Forecast Discussion:

We warm up to near normal for a day today as a short wave ridge zips past. (As seen in Figure 6, normal highs are around 55F and lows around 27F this week of the year.)

The ridge is the blue line to our west-ish in Figure 1.  Our big trough, for the weekend storm, is down to the southwest of us. We’ll cover that in Figure 2 and the longer range forecast below…

Figure 1: The water vapor satellite image from Friday AM from NOAA. Longmont is the pink dot. Red lines are approximate locations of upper air troughs, blue lines upper air ridges.

The longer range forecast:

The upper air pattern for Sunday PM show the big trough consolidating north to south and is sliding towards us (Figure 2). That is the lift needed for the next snow storm.  Figure 3 is the abnormally cold air (in blue). There are three blobs, one coming out of Canada, one pressed up against the Rockies over us, and one down in Texas.

What do the models say currently about snow amounts?  Weatherunderground is calling for 1-3 inches (Figure 6). The GFS has about the same 1-3 inches (Figure 4). The NAM has about 2.5 to 3.5 inches (Figure 5).

Figure 2: The 500mb forecast upper air analysis for Sunday PM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 3: The temperature departure from normal national forecast map for Sunday midday. Longmont is the pink dot.
Figure 4: The forecast accumulated snow map from the GFS and weather5280.com for Colorado for the next 4 days, through Monday PM. Longmont is the pink dot, as always.
Figure 5: The forecast accumulated snow map from the NAM and tropicaltidbits.com for Colorado for the next 3 days, through Monday noon. Longmont is the pink dot, as always.
Figure 6: the piece of the next 10 days of the graphical forecast for Longmont, CO from weatherunderground.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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