ECM Total 5 Day Precip (WeatherBell)First week in some time we are not talking about SNOW in Denver! Instead we have a great shot for more beneficial moisture, only this time in the form of liquid. A few isolated storms have developed this afternoon, one bringing accumulating hail to Brighton, but chances for rain will become more widespread tomorrow into Thursday.

Models predict our slow moving low, now over southern California, will bring anyway from a trace to 2" of precipitation to eastern Colorado through Saturday. If you are to believe the ECM, the best chance for the highest totals will be from Denver south and east. There will likely be wide veriations in totals, especially with the storms more isolated in nature like today.

With this unsettled pattern, temperatures will remain cool through Saturday, but nowhere near the cold we have been experiencing over recent weeks. Highs will hover right around 60°, with lows in the lower to mid 40s. We will try for a better warmup and drier weather late in the weekend and next week, but will need to watch closely another shot of arctic air set to dive south next week, which could keep temperatures on the cooler side should it come down a little further west than currently forecast.

Severe Weather
It has been a very quiet start to the severe weather season! The pattern has simply not been conducive to severe weather outbreaks, with very cold air and slow moving upper level lows. As Dr. Forbes reports, this has been the slowest start to May for reported tornadoes since 1970.

There will be some active severe weather tomorrow and Thursday across Kansas, Oklahoma and Texas, but this does not look like a large tornado outbreak, as the main threat looks to be damaging wind and hail with these storms, and largely isolated tornado chances. The focus then starts to turn toward the latter half of the month, and the possibility of a bigger pattern shift. Ready for our first chase!

Snowfall forecast through WednesdayThe forecast remains mostly unchanged tonight, only a few minor adjustments to the Bust Index and totals. Rain has developed across northern portions of the forecast area, and will slowly move south through the overnight hours. Rain will begin to change to snow after midnight, but given the fact we are still at 53° in the city, that could take several hours. A Winter Weather Advisory goes into effect for Denver at midnight, and will remain so through Wednesday evening.

Our totals remain on the low side relatively. The thought is that our recent warm temperatures, and much of the snow falling during daylight hours Wednesday will lead to a fair amount of melting with this storm. Most snow accumulation will occur on grassy/raised surfaces, with some slush and accumulation on paved surfaces possible, especially under heavier snow bands and early/late in the day Wednesday.

Much like the last several storms, this system will bring more banded snowfall to the area. That means in all likelihood a wide variations in totals, as some of the heaviest bands may indeed be able to negate some of warmer surface and radiant energy issues outlined above. It is worth noting that several of the high res models have produced very good snow totals for the region today, and with that some folks may end up with a pretty impressive May snow!

In any case, Wednesday looks wet and cold. Stay warm, drive safe, and stay tuned for any adjustments that may need to be made to the forecast!

WPC 5 day precip totalsTricky forecast setting up for Front Range
As I mentioned in a quick Facebook update last night, the forecast continues to call for a dramatic cool down Tuesday into Wednesday for Denver, but big questions regarding snowfall potential for Denver remain. We hit 83° in the city today, Wednesday will be nearly 50° cooler, with a chance for snow.

The cool off begins Tuesday morning, though temperatures will remain quite pleasant especially south of I-76. Precipitation (initially rain) will begin north of the metro area and gradually moving south through the afternoon Tuesday. A few thunderstorms, especially east, should not be ruled out Tuesday afternoon, but the severe threat looks minimal at this time.

Here is where the forecast gets messy. While all models support a change over to snow with this system in Denver, they differ on just when that changeover will occur.

Over the last 24 hours or so, a blend of all the models would suggest 2 - 4" will be possible for Denver by Wednesday afternoon, with most of that on the grassy/raised surfaces, and melting throughout the day. That said, the Euro did come in just a bit cooler this afternoon, and the SREF has also shown a positive trend in snow totals since this morning as well. The best chance for accumulating snow will be at higher elevations in the Front Range foothills, and along the Colorado/Wyoming border where a Winter Storm Watch is already in effect.

What to watch for:
Temperatures: Tonight's model runs will hopefully offer some clues as to when the rain/snow changeover will occur. An earlier onset of snow means a better chance for accumulation in Denver, while later could mean mostly wet and cold with very little accumulation.

Storm Track: Models continue to differ on how far south our trough eventually digs. With that, highest confidence for the most rain/snow continues to be northern Colorado, while the eventual storm track could certainly effect totals (both rain and snow) in Denver and south. It does appear that all of northeast Colorado will see some truly beneficial moisture with this system, with anywhere from 0.5" to 2" QPF for the entire region.

We will no doubt have more to come on this weather change later this evening and through the day tomorrow. I imagine this to be a rapidly evolving forecast as the ingredients begin to come together, so certainly subscribe to be kept up to date with all the latest!

We all heard it, the collective sigh of relief last Wednesday by many spring-craved Coloradans when they saw 70s in the forecast for this weekend. Spring had finally sprung, and after weeks of on-again, off-again snow and below normal temperatures, we had finally seen the last of it. The European model, however, was saying otherwise, and over the last 24 hours the CMC and GFS models have (not surprisingly) come around as well. We will flirt with 80° Monday, but then get ready for another blast of unseasonably cold air, rain, and possibly some snow.

Take a look at what the ECMWF tries to do this week. Round number one brings a winter wallop to Colorado Wednesday, round two brings heavy snow to western Iowa and Minnesota Friday. Needless to say, should this solution come to fruition, it would be quite a memorable May snow for many!



I will no doubt have many people explaining to me this is not possible - it has been far too warm, and it is May! You may be right. We are several days out from this storm, temperatures on the onset will no doubt be marginal for snow, surface temps will be quite warm, storm track may change, it may well be a very elevation driven rain/snow event, and. . . we will be watching it all. For all the reasons mentioned, it gets quite hard to see >5" this time of year, but should all the ingredients align, it could happen. It would not be the first time >70° was followed by accumulating snow in the Mile High City.

A lot to watch over the coming days, and I am by no means forecasting the totals shown above at this time. Just something to watch, as cooler wet weather is looking more and more probable by midweek in Denver.