Next 72 Hours: Much Cooler, Dreary & Rainy

I, for one, am looking forward to the cooler temperatures we have in store tomorrow through the weekend, as July and the first half of August have been warmer than normal. I also know we need the rain, but I'm not thrilled with the prospect of overcast skies setting up shop over central Colorado Friday though the entirety of the weekend.

A dip in the jet stream is allowing for much cooler air to filter south into the region. That coupled with an area of low pressure to our north, also sinking south will produce temperatures more than 20 degrees below normal over the next 72 hours, along with the potential for 1-2" of rain to fall during this period.

Friday:
Expect overcast skies through the entire day along with periods of showers and occasional heavier rain. The rain will be more periodic than continuous. High temperatures will struggle to make it much above 60 degrees (25 degrees below normal). Expect overcast skies and continued occasional showers Friday night with chilly overnight lows in the upper 40s to low 50s.

Saturday:
Saturday's conditions will be very similar to those on Friday. Plan on continued overcast skies and periods of showers -- likely more numerous during the second half of the day. High temperatures will remain in the low 60s with overnight lows punctuated by continued occasional showers near 50.

Sunday:
Some slight improvement can be expected on Sunday. We'll call for mostly cloudy skies instead of overcast skies (there may be some bright patches in the sky) with more widely scattered showers than Friday or Saturday. Temperatures will also rise about 10 degrees, so you can expect more comfortable highs in the low 70s.

Outlook:
Monday through at least the middle of next week is likely to feature (for a change) mostly sunny and dry weather with temperatures zooming back up to their normal levels: low to mid 80s for highs; mid to upper 50s for lows.

July Recap & A Look at August Hot Through Start of Next Week

It's been several months since I last posted (I normally only post during the "snow season"), so I thought I would take this opportunity to give you a meteorological update.

It has been a very hot and dry July in central Colorado. We ended the month 3.5 degrees warmer than normal -- with 60% of the days this month having afternoon highs at or above 90 degrees. July was also notable for how incredibly dry it was; an official total of only 0.05" of rain fell in Boulder -- which is only 3% of the usual amount! (Denver barely fared better with 0.24" of rain or 11% of the normal amount).

That leaves us, according to the Climate Prediction Center, with "abnormally dry conditions." However, if this dryness persists well into August -- which I think it very well may -- it is probable that we will reach "moderate drought" status fairly soon. (The further south and east you go in Colorado, the worse the drought conditions are at present.)

Unfortunately for those (like me) seeking a reprieve from the heat, you're going to have to be patient as a ridge of high pressure sits over top of the central US (see image). Temperatures Friday through the weekend will average some 10+ degrees above normal and could hit 100 any of those days; no precipitation is expected during this period. It looks like temperatures will drop just a bit for the start of next week, with highs near 90 Monday and Tuesday perhaps dropping down to the much-more-comfortable mid 80s my midweek.

The longer term outlook, from this far vantage point, suggests that temperatures are likely to be close to normal (mid 80s for highs/mid 50s for lows) for the first half of August, with the likelihood for continued drier than normal conditions.

Will it Snow? Yes. Will it Stick? No.

Not too much to report here, folks. As previously advertised, a strong cold front (and associated trough of low pressure) will push through Colorado during the day Thursday. This will lead to high temperatures some 35-40 degrees cooler than yesterdays high temperatures near 80. While the incoming airmass will be cold enough to produce some conversational-type wet snow, surface temperatures will be way too warm in the greater Boulder/Denver area for anything to stick.

So, while a mix of rain and wet snow -- perhaps, at times, even mostly snow -- may fall during (primarily the second half of the) day Thursday, I do not anticipate any accumulation -- even on the colder non-paved surfaces -- for areas below 7500ft. (Reminder: Boulder/Denver "live" at around 5500ft.)

That being said, areas above the 7500ft threshold may very well see 2-6" of accumulation -- primarily on grassy surfaces. (And I would not be shocked if some isolated locations in the high mountain country well to our west see up to 10" of heavy, wet snow.)

A few snow showers may linger into the evening hours Thursday, which carry with them the slight (<20%) chance of leaving a light coating of wet snow on grassy surfaces overnight into Friday.

THE BOTTOM LINE: except in the higher mountain country well to the west, this system will only bring conversational, nuisance snow -- nothing more.

Nuisance, Conversation Snow to Fall May 1

Yes, we will see snow on Thursday, May 1 in Boulder/Denver. No, I don't think it will stick -- despite the fact that Accuweather is currently calling for 1-3".

I'll have a full update later tonight or early tomorrow.

(It's possible these will not be the last flakes we'll see this spring: on average, 1.6" of snow fall in Boulder in May, and it has snowed as late as June 7.)

April Snowstorm to Bring 2-5" of Snow to Area Unlikely to stick to paved surfaces

I'm sticking with yesterday's call for 2-5" of snow for the Boulder/Denver area. When I made that prediction, the National Weather Service was calling for 4-8"; as of this afternoon, they've lowered their prediction to 3-6." Even still, I believe that accumulations will most likely end up on the lower end of my range (i.e., 2-3") than the upper end of my range (i.e., 4-5"). In addition, except for decreased visibilities, there should be little or no travel disruptions since temperatures on Thursday will climb into the mid 30s coupled with a high April sun angle. I do not expect any of the snow that falls to stick on paved surfaces at elevations under 7000ft; for reference, Boulder/Denver are around 5500ft.

