Forecast Discussion:

The Wednesday p.m./Thursday a.m. storm didn’t do much around the Front Range but it did kick up chilly, breezy conditions. Thursday midday (Figure 1) I’ve outlined the invasion of cold air down into the U.S. We are sitting firmly north of this boundary with temperatures in the next few afternoons only climbing into the 40’s F. Brrr.

The next storm is in the longer range forecast below…


Figure 1: The Infrared Satellite Image (cold temperatures are yellow/green, warm are dark blue) and the surface frontal analysis and pressure from Thursday midday from NOAA.

The longer range forecast:

We’ll have southwest flow in the lower atmosphere on Saturday that will push us up to the 50’s F before a cold front slides south over the region hitting Longmont around 5 p.m. (See Figure 3). The stronger up-slope flow won’t start until later in the evening with the bulk of the lift and snow occurring Sunday morning, day, and on into the evening. This is related to the complexity of short wave troughs in the upper atmosphere invading the state on Saturday into Sunday (Figure 2).

The model (Figure 3 again) gives us 1-3 inches of snow between 1 a.m. Sunday and 5 a.m. Monday. Not a gigantic storm, but a nice coating. The GFS, Figure 4, has us right around 2 inches of snow through Monday p.m. (the window I chose). They are agreement at this point, so be prepared for a cloudy, snowy, cold, raw Sunday and a cold Monday. (We’ll see a low of about 18°F Monday morning followed by a high barely above freezing). Get that coat ready!

Figure 2: The 500mb forecast upper air analysis for Saturday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 3: the piece of the next 10 days of the graphical forecast for Longmont, CO from
Figure 5: The forecast accumulated snow map from the GFS and for Colorado for the next 4 days, through Monday PM. Longmont is the pink dot, as always.
Previous articleLongmont Observer Taco Time: Benny’s Tacos
Next articleMorning Brief: League of Women Voters post election message
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.

Leave a Reply