In Brief:

In typical Colorado fashion, a ridge is passing the state Friday/Saturday will lead to a very comfortable warm up. Then a trough moves in, cold air pours out of Canada Sunday evening and we return to the ice box with a chance of snow/ice again. It is short lived and we pop back to relative warmth on Tuesday and beyond. You are also invited to see a transit of Mercury Monday morning (clouds permitting) at the Cherrywood Observatory. Details below…

Forecast Discussion:

Today and Saturday – we enjoy the wonders of a big ridge (Figure 1) with a bit of down slope flow to warm things a few more degrees. Temperatures Saturday will be up to 10-15 degrees above normal (Figure 2). This warmth comes to an end Sunday afternoon as another front hits around 4pm (Figure 5 – dotted line). This is powered by a fast moving trough and a brief blast of northwesterly winds over the state (Figure 3). The cold air that flows down Sunday is quite shallow and doesn’t make it over the mountains to the west (Figure 4).

After the front passes, up slope flow and some moisture comes back in. The window for precipitation will run from about 9pm (Sunday) to 9am (Monday). The Plains from the Palmer Divide north should see a coating to an inch of snow (maybe 2 inches in lucky spots- Figure 6) with not much rain- except further north near Wyoming, maybe as far south as Longmont- Figure 7.

The Longer Range Forecast:

The cold air is whisked away on Tuesday and beyond. We don’t get really warm, but mild and dry mainly in the 50’s for highs all week.

Cherrywood Observatory Mercury Transit Invitation:

Monday morning at sunrise, Mercury will be transiting (crossing the face of the sun like a mini-eclipse). If it is clear, I’ll have the telescope set on the sun (with a proper and safe filter) so you can stop by and see the little dot on the face of the sun. I’m near Pace and 17th at the intersection of Cherrywood Dr. and Cherrywood Cir. east of Alpine. The sun should clear my neighbor’s house around 7am and the transit ends at 11:04am. I’ll be out to peek now and then – just come in the yard and look through the scope in the observatory building.

Figure 1: The 500mb forecast upper air analysis for Friday PM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 2: the surface temperature anomaly (departure from normal) from the GFS for Saturday night from weather5280.com.
Figure 3: The 500mb forecast upper air analysis for Saturday PM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 4: the surface temperature anomaly (departure from normal) from the GFS for Sunday noon from weather5280.com.
Figure 5: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 6 : The forecast snowfall totals for the next 5 days from the GFS and weather5280com for Colorado made Tuesday noon.
Figure 7: The forecast rainfall totals for the next 5 days from the GFS and weather5280com for Colorado made Tuesday noon.
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John Ensworth works from Longmont as the Principle Investigator for the NASA Science Mission Directorate Earth and space science education product review through the IGES (The Institute for Global Environmental Strategies – www.strategies.org) . He is in his 14th year running this review. He is an astronomer (from the 2nd grade onward) and became a meteorologist (in the 5th grade) when a thunderstorm in Arizona rained on his telescope when the weather service had only forecasted a 10% chance of rain. He has college degrees in physics and astronomy and climatology and a graduate degree in meteorology and earth science. He lectures at the Little Thompson Observatory in Berthoud, the Estes Park Memorial Observatory in Estes Park, and for a number of online universities. He built and runs a backyard observatory near Pace and 17th in northeast Longmont where he has lived for 8 years with his wife, daughter, son, and two cats. Invitations to open house nights at this observatory, LTO, and EPMO will be posted with future discussions when they are scheduled. Forecasting severe weather and snow amounts via text lead to this column. He began texting friends about the weather right after the September 2013 flood. The readers of this column will, hopefully, keep him honest in what he ‘thought’ he had forecasted for ‘the most recent’ storm.

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