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Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – November 21, 2018

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

Forecast Discussion:

The cold air is plunging south of the U.S. into the tropics (blue arrow). Moisture is finally pouring in from the Pacific into California that should douse a lot of fire activity (but, as we know well here, flooding and mud slides in burn scars will be a problem - Figure 1 green arrow).

For Thanksgiving Eve today, the high will be 62°F and the low 25°F with very light winds and mostly clear skies.

For Thanksgiving, the high will be 56°F with a low of 36°F with stronger westerly breezes and mostly cloudy skies.

Figure 1: The forecast surface map for Wednesday PM. From NCEP.

The longer range forecast:

The weekend storm (in most models) is quite minimal now (Figure 4) for us, even if the mountains get some nice snow. (The European model still has a stronger storm with a low south of the state.)

To see the interesting model change from two days ago (when it looked like a lot of snow was coming - Figure 3) and the forecast for the exact same time from today (Figure 2). In Figure 2, the center of the nation has a broad, less focused, area of lowered heights. There is a trough back in Utah and Wyoming, but it is pretty shallow compared to the overall flow. In Figure 3, from two days ago, that trough was much deeper and stronger, extending all the way down into Mexico.

Figure 4, then, shows a small chance of rain with not-so-cold temperatures (some warming from down slope flow may be at play as well, limited precipitation amounts too). We do remain chilly in the 40's F for highs into the next week. It will begin to feel a lot like Christmas.

Figure 2: The 500mb forecast map MADE TODAY for the Saturday AM, during the weekend storm, from the GFS and tropicaltidbits.com

Figure 3: The 500mb forecast map MADE two days ago for the Saturday AM, during the weekend storm, from the GFS and tropicaltidbits.com

Figure 4: the graphical forecast for the next 10 days forecast for Longmont, CO from weatherunderground.com

Current Weather

Cloudy

Cloudy

69°F

UV Index
3 Moderate
Pressure
29.59 Steady
Visibility
8 miles
Dewpoint
32 °F
Humidity
25%
Wind
WNW 5.5 mph
Gust
11.2 mph
Wind Chill
69 °F

Hourly Forecast

Today
2 PM
69°F
Thunderstorms
Today
3 PM
70°F
Intermittent clouds
Today
4 PM
68°F
Intermittent clouds
Today
5 PM
66°F
Mostly cloudy
Today
6 PM
61°F
Thunderstorms
Today
7 PM
58°F
Thunderstorms
Today
8 PM
56°F
Cloudy
Today
9 PM
53°F
Cloudy
Today
10 PM
51°F
Thunderstorms
Today
11 PM
49°F
Thunderstorms
Tomorrow
12 AM
48°F
Cloudy
Tomorrow
1 AM
48°F
Cloudy

7 Day Forecast

Mostly cloudy w/ t-storms

Friday

70 °F

A shower in spots late this morning followed by a couple of thundershowers this afternoon; gusty winds and small hail can accompany any downpour


Thunderstorms

Friday Night

44 °F

Cloudy; a couple of showers and a thunderstorm this evening followed by periods of rain late; gusty winds and small hail can accompany any downpour


Rain

Saturday

47 °F

Chilly with periods of rain and a thunderstorm; travel in the foothills and mountains will be slippery due to snow


Rain and snow

Saturday Night

36 °F

Cloudy with rain, mixed with a little snow late; travel in the foothills and mountains will be slippery due to snow


Mostly cloudy

Sunday

61 °F

Mostly cloudy and warmer


Intermittent clouds

Sunday Night

36 °F

A thunderstorm in spots in the evening; otherwise, partly cloudy


Partly sunny

Monday

71 °F

Partly sunny, pleasant and warmer


Partly cloudy

Monday Night

45 °F

Partly cloudy


Mostly sunny

Tuesday

73 °F

Pleasant with sunshine and patchy clouds


Partly cloudy

Tuesday Night

43 °F

Partly cloudy


Sunrise and Sunset

Sunrise
6:06 AM
Sunset
7:51 PM

Based on AccuWeather data