Forecast Discussion:

While incredibly awesome weather rolls on, we finally have a storm to focus on.  But first the amazing warmth Monday can be seen in Figure 1 – oranges are how ‘above average’ the temperatures were. Longmont is around 15F up.  We’ll be nice again today (Tuesday) but a dry cool front is on the way.  Figure 2 shows the front just past Longmont 6pm Tuesday.  Figure 3 has the front far to the south by 6am Wednesday.  Note, there is no precipitation to be seen.

Figure 1: The departure from normal surface temperatures from Monday evening.
Figure 2: The NCEP surface analysis forecast for Tuesday PM.
Figure 3: The NCEP surface analysis forecast for Wednesday AM.

The longer range forecast:

But there IS a storm coming.  It is still not impressive (for Longmont), but it is something! Figure 4 is the upper air map for Friday early morning. There is a broad trough over Colorado with embedded short wave troughs (red lines). The ridges are far to the west and east (blue lines.

The GFS precipitation forecast (rain and melted equivalent of water from snow, ice etc.) in Figure 5 shows the mountains to our west getting some nice water.  Figure 6 shows the western slopes and north and central mountains getting some good snow… but Longmont (in this run) is on the edge of nothing – rain or snow.  The gap along I-25 is the result of down slope during the storm what will warm us to the edge of snow/rain AND inhibits precipitation.  Right now, Longmont only gets a trace of something wet Thursday PM into Friday AM, but we’ll watch for changes as the week goes on.   Maybe you should go wash your car and leave it out at the end of the week… I’m just sayin’.

Figure 4: The GFS 500mb upper air analysis forecast map for Thursday PM/Friday AM.
Figure 5: The GFS forecast total precipitation map from Monday PM to Friday PM. Longmont = pink dot.
Figure 6: The GFS forecast total snow map from Monday PM to Friday PM. Longmont = pink dot.


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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.