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11/18 8am Update: Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – November 18-19, 2019

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

In Brief:

We start the week very mild (above average about 10-12F) until fronts hit Tuesday night and Wednesday morning. Temperatures drop and snow will fall from Wednesday afternoon through most of Thursday into Friday early morning. Still, only a few inches if snow is expected to build up. Another storm is showing up on the horizon middle of next week.

11/18 8am update:

This is a quick check in with the GFS concerning the Wednesday/Thursday storm. The trend is away from as much snow in northern Colorado and the NE Plains with the best snow building up in the SW mountains of the state (Figure 1 update). We are still sitting in the, roughly 1-2, locally 3 inch area in our snowfall expectation. It will start as rain before temperatures drop low enough for snow. Thursday will be quite chilly but lows at night will only be in the 20'sF - this is pretty normal for this time of year.

Figure 1 update: The forecast snowfall totals for the next 5 days from the GFS and weather5280com for Colorado made Monday morning.

End 11/18 8am update.

Forecast Discussion:

We are high and dry except for some showers in the northern mountains (Figure 1). With a healthy ridge overhead (blue line in Figure 3) we are sitting about 10-12F above average Monday and Tuesday (Figure 2). It is a boring-weather start to the week.

The Longer Range Forecast:

But fun is coming. There is a west coast trough approaching in Figure 3 with a cut-off low pulling moisture into the desert southwest visible to our distant southwest. By Wednesday and Thursday that cutoff merges with the trough and the whole thing slows down giving us cold air, up slope flow, and moisture (Figure 4). Weather underground shows about 2 inches of snow falling from Wednesday evening (after some rain) through early Friday morning. The GFS gives us about 2-3 inches over this storm (Figure 5) while the NAM gives us about 2-4 inches (Figure 6).

Figure 1: The forecast surface map for Monday evening from NCEP.
Figure 2: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 3: The 500mb forecast upper air analysis for Tuesday morning. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 4: The 500mb forecast upper air analysis for Tuesday morning. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 5: The forecast snowfall totals for the next 5 days from the GFS and weather5280com for Colorado made Thursday morning.
Figure 6: The forecast snowfall totals through Thursday early morning from the NAM and tropicaltidbits.com for Colorado.



Comments

Cloudy

Cloudy

68°F

UV Index
0 Low
Pressure
29.98 Steady
Visibility
10 miles
Dewpoint
53 °F
Humidity
58%
Wind
E 5.8 mph
Gust
5.8 mph
Wind Chill
68 °F

Forecast


Intermittent clouds

Tuesday

81 °F

Cooler with intervals of clouds and sunshine


Partly cloudy

Tuesday Night

56 °F

Patchy clouds


Partly sunny w/ t-storms

Wednesday

85 °F

Sunshine and some clouds with a shower or thunderstorm in the afternoon


Mostly clear

Wednesday Night

57 °F

Clear to partly cloudy


Partly sunny

Thursday

93 °F

Partly sunny with a thunderstorm in spots in the afternoon


Intermittent clouds

Thursday Night

60 °F

Partly cloudy


Intermittent clouds

Friday

97 °F

Very warm with times of clouds and sun


Partly cloudy

Friday Night

63 °F

Partly cloudy


Intermittent clouds

Saturday

99 °F

Very warm with times of clouds and sun


Mostly clear

Saturday Night

65 °F

Mainly clear and mild


Sunrise and Sunset

Sunrise
11:44 AM
Sunset
2:29 AM

Based on AccuWeather data