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Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – April 18, 2019

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

Forecast Discussion:

We had a nice splash of rainfall midday Wednesday from a convective cell that slid off the mountains and dissipated not long after it got the ground wet around town. We are high and dry today (Thursday) with a warm up beginning (Figure 1).

The longer range forecast:

That warm up is shown in the red oval in Figure 2. We are almost up to 80°F by Saturday. Figure 3 shows the entire state, Saturday, is a bit above normal up to 20°F above normal. Unfortunately, a big wet storm system is moving in later on Saturday. We also cool down to just a bit below normal (Figure 2, blue oval).

The weatherunderground.com model gives us 1/3rd an inch of water Saturday evening (Figure 2). The storm is largely north of the state Sunday morning (Figure 4) with a rather complex couple of short waves around the state (Figure 5) in the jet stream flow aloft.

Sunday morning (outdoors sunrise services); up-slope flow will be starting and rain showers will be increasing in coverage and intensity (Figure 6). The main precipitation event kicks in later on Sunday overnight and into Monday (Figure 7). Temperatures at sunrise Sunday will be around 46°F.

The total rainfall Saturday PM through Tuesday AM may be as high as 0.75 to 1 inch (according to the GFS at this time - Figure 8). Snowfall will be healthy for the mountains but should miss Longmont with the temperatures being too warm (Figure 9).

Figure 1: The forecast surface map for Thursday PM from NCEP.
Figure 2: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 3: The forecast temperature departure from normal map from the GFS and weather5280.com for Colorado, Saturday noon.
Figure 4: The surface forecast analysis for Sunday morning. Shades of green are precipitation intensity.
Figure 5: The 500mb forecast upper air analysis for Sunday morning. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 6: Snapshot of weather conditions and surface pressures over 6 hours ending Sunday 6am from the GFS and weather5280.com
Figure 7: Snapshot of weather conditions and surface pressures over 6 hours ending Sunday night midnight from the GFS and weather5280.com
Figure 8: the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, through Tuesday noon.
Figure 9: the forecast accumulated snowfall map from the GFS and weather5280.com for Colorado, through Tuesday noon.

Current Weather

Mostly cloudy

Mostly cloudy

64°F

UV Index
1 Low
Pressure
29.75 Falling
Visibility
9 miles
Dewpoint
22 °F
Humidity
20%
Wind
SW 5.1 mph
Gust
13 mph
Wind Chill
64 °F

Hourly Forecast

Today
5 PM
63°F
Partly sunny
Today
6 PM
61°F
Partly sunny
Today
7 PM
58°F
Partly sunny
Today
8 PM
55°F
Intermittent clouds
Today
9 PM
51°F
Intermittent clouds
Today
10 PM
48°F
Intermittent clouds
Today
11 PM
45°F
Intermittent clouds
Tomorrow
12 AM
43°F
Intermittent clouds
Tomorrow
1 AM
41°F
Intermittent clouds
Tomorrow
2 AM
39°F
Intermittent clouds
Tomorrow
3 AM
38°F
Intermittent clouds
Tomorrow
4 AM
37°F
Intermittent clouds

7 Day Forecast

Partly sunny

Thursday

65 °F

More sun than clouds


Intermittent clouds

Thursday Night

34 °F

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