Saturday, September 21, 2013

Signs of an Approaching Cold Front

There are many signs of an approaching cold front. The first sign is a happy meteorologist. This sign is especially noticeable in early fall when the first front of the season pushes by.

In the last 24 hours we've seen quite a drop in pressure in Spanish Fork. Decreased pressure is another sign some kind of weather pattern change.


We've also seen a consistent and strong southwest flow. It'll be breezy the rest of the day with winds picking up as the front gets closer.


You might not expect it, but another sign of a cold front is rising temperatures. Even this morning we've see temperatures rise quickly. I expect we'll be in the mid 80's by the afternoon.


Now we can look at a weather model and see when the cold front is expected to come through Utah and Spanish Fork. The below figure is the GFS (Global Forecast System) model run at 12z. The forecast shown is for Sunday at 18z (12:00 MT). This model shows the front will pass through Utah between midnight and 3:00 Sunday morning. There is a lot of information here, so I'll only point out some of the most interesting parts.

The upper-left figure shows the height of the dynamic tropopause. All that means is the blue color indicates low heights and orange colors indicate high heights. The blue, low heights indicates a trough or approaching cold front.
The bottom-right figure shows 6 hour precipitation. The model doesn't show much rain will accumulate in northern Utah, but the mountains have a good change. If it's cold enough, the mountain tops may see some snowflakes. Yep, winter is on it's way again. It seems like it comes around every year.


So enjoy this warm September day, but keep you jacket in a place you can find it. You'll need it tomorrow morning.

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