In Brief:

Rain chances and cooler weather behind our weekend front lingers today with our lowest high temperature of the recent summer in just the upper 70’s F. The front pulls away and we return to upper 80’s F for highs. Monsoon-like moisture returns Wednesday giving us afternoon storm chances again.

7:30am Update:

The Plains have been cooled by air flowing in from Canada, but a few storms may fire in the mountains and approach severe limits as far east as the I-25 corridor. The SPC (Figure 1 update) has painted the area as being under a Marginal Risk – for large hail and high winds. It looks like only a couple or a handful of cells will form that get that strong – most folks won’t see severe conditions.

Figure 1 update: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Monday for Monday.

End 7:30am Update.

Forecast Discussion:

Our weekend front finally begins to head to the east Monday night (Figure 1) after we see a high today (Monday) only around 78° F (Figure 2). Marginally severe weather might return in the afternoon (but is not currently expected). I’ll update here again if that changes. The GFS gives us about 1/2 inch of rain from Sunday afternoon to Monday evening (Figure 3). The wunderground model thinks we’ll see only about 1/3rd inch of water.

The Longer Range Forecast:

A big upper high sets up for a while in the southwest/four corners area (Figure 4). Tropical moisture will wrap around it into Colorado suppressing the high temperatures that might have occurred. This moisture will also mean afternoon storm chances return Wednesday – but highs struggle to break 90° F this week.

Figure 1: The forecast surface map for Monday night from NCEP.
Figure 2: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 3: the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, for the next 2 days.
Figure 4: The 500mb forecast upper air analysis for 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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