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We often see a stationary line of low precipitation during a storm. Eventually it moves away.
What could cause this?
Weather modification means somehow, on a local or regional basis, to dramatically change the character of weather. It's not raining- changed to-it's now raining. Weather moderation means modestly changing the existing weather for a better, more beneficial condition. Its raining too much in a flood prone area- changed to- some of the excess rain is translocated to a drier area.
Many Western states now attempt weather modification with cloud seeding using silver iodide crystals or salt and smoke particles. The effectiveness is still under study. California, for example, uses cloud seeding in an attempt to increase snow in the Sierra Mountains. By definition, moisture in the atmosphere must be available and that moisture that comes down as rain is removed from the atmosphere. It's a dramatic change because without cloud seeding maybe that moisture would provide snow in the Utah mountains. In the West, stealing someone's water is bad juju .
On the other hand, if it's raining so much that Western coastal areas are in flood, somehow moving that excess rain to the high mountains as snow is termed moderation. Most of the rain that floods the coast is lost to the sea. So moving some of that excess moisture (as rain-runoff) from the coast to the high mountains (as snow-stored) is beneficial. It's raining-Moderation applied-it's still raining. No moisture is stolen from the atmospheric river.
The weather modification case is bad as moisture that could be shared or intercepted by other mountains of the West is "stolen" by the Sierra cloud seeding effort. The weather moderation case is beneficial in that it saves moisture that would otherwise flood to the sea and saves it as snow. My following post will discuss my moderation method and the evidence I have gathered to demonstrate that the method works.
As we near the close of March, we look forward to April and the real signs of Spring that surely make it feel like we are turning the corner into warmer weather. April is one of the fastest warming months our of the year and it appears likely that it will be in high gear for the opening week of the month. In years past, we have seen some anomalously cold outbreaks and very quiet severe weather. This year, however, IMO we will flip that script and severe wx will be on the rise once we get past Easter weekend. The pattern setting up this month will feature 1st half warmth and then the LRC's signature block will show up near eastern Canada. Those of you living closest to that block will likely see impacts of that blocking and cut-off troughs. The plains and Upper MW may not see as much cooler wx, but I suspect a couple significant cool/cold troughs to swing through.
Alright, who's ready for a delightful Easter weekend? The heat will build out in the SW where I am rising ATM and SW flow aloft will push this warmth east, coupled with Chinook winds temps, will soar into the 70's/80's into the Plains/Upper MW along will bountiful sunshine! What a treat for the holiday weekend.
Looking deeper into the month, the farther west/north you live, the better chances of more sustained warmth is my thinking...however, now the models are picking up on a stout -NAO block and there are some shenanigans showing up farther east. I'm really curious to see how the models handle the high lat blocking which I have opined the models do not have a clue in the LR. The LRC does point to this being a common feature as the jet really slows down to a halt. Sign of things to come for the Summer? Probably.
CFSv2 temp/precip trends...