Severe and Extreme drought for COAfter a dry and mild start to our winter, we have seen quite a turn around this March and April. Just a few short months ago Denver was just 50% of normal for seasonal snowfall totals, but all that has changed since March. With this week's 6.5" of snow recorded at DIA, if we were to receive no more snow this season we would end it several inches above normal with 61.4" of snow officially at DIA since last September! It is worth noting, however, that in the city these numbers are lower. If the official weather station had not moved from the old Stapleton Airport to DIA, that official number would only read 41.6", thanks to my friend at Thornton Weather pulling these numbers. Nonetheless, a promising trend as we continue to try and make a dent in the drought conditions across our state.

Much of the nation remains locked in cold. This week we set an all time record low for April 10 of 6° F, and the first record low since October, 2009. Despite a common misconception, we do see snow in April pretty regularly (though not the last few years), but such extreme cold temperatures are not nearly as common.

This weekend seasonal temperature return to the Front Range, if only briefly. Highs Saturday will be in the mid 60s, before cooling slightly with a chance for rain on Sunday. More cold weather is set to return next week, as strong upper level trough moves in from the west. Here is the 2 meter temperature anomaly for this coming Tuesday, it has much of eastern Colorado 30° BELOW normal!



The other part of the story we will be watching very closely over the next few days is the chance for snow again in Denver. As to not be misinterpreted, I am NOT forecasting the winter wallop of the century next week (for now), but it certainly makes sense to point out that all of the medium range models have been very consistent over the last few days in bringing another chance for significant snowfall to Denver during the Monday through Wednesday timeframe. There are a number of details to be worked out for this to come to fruition, but at the very least, next week looks wet and soggy in addition to the cold - if not even snowy.

Snow totals updated 8:15pm. . .

The National Weather Service has downgraded their Winter Storm Warning to a Winter Weather Advisory through 6pm this evening. Their forecast calls for an additional 1 - 3". Light snow showers will continue to diminish through the evening.

Everyone wants to know, what happened? The short of it is, nothing that we have not been warning about each and every day on the blog this past week. Despite considerable agreement over the last few days by all the major models (GFS, EURO, NAM) suggesting a significant snowfall for Denver, we had our concerns here at Brendan's Weather. I hope we effectively communicated those, although judging by some of the emails and comments I have received I suspect that might not be the case. Truth be told, we thought all of the positive factors would negate the negative, but it was not to be, and that became quite clear as the storm initiated last night. No one wants a blown forecast less than us, of this you can be sure.

Dry slots, convective explosions, cold temperatures, storm track, speed, energy. . . chaos.
There are no shortage of explanations as to what went wrong. The biggest issue was, as expected, the convective activity out east yesterday afternoon. Matt gave a great explanation of what happened his on his Facebook page this afternoon, but basically, those storms robbed a heck of a lot of energy and moisture from us, and released a whole lot of heat into the atmosphere which slowed and derailed our low rather dramatically. With this, we had a substantial amount of dry slotting over Denver (one of my key concerns yesterday), and therefore we saw limited totals.

By the time we recovered a bit this morning, it was too late. We lacked the moisture, we lacked the intensity, radiant energy this time of year can cause melting even in sub-freezing temperatures, and we were reduced to light (cold!) fluff that just never amounted to much in the city.

Despite "bust" some impressive weather
Not all was lost with this storm, it was absolutely fascinating from a meteorological perspective. Not only did we experience a 60° temperature drop from this time yesterday, but we also saw a downright impressive display by Mother Nature yesterday afternoon across eastern Colorado. There were up to 10 warnings and advisories issued across the northeast corner of the state at any given time, from tornado warnings, to blizzard warnings - often in the same county! Several tornadoes were confirmed out near Akron, where damage reports show several structures were lost. At one point, there was a confirmed tornado and snowfall within a stone's throw, something I have never seen before.

