Tuesday, December18, 2018 L-36.com

Marine Weather and Tides
Big Sky, MT

Version 3.4
What's New / NOTES
10/6/2018 Colors of tide XTide graphs changed to emphasize that they were upgraded. See next note. Comments welcome.
10/4/2018 I have fixed XTide and updated the harmonic files. There were some name changes so you might have to click EDIT to find the new station name.

Sunrise 7:58AMSunset 4:43PM Tuesday December 18, 2018 8:42 PM MST (03:42 UTC) Moonrise 2:23PMMoonset 3:03AM Illumination 88% Phase: Waxing Gibbous; Moon at 11 days in cycle
NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.
Marine Forecasts
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7 Day Forecast for Marine Location Near Big Sky, MT
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location: 45.26, -111.31     debug

Area Discussion for - Great Falls, MT
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Fxus65 ktfx 190243
area forecast discussion
national weather service great falls mt
740 pm mst Tue dec 18 2018

740 pm mst update... Will not be making any further adjustments to
current forecast. Bands of snow will move south along the
continental divide overnight, continuing the (at least) light snow
accumulation in the mountains and on the mountain passes; so will
leave the winter weather advisory in effect. Winds have been strong
in the high wind warning area, with a number of places already
exceeding high wind criteria earlier today, but they have generally
stayed below criteria this afternoon and evening. However, the
disturbance responsible for the winds should continue to advect
cooler air into the area into Wednesday, which may still cause some
sporadic strong gusts. Will therefore leave the high wind warning in
effect as well. Am a bit uncertain about temperatures as well (might
be a little cool), but it seems like there could be enough of a lull
in winds or break in clouds to allow temperatures to fall into the
forecasted range. Coulston
552 pm mst update... Quick update to forecast to add areas along the
continental divide south through central and southern lewis and
clark county to the winter weather advisory above 5000 feet. Minor
snow accumulations can be seen on mt dot web cameras at both
macdonald pass and rogers pass. Now that the Sun has set, light snow
should continue to accumulate there, making travel difficult due to
snow packed and icy roads, with some blowing snow possible. This
advisory does not include the helena and lincoln areas at this time.

Will consider further updates to the forecast in general over the
next couple of hours. Coulston

A strong pacific storm system moves into the northern rockies and
then the rest of the treasure state, today, bringing strong winds
to most of central montana east of the continental divide,
spreading into south-central portions of the state on Wednesday.

Rain and mountain snow, which may be heavy at times, will develop
over areas along and west of the continental divide today while
areas of snow develop over adjacent portions of southwest montana
this afternoon and tonight.

Updated 2345z.

Vfr conditions are expected for most of the terminals for most of
the next 24-hour TAF period, unless otherwise mentioned. A strong
mid- and lower-level westerly flow aloft will continue widespread
gusty southwest to west winds with mountain wave turbulence and low
level wind shear through the period; the strongest potential winds
will likely be between through 06z or so, with gusts of 50 to 70 kt
especially possible along the rocky mountain front. Otherwise, most
mountain tops will be obscured by clouds and blowing snow along the
continental divide and into southwest montana through around 15z,
with periods of MVFR conditions in the southwest valleys between 06z
and 12z.

Prev discussion
Issued 445 pm mst Tue dec 18 2018
today and tomorrow... Satellite imagery reveals a strong upper
level jet and moisture plume moving into wa or south of a
vigorous stacked low moving toward the ak panhandle. Little change
in the overall impacts expected as this moisture and region of
strong flow aloft moves east into the region today and tonight,
bringing widespread strong winds to much of central mt and heavy
snow accumulations to areas along the continental divide with
winds and mountain snow decreasing Wednesday as an upper level
ridge rebuilds along the west coast.

Strong wind gusts have developed along the immediate east slopes
of the rocky mtn front as the initial surge of strong west flow
aloft arrived in combination with favorable temperature wind
profiles for mtn wave downslope wind enhancement. Strong west flow
aloft overspreads much of north- central mt today, with gusts
peaking this evening. Strongest winds for eastern and southern
portions of central mt are most likely to occur with the passage
of the associated pacific surface cold front trough this evening.

