LATE APRIL STARTING TO GET "THAT LOOK"

Greetings everyone! Hope the weekend is treating you well. We have warmth! Temperatures ripped into the 60s and 70s across the region Saturday with widespread 70s anticipated Sunday as well. Despite the breezy and warm conditions the fire risk was somewhat kept in check by higher humidity levels. That will be the case Sunday as well, but there may be more fire concerns Monday.

Afternoon humidity levels on Monday could dip into the 30% range in the area with a well-mixed lower atmosphere. This is just something to be mindful of if you are planning any larger prescribed burns or controlled burns as we are heading into Plant 2025. Monday might be a day you want to hold off, but look for any official alerts from the National Weather Service like Red Flag Warnings.

The overall trend next week is on the warmer side of normal. Temperature anomalies for the central and eastern US are positive, especially starting around April 16-18 and continuing through the end of the month. This will be fueled by rather strong southerly flow bringing not only the warmth, but also Gulf moisture which will lead to increasing rain chances, and potentially severe weather.

Late April has "that look" if you are a storm chaser (like myself) or a least are looking for thunderstorms with beneficial rainfall. A five-day smoothed average on the 500mb chart is quite classic with west-coast troughing and pronounced southwest flow over the central US. This likely will facilitate a multi-day severe weather event starting approximately April 17 and potentially persisting through the end of the month.

These supercell composite parameter maps courtesy Dr. Victor Gensisi from Northern Illinois University show the increasing likelihood of severe weather late April into early May. This is essentially showing the potential environment and whether it is supportive of severe weather. These maps, on their own, are not incredibly useful, however when partnered with synoptic maps (like the previous 500mb map) or precipitation maps that show a storm threat, it can help add some more insight into an environment not only capable of rain, but severe storms.

The GEFS is incredibly bullish with precipitation in late April. Seven-day anomalies from the Canadian border to the Gulf are pushing 1" above normal in spots. Again, putting this alongside the previous supercell composite maps, you can see there is an environment favorable for severe weather from the Great Lakes to Texas, and based on the above-normal precipitation forecast, it would be wise to anticipate a prolonged stretch of severe weather.

One of my favorite tools in the toolbox for assessing a threat of severe weather in the longer term (1 week or more in the future) are analogs. We look at what the models are showing in terms of the state of the atmosphere, and based on similar-looking days in the past, we can add probabilities for various parameters including the threat of at least one severe weather report.

In these analogs above, dated April 17 through April 26, there are large areas in the US with at least a 30-percent chance of severe weather reports. Even at 12-14 days in the future the analogs are putting values as high as 60-70% of severe weather across the Central US.

This is quite typical to see this increase in storm chases based on climatology. By late April we really see the chances of severe weather increase and spread northward. We are too far out to discuss just how active things may get, the exact timing and impacts. What we do know is that the pattern is looking quite active.

The chart above is some very "weather weenie" type of information, so feel free to skip passed this... BUT what we are looking at here is a pretty useful chart for assessing the potential impacts of teleconnections on weather in the US. What we are likely looking at in the late-April time frame is strong upper-level divergence over the equatorial waters of the eastern Pacific. This divergence can help "carve out" troughs in the western United States to the north as these "waves" propagate into the mid-latitudes. This activity can also strengthen the subtropical jet, the southern stream of the jet stream, that favors enhanced severe weather in the southern United States.

This is almost a visual look at the MJO that Chief Swails loves to talk about. This activity is located over phases 7 and 8 of the MJO which are quite favorable for severe weather in the United States based on numerous studies.

You can see how some of the models are indeed swinging that MJO phase into 7 and 8. Yesterday, Terry discussed the temperature implications of this, so make sure to check that out!

I'll wrap up this post with a launch on Saturday night from the Florida Space Coast. Another batch of Starlink satellites was sent to space on a perfectly clear moon-lit night. Have a great rest of the weekend!

-Meteorologist Nick Stewart