Marine Weather and Tides
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 6:25AM||Sunset 5:56PM||Thursday March 4, 2021 2:37 PM MST (21:37 UTC)||Moonrise 12:19AM||Moonset 10:43AM||Illumination 64%|
7 Day Forecast for Marine Location Near Brighton, COHourly EDIT Help
Area Discussion for - Denver/Boulder, CO  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXUS65 KBOU 041807 AFDBOU
Area Forecast Discussion National Weather Service Denver/Boulder CO 1107 AM MST Thu Mar 4 2021
UPDATE. Issued at 1056 AM MST Thu Mar 4 2021
Observations and radar showing increasing snowfall across the southern Front Range foothills, and given latest guidance expect advisory amounts through zone 36 as well. Have issued a winter weather advisory for this area.
UPDATE Issued at 942 AM MST Thu Mar 4 2021
Upper low circulation is across east central Utah and nosing into southwest Colorado this morning with moderate to strong QG ascent already into central Colorado now. The best forcing will shift into east central Colorado this afternoon with showers expected to rapidly develop with saturation and decent ascent. Already, radar imagery showing moderate to heavy snow has developed over the higher mountains and area web cameras showing roads becoming icy and snowy. Have already issued a winter weather advisory for zones 33..34 for 4-8 inches of snowfall. There is decent instability so could see some embedded heavier snow showers this afternoon over the mountains.
Across lower elevations radar is showing scattered showers developing but mostly virga showers right now and not reaching the ground. This will change rapidly later this morning and afternoon as airmass begins to saturate with support of the strong QG ascent moving overhead. VAD winds from radar are all southeasterly currently back will continue to back to the northeast this afternoon as the low approaches to our south. Latest high resolution models are showing a decreasing trend in qpf/snowfall over the I-25 corridor, especially from Denver northward with the heavier shift of qpf further east and south of the county warning area. Will monitor these trends and adjust forecast as necessary. Might need to add a bit more snowfall to those areas but will be lightning the warmth and warm road temperatures to have much impact. The low will rapidly shift east of Colorado by later this evening with decreasing precip from west to east from late evening to the overnight hours. For now, steady as she goes.
SHORT TERM. (Today and tonight) Issued at 458 AM MST Thu Mar 4 2021
Not much change to the forecast thinking as a closed low passes across southern Colorado today and tonight. Despite very similar mass/wind fields, the models produce different amounts of precipitation. The rain/snow line will also be around 5000-6000 feet most of the time, which makes the precipitation type and snow amounts difficult to forecast.
There look to be two opportunities for significant snowfall. The first would be with any strong convection over the mountains. The models that tend to produce stronger convective precipitation do some of this, mainly in the deformation band which is currently lifting through western Colorado as it progresses eastward into the northern mountains this morning. There's probably not enough instability for thunder, but some heavy showers look like a good bet. We've hedged away from the specific bullseyes in the models, but generally increased the snow amounts in the northern mountains during the day today.
The second place of concern is the new warm conveyor belt transitioning into the deformation band on the north side of the low this afternoon and evening. The models agree on having this feature, but have different intensities. The general plan is for this to form well east of Denver and then wrap back towards Denver in the afternoon and drop south of the city this evening. There's pretty good agreement on this being the dominant feature controlling the precipitation, with the upslope against the Front Range foothills in the early afternoon getting cut off a bit as winds at low levels along the foothills go east. This may be a similar evolution to our last snow event, though not necessarily with that intensity. This also isn't a configuration where the band would stall as everything points to a steady southward movement. But still it could produce a couple of hours of moderate to heavy snow as it passes. If there is a pivot point that this would stay over longer it's likely east of Denver where the rain vs snow is more questionable.
As for temperatures, there's little additional guidance here. There's actually low/mid level warm advection, or perhaps neutral, all through the event. The cooling comes from a combination of evaporative cooling at the surface, and some dry advection from the north as the precipitation is developing this afternoon, and then the lifting. The snow level should come down to between 5 and 6 thousand feet as the precipitation saturates the low levels, but then it won't drop any further as there's no colder air to be found. This means snow is likely across Denver, but temperatures may stay above freezing while it's snowing so there will be lots of melting on roads. We'll continue to show a substantial gradient with elevation between 5 and 7 thousand feet, and a focus south of Denver where colder temperatures and the north wind should enhance snowfall. The southern foothills are a question mark as the amount of upslope and how far west the band goes are both uncertain.
