Wednesday, January19, 2022
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Marine Weather and Tides
Granby, CO

Version 3.4
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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 7:17AMSunset 5:05PM Tuesday January 18, 2022 11:59 PM MST (06:59 UTC) Moonrise 5:48PMMoonset 8:13AM Illumination 97% Phase: Waning Gibbous; Moon at 16 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 Granby, CO
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location: 40.15, -105.89     debug


Area Discussion for - Denver/Boulder, CO
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FXUS65 KBOU 190333 AFDBOU

Area Forecast Discussion National Weather Service Denver/Boulder CO 833 PM MST Tue Jan 18 2022

UPDATE. Issued at 833 PM MST Tue Jan 18 2022

All the ingredients are in place for freezing drizzle early Wednesday morning. As is nearly always the case in these events, uncertainty is very high in timing, duration, and amounts. That's because minor fluctuations in temperature of the saturated layer, and how moist the near surface layer can become, determine a large part of how much FZDZ can occur and thus, how much ice to expect on bridges, overpasses, sidewalks, and some roads (or most roads if enough drizzle falls). The cold front responsible for all of this is still up in Nebraska and east-central Wyoming. It should arrive by midnight but saturation in the low levels will take a few hours after the winds shift northeast. By 3 AM saturation may be reached across the northeast plains, and by 5 AM pretty much all of our area along the east slope foothills below 8,000 ft, the I-25 corridor, and all of the plains could start to see drizzle due to saturation in the lowest several thousand feet, shallow upslope flow, and the fact that the temperatures in the saturated layer continue to only be around -8 degC through midday. Thus, freezing drizzle could occur across the I-25 corridor from 4 or 5 AM through about noon. If that happens, and the lift/moisture is enough to generate decent drizzle, significant impacts to travel could occur for the morning commute. Confidence in those impacts is very low, and focused on how much drizzle might occur. Temperatures will be plenty cold for it to freeze to elevated surfaces and even some roads and sidewalks. That is the reason for the Winter Weather Advisory: There are enough ingredients in place, and the ensuing impacts could be significant if enough drizzle falls.

The HRRR has recently picked (or technically re-picked) up on the FZDZ for our area, perhaps providing a tiny bit of increased confidence that impacts could materialize. Normally even CAMs have a hard time generating FZDZ because of the shallow nature and extreme sensitivity to temp/moisture profiles in time and space. The overall forecast from this afternoon hasn't changed much at this point. We will know much more about drizzle amounts a few hours after FROPA late tonight via surface obs, spotters, and webcams. Snow amounts for the afternoon/evening hours are much more certain, as the signal remains for some QG lift to overspread the drizzle layer, and seeder/feeder processes will quickly win out to generate light snow across much of the area, but additional travel impacts (or for areas that don't see any drizzle) due to snow are expected to be limited.

SHORT TERM. (This evening through Wednesday) Issued at 348 PM MST Tue Jan 18 2022

Main concern for impacts will be the potential for areas of freezing drizzle and light snow late tonight into Wednesday extending from the plains into the urban corridor. A light glaze is possible on roads and other hard surfaces which may impact the AM commute. A Winter Weather Advisory is in effect for the plains and foothills early Wednesday morning into Wednesday evening.

Cross-sections show the post-frontal airmass further cooling and moistening overnight. Light shallow upslope and weak synoptic lift in combination with a moist layer to the surface will support light precipitation and low ceilings. This will start in the NE corner of CO and gradually progress westward Wednesday morning. Sounding profiles have been consistently signaling potential for freezing drizzle. Temperature profiles in the moist layer hold above -10 C limiting ice crystal growth along with a dry layer above. With below freezing surface temperatures, freezing drizzle is a possibility. By early Wednesday morning, freezing drizzle chances increase westward into the urban corridor in time for the morning commute. A light glaze is possible on roads, sidewalks, and elevated surfaces which may impact the AM commute. Model soundings show the NE plains to cool quickly through the morning, so development of flurries/light snow become more likely. Chances for freezing drizzle decrease from east to west Wednesday afternoon and chances for light snow increase as temperatures profiles further cool. Snow accumulations are expected to be minimal.

