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Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – September 17, 2019

This content was originally published by the Longmont Observer and is licensed under a Creative Commons license.

In Brief:

We say goodby to upper 80'sF after Tuesday. A pretty strong cold front slides across Colorado Tuesday afternoon/evening. The western slopes will see rain and thundershowers over the next week, but the eastern Plains won't see much. The higher elevations will pick up a bit of snow over the next 5 days; really up high, and just a bit.

Forecast Discussion:

The pattern change that is bringing in more Fall-like weather is visible as the trough coming in on the West Coast and the low center off the coast of Canada (Figure 1). This first short wave will usher in a cold front that is visible sweeping out of Wyoming later today (Tuesday - Figure 2, and the first blue lie in Figure 4).

The Longer Range Forecast:

Wednesday we drop to lower 80'sF then another cold front Thursday (pushed in by another deep trough - Figure 3) gives us a small chance of showers and another cool down (from mid 80'sF) to first 80F Friday and then another front (another trough - Figure 4) and a cool down to about
75 F temperatures for the weekend (Figure 5).

Just for fun, the higher elevations should see a dusting of snow over the next 5 days (Figure 6). Can coats, sledding, and Christmas presents be far off...?

You can also say goodbye to hurricane Humberto out in the Atlantic, if you wish (Figures 1,2,3,4).

Figure 1: The 500mb forecast upper air analysis for Tuesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 2: The forecast surface map for Tuesday PM from NCEP.
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 500mb forecast upper air analysis for Saturday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 5: the graphical forecast for the next 10 days for Longmont, CO from
Figure 6: The forecast snow totals for the next 5 days from the GFS and





UV Index
0 Low
30.09 Steady
7 miles
58 °F
N 0 mph
2.9 mph
Wind Chill
75 °F


Partly sunny w/ showers


87 °F

Sunny to partly cloudy and not as hot; a shower in spots late this afternoon

Mostly clear

Monday Night

57 °F

An evening shower in spots; otherwise, mainly clear

Partly sunny


95 °F

Very warm with partial sunshine

Partly cloudy

Tuesday Night

59 °F

Partly cloudy

Partly sunny


95 °F

Partial sunshine


Wednesday Night

60 °F


Partly sunny


96 °F

Partly sunny and very warm

Mostly clear

Thursday Night

65 °F

Mainly clear

Mostly cloudy


97 °F

Very warm with sun followed by clouds

Intermittent clouds

Friday Night

58 °F

Partly cloudy

Sunrise and Sunset

6:08 AM
8:03 PM

Based on AccuWeather data