Temperatures have hovered in the teens all day in Colorado. We set the all time low-MAXIMUM for the date, the previous record being 27°. Especially impressive given that just 24 hours prior most of us were enjoy temperatures at or near 70°. Tonight will be cold as well, with overnight lows very likely dropping into the single digits for some.

Yes, snow totals all in all were below forecast totals. Despite the fact this became all too evident last night, many school districts, airlines, and other offices shut their doors today. This has only helped to fuel the outcry by many that this storm was overhyped and under forecast. That said, still some good totals to report this afternoon including a handful of locations over eight inches. Here are a few totals from NWS trained spotters:

• 17.9" Eldorado Springs
• 16.5" Orodell
• 13.1" Boulder
• 10.3" Idledale
• 8.5" 3 miles SSE Morrison
• 8.2" Genesee
• 8.0" Roxborough Park
• 7.8" Ken Caryl
• 6.8" Chatfield Reservoir
• 6.5" 4 miles west Denver International Airport
• 5.8" Westminister
• 5.7" Aurora
• 3.5" Downtown Denver

If I have left something unexplained, please do not hesitate to ask. I have the Feedback option on the site exactly for this reason, or feel free to comment below. We try to bring you as much information in as clear, transparent and concise way as we possibly can, and if there are ways this can be improved, please let us know!

I leave you with this image from the 12z GFS. . . Will we be doing this again next week? Maybe.

8:00am infrared 8:00am UPDATE
Somewhere around the middle of the night last night it became increasingly clear that we would be playing catch up through the remainder of the storm. Dry air worked its way into Denver after the initial burst of snow, effectively killing the snow machine for many hours. As we have stressed over and again this week, dry slots and yesterdays convective storms would be working against us with this system.

The forecast still calls for snow off and on through the remainder of the day, and current radar finally shows a bit of heavier snow filling in to our north. I have lowered the Bust Index, but that means I have also lowered totals. HiRes models continue to suggest ~6" for Denver, but this greatly depends on how our low eventually tracks over Colorado. It has been at a virtual stand-still for several hours now. A more northern track = less snow, a more southern track = more snow.

One thing that has not changed are the bitter cold temperatures. This morning we sit at 18° F, and I do not expect us to go much (any) warmer than that. Temperatures could fall to the single digits tonight.

11:30pm UPDATE
Despite a good show by the 0z model suite (still awaiting 0z EURO), there are some things not to like. . . Current radar shows dry air pushing into Denver for the time being, and this after only about a 1/2" of snow has fallen. Some of the short range RAP models continue to show less snowfall than the GFS / NAM / EURO are showing. Considering it is now 6z, and we have received less precip than all the major models had forecast, I will be upping the Bust Index to 7. Those storms out east this afternoon could have been trouble for us.

No need to throw in the towel yet, still very early on in the storm - but I always like to stress the caution. I will go on record as being quite surprised that many school districts in the area canceled school Tuesday with absolutely no snow on the ground yet. . .?

10:00pm UPDATE
0z models continue with good agreement, and right in inline with our going forecast. Snow has already developed across portions of the Front Range, with several tornadoes (and even "snownadoes"(!)) being reported out east! Temperature guidance for tomorrow continues to look impressively cold, with highs tomorrow afternoon in the teens for Denver. If we can avoid the dreaded dry slot, all looks good for a for a significant snowfall in Denver.

Many questions have been coming in all day with regard to snow day potential - looks like many of you have got your wish! The Denver Post is reporting that several districts have already closed for tomorrow, despite a lack of snow on the ground at this hour. . . enjoy your day off!

Previous discussion. . .
After a rough night last night with the models, we appear to be back from the brink of disaster this afternoon. Models across the board have recovered most of the QPF (precipitation) that went 'missing' last night, and this afternoon sit about 30% more than this morning. With that, we have lowered the Bust Index from an 8 to a 6, and we have better confidence in our 6 - 12" forecast for Denver going into this evening.

