Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 kbyz 230609 
afdbyz

Area forecast discussion
National Weather Service Billings Montana
1209 am MDT Mon Oct 23 2017

Update...
have updated to cancel all high wind warnings that were set to
expire at midnight. Wind gusts have decreased to 45 mph or less,
and will continue to decrease gradually through the night. Will
leave Sheridan, southern Big Horn and southern Rosebud counties in
a warning. Latest water vapor imagery shows subsident region
approaching north central WY, and showers have nearly ended, so
there is an opportunity for some increase in wind over the next
few hours, especially along the east slopes of the bighorns.
Guidance has been suggesting peak winds at Sheridan overnight. Jkl

&&

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. Northwest 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 Montana 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 northwest to southeast
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...

Windy conditions will continue through the night. However, the
very strong wind gusts will diminish from kbil and areas west by
06z but will continue east and southeast of kbil through 12z.
Skies will be mostly cloudy through the night with an isolated
shower possible. However, VFR conditions are expected to prevail.
The mountains will be obscured at times throughout the night.
Hooley

&&

Preliminary point temp/pops...

Mon Tue Wed Thu Fri Sat sun
-----------------------------------------------------------
bil 042/057 037/068 045/074 038/046 026/048 033/057 039/060
00/north 00/u 00/north 43/west 00/b 01/b 11/b
lvm 041/054 035/067 041/072 034/045 024/051 032/058 036/059
00/north 00/north 01/north 63/west 00/u 11/u 21/u
hdn 042/058 032/068 038/076 037/047 023/049 028/058 033/062
00/north 00/u 00/u 53/west 00/b 01/b 11/b
mls 040/056 031/064 040/073 037/043 021/043 024/054 032/057
00/north 00/u 00/u 32/west 00/b 01/b 11/u
4bq 040/054 031/063 039/075 036/043 022/042 025/052 031/058
00/north 00/u 00/u 43/west 00/b 01/b 11/b
bhk 038/053 029/060 037/068 035/039 021/039 023/049 030/054
00/north 00/u 00/u 24/west 10/b 01/b 11/b
shr 039/053 030/066 036/076 035/042 020/046 024/056 030/060
00/north 00/u 00/u 64/west 00/u 01/b 11/b

&&

Byz watches/warnings/advisories...
Montana...High Wind Warning in effect until 6 am MDT early this morning
for zones 38-58.
Wyoming...High Wind Warning in effect until 6 am MDT early this morning
for zone 99.

National Weather Service Glossary of Abbreviations