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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – April 12, 2018

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

Forecast Discussion:

First is today's Red Flag Fire Warning from the National Weather Service

Alert brief: Red Flag Warning issued April 11 at 12:32PM MDT expiring April 12 at 9:00PM MDT by NWS Denver CO.  Critical fire danger has developed across the Front Range Foothills, Park County, and all of the plains today as near record warmth combines with gusty winds and very low humidities. Fire danger may become extreme in some areas by Thursday as winds continue to strengthen in this very warm and dry airmass. The highest danger on Thursday will likely develop from South Park and the Southern Foothills across the Palmer Divide area. Critical conditions will be possible farther north, but confidence is not as high north of I-76.
There is also a High Wind Watch for Longmont today.

Figure 1 shows the extent of the elevated, critical and extreme fire danger today.  Do whatever you can to not create an ignition source outside today.  And if you smell or see smoke, get 911 on your phone ASAP!

Figure 2 are the winds for today at noon.  Sustained winds are 20 mph for Longmont, and 30mph just to our west.  Expect gusts to 40 or 50mph.

For Friday, after the cold front comes down and temperatures drop 40F, the winds will pick up even more!  Models are indicating sustained winds 30-40mph with gusts from 50mph - 70mph. Colder temperatures and higher humidities will help, some, with the fire danger.

Figure 1: The fire danger map for Thursday from NOAA.

Figure 2: The forecast surface pressure (black lines) and wind speeds (color regions) for midday Thursday from weather5280.com.

The longer range forecast:

Tomorrow, our upper air low rolls in bringing in much colder air and the high winds described above (Figure 3). We should have substantial down slope flow behind the retreating (eastward) surface low.  Figure 4 shows the big hole in the snowfall that includes Longmont. Lucky places in the higher mountains get 10-12 inches of snow. Figure 5 is rainfall, and we get skipped again by this substantial dry slot in the storm/ down slope region.

We warm up behind that low on Monday (Figure 6) as another ridge passes.  This is a progressive pattern with shorter waves in the jet stream - so we should get cool and windy around Tuesday next week from the trough on the West Coast visible on this map.

Figure 3: The 500mb upper air forecast map for Friday morning. Troughs are red lines, ridges are blue. Longmont is the pink dot (right next to the L for low height center).

Figure 4: The forecast total snowfall between Wed. PM and Sat. noon from weather5280.com.

Figure 5: The forecast total precipitation between Wed. PM and Sat. noon from weather5280.com.

Figure 6: The 500mb upper air forecast map for Monday morning. Troughs are red lines, ridges are blue. Longmont is the pink dot. L's for low height centers.

Current Weather

Partly cloudy

Partly cloudy

58°F

UV Index
0 Low
Pressure
29.89 Steady
Visibility
5 miles
Dewpoint
44 °F
Humidity
60%
Wind
NNW 4.5 mph
Gust
9.6 mph
Wind Chill
58 °F

Hourly Forecast

Today
1 AM
52°F
Partly cloudy
Today
2 AM
50°F
Mostly clear
Today
3 AM
47°F
Mostly clear
Today
4 AM
45°F
Clear
Today
5 AM
43°F
Mostly clear
Today
6 AM
41°F
Mostly clear
Today
7 AM
45°F
Partly sunny
Today
8 AM
50°F
Partly sunny
Today
9 AM
55°F
Partly sunny
Today
10 AM
62°F
Intermittent clouds
Today
11 AM
66°F
Intermittent clouds
Today
12 PM
70°F
Intermittent clouds

7 Day Forecast

Mostly sunny

Wednesday

75 °F

Mostly sunny, pleasant and warmer


Partly cloudy

Wednesday Night

41 °F

Patchy clouds


Mostly cloudy w/ t-storms

Thursday

75 °F

Turning cloudy, warm; breezy, a thunderstorm around in the afternoon


Thunderstorms

Thursday Night

49 °F

A thunderstorm in spots in the evening; otherwise, considerable cloudiness


Thunderstorms

Friday

70 °F

Mostly cloudy with a couple of thundershowers


Thunderstorms

Friday Night

46 °F

Cloudy with a couple of thundershowers


Rain

Saturday

50 °F

Chilly with periods of rain and a thunderstorm


Rain and snow

Saturday Night

39 °F

Cloudy with rain, mixed with a little snow late


Mostly cloudy

Sunday

59 °F

Mostly cloudy with a stray thundershower in the afternoon


Partly cloudy

Sunday Night

36 °F

Partly cloudy


Sunrise and Sunset

Sunrise
6:08 AM
Sunset
7:49 PM

Based on AccuWeather data