In Brief:

We say goodby to upper 80’sF after Tuesday. A pretty strong cold front slides across Colorado Tuesday afternoon/evening. The western slopes will see rain and thundershowers over the next week, but the eastern Plains won’t see much. The higher elevations will pick up a bit of snow over the next 5 days; really up high, and just a bit.

Forecast Discussion:

The pattern change that is bringing in more Fall-like weather is visible as the trough coming in on the West Coast and the low center off the coast of Canada (Figure 1). This first short wave will usher in a cold front that is visible sweeping out of Wyoming later today (Tuesday – Figure 2, and the first blue lie in Figure 4).

The Longer Range Forecast:

Wednesday we drop to lower 80’sF then another cold front Thursday (pushed in by another deep trough – Figure 3) gives us a small chance of showers and another cool down (from mid 80’sF) to first 80F Friday and then another front (another trough – Figure 4) and a cool down to about
75 F temperatures for the weekend (Figure 5).

Just for fun, the higher elevations should see a dusting of snow over the next 5 days (Figure 6). Can coats, sledding, and Christmas presents be far off…?

You can also say goodbye to hurricane Humberto out in the Atlantic, if you wish (Figures 1,2,3,4).

Figure 1: The 500mb forecast upper air analysis for Tuesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 2: The forecast surface map for Tuesday PM from NCEP.
Figure 3: The 500mb forecast upper air analysis for Thursday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 4: The 500mb forecast upper air analysis for Saturday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 5: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 6: The forecast snow totals for the next 5 days from the GFS and weather5280.com
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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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