Friday, April 3, 2009

Downgrading Forecast: Expect 3-8"
Temperatures Will Limit Accumulations

I have wrangled over this forecast for quite a lot of time now have decided to reluctantly downgrade yesterday's first call of 6-12" to 3-8". It's not that the moisture is not there, it's that I think ground and surface temperatures will allow for a lot of melting that the models are not necessarily picking up on. At the moment, the NWS is forecasting 5-10"; this is not a bad forecast, and they may very well end up being right, but I think lower amounts are more likely. Why?

First of all, the cold air is really lagging the moisture with this system; that means that we'll have quite a bit of "potential snow" that falls as rain at the onset. (Indeed the amount of rain we see before a changeover to snow may be the equivalent of 3-5" if there were more cold air in place and it had fallen as snow.) Also, temperatures soared all the way into the mid and upper 50s today with a decent amount of sunshine; the sun angle at this time of year is such that the ground is considerably warmer (even if the air temperature were exactly the same) than it was two months ago. While the bulk of the snow will fall overnight, which may mitigate these factors somewhat, I think that we may "lose" several inches of snow to melting.

Now, quite frankly, I hope that I'm wrong -- this ardent snow lover wants to see Mother Nature's bring as much as she possibly can our way -- but at the moment I think the NWS' forecast for 5-10 is a bit on the high side. That being said, the impact of almost all of the extenuating aforementioned factors (mostly the result of the fact that we're already into April) is very difficult to gauge; so, regrettably, my confidence in my forecast from 1 (lowest) to 10 (highest) is only about a 3 or a 4. It's definitely quite possible that the NWS' forecast for 5-10" ends up being right; hell, I wouldn't be shocked if a few isolated locations see up to a foot if this system really gets cranking and temperatures run a bit colder than we're currently expected.

Forecast for the greater DENVER METRO AREA is:

THREE to EIGHT inches

Expected timeline (+/- a few hours):

6pm - 10pm Friday:
  • Scattered showers -- perhaps even a thunderstorm
  • Temperatures dropping through the 40s
10pm Friday - 1am Saturday:
  • Showers mixing with then changing to all snow by 1am
  • Temperatures dropping into the mid 30s
  • Little accumulation, especially on paved surfaces expected
1am - 6am Saturday:
  • Moderate to heavy wet snow
  • Gusty northerly winds 15-30mph (occasional gusts to 45mph)
  • Temperatures drop to near 30
  • 2-4" possible during this time
6am - 10am Saturday:
  • Periods of light to moderate snow
  • Gusty northerly winds 15-30mph (occasional gusts to 45mph)
  • Temperatures drop to the mid to upper 20s
  • 1-3" possible during this time
10am - 4pm Saturday:
  • Snow decreases in coverage and intensity
  • Continued gusty northerly winds 20-40mph
  • Little additional accumulation expected after 3pm
  • Temperatures holding in the mid to upper 20s
*Note: image above courtesy


bwyman said...

Well, this has been a bummer. A dusting and some freezing drizzle here in Denver as of 10.45a on saturday. Don't see anything else coming out of this storm... total bust, much like the rest of this winter. :(

Josh Larson said...

@bwyman I agree! Though my forecast was a bust as well, I would like to narcissisticly point out that my 3-8" forecast was better than NWS' 5-10" forecast ;)