Monday, September27, 2021
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Marine Weather and Tides
Sheridan, CO

Version 3.4
NOTICE
3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 6:51AMSunset 6:50PM Monday September 27, 2021 9:56 PM MDT (03:56 UTC) Moonrise 9:41PMMoonset 12:22PM Illumination 58% Phase: Waning Gibbous; Moon at 21 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 Sheridan, CO
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location: 39.68, -105.06     debug


Area Discussion for - Denver/Boulder, CO
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FXUS65 KBOU 280257 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 857 PM MDT Mon Sep 27 2021

UPDATE. Issued at 852 PM MDT Mon Sep 27 2021

Other than a few isolated showers in southern Park County, the region is mostly dry. Water vapor imagery shows mid-level moisture advecting into portions of central and eastern CO, although profiles remain dry near the surface reducing chances for showers overnight. Can't rule out a stray shower over Park and Summit counties in the early morning hours. Dry air will likely prevent any rain from reaching the ground. We didn't change the forecast for Tuesday much, it is still looking like it will be 5-10 degrees cooler than Monday with increasing clouds throughout the day. Shower and thunderstorm chances increase in the afternoon with the best chances over the higher terrain. Model profiles appear to be quite dry at the surface and instability is limited which will reduce heavy rain potential; however, gusty outflow winds up to 25 mph are possible.

SHORT TERM. (This evening through Tuesday) Issued at 224 PM MDT Mon Sep 27 2021

Current observations across the region show dew points ranging from the upper 20s to lower 30s across the region while a high pressure system remains dominate over the state. This evening winds will decrease due to a low pressure system moving eastward decreasing the pressure gradients for areas east of Interstate 25. Above-normal low temperatures and party cloudy skies are expected tonight.

A change of pace will occur Tuesday as high temperatures will be cooler due to a trough arriving in the afternoon. The GFS and HRRR are in agreement with dry air still remaining east of Interstate 25. PoPs were increased between 18Z-00Z for areas west of Interstate 25 due to NBM and NAM keeping dew points higher and scattered thunderstorms for that area. Any thunderstorm that does form will have difficulty to sustaining especially east of the Interstate 25 due to a lack of instability and dry surface to mid levels. Areas west of I-25 could receive QPF ranging from 0.10-0.25 inches through Tuesday evening.

LONG TERM. (Tuesday night through Monday) Issued at 224 PM MDT Mon Sep 27 2021

Synoptic pattern in the long term sees a series of slow moving shortwave troughs with main branch of westerlies well north into Canada. Second half of the extended has a cut off low over northern plains. Temperatures trend near to below normal from Tuesday night onward, with periodic chances for precipitation.

Extended picks up at midnight Tuesday night, with lingering mountain showers and snow showers over the higher terrain behind departing weak shortwave trough. A cold front knocking on our door at midnight will sweep through the forecast area by sunrise, with a marked difference in temperatures and highs 15 to 20 degrees cooler than previous days.

Wednesday morning a sharpening, slow moving 500 mb trough moves out of the NW US and only reaches UT/CO border by 12z Thursday. Mid levels dry during the overnight hours, with 700-500 mb specific humidity around 3.5 g/kg in the mountains Wednesday, down from over 5 g/kg in the mountains 24 hours earlier. Precipitable Water also drops from around 1/2 inch on Tuesday to .3 inch on Wednesday. Higher moisture remains on the plains, around 1-2 standard deviations above normal for this time of year. Even with the lower moisture content cooler air associated with the trough keeps RH and POPs high, with likely to categorical pops in the mountains and high chance to likely on the plains for Wednesday. Precip type will be snow over the summits during this period.

Trough weakens and continues to move slowly Thursday, and by Friday is cut off from jet stream to north. However with trough axis and upper cold pool still over the region there will be enough instability to keep chance pops going mainly in the mountains. Snow levels in the center of the trough axis/upper cold pool drop to 8000 ft north to 9500 ft south early Thursday morning, then rise to over 10,000 ft west of the divide as heights rise behind the trough.

Heading into Saturday another shortwave trough moves across WY/MT, then cuts off over the northern plains Sunday and Monday. Upper low even retrogrades into eastern MT/NE WY Monday, with northern jet stream into the northern Canada provinces and weak flow over the CONUS. A very odd pattern for early October. Chance pops in the mountains into northeast plains with some cold air aloft and QG ascent late Saturday into Sunday, and continued cool temperatures.

AVIATION. (For the 00Z TAFS through 00Z Tuesday evening) Issued at 605 PM MDT Mon Sep 27 2021

VFR conditions will continue tonight through Tuesday. A period of increased winds is possible after 03z; however, gusts above 15 kts are not anticipated. Winds shift SE this evening returning to southerly drainage by the early morning hours. All terminals should stay dry overnight with dry air in place near the surface. Winds will be primarily out of the SE during the day Tuesday. Showers develop over the mountains and foothills in the early afternoon. Chances are low for showers to extend east; however, it can't be ruled out for a stray shower or two to wander onto the plains. This outcome could suggest the potential for gusty outflow winds in the 20-00z timeframe.

FIRE WEATHER. Issued at 224 PM MDT Mon Sep 27 2021

A cold front will move through the region early Wednesday morning with strong north winds, cooler temperatures and chance for rain showers with snow on the summits Wednesday. For Thursday snow levels dropping to 8000-9000 feet. Some drying Friday with lower pops, then a chance again into the weekend. Inversions will limit dispersion overnight, and during the day mixing will only extend up to 5,000- 7000 ft AGL.

BOU WATCHES/WARNINGS/ADVISORIES. None.

UPDATE . Mensch SHORT TERM . AD LONG TERM . Hanson AVIATION . Mensch FIRE WEATHER . Hanson


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Denver - Centennial Airport, CO14 mi63 minS 910.00 miPartly Cloudy69°F32°F25%1009.6 hPa
Broomfield / Jeffco, CO16 mi68 minWSW 510.00 miPartly Cloudy73°F28°F19%1015.9 hPa
Buckley Air Force Base Airport, CO17 mi58 minSE 1010.00 miPartly Cloudy69°F30°F24%1008.7 hPa
Erie Municipal Airport, CO23 mi61 minN 010.00 miFair69°F29°F23%1014.6 hPa
Denver, Denver International Airport, CO24 mi63 minSSE 910.00 miPartly Cloudy65°F27°F24%1007.9 hPa

Link to 5 minute data for KAPA

Wind History from APA (wind in knots)
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Last 24hrS6SW5S3SW3S4CalmS3SE4SW6SW3CalmCalmW4NW4NW5NE5E9E12
G20
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1 day agoS9SE5S6SE6CalmS3SE6SE6E5CalmSW5Calm3NW4N5NE5E8NE8
G18
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2 days agoW8S8S6SW8S8S3S6SE7SE6SE6SE4CalmW4E3E5SE7E5E56NE8E9SE4S4S10

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NOTE: This section has been updated as of 1/26/2021. If the image you are expecting is not showing, please let me know. You may use the EDIT function to update your location.
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