In Brief:

After roasting for a few days, moisture leaks back into the state and the ridge overhead weakens a bit. Thunderstorms – a few reaching severe limits – will be possible Tuesday through Friday afternoons. We return to the 80’sF with increased moisture then bounce back to the 90’sF for the weekend and seem to dry out (but we need to focus only about 2-3 days out at this time of year).

Forecast Discussion:

There is “a” way for moisture to get up the ridge axis into the state – but it is not a strong flow (Figure 1). We still have some Pacific moisture moving by as well. By Tuesday into Wednesday, the high pressure centers move off a bit and the weakness between them allows some moisture to return (Figure 2).

With lots of summer heat, solar energy, and atmospheric moisture – severe weather chances begin to creep back to the Front Range. For Tuesday afternoon, a Marginal Risk (1 out of 5) just touches Longmont in the current forecast (Figure 3). For Wednesday, we are deeper in the Marginal Risk zone (Figure 4).

The Longer Range Forecast:

The best chances for rain are the afternoons Tuesday through Friday – with a peak on Wednesday (Figure 5). Rain chances over the next 5 days (Figure 6) are light and confined to areas east of the Rockies. It looks like high temperatures in the 90’sF and dry weather returns for the weekend. Beyond that – who knows?!

Figure 1: 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 Monday PM.
Figure 2: The 500mb forecast upper air analysis for Wednesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 3: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Monday for Tuesday.
Figure 4: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Monday for Wednesday.
Figure 5: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 6: the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, for the next 5 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.

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