Isolated severe storm threat for Tuesday A look at the 500mb steering level of the atmosphere (~18,000 ft) at 3:30 AM shows the day's setup, which is meteorologically known as a mesoscale convective system (MCS). An MCS, by definition, is a collection of thunderstorms that act as a system. Since this system is in remnant form and decaying as it moves along the upper-level ridge, the short-term models disagree on how this will play out. In my experience with these over the years, I don’t trust model output. This is a “nowcast” situation, meaning the evolution of the day will dictate timing and impacts.  Heat and humidity are rising ahead of the MCS's arrival, which is fuel for thunderstorms. The general idea is that the region will experience an isolated risk of severe storms in the afternoon and evening over interior parts of the region. The severe threat diminishes after sunset, but the risk of overnight rumbles is there until what is left of the system clears the region early Wednesday morning.  The main threats for isolated storms are the risk of frequent lightning, damaging wind, and small hail. Given the juicy nature of the atmosphere, heavy rainfall may cause localized flash flooding is also possible. For those tuning into this update at various times of the day, I would suggest taking a peek at the PTW severe weather page that I have revamped to get the latest categorical threat from the Storm Prediction Center. SPC updates its current-day outlooks five times in a 24-hour period. I plan to monitor the day's activity and update through my Twitter/X feed. I am happy to report that automatic updates of weather bulletins have resumed in my feed on the medium. Storm threat continues through Thursday Tuesday 8 AM (12z) to Friday Midnight (4z) – A look at anomalous precipitable water values as compared to the average from the European model indicates the humidity level. The MCS feeds additional moisture into the atmosphere. This translates into dew point temperatures in the mid to upper 60s (isolated low 70s) as the PWATs soar upwards of 200-250% of normal at times through Thursday. This type of humidity fuels strong to severe storms and fog. Areas that receive heavy rainfall can expect fog, which could be locally dense in spots. The shorelines can expect a fog bank hanging out either just offshore or slightly onshore for MidCoast and DownEast areas as the cold ocean temperatures stabilize the atmosphere. The humidity gets shoved out of the region Friday morning. Outlook into the Memorial Day Weekend Friday 8 AM (12z) to Monday 8 PM (00z Tuesday) – The holiday weekend appears to start dry on Friday. Ensemble ideas like this show a series of disturbances that may bring the risk of light shower activity for the mountains and north heading into Saturday and Sunday, then the potential for a showery afternoon on Memorial Day Monday. Given the amount of convective activity going on over the continent, it’s difficult to take too much stock in model or ensemble ideas due to feedback issues beyond Friday at this point. I will continue to monitor and update as the week continues.  Always have MULTIPLE ways to receive weather alerts. Stay updated, stay on alert, and stay safe! - Mike PRINT MEDIA: Feel free to quote and cite my work here for your stories. Please give me the professional courtesy of knowing that you are referencing my material so I can read your final product and acknowledge it on my media and link it on the PTW IN MEDIA page here on the website. Feel free to send me a message via the Facebook page or Twitter (X) to get my phone number if necessary. Thank you! NOTE: The forecast information depicted on this platform is for general information purposes only for the public and is not designed or intended for commercial use. For those seeking pinpoint weather information for business operations, you should use a private sector source. For information about where to find commercial forecasters to assist your business, please message me and I will be happy to help you.
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Mike Haggett
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