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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – October 4th, 2018

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

Forecast Discussion:

We made up for not hitting 80F for the last few days by hitting 87F with strong down slope winds as the front approached. By tonight, the front will be draped somewhere east of I-25 with widespread showers possible over the entire state (Figure 1). All this instability is driven by the approaching upper level trough with a shortwave embedded in it to boot (smaller red trough line east of the main trough axis, Figure 2).

Figure 1: The forecast surface map for Thursday PMon. From NCEP.

Figure 2: The 500mb forecast upper air analysis for Thursday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.

The longer range forecast:

In Figure 3, I've drawn the 70F line in mustard, 60F in teal, 50F in violet and the freezing line in magenta.  This is an average, so though the error bars extend beyond freezing, the mean stays warmer than that magical, plant killing, temperature.  As for rainfall (the bottom panel) we have 3 distinct storm events over the next 3 days, then it becomes a messy confusing long-range period of daily rain chances.  What a change!

Looking at rainfall totals, the weatherunderground.com model gives us 0.60" through Sunday and a total of 1.10" of rain over the next 10 days.

Figure 4 is the GFS through Sunday and it looks like about 0.25 to 0.50".

Figure 5 is the GFS over the next 10 days and it is about 1.00 to 1.25".  They agree!

Figure 3: 10 day meteogram from weather5280.com for DIA.

Figure 4: The total precipitation between Wednesday PM and Sunday PM from the GFS and weather5280.com

Figure 5: The total precipitation for the next 10 days between Wednesday PM and Saturday 10/13 noon from the GFS and weather5280.com

Current Weather

Mostly cloudy

Mostly cloudy

36°F

UV Index
1 Low
Pressure
29.83 Steady
Visibility
8 miles
Dewpoint
30 °F
Humidity
77%
Wind
SSW 1.7 mph
Gust
4 mph
Wind Chill
36 °F

Hourly Forecast

Today
8 AM
39°F
Showers
Today
9 AM
41°F
Mostly cloudy
Today
10 AM
44°F
Intermittent clouds
Today
11 AM
47°F
Intermittent clouds
Today
12 PM
49°F
Intermittent clouds
Today
1 PM
51°F
Intermittent clouds
Today
2 PM
52°F
Intermittent clouds
Today
3 PM
52°F
Intermittent clouds
Today
4 PM
51°F
Intermittent clouds
Today
5 PM
50°F
Intermittent clouds
Today
6 PM
47°F
Mostly cloudy w/ showers
Today
7 PM
44°F
Intermittent clouds

7 Day Forecast

Partly sunny w/ showers

Friday

52 °F

Sun and clouds with a couple of showers; cooler


Showers

Friday Night

34 °F

A couple of showers this evening; otherwise, cloudy


Mostly cloudy

Saturday

60 °F

Mostly cloudy


Intermittent clouds

Saturday Night

34 °F

Partly cloudy


Intermittent clouds

Sunday

62 °F

Periods of clouds and sun


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


Mostly sunny

Tuesday

61 °F

Mostly sunny and milder


Clear

Tuesday Night

29 °F

Clear


Sunrise and Sunset

Sunrise
6:48 AM
Sunset
7:23 PM

Based on AccuWeather data