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000
FXUS65 KBYZ 170303
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
903 PM MDT Mon Oct 16 2017

.UPDATE...
Wind is the only weather element of interest moving forward with
dry high pressure prevailing over the region. Pressure gradients
have come down a bit in the western gap locations. They will
slowly start increasing again later tonight and through tomorrow.
The flow is decidedly westerly and not the best for gap wind at
this time. Stability at mountain top level is weak as well thanks
to the warm lower levels. So we believe winds will behave
themselves tonight and stay under our advisory criteria. Inherited
forecast looks fine as does the high wind watch for Wheatland
County starting tomorrow afternoon. We tweaked a few minor things,
but generally speaking there are no significant updates. BT

&&

.SHORT TERM...valid for Tue and Wed...

Dry zonal flow with above normal heights will keep temperatures
well above normal through tomorrow. Temperatures Tuesday will be a
little warmer than today in a pre-frontal regime, and some
locations may push 80 degrees (not unheard of in mid October).
Wednesday will be cooler behind a Tuesday night Pacific cold
front, but dry conditions will continue. Expect highs in the 60s
to near 70 degrees on Wednesday, coolest in our east.

Main forecast issue remains wind. Mixed winds today have
overachieved, with gusts in the 20s and 30s across the lower
elevations. These will relax across much of the area by sunset,
but with gustiness continuing along the western foothills. This
will result in a very mild night across our west, and some
locations may not fall below 50F. Mid level winds will back to the
SW and increase tomorrow in advance of a stronger Pacific
shortwave moving into southwest Canada. Steep low level lapse
rates will tap into the elevated mid level flow, resulting in
increased winds along the western foothills by afternoon. Expect
gap winds to be maximized in the evening just ahead of the cold
front, and confidence continues to increase that we`ll see gusts
to 60 mph at Livingston and Nye for a few hours, ending with the
cold advection which will arrive by midnight. Other area of
concern is further north at Harlowton and Judith Gap where 700mb
winds will be strongest, up to 60-65 kts during the night. This
will coincide with the frontal shift to the west and synoptic
subsidence. There is a chance that Wheatland County will see gusts
to 60 mph and have issued a High Wind Watch for this area.
Impacts include cross winds on Hwy 191, of course. The other spot
to watch is Big Timber, where a brief gust to 60 mph is possible
Tuesday evening, but they are south of the core of peak mid level
winds and away from the gap areas, so will leave northern Sweet
Grass County out of a highlight for now.

Gusty W-NW winds will spread across our eastern plains Tuesday
night, diminishing in our west by early Wednesday as surface high
spreads in from the west. This will be replaced quickly by next
period of lee side troffing and increasing SW winds along the
foothills (including Livingston) Wednesday night. A windy pattern
indeed.

JKL

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

Ridging over the region on Thursday will be replaced by a
shortwave trough and associated cold front moving through the area Friday
afternoon/night. Showers are possible behind the cold front,
lingering into Saturday with cyclonic flow over the area. Heights
begin to rise with zonal flow setting up over the area Sunday
into Monday, with some indications of another system bringing
precipitation chances for Sunday, although model differences
exist. Periods of gusty winds can be expected along the western
foothills through the long term with west to southwest flow aloft.
High temperatures will range from the 70s to near 80 degrees for
Thursday, with 60s west to 70s east on Friday as the
aforementioned cold front moves through the area. Behind the cold
front on Saturday, highs in the middle to upper 50s are possible,
with temperatures rebounding up into the 60s for Sunday and
Monday. STP

&&

.AVIATION...

WSW surface winds will gust to 40 kt at KLVM and in areas adjacent
to the western foothills tonight. These winds will continue
through Tuesday. Expect SW winds to become gusty across the
plains, including KBIL and KMLS on Tuesday. Gusts will be 25 to 30
kt. Otherwise, VFR will prevail across the area through Tuesday.
Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 047/076 046/068 047/076 049/070 041/058 039/063 041/062
    00/N    00/B    00/U    01/B    21/B    12/W    11/B
LVM 050/074 046/068 046/077 043/064 035/053 037/061 038/060
    00/N    00/N    00/N    03/W    42/W    12/W    21/N
HDN 038/076 044/068 041/079 043/075 038/060 035/065 039/063
    00/N    00/B    00/U    00/B    21/B    12/W    22/W
MLS 041/076 044/063 042/078 043/074 041/059 035/063 039/061
    00/U    00/B    00/U    01/B    21/N    11/N    11/B
4BQ 040/077 042/064 041/077 043/076 040/059 034/064 039/061
    00/U    00/U    00/U    01/U    21/B    01/B    21/B
BHK 039/076 041/061 039/078 041/075 040/057 034/062 037/059
    00/U    00/U    00/U    01/U    21/N    11/N    11/B
SHR 034/076 039/067 037/078 042/074 036/056 032/063 037/062
    00/U    00/U    00/U    01/B    21/B    11/B    21/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Watch in effect from Tuesday afternoon through late
      Tuesday night FOR ZONES 28-63.
     Red Flag Warning in effect from 11 AM to 7 PM MDT Tuesday FOR
      ZONE 117.
WY...None.

&&

$$
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