Forecast Discussion:

It really seems that Spring arrived with the calendar date/astronomical start of Spring. Today, there is cooler air out on the Plains (and some fog maybe pushing west of I-25 in the morning – Figure 1). Over the next 48 hours the mountains (and maybe Boulder) gets a dusting of snow – Figure 2. Figure 3 is the water content (rain and snow) – there are just light showers around over this time. The rain chances fade out after about 6 am today.

The longer range forecast:

Look at the 70’s F Tuesday and Wednesday as a big ridge slides past us. Warm and dry (Figure 4). Another trough approaches from the west later in the week (Figure 5). Temperatures drop to normal then below normal on Saturday. A healthy chance of rain begins Thursday am and continues through early Saturday morning. Models are divided on how much cold air comes in, but present consensus is that there will be some snow at the end of the storm.

Between now and Sunday, the GFS dumps 1.5 inches of rain on us (Figure 6). It also gives us about 5 inches of snow at the later, colder, part of the storm (it is more bullish than the weatherunderground model) -Figure 7. We have something to watch this week!

Figure 1: The forecast surface map for Monday PM from NCEP.
Figure 2 : the forecast accumulated snow map from the GFS and weather5280.com for Colorado, through Tuesday noon.
Figure 3 : the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, through Tuesday noon.
Figure 4: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 5: The 500mb forecast upper air analysis for Thursday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 6 : the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, through Sunday AM.
Figure 7 : the forecast accumulated snow map from the GFS and weather5280.com for Colorado, through Sunday AM.
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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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