Monday, November 19, 2007

Say Hello to Winter...and Some Snow!

Often on the day prior to a cold front's passage strong southerly winds transport warm air into the region "ahead" of the front. That's precisely what happened today, when gusty southwesterly winds to 40mph allowed temperatures to climb to 74 in downtown Boulder, some 20 degrees above normal.

And while high temperatures in the low to mid 50s early in the day Tuesday will reach typical levels for this time of year, a very potent cold front will come barreling through shortly after noon. I expect that temperatures near 55 at noon will drop to the low 40s by late afternoon, low 30s by 6pm, and into the mid 20s by mid-evening! To add insult to injury, gusty ENE winds 20-40mph during the afternoon and early evening will allow for wind chills (perceived temperatures) in the low 20s by 5pm.

Pictured above: forecast temperatures (blue) and wind chills (pink) on Tuesday.

A fairly weak wave of low pressure will ride along the cold front, likely bringing snow showers and perhaps some heavier snow squalls to the region by mid-evening Tuesday -- best guess start time is 7-10pm. Periodic snow showers will continue during the overnight period, with temperatures dropping into the upper teens and wind chills near zero at times.

I expect that by sunrise Wednesday morning we'll be looking at 1-3" of snowfall in most places. Snow showers will become more scattered in nature during the day Wednesday with perhaps an additional inch or two possible; highs will likely not make it out of the mid 20s.


Pictured: estimated snowfall accumulations for Colorado -- Boulder County in red box; image courtesy

As a caveat, I should say first that it's known to be very difficult to accurately forecast snowfall totals in Boulder (due to local orographic variations) and also that there is some disagreement between the two major computer models: one is predicting slightly less (1-3"), while the other is suggesting considerably more (5-7"). I think our final totals will end up somewhere in the middle of these two ranges.

Will twitter updates as needed Tuesday. (I'm "joshlarson" on twitter.) Any specific questions, shoot me an e-mail at josh AT madkast DOT com.

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Adam said...

Let it snow!!!

Johann Moonesinghe said...

make it warmer!

Anonymous said...

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