Saturday, March17, 2018

Marine Weather and Tides
Big Sky, MT

Version 3.4
What's New / NOTES
3/3/2018 - There is a new GOES Satellite for the east coast that required rewriting that part of the code. Please report any issues.
6/25/2017 - NOAA is having a major issue that impact the 7 day forecast load times. Many users are reporting problems. The issue has been reported.
5/23/2017 - Worked with NOAA again to speed up the 7 day forecast load times. Thanks to them for being responsive.

Sunrise 7:29AMSunset 7:35PM Saturday March 17, 2018 6:26 AM MDT (12:26 UTC) Moonrise 6:59AMMoonset 6:54PM Illumination 0% Phase: New Moon; Moon at 1 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 171141
area forecast discussion
national weather service great falls mt
537 am mdt Sat mar 17 2018
aviation section updated

A complex storm system will move through the area this weekend
bringing areas of snow and freezing drizzle. In the mountains,
the precipitation will mainly fall as snow. At lower elevations,
the precipitation type will fluctuate between snow and freezing
drizzle. Precipitation gradually winds down from west to east by
Sunday night.

Today through Sunday night... The forecast over the remainder of the
weekend is a complicated one with only moderate confidence, at best.

A slow-moving upper level low continues to edge east through the
pacific NW early this morning. Several shortwaves have been
pinwheeling around this low over the past several days and this will
continue through the weekend.

The next wave to impact our forecast area is moving north through
nevada at this time. This wave will continue north, eventually
merging with the low over the pac nw, before pushing NE through
montana. The models have continued the northward trend (seen over
the past few days) with the track of this low, which now places the
axis of heaviest snow further north as well. Further complicating
the forecast, the areas along south of the track of this low may see
more dry air than originally forecast, making snow rain totals
lower less certain. This also makes precip-type more questionable,
especially over the plains of central montana.

So, here is the way things look to shake out. An area of
steadier heavier precip moving north out of idaho will lead to
impactful snow at higher elevations of SW mt, primarily above 6500
feet. The winter weather advisory in this area has been adjusted and
now is only in effect for mountain passes and does not include
valleys such as dillon, ennis, or bozeman. This area of snow should
weaken with time as it pushes north. By this afternoon evening,
another band of steadier precip looks to setup from near helena ne
through parts of central montana. Again, the models have trended
further NW with this band which puts more emphasis on the rocky mtn
front and areas west of i-15. Because of this trend, the winter
weather advisory was expanded north. Along and east of i-15, the
precip-type will fluctuate between snow and freezing drizzle.

Ultimately, this will lead to lower snowfall amounts than originally
forecast, but the combination of snow and freezing drizzle will lead
to travel concerns and the winter weather advisory will stand for
now. Precip should begin to wind down from west to east on Sunday,
lingering longest in the mountains. Of note, across SW mt, enough
instability is expected for a few lightning strikes this afternoon
and again Sunday afternoon. Martin
Monday through Friday... Main forecast concerns over this portions of
the forecast period are chances for precipitation and temperatures
peaking around the Wednesday Thursday timeframe.

As was the case last evening, a very messy upper level pattern to
start the forecast period, as the main h500 trough closed low over
the past week fragments into numerous shortwaves strewn across the
western CONUS canada. A few of these disjointed shortwaves will
cross both north central and southwest montana during the day on
Monday, which will allow for continued chances for mostly light
snow, however, some light rain may mix in at lower elevations across
north central montana. Following the passage of the aforementioned
shortwaves, northwest flow sets up over the northern rockies for
Monday night and most of the day on Tuesday before another fast
moving shortwave dives southeast across the CWA Tuesday
afternoon evening. This shortwave will be moisture starved save for
across extreme southwestern montana, where slight chance pops exist
for the afternoon and evening hours on Tuesday. Transitory ridging
then quickly moves over the northern rockies behind the departing
shortwave during the day on Wednesday, and amplifies over the
northern high plains for the day on Thursday. Beneath this ridge
high temperatures are expected to climb into the 40s to mid-50s
(with the exception of liberty, hill, and blaine counties where an
expansive snow pack still resides). As the h500 ridge amplifies over
the northern high plains on Thursday, a longwave trough will begin
to slide southeast from the gulf of alaska and into the pacific
northwest. This will in turn cause the upper level flow to back to
the southwest across the northern rockies, which will allow for
increasing pacific moisture to work in across southwest and portions
of north central montana. Precipitation chances will begin to
increase throughout the day on Thursday from southwest to northeast
across the cwa. Precipitation chances continue then into the day on
Friday, as the main h500 shortwave begins to work east across the
intermountain west and into the northern rockies. - moldan

Updated 1137z.

