge builds in from the west on
Sunday. Walsh
&&

.AVIATION...

Gusty winds at all terminals this afternoon and evening. Winds
decrease overnight at MLS, BIL, and SHR and there is some
potential for LLWS as winds above the surface will remain quite
strong. Vicinity showers possible at all terminals this afternoon
although no reduced visibility or ceilings are expected at this
time. Walsh

&&

.PRELIMINARY POINT TEMP/POPS...

    Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 043/057 037/068 045/074 038/046 026/048 033/057 039/060
    20/N    00/U    00/N    43/W    00/B    01/B    11/B
LVM 042/054 035/067 041/072 034/045 024/051 032/058 036/059
    20/N    00/N    01/N    63/W    00/U    11/U    21/U
HDN 043/058 032/068 038/076 037/047 023/049 028/058 033/062
    20/N    00/U    00/U    53/W    00/B    01/B    11/B
MLS 043/056 031/064 040/073 037/043 021/043 024/054 032/057
    30/N    00/U    00/U    32/W    00/B    01/B    11/U
4BQ 042/054 031/063 039/075 036/043 022/042 025/052 031/058
    30/N    00/U    00/U    43/W    00/B    01/B    11/B
BHK 041/053 029/060 037/068 035/039 021/039 023/049 030/054
    30/N    00/U    00/U    24/W    10/B    01/B    11/B
SHR 043/053 030/066 036/076 035/042 020/046 024/056 030/060
    30/N    00/U    00/U    64/W    00/U    01/B    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Warning in effect until midnight MDT tonight FOR
      ZONES 28>35-37-41-42-57-63.
     High Wind Warning in effect until 6 AM MDT Monday FOR ZONES
      38-58.
WY...High Wind Warning in effect until 6 AM MDT Monday FOR ZONE
      99.

&&

$$
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