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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – July 4th and 5th, 2018

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

Forecast Discussion:

Though I'm camping these first two weeks of July, I got enough bandwidth and time to put together a more normal discussion. This post will cover the 4th and 5th.

There is a trickle of moisture coming up from the tropics that will interact with the next storm Wednesday night and Thursday (Figure 1). The forecast weather map for Wednesday morning shows the cold front that will push down into the state about as far as the Palmer Divide Wednesday into Thursday (Figure 2).

Tragically, fires are getting the upper hand in places in the west again and the forecast smoke map for later Wednesday shows a complex pattern of smoke at different levels around the state (Figure 3).

For Thursday, the front will be in place, some moisture will be pushed back to the west behind the front - and we'll see a chance of severe weather.  The severe risk will be marginal (1 on a scale of 1-5) for a few isolated cells that may produce large hail and strong damaging winds by evening (Figure 4).

The amount of rain across the state by Thursday afternoon will be spotty and based on where thunderstorms form. Some places will see nothing, while others may pull a quarter of an inch or more. Storm motion will be slow since the upper level steering winds under the Western ridge are going to be fairly light (Figure 5).

Figure 1: the water vapor satellite image from Tuesday AM. Reds/Oranges are dry air, greys/whites are moist air regions.

Figure 2: The forecast surface map for Wednesday morning. From NCEP.

Figure 3: The HRRR model forecast for smoke at all levels for Wednesday midday. From NOAA.gov

Figure 4: the day 2 SPC thunderstorm and severe weather forecast made Tuesday (valid Thursday).

Figure 5: total precipitation from the GFS between Tuesday midday and Thursday AM and weather5280.com. (the next 48 hours)

The longer range forecast:

Longmont cools to the upper 80's Wednesday and Thursday, then climb to the upper 90's F (it will be 100+F on the eastern planes nearby). A few afternoon storms may wander out of the mountains most days.  It is a fairly quiet summer pattern again!

Figure 6: the next 10 days of the graphical forecast for Longmont, CO from weatherunderground.com

Current Weather

Partly cloudy

Partly cloudy

30°F

UV Index
0 Low
Pressure
29.97 Falling
Visibility
8 miles
Dewpoint
23 °F
Humidity
75%
Wind
WNW 2.2 mph
Gust
4.3 mph
Wind Chill
30 °F

Hourly Forecast

Today
5 AM
28°F
Intermittent clouds
Today
6 AM
26°F
Mostly cloudy
Today
7 AM
29°F
Mostly cloudy
Today
8 AM
36°F
Partly sunny
Today
9 AM
42°F
Partly sunny
Today
10 AM
48°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

7 Day Forecast

Partly sunny

Thursday

64 °F

Partly sunny


Intermittent clouds

Thursday Night

35 °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

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

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