Fzfg will continue to cause significant aviation impacts across
central mt through this am.

The main concern this morning will be continued lifr vlifr
conditions across central mt due to very low clouds and fzfg br.

Seeing as there is no real mechanism to mix the fog out, conditions
will remain poor through at least late this morning, possibly even
lasting into early this afternoon. Attention then turns to the next
wave moving north from the great basin. This system will bring rain
and snow showers to SW mt, possibly even accompanied by some
lightning and gusty winds. Further north across central mt, this
system will bring -sn and -fzdz along with continued low CIGS vis.

The threat of -fzdz looks greatest from kgtf to khvr, where a light
glaze of ice is expected. Martin

Updated 17 400 am.

General lowland flooding from snowmelt will continue to be a
concern over the weekend, especially across SW mt where temps
won't be as cool as further north. We will continue to cover these
hazards with hydrologic outlooks and flood advisories for now.

Temperatures will warm each consecutive day to start the upcoming
work week, with highs peaking on Wednesday and Thursday in the mid-
40s to mid-50s across southwest and portions of north central
montana, or generally along and southwest of a lewistown, to great
falls, to browning line. This will lead to continued snowmelt for
snow remaining at both lower and even high elevations during the
daytime hours. A large upper level disturbance is then expected to
move across the northern rockies during the second half of the work
week, which could bring accumulating snow to the mountains of
southwest and north central montana and rain snow to lower
elevations. Any liquid precipitation on top of the remaining and
warmed snowpack, will only lead to additional flooding concerns
where poor drainage exists. Martin moldan

Preliminary point temps pops
Gtf 35 24 36 20 60 70 50 30
ctb 32 22 32 17 30 70 70 30
hln 37 28 38 22 60 60 70 50
bzn 40 22 39 19 40 30 40 30
wey 35 14 29 12 70 30 50 50
dln 38 20 36 17 60 40 60 50
hvr 33 19 34 16 10 60 70 40
lwt 37 22 35 20 20 30 30 30

Tfx watches warnings advisories
Flood advisory continues until further notice for snowmelt in
jefferson... Broadwater... And northern gallatin counties until Friday

Winter weather advisory from 3 pm this afternoon to noon mdt
Sunday above 5000 feet for central and southern lewis and
clark... Jefferson.

Freezing fog advisory until noon mdt today blaine...

cascade... Chouteau... Eastern glacier... Eastern pondera... Eastern
teton... Hill... Liberty... Northern rocky mountain front... Southern
rocky mountain front... Toole.

Winter weather advisory from midnight tonight to noon mdt Sunday
eastern glacier... Eastern pondera... Eastern teton... Hill...

liberty... Toole.

Winter weather advisory until 6 am mdt Sunday above 6500 feet
for beaverhead... Gallatin... Madison.

Winter weather advisory from 6 pm this evening to noon mdt
Sunday cascade... Chouteau.

Winter weather advisory from 6 pm this evening to noon mdt
Sunday northern rocky mountain front... Southern rocky mountain


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Bozeman, Gallatin Field, MT38 mi91 minWNW 610.00 miFair26°F18°F71%1008.9 hPa

Wind History from BZN (wind in knots)
Last 24hrSE6SE3E7S3NE3CalmNE5CalmCalmNE5NE5NE6E6E6S7S9SE8S6S6E4NE4SW5W6Calm
1 day agoE3S4CalmNE4CalmSE4SE5W8SW5E6E7E7E4SE4E3SE7SW3CalmS4CalmCalmS4SE9S6
2 days agoSW4CalmSW3CalmCalmNE4W6E4E5SE3SW5E5NE7W93S8SW7SW5SW4SW8S6S3CalmE4

Tide / Current Tables for
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Weather Map and Satellite Images
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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.
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Wind Forecast for Great Falls, MT (8,2,3,4)
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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 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 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.