The snow should end in Denver by about midnight as everything drops away to the southeast. It looks like clearing skies but a little surface wind still . and no cold advection . so forecast lows a little below freezing look good.
A note . we're having trouble with our probabilistic snowfall graphics this morning. We made a grid that had a 90th percentile of 4 inches at DIA and 8 inches in Douglas county, but we haven't been able to get that out to the world yet. Those kind of amounts would be possible with a couple degrees of cooling and the higher end QPF. We hope to get this issue resolved later this morning.
LONG TERM. (Friday through Wednesday) Issued at 458 AM MST Thu Mar 4 2021
By Friday morning the center of the closed low will be over central Oklahoma with a trailing ridge and increasing subsidence over the region. This will bring partly cloudy conditions with temperatures warming once again into the upper 50s to lower 60s over the far northeastern plains. The upper ridge will continue to build in Saturday bringing upper level flow to the southwest and clearing out most of the remaining clouds to bring sunny conditions and the warmest temperatures of the week with highs reaching into the mid- 60s for most areas of the lower elevations and 40s to low 50s for the high country. For Sunday, the fast moving shortwave has now moved further north with the latest model runs so it is looking less likely that areas will see any precipitation. Instead, a lee side low sets up pulling in increasing southwest downslope winds that will help to bring highs back into the 60s for a second day across the lower elevations with mostly 40s over the higher terrain with mostly sunny skies prevailing.
For the start of the week models are showing a weak shortwave embedded in the southwest flow aloft impacting the region late Tuesday into Wednesday. There is some weak lift and moisture associated with this feature. This could bring just a slight chance of some precipitation for the higher elevations mainly south of I-70 late Tuesday into Wednesday. Otherwise Monday and Tuesday are on track to add to the string of warmer than average days with highs in the mid to upper 60s. Tuesday late will see the slight impact from the shortwave with increasing southwest flow aloft from the nose of the jet streak pushing into the region with snow in the mountains but dry elsewhere. Temperatures will also respond with highs dropping into the 50s for Wednesday.
AVIATION. (For the 18Z TAFS through 18Z Friday afternoon) Issued at 942 AM MST Thu Mar 4 2021
VFR at local terminals at the moment but expect ILS/MVFR conditions developing between 10 am and noon as showers become more numerous and some mix of snow possible. Expect all snow by this evening with possible light accumulation's at APA/DEN around an inch or less. Expect northerly winds to increase this afternoon as the low intensifies to our south. Improving conditions after midnight as the storm pushes away from Colorado.
BOU WATCHES/WARNINGS/ADVISORIES. Winter Weather Advisory from 2 PM this afternoon to 2 AM MST Friday for COZ041.
Winter Weather Advisory until midnight MST tonight for COZ036.
Winter Weather Advisory until 9 PM MST this evening for COZ033- 034.
UPDATE . Entrekin SHORT TERM . Gimmestad LONG TERM . Bowen AVIATION . Entrekin
Weather Reporting StationsEDIT (on/off)  Help NOTE: Click on distance to see the station location on a map
Airport ReportsEDIT (on/off)  Help Click EDIT to display multiple airports. Follow links for more data.
|Denver, Denver International Airport, CO||8 mi||45 min||WNW 14||10.00 mi||Overcast||42°F||28°F||58%||1014.4 hPa|
|Buckley Air Force Base Airport, CO||15 mi||1.7 hrs||NNE 12||7.00 mi||Light Snow||37°F||30°F||76%||1014.4 hPa|
|Erie Municipal Airport, CO||16 mi||43 min||N 13 G 19||10.00 mi||Partly Cloudy||45°F||26°F||47%||1015.9 hPa|
|Broomfield / Jeffco, CO||19 mi||1.7 hrs||N 12 G 15||10.00 mi||Overcast||45°F||19°F||37%||1015.6 hPa|
Link to 5 minute data for KDEN
Wind History from DEN (wind in knots)
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