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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – August 15th, 2018

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

Forecast Discussion:

The moisture and upper level support returned. We had, quite suddenly, a storm on Tuesday. I took this picture in front of the Cherrywood Observatory Tuesday afternoon (Figure 1). At the last second, the SPC drew a marginal risk down the I-25 corridor as these storms began to form. (A bit late in my opinion - Figure 2). My rain gauge is showing somewhere over 3/4th of an inch of rain (and some hail melt). The hail at my house ranged from pea to dime sized.

For today, a cool front sags down into northern Colorado (maybe making it to Longmont Figure 3) and a good amount of moisture is still in place for storms (Figure 4) as tropical left-overs from tropical system John et al. flow into the southwestern U.S.

This upper-air flow is still bringing in a lot of western fires and local fire smoke (Figure 5).  With moisture, clouds, and smoke, the sky will be murky today.

The upper-level forecast for today shows another upper-level wave approaching as the big western ridge collapses and shrinks south (Figure 6). All that will come together for another round of severe weather today along I-25 (primarily hail and high winds - Figure 7).

Figure 1: Storm image rain and hail in front of the Cherrywood Observatory - (c) 2018 John Ensworth

Figure 2: the day 1 SPC thunderstorm and severe weather forecast made Tuesday (valid Tuesday).

Figure 3: The forecast surface map for Wednesday PM. From NCEP.

Figure 4: the water vapor satellite image from Tuesday PM. Reds/Oranges are dry air, greys/whites are moist air regions.

Figure 5: The HRRR (high resolution rapid refresh) model forecast of smoke at all levels for Wednesday noon.

Figure 6: The 500mb forecast upper air analysis for Wednesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.

Figure 7: the day 2 SPC thunderstorm and severe weather forecast made Tuesday (valid Wednesday).

The longer range forecast:

We keep getting shots of moisture through the beginning of next week (Figure 8) and the ridge keeps fading, so we have steady cooling to the 70's F by next Tuesday. This will be nice, even if it is smoky. More tomorrow!

Figure 8: the next 10 days of the graphical forecast for Longmont, CO from weatherunderground.com

Current Weather

Partly sunny

Partly sunny

60°F

UV Index
9 Very High
Pressure
29.6 Steady
Visibility
9 miles
Dewpoint
21 °F
Humidity
22%
Wind
W 10.2 mph
Gust
22.2 mph
Wind Chill
60 °F

Hourly Forecast

Today
1 PM
59°F
Mostly cloudy
Today
2 PM
60°F
Intermittent clouds
Today
3 PM
62°F
Intermittent clouds
Today
4 PM
60°F
Intermittent clouds
Today
5 PM
58°F
Intermittent clouds
Today
6 PM
56°F
Intermittent clouds
Today
7 PM
54°F
Intermittent clouds
Today
8 PM
51°F
Intermittent clouds
Today
9 PM
48°F
Partly cloudy
Today
10 PM
45°F
Partly cloudy
Today
11 PM
43°F
Partly cloudy
Tomorrow
12 AM
42°F
Mostly clear

7 Day Forecast

Partly sunny w/ showers

Tuesday

62 °F

A couple of brief showers late this morning; windy with times of clouds and sun


Partly cloudy

Tuesday Night

34 °F

Partly cloudy and colder; there can be frost in the normally colder spots


Intermittent clouds

Wednesday

59 °F

Cool with times of clouds and sun


Mostly cloudy w/ showers

Wednesday Night

37 °F

Increasing clouds with a shower in spots late


Partly sunny w/ showers

Thursday

56 °F

Times of clouds and sun with a couple of showers; cool


Partly cloudy

Thursday Night

40 °F

Partly cloudy


Mostly cloudy

Friday

63 °F

Mostly cloudy and warmer


Clear

Friday Night

40 °F

Clear


Mostly sunny

Saturday

74 °F

Mostly sunny, pleasant and warmer


Mostly clear

Saturday Night

43 °F

Mainly clear


Sunrise and Sunset

Sunrise
5:52 AM
Sunset
8:02 PM

Based on AccuWeather data