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

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

In Brief:

Our first cold front is moving in to knock 5F off the temperatures and give the western slopes some rain/thundershowers. We'll mainly see increased clouds east of the Rockies with a possible sprinkle. A couple of additional cool fronts will lower us to the 70'sF for highs over the weekend with afternoon showers possible. Next week seems dominated by 70'sF weather for highs and better rain chances.

Forecast Discussion:

Our first cool front is on its way and is kicking off showers over the western counties of Colorado (Figure 1). Down slope flow on this side of the mountains will assure that very little water falls from the sky. By Wednesday morning, the front will be draped down the Front Range into the southeastern parts of the state. A bit more moisture will return behind the front (Figure 2).

The Longer Range Forecast:

Later in the week, a deeper trough starts its trek across the nation (Figure 3). This will kick a couple more cool fronts past us, cooling us to the 70'sF for the weekend. The warmth before the weekend will feel a contribution from that same down slope warming/drying we are experiencing today (Figure 4).

Next week, the trough seems to hold on (or get reinforced) and we stay cool with better rain chances returning (Figure 4). The GFS gives the somewhat dry western and southwestern parts of our state the best rainfall over the next 10 days (Figure 5).

Figure 1: SW US current surface map analysis from Tuesday midday from weatherunderground.com
Figure 2: The forecast surface map for Wednesday AM from NCEP.
Figure 3: The 500mb forecast upper air analysis for Friday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 4: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 5: The forecast rainfall totals for the next 10 days from the GFS and weather5280.com

Current Weather

Mostly sunny

Mostly sunny

95°F

UV Index
2 Low
Pressure
29.87 Falling
Visibility
8 miles
Dewpoint
40 °F
Humidity
15%
Wind
ESE 2.9 mph
Gust
6.7 mph
Wind Chill
95 °F

Hourly Forecast

Today
7 PM
90°F
Intermittent clouds
Today
8 PM
86°F
Intermittent clouds
Today
9 PM
82°F
Intermittent clouds
Today
10 PM
79°F
Intermittent clouds
Today
11 PM
75°F
Intermittent clouds
Tomorrow
12 AM
72°F
Intermittent clouds
Tomorrow
1 AM
69°F
Intermittent clouds
Tomorrow
2 AM
68°F
Intermittent clouds
Tomorrow
3 AM
67°F
Intermittent clouds
Tomorrow
4 AM
66°F
Intermittent clouds
Tomorrow
5 AM
65°F
Intermittent clouds
Tomorrow
6 AM
64°F
Intermittent clouds

7 Day Forecast

Partly sunny

Thursday

95 °F

Very warm with sunshine mixing with some clouds


Intermittent clouds

Thursday Night

64 °F

Partly cloudy


Partly sunny w/ t-storms

Friday

89 °F

Partly sunny with a thundershower in spots in the afternoon


Clear

Friday Night

61 °F

Clear


Partly sunny

Saturday

93 °F

Partly sunny


Clear

Saturday Night

56 °F

Clear


Partly sunny

Sunday

89 °F

Partly sunny with a stray thunderstorm


Clear

Sunday Night

57 °F

Clear


Partly sunny

Monday

93 °F

Partly sunny


Clear

Monday Night

57 °F

Clear


Sunrise and Sunset

Sunrise
5:36 AM
Sunset
8:33 PM

Based on AccuWeather data