Skip to content

Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – February 17, 2019

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

Forecast Discussion:

The first cold front hit and had a period of moist uplift after its passage significant enough to drop 1/2 inch of snow on my part of town (Figure 1). I didn't directly forecast that but did show maps hinting at some minimal snow amounts near Longmont. (This post will go up early since we are mid-storm and serious cold is coming soon.)

The cold fronts will keep coming, the temperatures will keep dropping, and snow will soon coat everything. A nice period of winter returns. For today (Sunday), we are briefly between surges of moisture from the Pacific and cold front passages. We start the day dry (Figure 2).

The next period of snow begins around 6 pm today (Sunday) with snow chances fairly continuous through midday Tuesday (Figure 3). Note that the high on Monday may only be in the teens and Tuesday not much better in the lower 20's F.

This is all what a giant trough in the west does with cold Canadian air flowing south over the ridge off in the eastern Pacific (Figure 4). Ripples in the flow will bring periods of instability over the area and surges of colder and colder air. By tomorrow morning (Monday am), figure 5 shows that snowfall will be spreading over much of the state.

The longer range forecast:

The weatherunderground model in Figure 3 gives us about 2-4 inches of snow through Monday pm. The forecasters at weather5280.com's hand-drawn forecast gives us a trace to three inches (Figure 6). The GFS paints us with 1/2 to 2 inches through Monday pm (Figure 7). By 24 hours later (Figure 8) the GFS gives us 2-3 inches of snow.

Looking back on Figure 3, we warm to the 30's F on Wednesday and see a late week return of snow. More on that after the current storm plays its hand.


Figure 1: picture by John Ensworth at the Cherrywood Observatory of the Saturday midday 1/2 of snow.
Figure 2: The forecast surface map for Saturday noon. From NCEP.
Figure 3: the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 4: The 500mb forecast upper air analysis for Monday AM. Pink dot is Longmont. Red lines are troughs, blue lines are ridges.
Figure 5: The forecast surface map for Monday AM. From NCEP.
Figure 6: the hand drawn snowfall forecast from the forecasters at weather5280.com (highly recommend reading their info as well!!).
Figure 7: the forecast accumulated snow map from the GFS and weather5280.com for Colorado, through Monday PM.
Figure 8: the forecast accumulated snow map from the GFS and weather5280.com for Colorado, through Tuesday PM.

Current Weather

Sunny

Sunny

36°F

UV Index
2 Low
Pressure
29.98 Steady
Visibility
8 miles
Dewpoint
27 °F
Humidity
71%
Wind
WNW 1.6 mph
Gust
3.2 mph
Wind Chill
36 °F

Hourly Forecast

Today
10 AM
47°F
Partly sunny
Today
11 AM
53°F
Partly sunny
Today
12 PM
57°F
Partly sunny
Today
1 PM
60°F
Partly sunny
Today
2 PM
62°F
Partly sunny
Today
3 PM
63°F
Partly sunny
Today
4 PM
64°F
Partly sunny
Today
5 PM
63°F
Partly sunny
Today
6 PM
61°F
Partly sunny
Today
7 PM
58°F
Partly sunny
Today
8 PM
55°F
Intermittent clouds
Today
9 PM
51°F
Intermittent clouds

7 Day Forecast

Partly sunny

Thursday

64 °F

Partly sunny


Intermittent clouds

Thursday Night

34 °F

Partly cloudy


Partly sunny w/ showers

Friday

54 °F

Cooler with times of clouds and sun; a couple of showers late in the afternoon


Showers

Friday Night

32 °F

A couple of showers in the evening; otherwise, cloudy


Mostly cloudy

Saturday

60 °F

Mostly cloudy


Intermittent clouds

Saturday Night

36 °F

Partly cloudy


Intermittent clouds

Sunday

62 °F

Times of sun and clouds


Mostly cloudy

Sunday Night

36 °F

Becoming cloudy with a shower in spots late


Showers

Monday

50 °F

Mostly cloudy and cooler with occasional rain; windy in the afternoon


Intermittent clouds

Monday Night

31 °F

Windy in the evening; partly cloudy


Sunrise and Sunset

Sunrise
6:50 AM
Sunset
7:22 PM

Based on AccuWeather data