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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – October 9, 2017

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

Forecast Discussion:

As printed in the prior special post, we are under a Winter Storm Warning for most of today and a Freeze Warning through Tuesday morning.  I finished winterizing my camper at 5pm Sunday.  That might have been playing it too close.

The front did hit around 6pm, and rain started around 8pm, an hour earlier than I called for. As I write, it is snowing in Cheyenne, WY, but rain has not changed over to snow in Fort Collins or Longmont yet (10pm).

Figure 1 shows the front making its powerful push into Colorado Sunday night. Figure 2 is the noon Monday forecast surface map showing a large shield of snow over most of our state. The pink dot is Longmont. Figure 3 is the same map but Monday PM as the storm weakens and warms a bit.  We are on the edge of rain/snow.

The radar image from Sunday night shows the snow moving down out of Wyoming. This forecast tool has 8" total (not counting melting and compacting) over Longmont for this storm (and 12" amounts up in the northern mountains). But the GFS total snow accumulation through Monday PM pegs us in the 3-4" area.

Figure 1: Sunday PM surface map and infrared satellite image.

Figure 2: NCEP forecast surface analysis Monday noon.

Figure 3: NCEP forecast surface analysis Monday night.

Figure 4: "Current" radar image from Sunday PM with NWS forecasted snow depth for Longmont (8").

Figure 5: GFS total snowfall accumulation through Monday PM

In the longer range:

We warm up quite quickly after this storm (with Wednesday morning seeing one more hard freeze for the next week, or so. The jet-stream is north of us on Thursday morning when we might be back in the 70's. Hang in there today (Figure 6)!

Former hurricane Nate is speeding across the Tennessee Valley past the Ohio Valley. It may have the record for being the fastest moving Gulf storm observed.

Figure 6: Thursday morning GFS upper air 500mb forecast map. Red circle is the strongest "jet stream" gradient to the NW of Colorado. We sit in the warm region.

Current Weather

Mostly sunny

Mostly sunny

41°F

UV Index
1 Low
Pressure
29.86 Steady
Visibility
7 miles
Dewpoint
34 °F
Humidity
76%
Wind
NW 1.2 mph
Gust
4 mph
Wind Chill
41 °F

Hourly Forecast

Today
7 AM
42°F
Mostly sunny
Today
8 AM
47°F
Partly sunny
Today
9 AM
52°F
Partly sunny
Today
10 AM
57°F
Intermittent clouds
Today
11 AM
62°F
Mostly cloudy
Today
12 PM
65°F
Cloudy
Today
1 PM
69°F
Cloudy
Today
2 PM
73°F
Cloudy
Today
3 PM
75°F
Cloudy
Today
4 PM
77°F
Cloudy
Today
5 PM
76°F
Cloudy
Today
6 PM
75°F
Cloudy

7 Day Forecast

Mostly cloudy

Sunday

77 °F

Rather cloudy and warmer; breezy this afternoon


Mostly cloudy

Sunday Night

48 °F

Cloudy most of the time


Windy

Monday

57 °F

Winds gusting past 40 mph; cloudy and cooler


Intermittent clouds

Monday Night

43 °F

Partly cloudy


Intermittent clouds

Tuesday

59 °F

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

35 °F

Partly cloudy


Mostly cloudy

Thursday

58 °F

Mostly cloudy and cool; breezy in the afternoon


Intermittent clouds

Thursday Night

39 °F

Partly cloudy


Sunrise and Sunset

Sunrise
5:54 AM
Sunset
8:00 PM

Based on AccuWeather data