Very windy conditions are likely to continue into Wednesday
morning for many areas with winds gradually diminishing Wednesday

Snow increases across areas along the continental divide west of
the rocky mtn front then spreads across the higher elevations of
sw mt near the id border. Downslope drying will likely keep lower
elevations dry through this afternoon but snow showers will
become more widespread across SW mt and southern portions of
central mt tonight as stability decreases with incoming colder air
aloft behind the front. Heaviest snow accumulation and winter
weather impacts are expected near marias pass today and tonight
where a winter weather advisory is in place. A winter weather
advisory is also in effect for beaverhead county, including big
hole pass and chief joe pass. Several inches of snow accumulation
is possible across the mtns of SW mt tonight from multiple rounds
of snow showers. Hoenisch
Wednesday night through Tuesday... The progressive pattern that we
have been in for the past or so looks to continue through the
early part of next week. The ongoing pattern of shortwave troughs
followed by shortwave ridges will continue to shift the weather
regimes from wet and windy weather, mild and dry weather. The
focus for impactful weather remains on the passage of shortwave
troughs Thursday night into Friday, Sunday morning into Monday
morning, and again on Tuesday. The initial trough Thursday night
into Friday looks to bring another round of gusty winds and
mountain snowfall to the area, especially along the rocky mountain
front. The next system currently looks weaker in the models with
regards to precipitation along the mountains and gusty winds. The
final system on Tuesday looks to be the weakest with regards to
the winds, but has more precipitation making it over the divide
as there should be less downsloping effect with the weaker cross-
barrier flow. However, confidence at this time is lower with
regards to the second and third systems from Sunday into Tuesday,
due to these scenarios being further out in the forecast period
and current discrepancies between the different model runs during
this timeframe. -tp

Preliminary point temps pops
Gtf 35 47 30 51 10 0 0 0
ctb 34 43 28 45 20 0 0 10
hln 32 45 25 42 30 10 0 0
bzn 27 43 19 41 40 10 0 0
wey 20 30 14 31 80 30 10 0
dln 26 39 18 37 40 10 0 0
hvr 35 47 25 45 10 0 0 10
lwt 32 42 24 46 0 0 0 0

Tfx watches warnings advisories
High wind warning until 5 pm mst Wednesday broadwater...

cascade... Central and southern lewis and clark... Chouteau...

eastern glacier... Eastern pondera... Eastern teton... Fergus...

jefferson... Judith basin... Liberty... Meagher... Toole.

Winter weather advisory until 8 am mst Wednesday above 5000 feet
for central and southern lewis and clark... Northern rocky
mountain front... Southern rocky mountain front.

Winter weather advisory until 8 am mst Wednesday above 6500 feet
for beaverhead.

High wind warning until 8 am mst Wednesday blaine... Hill.

High wind warning until 5 pm mst Wednesday northern rocky
mountain front... Southern rocky mountain front.


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Bozeman, Gallatin Field, MT38 mi1.8 hrsN 010.00 miOvercast42°F30°F62%1011 hPa

Wind History from BZN (wind in knots)
Last 24hrNE3E85E5CalmE4SE7SE7E5SE6E4E5SE9SE3E6NE3CalmSW14
1 day agoS4SW5SE9CalmCalmCalmSE8SE5S6SE5S6SE7S5SE3E3CalmE3CalmSW10
2 days agoSE6SW8S4SE5SE5S6CalmSE4SE4SE5SE5NW3CalmS3CalmSW3CalmCalmN3SE3S3S6SE10N4

Tide / Current Tables for
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Tide / Current Tables for
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Weather Map and Satellite Images
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GOES Local Image of    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
Link to Loop

Other links: Northern Pacific     Contential US     Full GOES-East
Wind Forecast for Great Falls, MT (22,6,7,8)
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Ground Weather Radar Station Billings, MT
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The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerious of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.