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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – December 9, 2017

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

Forecast Discussion:

3-2-1 ...let the unusually beautiful weather begin again. Figure 1 says it all. There is a big ridge of high pressure in the western states and no precipitation anywhere except up in the Great Lakes and the extreme southeastern states.

Figure 1: Current surface map from weatherunderground.com from Friday PM.

The longer range forecast:

Figure 2 and 3 are the upper air patterns for this morning (Saturday) and then the forecast for Friday morning at the end of the week.  The ridge (with a small trough deep down south) dominates the West all week and a deep trough dominates the East all week.  It is really impressive how little things change.

With the jet stream flowing from the northwest to the southeast, we are back to the regime where fronts of various strengths will drift into the state all week.  In figure 4, I've drawn the weaker fronts (with little wind and little cooling) in thin blue lines.  The thickest blue lines denote the stronger wind shifts and temperature drops.  There is roughly one-a-day except for Tuesday and Friday.  The dryness continues, temperatures hover around 15-20 degrees above normal, and my forecast discussions may remain sort of short this week.

Figure 2: The upper air forecast 500mb map for Saturday morning.

Figure 3: The upper air forecast 500mb map for Friday morning.

Figure 4: The 10 day graphical forecast for Longmont from weatherunderground.com

Current Weather

Mostly cloudy

Mostly cloudy

46°F

UV Index
0 Low
Pressure
29.58 Steady
Visibility
8 miles
Dewpoint
41 °F
Humidity
85%
Wind
SW 2.2 mph
Gust
5.7 mph
Wind Chill
46 °F

Hourly Forecast

Today
8 AM
50°F
Cloudy
Today
9 AM
54°F
Cloudy
Today
10 AM
58°F
Cloudy
Today
11 AM
63°F
Cloudy
Today
12 PM
68°F
Cloudy
Today
1 PM
67°F
Mostly cloudy
Today
2 PM
70°F
Mostly cloudy
Today
3 PM
68°F
Mostly cloudy
Today
4 PM
67°F
Mostly cloudy
Today
5 PM
65°F
Cloudy
Today
6 PM
58°F
Thunderstorms
Today
7 PM
56°F
Thunderstorms

7 Day Forecast

Thunderstorms

Friday

70 °F

Mostly cloudy with a couple of thundershowers this afternoon; gusty winds and small hail can accompany any downpour


Thunderstorms

Friday Night

45 °F

Cloudy; a couple of showers and a thunderstorm this evening followed by periods of rain late; gusty winds and small hail can accompany any downpour


Rain

Saturday

48 °F

Chilly with periods of rain and a thunderstorm; travel in the foothills and mountains will be slippery due to snow


Rain and snow

Saturday Night

39 °F

Cloudy with rain, mixed with a little snow late; travel in the foothills and mountains will be slippery due to snow


Mostly cloudy

Sunday

59 °F

Mostly cloudy and warmer


Partly cloudy

Sunday Night

36 °F

Partly cloudy


Partly sunny

Monday

71 °F

Partly sunny, pleasant and warmer


Partly cloudy

Monday Night

45 °F

Partly cloudy


Mostly sunny

Tuesday

73 °F

Mostly sunny, breezy and pleasant


Partly cloudy

Tuesday Night

43 °F

Partly cloudy


Sunrise and Sunset

Sunrise
6:06 AM
Sunset
7:51 PM

Based on AccuWeather data