Synopsis. . .
Thunderstorms have already popped this afternoon, prompting the NWS to issue Severe Thunderstorm Watches and Warnings for a good portion of eastern Colorado. Our cold front is about to move into Colorado from the north at this hour, and will very likely be moving through Denver during tonight's rush hour. Behind the front, temperatures will quite literally crash from the 70 degree readings we saw around town this afternoon to near or below freezing by midnight.

Scattered rain showers will transition over to heavy, wet snow showers by midnight at the latest, though perhaps as early as 9pm depending on how quickly the front moves through. Good bet that our weather will be quite dramatic as things get underway this evening, with the potential for some thundersnow during the initial hours due to the convective nature of the precipitation!

Tuesday will feature near-record cold. Highs will only make it to the mid 20s, and will be falling throughout the day. By mid afternoon most of us will be in the teens across northeast Colorado, which is more than 50 degrees colder than this afternoon. Winds 15-30mph at times will produce wind chills near ZERO at times.

Our snow will come in two waves. I think we get some accumulation overnight tonight, especially with some of the heavier banding I exp ect to happen, and then another round of moderate snow on Tuesday. Totals could quite literally range from 3 - 18" across northeast Colorado, with general accumulations for metro Denver in the 6 - 12" range. Communities north of Denver (like Fort Collins and Greeley) appear to have the best chance at breaking the 12" mark, with the heaviest snow associated with this storm back up into Wyoming, Nebraska, and South Dakota. Updated snowfall probability chart

Concerns. . .
Dry slotting - Fact of the matter is, these April storms are prone to bust. It has happened countless times, a 6 - 12" storm delivering absolutely nothing. I think enough of the ingredients are in place to have good confidence this will not happen (COLD temps, great positioning of surface low, etc), but models have continued to suggest some of the convective activity this afternoon could rob Denver of moisture in the end. We will be watching for "dry slotting" closely as we head into the thick of the storm. At this point, it appears the greatest threat for this will be east of Denver, but the potential at least exists for us to see much lower totals should dry slotting occur over Denver.

Surface temps - only initially! This storm will bring near-record cold for this time of year. If snow falls as heavily as we expect, with essentially 'flash freezing' conditions, even roads (especially secondary ones) may become snow-packed and/or icy despite warm ground temperatures and a high April sun angle.

More updates as the storm gets underway - hope for the best now, and enjoy!

18z GFS less widespread heavy snow than 24 hours priorLittle change to the going forecast this evening. Early Sunday morning the National Weather Service issued a Winter Storm Watch for all of northeast Colorado for the potential of 9 - 13" inches of snow Monday night through Tuesday. As of 7:30pm tonight that watch remains in effect, and has not yet been upgraded to a Winter Storm Warning.

Our forecast remains much inline with the NWS on this storm. While again Josh and Greg are the more bullish among us, the Brendan's Weather forecast as of Sunday night calls for 7 - 14" of snow for Denver, with locally higher amounts possible. This storm will bring with it some very cold temperatures for April, and a good dose of strong winds as well.

If you live across far eastern portions of Colorado, please stay tuned to local media and NWS outlets Monday, as the SPC has issued a slight risk for severe storms across the plains tomorrow associated with this storm: http://www.spc.noaa.gov/

You may have also noticed the new "Bust Index". Currently a six, this chart shows the potential for our current forecast to bust high, with lower actual accumulations from this storm. The reason for the uncertainty remains twofold:

1) Still some run to run differences in the exact track of this storm. Consensus is pretty good, but we all know what a few miles difference in the track of our surface low can do to snow totals around here.

2) As Matt has pointed out, there is concern that thunderstorms Monday afternoon could actually "steal" potential moisture from our snow machine, thus limiting totals in the end. In fact, this is one reason the NWS has yet to upgrade our watch to a warning.

Snowfall potential chart prepared by Josh More models coming in over the next few hours, and with our system not due in until later in the day Monday we will still have some time to iron out any last details tomorrow. Please stay tuned as our forecast totals may change, and you will want to stay on top of this potentially significant winter storm.

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