Stuck in a blocking pattern. What’s the impact


Over the past 8 days, with the exception of Tuesday, we’ve seen the sky coverage at 80% or higher. On top of that we’ve dealt with back to back fog advisories during the overnight hours.

So what’s with the repetitive forecast?
Well, this occasionally happens from time to time, due to a multitude of blocking patterns.
Earlier we were dealing with what is known as a Rex Blocking pattern. This occurs when the area of high pressure gets stuck with a low pressure system off to it’s south.
As the upper level flow has persisted things eastward, it appears this blocking pattern is looking closer to what is known as an Omega Blocking pattern. This occurs when high pressure is stuck between two low pressure systems resembling an Omega shape.

What difference does this make? Not much at all, other than both have allowed the blocking pattern to continue, causing a stagnant weather forecast.

One of the biggest changes in the forecast today is we’re done with the foggy conditions. So why did we have so many days back to back with dense fog advisories?
Due to the set up of the rex block, the surface winds were bringing in warm, moist air from the south into our area. With the fresh sheet of snow and ice from the new years day system, this caused multiple days of foggy conditions. Today with the placement of the high pressure system to our North West, we have northerly winds bringing in cold dry air. This also explains the temperature drop for this weekend.

As this blocking pattern continues we will continue to deal with calm and cloudy conditions. Come Sunday evening and into Monday, this blockage is looking to finally move. Sunday evening, the high pressure system will begin to dissolve and move South a bit and allow Cold Air Advection (CAA) to move into the area which will pull down cold dry air, thus clearing out the cloud cover.

Clouds return to the forecast again by Wednesday as a low pressure system will bring our next chances for rain and snow.

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