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Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – March 2, 2019

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


First! From the National Weather Service (NWS) -
Longmont is under a Winter Weather Advisory:

Winter Weather Advisory
Issued: 4:18 PM Mar. 1, 2019 – National Weather Service

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 9 AM SATURDAY TO 11 AM MST SUNDAY... 
* WHAT...Snow expected. Total snow accumulations of 4 to 7 inches expected.
* WHERE...Boulder and the western suburbs of Denver, Denver, Castle Rock and Greeley.
* WHEN...From 9 AM Saturday to 11 AM MST Sunday.
* ADDITIONAL DETAILS...Plan on slippery road conditions.

PRECAUTIONARY/PREPAREDNESS ACTIONS... A Winter Weather Advisory for snow means periods of snow will cause primarily travel difficulties. Expect snow covered roads and limited visibilities, and use caution while driving. The latest road conditions for the state you are calling from can be obtained by calling 5 1 1.

Forecast Discussion:

This post is going up early (the timing of these storms is necessitating it) again. Figure 1 shows that bands of snow have formed rapidly north of town Friday evening and are moving in quickly. The HRRR shows about 1 inch of snow on the ground by 9 am Saturday (Figure 2).

Figure 3 is the 10 day graphical forecast again. Even with a relative lull in the snow probabilities after midnight Friday into Saturday morning, the snow picks up midday on towards Sunday morning. The accumulation line for Figure 2 is drawn showing over what time period that first inch, or so, will fall.

The bulk of the storm, with the low sliding down into northern New Mexico, hits Saturday afternoon and Saturday night. Figure 4 is Saturday evening. Figure 5 is midnight Saturday into Sunday. That is a large portion of our state getting hit by strong winter weather conditions. The GFS based
7! timer model (Figure 6) shows snow falling continuously for more than two days. I've never seen that before on that output.

The model round-up:

The storm total to midnight Monday/Tuesday (drawn on Figure 3 as well) from the:
GFS (Figure 7) is about 5 inches.
NAM (Figure 8) is 7-8 inches.
GEM (Figure 9) is 3-4 inches.
The forecasters at weather5280.com (Figure 10) give us 6-12 inches.
The NWS (in the advisory above) is for 4-7 inches.
My forecast is for 4-6 inches.

The longer range forecast:

We return to above freezing temperatures midday Wednesday for the first time since teens on Sunday/Monday with lows in the negative single digits. There are more precipitation chances in warmer air later in the week. This is a chilly, active, pattern! I'll update this page with any new watches or warnings if they are issued. Be safe!

Figure 1: The current radar from 7:45pm Friday from Radar Scope iOS app.
Figure 2: the HRRR snowfall prediction up to 9am Saturday from weather5280.com
Figure 3 the graphical forecast for the next 10 days for Longmont, CO from weatherunderground.com
Figure 4: The weather conditions and isobar map for Saturday evening from tropicaltidbits.com and the GFS.
Figure 5: The weather conditions and isobar map for Saturday midnight to Sunday from tropicaltidbits.com and the GFS.
Figure 6: the next 3 days forecast of sky conditions and precipitation showing snow beginning Friday 8 pm and continuing for more than 2 days.
Figure7: the forecast accumulated snow map from the GFS and weather5280.com for Colorado, through the next 4 days.
Figure 8: the forecast accumulated snow map from the NAM and tropicaltidbits.com for Colorado, through the next 4 days.
Figure 9: the forecast accumulated snow map from the GEM and tropicaltidbits.com for Colorado, through the next 4 days.
Figure 10 update: the hand-drawn snowfall forecast for the Friday- Sunday snowstorm from weather5280.com

Current Weather

Mostly cloudy

Mostly cloudy

49°F

UV Index
0 Low
Pressure
29.76 Steady
Visibility
8 miles
Dewpoint
26 °F
Humidity
41%
Wind
SSE 2.8 mph
Gust
6.1 mph
Wind Chill
49 °F

Hourly Forecast

Today
1 AM
44°F
Cloudy
Today
2 AM
42°F
Intermittent clouds
Today
3 AM
40°F
Intermittent clouds
Today
4 AM
38°F
Intermittent clouds
Today
5 AM
36°F
Intermittent clouds
Today
6 AM
34°F
Intermittent clouds
Today
7 AM
36°F
Intermittent clouds
Today
8 AM
38°F
Intermittent clouds
Today
9 AM
41°F
Intermittent clouds
Today
10 AM
44°F
Intermittent clouds
Today
11 AM
47°F
Intermittent clouds
Today
12 PM
50°F
Intermittent clouds

7 Day Forecast

Partly sunny

Thursday

65 °F

Partly sunny


Intermittent clouds

Thursday Night

34 °F

A shower in spots late this evening; otherwise, partly cloudy


Partly sunny w/ showers

Friday

53 °F

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


Showers

Friday Night

33 °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

33 °F

Becoming cloudy


Showers

Monday

52 °F

Cloudy and cooler with occasional rain; windy in the afternoon


Intermittent clouds

Monday Night

29 °F

Windy in the evening; partly cloudy


Sunrise and Sunset

Sunrise
6:50 AM
Sunset
7:22 PM

Based on AccuWeather data