In Brief:

It has been pretty quiet for a few days – just a few isolated cells were able to fire each day (but if you were under them, you knew it!). Most Front Range residents did not see measurable precipitation. The high pressure center that is running the show will jog to the distant southeast and open up tropical flow across Colorado again. Short waves coming from a trough on the west coast will also be able to aid in kicking off more organized storms. This wetter afternoon thunderstorm pattern will fade out early next week as the high becomes a big ridge across the southern U.S.

Forecast Discussion:

Figure 1 is a new-ish map that shows, not rigorous heights of the 500mb pressure level, but the flow of air in the upper atmosphere. The high near El Paso, TX is plain to see as is the flow northward on the western side of this persistent pressure system. The moisture (white and grey colors (+ pinks)) is flowing up into the Western U.S (Figure 2). The moisture over Colorado has been drifting around the deserts to our southwest for a couple of days (it has been ‘recycled so to speak).

We’ll still see very warm weather today (Wednesday – Figure 4) and only a marginal increase in afternoon storms. The chance of severe weather will remain over the northeast corner of Colorado (Figure 5). It isn’t too far away.

The longer range forecast:

By Thursday, the high center is located over Louisiana and there is better (but still not at record levels of) direct moisture flow from the Gulf of Mexico (Figure 3). Thursday will see our best chance of rainfall with weatherunerground models giving us less than 1/10th of an inch (unless we get a lucky direct hit – figure 4).

By Friday the high begins to inch back as a ridge builds back into Colorado (Figure 6). At the start of next week, there is a ridge to the south and overhead. That “recycled” moisture will still be around to create some afternoon storms, but nothing to write a book about.

Figure 1: stream line map (wind flow lines) from the weatherchannel for early Wednesday.
Figure 2: the water vapor satellite image (browns/reds are dry air, whites and light grey is moist air, purple/blue is ice and high cloud tops). From the the Weather Channel from Tuesday.
Figure 3: The 500mb forecast upper air analysis for Thursday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 4: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 5: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Tuesday for Wednesday.
Figure 6: The 500mb forecast upper air analysis for Friday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 7: The 500mb forecast upper air analysis for next Tuesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
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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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