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Before I get into this evening's update, I would like to pass along an update. The 2025 summer internship program will come to a close on August 8th. It has been my pleasure to work with Jenna, Trey, Harry, and Daniel. I am proud of them and the efforts they have put into it. While it may appear that I have been taking time off, that has hardly been the case. The pattern has been active. These students are using new tools that they don't use in school. Summer forecasting is a challenge because there are many small details to consider. Water temperature, smoke, air quality, tides, and marine forecasts, to name a few. Forecasting for Maine is not easy, and with guidance as erratic as it has been due to the reduction of upper air data collection, it's been more of a challenge. Add to that, I am a stickler for details, and to share the how and the why. My role this summer has been proofreader, editor, website builder, and mentor. It has been overwhelming at times for them, as well as for me. For you, the reader, and the financial contributor, I appreciate your patience, and thank you for your support. Upper low spins waves through late week The upper-low situated over Hudson Bay gnaws away at the death ridge (heat dome) over the south, and continues through the rest of the week. The waves spinning through the northeast bring a bit of a break to the steam bath going on over the south. The first wave on Wednesday brings a region-wide chance for showers and storms. The trailing wave arrives Thursday and is the feature to watch over the south for shower chances there, as the boundary may stall out. A trough brings cool Canadian high pressure in to start the weekend, with a weak ridge expected to bring temperatures up on Sunday into Monday. Showers with storms possible Wednesday An annoying flaw in guidance this summer has been the timing of frontal boundaries. Even within the 48-hour window, the time can vary by an hour or two. Forecasting severe weather, timing is everything. With more of a WNW flow aloft, storms that pop up have their anvils blown off, which dims the sun and drops the temperature, and thus takes the steam out (literally and figuratively) of the potential for damaging storms. The adage that I have preached for years is that if the sun is out, the thunder guns are likely to come out. It's not an alarm situation, it's an awareness situation. In their Tuesday afternoon update, the Storm Prediction Center has a Level 1 - Marginal risk of isolated severe storms possible for much of the west, east, and south. While the severe threat appears minimal over the north, I can't rule it out... because timing is everything. Given the sharp shortwave, ample shear, dew points pushing into the mid-to-upper 60s (a few 70°+ possible), and cooling temperatures aloft, there is a risk for damaging wind and large hail in any isolated supercells that may develop.  Given the elevated dew points and precipitable water values (amount of moisture in the air column) pushing 1½-1¾" sets up the risk of locally heavy rain makers, which could cause isolated flash flooding, reduced visibility, ponding on roadways, and soggy campers. The rain would be most welcome in some areas where it occurs. At my location in Kennebunk, my weather station is sitting at 1.57" for the month and 3.79" since the first of June (for those keeping score, that is 4.25" below normal). While the area around the Allagash has done quite well with rainfall during that same timeframe, along with some areas that have benefited from potluck dumpers, much of the region could use a good soaker at this point. I don't see it happening anytime soon.  Wednesday 6 AM to Thursday Midnight - Showers are possible for the rooftop of the state to start the day as outflow ahead of the boundary works into the region. Things get more interesting in the afternoon as showers and storms form as the cold front approaches. It is important to note that this model is most aggressive in storm formation compared to other ideas. As I've mentioned, cloud cover from storms that form initially in the afternoon and spill overhead will tell the tale of how the rest of the afternoon plays out. It's a wait-and-see scenario as they most often are, and bust potential is there as a result. Heading toward sunset, the atmosphere cools down, which will help mitigate any severe threat, but I can't rule out a rumble or two for interior coastal areas as the front slides through. Showers are expected to become isolated heading into the late evening. Chance for showers south on Thursday Thursday 2 AM (06z) to Friday 8 PM (00z Saturday) - The second wave enters on the heels, and this is where the plot thickens a bit. The Bermuda High and associated ridging become irritated by the upper-low to the northwest, causing it to flex, which presents the idea of the frontal boundary stalling out for a time over Southern New England. This loop of the European AI model idea at 700mb (~10,000 ft.), which is commonly the rain level atmospherically, indicates some juice that could bring showers to the south through the day. That idea is consistent. The questions that come into the forecast are whether showers continue into the overnight and possibly Friday morning. While this idea is progressive in ushering in dry air, it's not a certainty at this point. Any showers Friday morning are likely to end by midday, with the sky clearing out with a freshening breeze in the afternoon. For the west, east, and north, a dry day is expected with dew points in the 40s and 50s. Humidity levels over the south gradually fall into the 50s by Thursday evening. Outlook into the weekend Friday 8 PM (00z Saturday) to Monday 8 PM (00z Tuesday) - As the upper-level trough heads for the North Atlantic, its presence lingers in the region in the form of below-average temperatures. Northwestern areas of The County may see a run of overnight low temperatures in the 40s from Thursday into Saturday. Given the pattern, this keeps the humidity away, and it may stay away as the death ridge expands and heads west, with upper-level troughing continuing into next week. Temperature outlook through Monday The PTW Weather Wall Updates 24/7 Your financial contributions support the future of PTW |
Mike Haggett
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