Region could see colder weather by Thanksgiving

We are over half way through November and it seems the forecast for a warmer than average winter may be well on the way thanks to El Nino.

El Niño is a climate cycle in the Pacific Ocean with a global impact on weather patterns. The cycle begins when warm water in the western tropical Pacific Ocean shifts eastward along the equator toward the coast of South America. This influences the jet stream pattern, or storm track across the United States.

While we’ve had some bouts of cool weather over the last few weeks, temperatures so far this fall have remained above normal.

Over the last couple of weeks, meteorologists have begun to notice a bit of a change in our pattern. Storms are becoming more active across the Central and Southern Plains, sometimes even spawning threats for severe weather.

That pattern appears to be repeating itself this week. The difference this week is that the storm system that is developing now in the Plains is forecast to shift north-northeastward into central Canada, strengthening as it heads north. This system is forecast by the models to get strong enough to change the position of the jet stream forcing it southward into the northern United States. This would finally allow very cool air to head southward, eventually into the Ohio Valley. The latest forecast from the Climate Prediction Center is forecasting temperatures to drop below average for the week of Thanksgiving.

The bigger question as we head toward the holiday period will be if a big enough storm system can move into our area while the colder air is still around.

The active southern branch of the jet stream is allowing large storm systems to move from California into the Plains and strengthen. The result is has been wind-driven storms the last two weeks with yet another one arriving as early as Wednesday. There are some indications this southern branch of the jet stream may get pushed farther to the south as the northern jet stream that is bringing the colder air shifts south.

It is unclear if the northern branch of the jet stream will become active, bringing with it the threat for precipitation. If this does happen, there is a chance we could get enough cold air in place to allow for some frozen precipitation to reach into the Miami Valley over the next week to 10 days.

The average date for the first measurable snow in Dayton is Nov. 24. We may just get very close to that if the forecasted weather pattern holds. However, if the El Nino pattern holds, which almost every forecast says it will, then don’t look for temperatures to remain below average for very long.

Eric Elwell is WHIO Storm Center 7 Chief Meteorologist. Contact him at eric.elwell@coxinc.com or follow him on Facebook and Twitter.

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