18z GFS Snowfall through Sunday We are continuing to track big changes to our weather pattern, the initial effects of which are already being felt today, but by no means is this the main event. Scattered rain showers will persist across northeast Colorado into Thursday evening, with even a rumble of thunder or two mixed in possibly. By Friday, highs will only make it to the mid 40s as our weekend storm approaches from the west.

Here is where the forecast gets fuzzy, or at the very least debatable. The EURO, GFS and GEM models have admittedly been rather consistent with bringing a moderate snowfall event to Denver Saturday, with a general 6 - 12" being shown over the last few days. If you follow along on Twitter, you'll know that not all of us here at Brendan's Weather have seen eye to eye on this scenario. While it gets harder and harder to argue against the consistencies in the models, I feel at the very least it is prudent to explain why I am *still* skeptical of greater than 6" in Denver proper this weekend. It is fair to say I hope I am in the wrong here.

Upslope. My biggest concern at the moment is the lack of upslope depicted by the models. Ordinarily, our best snowfall events come from good positioning of the surface low and therefore a strong upslope event. Below is the positioning of the surface low midday Saturday. This is about as far north as it gets east of Denver, before diving south Saturday afternoon. If we see a northern shift, upslope could look a bit more promising. The National Weather Service has issued a Winter Storm Watch this afternoon for areas east of Denver, and no advisories, yet, for the city. Source: WeatherBell

The 500 pattern. The pattern above the surface worries me too. It has been far too progressive run after run for a traditional snow-getter storm in Denver. Without the low cutting off, our period for snowfall will be much shorter, and we will be depending on good dynamics.

NAM, RPM models. Despite the fact we have generally been throwing out the NAM this winter, seems worthwhile to point out it has not been nearly as gung-ho as the other models. The RPM shared by Makens, has consistently shown a very sharp cut off from north to south for snow totals, the Palmer Divide, foothills, and eastern plains being the winners. This is echoed in most of the models, but to a lesser extent, and certainly catches the 1) lack of upslope, and 2) southern positioning of the surface low.

Time of day. And finally, the time of day. Less of a concern than we had a few weeks ago due to the *much* colder temperatures associated with this system, but melting initially will be an issue with the warmer ground temperatures.

Now, in an effort to completely confuse things, I will again concede that I expected today's 12z model runs to reflect my hypothesis a bit more, and quite frankly they have not. The EURO and GFS actually bother increased QPF (if only slightly in the case of the EURO), but nevertheless both suggest double digit snowfall totals are *possible* with this storm. We will see.

Cold temperatures!
In addition to our chance for snow this weekend, the other thing we will be monitoring is much colder temperatures for the forecast area as we head into the first full week of Spring. Temperatures this weekend will remain in the 20s for highs, with single digits possible by Tuesday morning. The weather will remain unsettled into early next week (maybe another shot of snow Monday!), with below average temperatures through the end of the week.

Much more to come as this system continues to take shape!

Forecast Breakdown:
I'll leave you with our preliminary spread of snowfall totals - subject to change!
Brendan: Denver: 3 - 5", Greeley: 2 - 5", Palmer Divide / foothills: 5 - 12 "

Greg Moore and Josh Larson: consistent EURO, higher snow ratios (12:1), an easily discounted NAM, and in general all the positives listed above as reason for higher totals and with that are sticking with 6 - 10" in Denver, and 4 - 8" for the northern suburbs.

Chris Tomer: 4-7" Denver, 4-5" Northern Front Range, 6-12" Foothills & Palmer Divide

Matt Makens: Trace to 3" northern Front Range, Denver metro 3 - 6", isolated higher than 3 - 6" Palmer Divide, 5 - 10" eastern plains / foothillsRPM

12z GFS 6 Hour Precip Just finished going through all of the day's data. The weekend series of storms looks more promising for snow for the Front Range.

