Skip to content

Monday Update: Longmont Weather Forecast: Two days of heat + smoke, rain and cool return

In Brief:

Heat and smoke for a couple days, thunderstorms, rain, and cooler weather for the end of the week.

Monday update:

The wind will switch to coming out of the northwest again overnight. This will bring back the heat and smoke (Figure 3 update). We'll shoot back to the mid-90's again.  Don't fret, though... a significant trough and cold front will return us to receiving thunderstorms, rain, and cooler weather starting midday Thursday, continuing through the weekend.  More to come on a full post (the mountain library I'm in is a great place from which to watch the weather!).

 

Figure3u_06212021aFigure 3 update: the HRRR smoke at all levels forecast for Tuesday AM by NOAA

End Monday update.

 

Saturday update:

A bubble of cool air aloft over Utah is moving our way. The heat we still have here, plus the remnant of the cool front in place, will give lift and focus needed for some severe weather across eastern Colorado today.  The marginal risk (1 on a scale of 1-5) extends from a few miles west of I-25 off across all of the eastern Colorado Plains (Figure 1 update).  The risk near Longmont and I-25 is for high winds and hail. There is a risk of an isolated tornado or two out in the Slight Risk zone further east. The storms should affect I-25 communities between 1-5 p.m. (Figure 2 update) today. The next front, or two, will come through on Sunday.  Light rain and weak storm chances stretch from Sunday night into late morning Monday. What a beautiful cool down!  (Don't look at Tuesday's high though... don't!).

 

Figure1u_06192021Figure 1 update: the SPC Day 1 (Saturday) severe weather forecast.

 

Figure2u_06192021Figure 2 update: a snippet of the weatherunderground.com graphical forecast for Longmont.

 

End Saturday update.

Forecast Discussion:

A cool front swept down the I-25 corridor Friday and another cool shot arrives very early Monday morning (Figure 1). Amazingly, we drop from the lower 100s to the upper 70s for a short while. With these fronts, and an upper air pattern switch to northwest flow (air from the northwest aloft - Figure 2) we cool down and passing short waves can kick off thunderstorms and rain showers. Our first best batch of showers comes Saturday night (Figure 1 and Figure 3). There is another front arriving with this flow Sunday (Figure 4). Smoke levels are diminished a bit, and severe weather chances are removed for a bit as well (not shown graphically).

 

Figure1_06182021Figure 1: the 10 day graphical forecast from weatherunderground.com for Longmont, CO.

 

Figure2_06182021Figure 2: the 500mb upper air forecast map for Sunday noon from the GFS and tropicaltidbits.com

 

Figure3_06182021Figure 3: the 6 hour averaged precipitation around Saturday evening/sunset from the GFS and tropicaltidbits.com

 

Figure4_06182021Figure 4: the surface forecast analysis for Sunday AM from NCEP.

 

The Longer-Range Forecast:

Another short wave will kick off a round of up-slope showers with the front Sunday night (Figure 5). Overall, rainfall totals will average less than a quarter-inch. This isn't a "too exciting" weather system other than the nice break from the heat (Figure 6). We do return to 'mainly' hot and dry conditions when the ridge returns Tuesday and beyond (Figure 1).

Programming note:  I'll begin a two week camping trip this weekend.  I'll be using a nearby library to post new posts and updates. Please be patient if there is a day or two missed. This is a typically a less dynamic time of year with only slight variations between hot and dry and warm and stormy.  I'll do my best to keep up as I get some vacation time.  Thanks for your understanding!

 

Figure5_06182021Figure 5: the 6 hour averaged precipitation around Sunday/Monday midnight from the GFS and tropicaltidbits.com

 

Figure6_06182021Figure 6: the 5 day precipitation total from the GFS and weather5280.com

 

 


About the Author: John Ensworth

John Ensworth used to work from Longmont as the PI for the NASA through the IGES (The Institute for Global Environmental Strategies). He now teaches technology, algebra, astronomy, meteorology, film school, and Lego robotics to middle/high school.
Read more


Comments


Current Weather

Mostly cloudy

Mostly cloudy

51°F

UV Index
0 Low
Pressure
29.77 Steady
Visibility
8 miles
Dewpoint
25 °F
Humidity
37%
Wind
SW 3.2 mph
Gust
7 mph
Wind Chill
51 °F

Hourly Forecast

Tomorrow
12 AM
45°F
Showers
Tomorrow
1 AM
43°F
Intermittent clouds
Tomorrow
2 AM
41°F
Intermittent clouds
Tomorrow
3 AM
39°F
Intermittent clouds
Tomorrow
4 AM
37°F
Intermittent clouds
Tomorrow
5 AM
36°F
Intermittent clouds
Tomorrow
6 AM
34°F
Intermittent clouds
Tomorrow
7 AM
35°F
Intermittent clouds
Tomorrow
8 AM
38°F
Intermittent clouds
Tomorrow
9 AM
41°F
Intermittent clouds
Tomorrow
10 AM
44°F
Intermittent clouds
Tomorrow
11 AM
47°F
Intermittent clouds

7 Day Forecast

Partly sunny

Thursday

65 °F

Partly sunny


Intermittent clouds

Thursday Night

34 °F

A shower in spots late this evening; otherwise, partly cloudy


Partly sunny w/ showers

Friday

53 °F

Cooler with times of clouds and sun; a couple of showers late in the afternoon


Showers

Friday Night

33 °F

A couple of showers in the evening; otherwise, cloudy


Mostly cloudy

Saturday

60 °F

Mostly cloudy


Intermittent clouds

Saturday Night

36 °F

Partly cloudy


Intermittent clouds

Sunday

62 °F

Times of sun and clouds


Mostly cloudy

Sunday Night

33 °F

Becoming cloudy


Showers

Monday

52 °F

Cloudy and cooler with occasional rain; windy in the afternoon


Intermittent clouds

Monday Night

29 °F

Windy in the evening; partly cloudy


Sunrise and Sunset

Sunrise
6:50 AM
Sunset
7:22 PM

Based on AccuWeather data