So here's the detailed forecast:

Tonight 4/9:

• Scattered showers, even a rumble of thunder in the evening; temperatures hold in the 40s.
• By late evening, temperatures will drop into the 30s and some snow will mix with the rain.
  
• After midnight, temperatures will fall to near freezing and precipitation should be all snow.
• Light to moderate snow will fall during much of the early morning hours.
• Expect to wake up to 1-3" of wet snow, mainly on grass surfaces Thursday AM.

Thursday 4/10:

• The morning will feature periods of light to moderate snow; temperatures in the low 30s.
• Temperatures will climb to the mid 30s by early afternoon with snow tapering somewhat.
  
• A few scattered snow showers may linger into the early evening hours.
• Expect 1-2" of additional accumulation on Thursday.

TOTAL EXPECTED ACCUMULATION
TWO to FIVE INCHES*

*Ski areas to the west will generally see 6-12" of snow, with some isolated locations seeing closer to 15".

As a bonus, check out my journalism major friend -- Jimmy Himes' -- video report based off my forecast.

Once Again, Don't Believe the Hype! I think 2-5" (at most) likely; not 4-8"

I'm sorry (to the small minority of Coloradans, like me, who want to see a big snow in April) to say that I'm once again going to disagree with the official local National Weather Service (NWS) forecast for the upcoming winter storm. At press time, they have issued a Winter Storm Watch and are predicting 4-8" of snow for the Boulder/Denver area.

For the reasons listed below, my preliminary forecast is for 2-5" in the greater Boulder/Denver area -- close to half of what the National Weather Service (NWS) is currently predicting for the area.

Why am I expecting so much less snow? We are now almost into the middle of April and the sun angle right now is very different than it was two months ago.

What does that mean? A significantly higher amount of incoming solar radiation at this time of the calender year will make it quite difficult for snow, even during heavy snowfall, to stick to non-grassy surfaces in areas below 7,000ft+ (i.e., Boulder & Denver) and much melting will occur when flakes do fall. Add to that the potential for rain to mix in with the snow, especially during daylight hours, and I don't see the potential for a lot of snow.

That being said, ski areas to the west of Boulder/Denver -- i.e., from western Boulder County (i.e., Ward, CO and further west) stand the chance for 7-14" of fresh snow, or even more in some isolated locations; I would not be shocked if Vail or Keystone pick up close to 2 feet of new snow!

This is just a preliminary forecast, and I will provide a full update and detailed accumulation forecast and timeline later in the day on Wednesday.

However, my forecast at the moment is for:

2-5" TOTAL ACCUMULATION*
in the Boulder/Denver area (<6,000ft)

*Most of which will not stick to paved surfaces.

Thanks for stopping by!

You can anticipate an updated forecast/blog post by mid-evening Wednesday 4/9/08.

Complex Forecast, But Don't Believe the Hype 3-6" Likely, *NOT* 5-10" That NWS Predicts

6:30pm Update: Switch to mostly snow has occurred earlier than expected. Also, if you have any specific questions regarding the forecast, leave a comment and I'll answer it!

Late winter/early spring storms in this area are often especially tough to forecast due to temperatures right around freezing (and not colder), more moisture rich systems than most that impact the area earlier in the winter, a higher March sun angle and warmer ground/pavement temperatures. All of these issues come into play for the storm system that will bring moderate amounts of snow to the area tonight through Monday.

After taking a look at all of these issues in concert along with the most recent computer model guidance, it appears to me that we are likely to see less snow than the National Weather Service's forecast of 5-10" in Boulder. I think we are looking at more of a 3-6" storm of wet snow. Note that while much of what falls overnight may stick to paved surfaces, I believe that the vast majority of snow that falls during the day Monday will not stick on paved surfaces. It is possible that by mid-morning Monday many roads in Boulder on Monday are wet as opposed to snowy or icy.

Note that higher snowfall amounts are possible in areas north and east of Boulder (which is somewhat atypical of most winter storms here which tend to bring higher amounts to the west of Boulder).

And now, the detailed forecast:

REST OF TODAY 3/16:

• A mix of rain and wet snow along will transition to more snow than rain by early evening with temperatures dropping to the low to mid 30s.
• By 9pm, precipitation will be primarily snow as temperatures drop below freezing.
  
• After midnight, moderate to heavy snow will fall as temperatures drop through the upper 20s.
  
• By 7am Monday, I expect that 2-4" of snow will have fallen.

MONDAY 3/17:

• Snow, sometimes moderate, will continue to fall during the first half of the day Monday.
• Due to a rather high late March sun angle, along with temperatures just at - or perhaps even a couple degrees above - freezing, most of what falls during the day will only stick to grassy surfaces.
  
• By afternoon, snow will taper to scattered light snow showers which may linger until the early evening.
• By 7pm Monday, I expect that an additional 1-2" of snow will have fallen.

TOTAL EXPECTED ACCUMULATION:
THREE to SIX INCHES*

* = I concede that there is an outside chance (<25%) of up to 8" of snow falling in some spots, especially in western Boulder County or areas well to the northeast of Boulder.