In Brief:

After a possible round of strong later night storms Tuesday PM, we’ll have warm to hot weather and afternoon storms most days this week. Severe weather chances are just to our east and may get bumped any day back to include I-25 folks. Keep aware!

3pm Update:

The NWS and high resolution models were correct and the outflow from the storms, that formed to the distant east earlier in the day Tuesday, hit the Front Range late in the evening and triggered hail producing storms. My rain gauge picked up under 1/10th of an inch of rain.

There were hail, tornado, and high wind reports in Colorado and just over the line into Kansas yesterday. Longmont is the big pink dot (Figure 1 update).

A similar situation is occurring again today (Wednesday) but the outflow boundary headed for us this evening is not expected to be able to trigger activity this time (due to moisture levels and the vertical temperature structure of the atmosphere).

Figure 1 update: the SPC storm reports up to 7am Wednesday.

End 3pm Update.

Forecast Discussion:

There was some rich, shallow, moisture east of a dryline that formed east of Longmont Tuesday. This situation will keep repeating each day for the next few days (Figure 1). The High Resolution Rapid Refresh model (HRRR) and others are predicting some strong storms to form – yet – Tuesday night. The HRRR (Figure 2) has 2/3rds of an inch hit the town tonight and the weatherunderground model is very similar (green arrow in Figure 3). We’ll see, but the NWS is expecting it too.

For Wednesday, we have a repeat that may be not as severe for the state (there was record breaking hail and a number of tornadoes out on the eastern Plains Tuesday). The severe chances are close – a Marginal Risk is maybe 50 miles to the east (Figure 4).

The Longer Range Forecast:

We see 90’sF continue, severe storms nearby (Thursday’s Marginal Risk to our east is seen in Figure 5). The fine details will be better seen a day or two out as the week goes on.

Figure 1 update: 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 PM.
Figure 2: The HRRR model 15 hour precipitation forecast up to 9am Wednesday from
Figure 3: the graphical forecast for the next 10 days for Longmont, CO from
Figure 4: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Tuesday for Wednesday.
Figure 5: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Tuesday for Thursday.
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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 – . 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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