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Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – August 20, 2019

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

In Brief:

After roasting for a few days, moisture leaks back into the state and the ridge overhead weakens a bit. Thunderstorms - a few reaching severe limits - will be possible Tuesday through Friday afternoons. We return to the 80'sF with increased moisture then bounce back to the 90'sF for the weekend and seem to dry out (but we need to focus only about 2-3 days out at this time of year).

Forecast Discussion:

There is "a" way for moisture to get up the ridge axis into the state - but it is not a strong flow (Figure 1). We still have some Pacific moisture moving by as well. By Tuesday into Wednesday, the high pressure centers move off a bit and the weakness between them allows some moisture to return (Figure 2).

With lots of summer heat, solar energy, and atmospheric moisture - severe weather chances begin to creep back to the Front Range. For Tuesday afternoon, a Marginal Risk (1 out of 5) just touches Longmont in the current forecast (Figure 3). For Wednesday, we are deeper in the Marginal Risk zone (Figure 4).

The Longer Range Forecast:

The best chances for rain are the afternoons Tuesday through Friday - with a peak on Wednesday (Figure 5). Rain chances over the next 5 days (Figure 6) are light and confined to areas east of the Rockies. It looks like high temperatures in the 90'sF and dry weather returns for the weekend. Beyond that - who knows?!

Figure 1: the water vapor satellite image (browns/reds are dry air, whites and light grey is moist air, purple/blue is ice and high cloud tops). From the the Weather Channel from Monday PM.
Figure 2: The 500mb forecast upper air analysis for Wednesday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 3: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Monday for Tuesday.
Figure 4: The severe storm weather forecast for the U.S. from the Storm Predication Center in Norman, OK. Made Monday for Wednesday.
Figure 5: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 6: the forecast accumulated precipitation map from the GFS and weather5280.com for Colorado, for the next 5 days.

Current Weather

Clear

Clear

59°F

UV Index
0 Low
Pressure
29.37 Falling
Visibility
8 miles
Dewpoint
33 °F
Humidity
37%
Wind
SSE 5.7 mph
Gust
12.4 mph
Wind Chill
59 °F

Hourly Forecast

Today
4 AM
52°F
Showers
Today
5 AM
50°F
Cloudy
Today
6 AM
49°F
Cloudy
Today
7 AM
47°F
Cloudy
Today
8 AM
49°F
Cloudy
Today
9 AM
51°F
Cloudy
Today
10 AM
53°F
Cloudy
Today
11 AM
54°F
Cloudy
Today
12 PM
55°F
Cloudy
Today
1 PM
55°F
Cloudy
Today
2 PM
55°F
Cloudy
Today
3 PM
55°F
Cloudy

7 Day Forecast

Intermittent clouds

Sunday

76 °F

Warmer with intervals of clouds and sunshine


Mostly cloudy w/ showers

Sunday Night

47 °F

Turning cloudy; windy late with a stray shower


Windy

Monday

55 °F

Winds gusting past 40 mph; cloudy and cooler


Windy

Monday Night

42 °F

Very windy this evening; partly cloudy


Partly sunny w/ showers

Tuesday

59 °F

A couple of showers in the morning; otherwise, windy and cool with times of clouds and sun


Partly cloudy

Tuesday Night

32 °F

Partly cloudy


Intermittent clouds

Wednesday

60 °F

Times of clouds and sun


Intermittent clouds

Wednesday Night

38 °F

Partly cloudy


Intermittent clouds

Thursday

56 °F

Cool with times of clouds and sun


Cloudy

Thursday Night

39 °F

Cloudy


Sunrise and Sunset

Sunrise
5:54 AM
Sunset
8:00 PM

Based on AccuWeather data