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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – September 25, 2017

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

Forecast Discussion:

My backyard rain gauge in Longmont collected just about 0.90" of rain with the heavy period of showers Saturday night and additional overnight light rain.  Very nice! Figure 1 shows that the front has passed through most of Colorado with another wave of showers moving through northern counties Sunday night. Figure 2 illustrates how far south and east the cold air (blues) has moved.  Pretty impressive over the last 3 days.

We'll have rain showers, with periods of heavier rain, all day Monday- decreasing to wandering showers through Tuesday morning. Figure 3 shows the front further to the southeast by Monday night, but rain still hanging on in eastern Colorado. Figure 4 is the GFS total rainfall through Tuesday morning. Longmont is the pink dot and seems to get about another 0.5" total from Sunday PM to Tuesday AM. Figure 5 is the same map with snowfall totals through that same period. Very high elevations along the Divide get up to 4-5" but it really is only on the high mountains that snows that build up significantly.

Figure 1: Surface analysis with radar from Sunday PM.

Figure 2: Surface temperature map from Sunday PM.

Figure 3: Forecast surface analysis Monday PM from NCEP.

Figure 4: Forcasted GFS precipitation total from now to Tuesday morning. Longmont is the pink dot.

Figure 5: Forcasted GFS snow total from now to Tuesday morning. Longmont is the pink dot.

The Longer Range forecast:

With the current storm not yet cleared in Colorado, I'll only glance at Hurricane Maria today. The National Hurricane Center shows it (Figure 6) as a Category 1 storm that will get close to the Outer banks Tuesday and Wednesday. Tropical storm force winds extend far from the storm center, but it is moving into cooler ocean water left behind by Jose, cooler water created by its own large wind field, and cooler water north of Gulf stream - it should not intensify.  There is still a chance that some U.S. land will get a period of Cat 1 winds, but that is all.

Figure 6: The NHC 5 day forecast for Maria.

Current Weather

Mostly clear

Mostly clear

65°F

UV Index
0 Low
Pressure
29.85 Rising
Visibility
8 miles
Dewpoint
38 °F
Humidity
37%
Wind
S 2.2 mph
Gust
4.3 mph
Wind Chill
65 °F

Hourly Forecast

Today
9 PM
65°F
Mostly clear
Today
10 PM
62°F
Mostly clear
Today
11 PM
59°F
Mostly clear
Tomorrow
12 AM
57°F
Mostly clear
Tomorrow
1 AM
55°F
Mostly clear
Tomorrow
2 AM
53°F
Mostly clear
Tomorrow
3 AM
51°F
Mostly clear
Tomorrow
4 AM
49°F
Clear
Tomorrow
5 AM
47°F
Clear
Tomorrow
6 AM
46°F
Mostly sunny
Tomorrow
7 AM
50°F
Sunny
Tomorrow
8 AM
57°F
Mostly sunny

7 Day Forecast

Sunny

Thursday

77 °F

Sunny and pleasant


Mostly clear

Thursday Night

46 °F

Clear to partly cloudy


Mostly sunny

Friday

85 °F

Mostly sunny and very warm


Partly cloudy

Friday Night

47 °F

Partly cloudy


Partly sunny w/ t-storms

Saturday

77 °F

Sunny to partly cloudy with a thunderstorm in spots in the afternoon


Partly cloudy

Saturday Night

47 °F

Partly cloudy


Mostly sunny

Sunday

84 °F

Mostly sunny, breezy and very warm


Partly cloudy

Sunday Night

47 °F

Partly cloudy


Intermittent clouds

Monday

70 °F

Cooler with clouds and sunshine; an afternoon thunderstorm in spots


Showers

Monday Night

43 °F

A couple of evening showers; otherwise, mostly cloudy


Sunrise and Sunset

Sunrise
5:43 AM
Sunset
8:11 PM

Based on AccuWeather data