Wednesday, May 12, 2021

Weather Discussion for Wednesday May 12, 2021

 Normal high/ low temperatures for May 10-May 17 (high/low) Redding 81/54, Chico 80/51, Quincy 72/38, Chester 67/35, Susanville 70/39, Grass Valley 71/46, Weaverville 76/39, Mt. Shasta 67/40, Yreka 73/41, Alturas 67/33

This blog will be issued every Monday, Wednesday, and Saturday morning and updated if the weather is changing or critical or interesting weather events are occurring. 

High pressure continues along the coast.  Sunny today and Thursday with daytime temperatures 10 to 15 degrees above normal.  Winds will be light.  

In the last blog I said a low pressure trough would pass through Western Canada and the Pacific Northwest Friday and Saturday.   The trough will still reach the Pacific Northwest Friday.  However, it now looks like the southern end of this trough will cutoff from the jetstream and drop southward over California, ending up over Central California by Saturday (see map below).   The low will trigger a few afternoon and evening thunderstorms over the foothills and mountains Friday and Saturday.  There is a slight chance of a thunderstorm in the north end of the valley.  Temperatures will cool but still be above normal.  Moderate north winds will occur in some areas Saturday.  Sunday the low will be moving eastward but still could trigger afternoon thunderstorms over the Sierras.  

Monday through the mid part of next week another low pressure trough will move through Western Canada and the Pacific Northwest.  While this one isn't expected to split and our area should stay dry, it will keep the high pressure ridge from pushing northward.  Look for sunny skies with a few high clouds.  Temperatures will be a few degrees above normal.

The Old Forecaster
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  1. what are the reasons/ conditions that makes the LP being cut off from the jet stream and have an indipendente pattern by itself , as you describe ?

  2. Hard to describe in a few sentences. The structure of the trough changes so the jetstream cant drop down the back of it and the bottom part ix cutoff from the main flow or steering winds.