Just when you thought we couldn't possibly see anymore spring snowfall events in the Denver area (especially following a weekend of 75-80 degree temperatures)... it's going to happen again... this time on May 1st.
A deep and powerful low pressure trough is diving southward toward Colorado as we speak, bringing with it another blast of unseasonably cold air and upslope precipitation. Denver is going to see snow fall for most of the day Wednesday, but I don't think the city will receive nearly as much snow accumulation as what the National Weather Service and other outlets are predicting (more on that below).
Several days of warm and sunny weather concluded yesterday with a high of 80F in Denver, before an initial cold front ahead of the main system moved through early this morning, bringing much cooler weather today (temps are currently in the mid to upper 50's across the metro area). The cold front moved through earlier than what models were forecasting, making me think the main cold front will reach our area earlier tonight as well, meaning perhaps an earlier onset of snowfall after precipitation starts out as rain.
This system is going to produce substantial precipitation once again for Northern Colorado, which is nothing but good news as our spring weather pattern continues to put a dent in the drought (excluding Southern Colorado, which has been MUCH drier than Northern Colorado this spring). As for snowfall, the Front Range foothills and mountains, as well as the northern I-25 corridor from Ft. Collins to Cheyenne, should receive the heaviest amounts, with up to a foot possible in the foothills, and up to 20" possible for areas in Rocky Mountain National Park, the Cameron Pass region, and the Indian Peaks. Even though the areas along and east of the Continental Divide will be favored for upslope snow, a band of heavy snow associated with the system will set up across Northern Colorado, providing good snowfall totals for areas west of the Divide as well, such as the Park Range/Steamboat, Gore Range, Vail, and Summit County.
In Denver, the NWS has issued a Winter Weather Advisory for 4-7" of snow in the city proper, but I believe we have too many factors working against us to see this much snow. The best snow-producing conditions are going to exist during the daytime hours tomorrow, but that doesn't mean we'll see good snow-accumulation conditions, despite what the models are showing. The surface is going to be very warm following several days of 70+ degree temperatures, and it's also May 1st tomorrow, meaning of course that solar radiation is very strong at this time of year... because of this, I do not think we will see much accumulation during the daytime hours, even though temperatures will be near freezing at daybreak and gradually falling into the upper 20's by the afternoon (yes, WAY below average for the first of May).
I do think the cold front and subsequent changeover to snow will occur earlier than what models are forecasting, though, likely in the overnight hours... so I think there's a good chance Denver could wake up to 2-3" of wet snow by daybreak, but given the recent warmth and marginal freezing temps at the start of the event, I'm willing to bet the roads will remain snow-free in the city. Once the sun is up, however, I think the warm surface and strong solar radiation will prevent much snow from accumulating. The only way I really see these factors being overcome is if a band of very heavy snow sets up over Denver, and heavy snowfall rates are able to accumulate snow faster than surface conditions are able to melt the snow, and while this is possible, I'm not willing to bet on it given the unpredictable nature of these heavy snow bands in spring time snow events such as this (where snowfall accumulations can vary significantly over short distances).
Looking outside of Denver, I do think that areas on the western side of the metro area, at slightly higher elevations, could see noticeably more snowfall than Denver, due in part to enhanced precipitation rates from the upslope effect of higher terrain, as well as relatively less surface heating from being farther removed from the urban heat island effect of central Denver, where more concrete surfaces can trap and hold more heat, when compared to grassy surfaces (it's a localized effect, but can sometimes make a difference in these type of situations).
I believe Denver will see 2-4" of snow overall (most occurring overnight tonight, and perhaps a little more in the late afternoon/evening hours tomorrow), and even this may be a little high, while I'm more confident western metro cities from Boulder to Arvada to Golden will see 4-8". I also think Ft. Collins will fall into the 4-8" range (maybe on the lower end of the range, though), as the region close to the Wyoming border will see the colder air and precipitation move in sooner tonight, and heavier bands of snow could set up overnight as well. In the foothills west of the metro area and up to the Continental Divide, 8-15" will be possible, especially above 7,000 ft., and I wouldn't be surprised to see some totals in the 18-24" range in Rocky Mountain National Park.
Snowfall should wind down tomorrow evening, and depending on how quickly the skies clear, record low temperatures will be in jeopardy once again (I believe the record low for the date in Denver is around 22-23F). Denver's all time record low for the month of May is 19F, and it is not out of the question we could reach this mark, although I think we'll come up a few degrees shy of that mark. Sunshine returns on Thursday, quickly melting whatever snow is on the ground in Denver, but temperatures will only reach the mid to upper 40's... still about 20 degrees below average.
Northerly flow will continue through the weekend as the low pressure system stalls to the east of us, so slightly unsettled and chilly weather will continue... with highs in Denver topping out in the mid to upper 50's this weekend, with scattered clouds and rain chances possible, along with some snow showers in the mountains. Models are not in great agreement about this weekend in regards to precipitation, though, so all I can say for now is that we might see some rain, or even some thunderstorm chances, but I am pretty confident that the metro area will not see snow this weekend.
We have had a remarkable spring in terms of snowfall this year, which has many people complaining of course, but we need to put things in perspective... last spring was a disaster, with almost no snow and precipitation, and as a result we quickly fell into a drought situation and suffered through a devastating wildfire season. For most of the winter, the drought continued, and the situation heading into the spring did not look good for our snowpack or our water resources... this spring has basically been a miracle for northern Colorado, with our mountain snowpack (in northern and central CO at least) rebounding to near normal for this time of year (less than peak average, but normal for late April), after being well below normal all winter long, and the amount of moisture Denver and the Front Range have received in March and especially April have been enough to put a huge dent into our drought, and will help replenish our water resources and lower our wildfire danger this summer... not to mention, it will "green up" the landscape this spring and into early/mid summer. So keep these things in mind if/when you catch yourself complaining about the snow tomorrow... more spring snow just means that much better of a summer.
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