Forecast Discussion:

An interesting change has occurred in the models this morning concerning the week-end storm, but first we’ll be warm today and chilly and windy tomorrow… let’s look at it:

Figure 1 shows the upper air pattern from Sunday with the departing low and trough and the approaching ridge. That ridge passes overhead today making things quite warm (the fact that the wavelengths are shorter than the distance between the US east and west coast means they are on the move – progressing eastward).

Figure 2 has Longmont some 18F above normal today!  Figure 3, the upper air map for tomorrow, shows the next trough here already here. Figure 4 is the temperature anomaly for Tuesday; Longmont is about 4 degrees below normal. An almost 20F drop in one day will be noticeable!

Figure 1: The ‘current’ 500mb upper air map from Sunday PM. Troughs = red lines, ridges = blue lines, Longmont = pink dot.
Figure 2: The forecast surface temperature anomaly (departure from normal) for Monday PM from the GFS and weather5280.com
Figure 3: The forecast 500mb upper air map for Tuesday AM from the GFS. Troughs = red lines, ridges = blue lines, Longmont = pink dot.
Figure 4: The forecast surface temperature anomaly (departure from normal) for Tuesday PM from the GFS and weather5280.com

The longer range forecast:

Figure 5 is the week-end storm.  Notice (like yesterday’s discussion) how much further south the Low center is on that trough.  Colder, slower, and wetter is the story. But, as we can see in Figure 6 the model run from 6am on Sunday has Longmont only receiving a couple of inches of snow (and nothing just down in Niwot)-Figure 6.  Compare this to the model run at midnight Saturday into Sunday (Figure 7) and we were getting 8 inches or more.  Things are suddenly coming out MUCH warmer for this storm.  Back to the model run from later Sunday morning, we are still getting a lot of water (Figure 8) with Longmont getting 1.5 inches of rain or more.

We’ll keep on this storm all week.

Figure 5: The forecast 500mb upper air map for Friday AM from the GFS. Troughs = red lines, ridges = blue lines, Longmont = pink dot.
Figure 6: the total snowfall between Sunday PM and midday Saturday from the GFS and weather5280.com from the computer run at 6am Sunday.
Figure 7: the total snowfall between Sunday PM and midday Saturday from the GFS and weather5280.com from the computer run at 12am Sunday.
Figure 8: the total precipitation between Sunday PM and midday Saturday from the GFS and weather5280.com from the computer run at 6am Sunday.
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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.