LONG TERM. (Wednesday night through Tuesday) Issued at 348 PM MST Tue Jan 18 2022

Models still show a subtle shortwave sliding across our area Wednesday night. It's trending weaker and further southwest though. There's always been a question of how much that would interact with the low level cold air, but there's at least a chance it could reinvigorate some light snow for a while overnight. This is now looking more likely over the mountains and southern part of our area. Otherwise, the low level forcing for precip will be fading and dropping south of our area during the evening. We'll hang on to the Winter Weather Advisory for the foothills and Palmer Divide areas until 8 PM in case there's enough snow to keep things slick, but we may just have very light snow continuing.

Temperatures Thursday are a challenge. There will be clearing, but there might still be some clouds in the morning. This will also depend on how much snow there is. We compromised between the various solutions and will keep temperatures in the 30s on the plains. Clouds will spread back in Thursday night ahead of the next shortwave. There's getting to be pretty good agreement now on the Friday system. We're on the edge of the QG lift as the system shears out to our west, and the low level wind and temperature fields aren't too exciting. But there will be a zone of low level convergence, a little cooling aloft, and upslope into the foothills that will produce light snow over the mountains and there's a pretty good threat of a few hours of light snow on the plains as well. This will mainly be during the day, though upslope areas west and south of Denver could hang on into the evening and these areas should have the greatest snowfall. Like Wednesday's system, it doesn't look like much precipitation, but the placement/timing could still mess up the Friday evening rush hour around Denver and into the mountains.

Behind the trough, we'll have NNW flow over the weekend with a bit more wind in the mountains. Saturday looks sunny, but we might not have displaced the cold air from the plains much yet. There should be more of this on Sunday, with warmer temperatures at least near the foothills and possible across the plains as well. The models are slowing with the development of the next upstream trough (lift arriving Tuesday instead of Monday now), but there is a weak front in northwest flow bringing just a little cooling and probably more clouds for Monday. There will be another chance of snow along with cooler temperatures when the next trough arrives. For now, this is slated for Tuesday into Wednesday, but it looks like another system that might shear off more to the southwest so some degree of additional cooling is likely but the threat of snow is more speculative.

AVIATION. (For the 00Z TAFS through 00Z Wednesday evening) Issued at 457 PM MST Tue Jan 18 2022

This is challenging forecast for Wednesday. The general ingredients are well understood, but trying to pin down details and the impacts to aviation operations will be very challenging. At a high level, a cold front moves through a little before midnight, with ENE winds shifting to E and going from 12-15 kt to 10 kts or so by 1-3 AM. IFR CIGs will be delayed until midnight or an hour or two after midnight given significant dry air to overcome. Eventually the lowest levels saturate but it remains dry aloft, a classic set up for freezing drizzle. The freezing drizzle will transition to snow at some point Wednesday afternoon or early evening. Amounts of FZDZ and snow will be light, but even a few hundredths of FZDZ can cause impacts to runways and aircraft, especially if VIS drops to under 1 mile and the CIG drops below 003, both of which could happen. The issue is it's a very low confidence scenario in terms of pinning down when the FZDZ may occur along with the lowest CIG/VIS. Our best bet for now is some time between 3 AM and 11 AM. Light snow is possible throughout the afternoon but under an inch of accumulation is expected, and IFR/ILS conditions should continue well past midnight into Thursday morning though not as low as during the Wednesday morning hours. If there is any good news to this forecast it is that winds should not be much of an issue. Much of the day Wednesday they should be out of the east at 10 kts or so.

VFR conditions should return around sunrise on Thursday morning and winds will be light out of the south.

BOU WATCHES/WARNINGS/ADVISORIES. Winter Weather Advisory from 2 AM to 5 PM MST Wednesday for COZ042-044-048>051.

Winter Weather Advisory from 5 AM to 8 PM MST Wednesday for COZ035-036-038>041-043-045>047.



UPDATE . Schlatter SHORT TERM . Danielson/Mensch LONG TERM . Gimmestad AVIATION . Schlatter


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Kremmling, Mc Elroy Airfield, CO26 mi85 minN 010.00 miPartly Cloudy0°F-4°F84%1019 hPa

Link to 5 minute data for K20V

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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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