Forecast Discussion:

The cold air and freezing drizzle and freezing fog did move in , now and then, on Friday.  The second front is pushing down out of Wyoming this evening (Friday PM). A period of snow should give everything a dusting Friday PM (just prior to this post going live).

Light snow showers are possible all morning before another period of lift and up slope settles over Colorado later today (Saturday) giving us light snow this afternoon and evening.

Figure 1 shows this cold air pouring down. The question over the last couple of days was ‘would’ that cold air move west over Longmont or further west. Figure 2 confirms (my blue line again) that it did a good job pushing up against the lower foothills. We spent the day below freezing.  The models incorrectly warm us up again in the next forecast maps as they don’t do well with such shallow, dense, cold air.

Pulling out to the big picture, Figure 3 is the 500mb upper air map and you can see the trough, that is pushing this storm, is very positively tilted stretching from the Great Lakes to Oregon.

Figure 4 is the Saturday midday surface map and the main push of snow is just forming in the northern counties and moving south. Figure 5 is Saturday evening and snow covers most of the state.

My forecast is for 1-3″ of snow in Longmont, but what do the models say now?

Figure 6 is the GFS idea – Longmont gets 2-3 inches.

Figure 7 is the WPC 50th percentile probabilistic idea with 3 to 3.5 inches.

Figure 8 is the NAM and it has us in the 2-3 inch area as well.  This storm will feature a number of hours of light snow at low temperatures. The snow will fluff up more than snow near freezing does.

After the storm clears late Saturday evening or just after midnight Saturday into Sunday – temperatures should drop to just above 0F.

Figure 1: The actual temperature from weatherunderground Friday PM. Cold air flow as blue arrows.
Figure 2: The temperature departure from normal for Friday PM from weather5280.com. Blue line shows westward extent of near normal to below normal temperatures. Oranges/yellows are above normal.
Figure 3: The 500mb forecast map from the GFS for Saturday morning.
Figure 4: The forecast surface map for Saturday morning from NCEP.
Figure 5: The forecast surface map for Saturday night from NCEP.
Figure 6: The total snowfall forecast between Friday PM and late Saturday night from the GFS and weather5280.com
Figure 7: The total snowfall forecast between Friday PM and late Monday night from the WPC 50th percentile forecast and weather5280.com
Figure 8: The total snowfall forecast between Friday PM and late Saturday night from the NAM and weather5280.com

The longer range forecast:

The Monday/Tuesday storm has faded to near nothing.  Quite normal, dry, weather will be the norm for most of the next 10 days.

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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.