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The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – September 18 2017

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

Forecast Discussion:

The lingering moisture and an upper air ripple (short wave) was enough to create thunderstorms that delayed the Denver game, but the Broncos shrugged it off.  Now it dries out and gets warm once again...but not for long.  Figure 1 shows the not-so-large ridge overhead today with the start of the west coast trough that will mean business later this week.  Jose and Maria are the most obvious tropical features over in the Atlantic.

The big news is the strong cold front and pattern change coming at the end of the week.  We linger in the 80's until Friday (as seen in the forecast graph in Figure 2). I marked the earliest arrival of the big front with a bold blue line. After that we get cloudy, cold, and wet. Real Fall weather. Figure 3 is the Thursday morning 500mb map showing the giant trough that will usher in this front.  Jose and Maria have traveled further on their treks at this time.

Figure 1: Monday morning GFS 500mb upper air map, troughs in red, ridge in blue

Figure 2: Weatherunderground 10 day graphical forecast Longmont

Figure 3: Thursday AM GFS 500mb upper air forecast map

In the Longer Range (Tropics Focus):

Figure 4 shows a quick view of the five named systems from the Eastern Pacific into the Northern Atlantic. Yes, we still have Jose around. Figure 5 is the 5 day forecast for Jose (currently still packing 115mph sustained winds). Incredibly, after brushing Cape Cod - it may begin to loop back around to the south.  And we need to start really watching Hurricane Maria in Figure 6. It is following a track south of Irma early on, then a bit north like Jose after that.  What will happen beyond day 5?  You'll have to tune in here to find out (or watch any of 100 hurricane Websites and apps <wink>).

Figure 4: The tropics at a glance from weatherunderground

Figure 5: The NHC 5 day forecast for Jose with current conditions.

Figure 6: The NHC 5 day forecast for Maria with current conditions.

Current Weather

Mostly cloudy

Mostly cloudy

69°F

UV Index
0 Low
Pressure
29.96 Steady
Visibility
8 miles
Dewpoint
42 °F
Humidity
37%
Wind
SW 3 mph
Gust
5.9 mph
Wind Chill
69 °F

Hourly Forecast

Today
8 PM
68°F
Showers
Today
9 PM
64°F
Showers
Today
10 PM
61°F
Partly cloudy
Today
11 PM
59°F
Partly cloudy
Tomorrow
12 AM
58°F
Partly cloudy
Tomorrow
1 AM
57°F
Partly cloudy
Tomorrow
2 AM
55°F
Partly cloudy
Tomorrow
3 AM
54°F
Partly cloudy
Tomorrow
4 AM
52°F
Partly cloudy
Tomorrow
5 AM
51°F
Partly cloudy
Tomorrow
6 AM
50°F
Partly sunny
Tomorrow
7 AM
53°F
Partly sunny

7 Day Forecast

Mostly cloudy w/ t-storms

Saturday

77 °F

Not as warm with increasing cloudiness; a thunderstorm in the area late this afternoon


Partly cloudy w/ showers

Saturday Night

50 °F

A couple of showers early this evening; partly cloudy


Mostly sunny

Sunday

81 °F

Sunshine and patchy clouds; breezy in the afternoon


Mostly clear

Sunday Night

49 °F

Mainly clear


Partly sunny w/ t-storms

Monday

70 °F

Not as warm with times of sun and clouds; a thunderstorm in spots in the afternoon


Thunderstorms

Monday Night

46 °F

Cloudy with a couple of thundershowers


Thunderstorms

Tuesday

60 °F

Mostly cloudy and cooler; a couple of afternoon showers and a thunderstorm


Intermittent clouds

Tuesday Night

37 °F

Partly cloudy


Partly sunny

Wednesday

73 °F

Pleasant and warmer with partial sunshine


Mostly clear

Wednesday Night

40 °F

Mainly clear


Sunrise and Sunset

Sunrise
5:41 AM
Sunset
8:13 PM

Based on AccuWeather data