Forecast Discussion:

The front has swept past Longmont and skies are dark. (I’ll post this early, since the storm is underway). The current radar image sows western slope snows have begun (Figure 1).

Figure 2 by Wednesday evening, the front is far to the south with western slope snows almost making it down to Lyons! By Thursday a.m. (Figure 3) the front is far far to the south, but mountain snows and ‘plains’ snows are falling in just about every direction but not here in town. A dusting IS possible.

Figure 4 is a model used by astronomers that predicts snow around 11 p.m. Wednesday.   The HRRR model, before 1 a.m. Thursday, puts 1-4 inches of snow down in the mountains, with snow almost making it down to Boulder, but not quite. Figure 6, the GFS, has snow south of Denver and up in the mountains from this storm, but nothing right in our town.  My dusting to a coating of snow is still possible.

Figure 1: Radar image from just before noon on Wednesday from
Figure 2: The forecast surface map for Wednesday night. From NCEP.
Figure 3: The forecast surface map for Thursday a.m. From NCEP.
Figure 4: the next couple of days of astronomical forecasting with precipitation type (11pm snow flurries). From 7! Timer.
Figure 5: The forecast accumulated snow map from the HRRR and for Colorado, through the next 15 hours.
Figure 6: The forecast accumulated snow map from the GFS and for Colorado, through the next 48 hours.

The longer range forecast:

We warm right up to the 50’s F and winds die down after Thursday. Very quiet weather will be the rule through Dec 22nd. That is VERY close to Christmas.

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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 – . 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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