I said a series of storms. The first, brings snow to the mountains tomorrow and Wednesday. Meanwhile Denver will have some sun tomorrow and then a rain chance Thursday. This is the system coming in from a less than favorable direction for lots of moisture that we talked about yesterday.

The one shown on this image is the second system in the series, for Friday night and Saturday. Temperatures will be much colder by then, and that system will be all snow for us. By the end of the weekend, the mountains will have 1-2 feet of snow. The Front Range and Denver area has a chance of good accumulating snow later Friday through Saturday night, too. The range among the models is 6-14" across the lower elevations. However, I have a couple "caution flags" to raise at those totals:

1. That is assuming a very slow system, taking 36 hours to move through... we haven't had a slow system yet this season and the overall pattern would suggest a faster system causing us to get less snow.
2. The position of the storm's center shown on this image is in the "sweet spot" for a good Front Range snow. However, I could see its position changing enough to move that good snow just outside of our area.
3. Temperatures will likely be less problematic than that storm two weekend ago, so we will be less concerned with how much snow melts before being measured.

As always, any snowfall forecast you hear that is more than 24-48 hours ahead of the storm should be taken for what it is... a shot in the dark. At least we have time to track the changes... and the caution flags raised will have worked themselves out by then. No matter how you slice it, it will be an unsettled first few days of spring... in like a lion!

Another night of breezy weather for Denver before calmer weather returns Tuesday. Highs will be in the 50s through Thursday, with even a chance we see some 60s Wednesday. Our pattern change arrives late Thursday, and will bring some much cooler air and possibly some moisture for the weekend!

Models have been tracking our next set of disturbances due in late week for several days now, but as I mentioned this weekend, the storm has looked most promising for the higher terrain of Colorado, and less so in Denver. Today we saw a shift in this trend, with some of the models coming around to a wetter solution for the city. There are few details to offer tonight, but we will continue with the colder weather and chance for rain and snow by the weekend as is already in the forecast. Accumulating snow is certainly a possibility this weekend, but for now will leave it out of the forecast until we get better (and more consistent) agreement between the models.

For those of you thinking it's far too late in the season for accumulating snow... think again. March is Denver's snowiest month, with 11.5" on average. In fact, today marks the 10 year anniversary for the March 2003 snowstorm which brought nearly 3 feet of snow to Denver, and upwards of 7 feet to the foothills to our west. April can also be quite snowy for Denver. On average the city sees about 9" of snow during the month, with several Aprils over the last 50 years seeing more than 20" for the month. More often than not, the difference between 12" and 0" in April often depends on the temperatures, the month typically brings some beneficial moisture to the region.

We will continue to track all the latest on this weekend's weather, and keep you posted as things evolve!

Rain showers possible through Saturday night
Big mountain storm possible by end of week After setting a record high on Friday of 76° F, cooler temperatures have returned to Colorado today. The moisture and cooler temperatures have helped crews fighting the Galena fire west of Fort Collins get a better handle of the fire, and according to the Denver Post evacuations are expected to be lifted by 8pm Saturday night. With more wind in the forecast, firefighters are warning all evacuees to be prepared to leave once more at a moment's notice. As of early Saturday afternoon the fire was 45% contained.

In Denver, temperatures have hovered around 50° all afternoon, under mostly cloudy skies. Rain showers will be possible through the night Saturday, with slightly warmer temperatures expected Sunday. There is only about a 40% chance we see some rain tonight, but I expect many will see a light shower or two.

The week ahead looks a little cooler than the end of last week. Highs Monday will drop into the 40s with windy conditions expected. Tuesday could be the pick day of the week with upper 50s and mostly sunny skies forecast. By Wednesday we will be tracking our next storm system out of the west, which has the potential to bring some significant snowfall to the Colorado high country to end the week. For Denver we will introduce a chance of showers (even a rain snow mix) Wednesday through Friday, but at this time this does not look like our storm. It will be a slow moving storm, and there is lot of time between now and then, so certainly worth monitoring, stay tuned!