Highly anomalous and potentially historic weather pattern is coming for Mother's Day weekend. A large portion of the United States will be dealing with record challenging cold, and even snow in the Northeast. Parts of interior New England could see an extremely unusual snowstorm to kick off the weekend. Late season skiing up there!
The Jet Stream will develop a large tough over the eastern U.S. allowing the air to come down from the top of the globe. This is a pattern you typically see only in December and January, maybe sometimes into February. The lines indicate the wind flow and colors on the map above the temperatures. Trace them "backwards" to the left with your eyes to see where our air is coming from.
Rain will move in Thursday evening after sunset, and last through the first half of the day Friday as low pressure moves by into eastern Kentucky (above image). The rain ends by early afternoon at the latest and that allows the sky to quickly clear but with pretty breezy weather. Winds could gust up to 25-30mph Friday afternoon and early evening from the NW. Sky should be clear by sunset as seen below.
Then high pressure moves overhead for Saturday and that allows a possibly historic temperature forecast to start the weekend. The exact degree of wind speed, clearing, and high pressure location will dictate just how low the temperatures can go. As of right now, the mid 30s seem like the most likely scenario given a light breeze that may linger late into Friday night.
Records for the morning of May 9th currently range between 31° in Carbondale, IL to 37° in Murray, KY. Our current forecast if for low temperatures to dip into the mid 30s by daybreak Saturday. Keep in mind the average low for this weekend is about 54°!
Just how uncommon is this cold coming? Historically since weather records starting being kept in Paducah in 1937, there is only a 5% chance of there being a 36° or lower temperature on May 9th! If by some chance this cold over-performs and we get to 32° Saturday morning, that would be the latest freeze ever in our area. The current standing record for the latest freeze into the spring is May 7th, 1944.
It will have a definite fall feel Saturday. Afternoon highs will struggle into the upper 50s to maybe just beyond the 60° mark.
This is a reminder too that frost can form with air temperatures above freezing! It requires the "ideal" recipe, but does frequently happen. The simple science behind it is that typically elevated surfaces that are a few feet off the ground can develop frost -- when your weather app or thermometer may read above 32°. If there is any moisture or water lingering on any of these surfaces, when it evaporates into the air, it cools the air in the near vicinity of said object. Thermodynamics says that evaporation is a cooling process, because when water changes phase from a liquid to a gas, it requires energy to do that, which comes from the air around it.
That is why your: mailbox, car roofs/hoods, trees, tall grass, picnic table, taller flowers, etc. may have a covering of frost, when most other things outside do not.