The stage is set for the next round of steam A weak frontal boundary will cross Maine today, bringing scattered showers and isolated thunderstorms, mainly across the interior part of the state. High pressure then builds in Tuesday into Wednesday, leading to drier and warmer conditions, with inland highs climbing into the upper 80s to low 90s. Heat and humidity will peak midweek, with the potential for heat index values near or above heat advisory criteria, especially away from the coast. A cold front approaching late Thursday into Friday will bring increased chances for showers and thunderstorms, followed by a cooling and drying trend heading into the weekend. By Saturday and Sunday, more comfortable, less humid conditions are expected, though a few pop-up showers or storms can’t be ruled out. Heat builds Tuesday Heat indices across Maine are expected to climb into the low 90s Tuesday afternoon, especially inland, as shown in this NDFD (map created based on official National Weather Service forecasts) heat index map. Light southwest flow and clearing skies will help mix out low-level moisture, but dew points will remain high enough to push heat index values several degrees above the actual air temperature. This sets the stage for even more oppressive conditions midweek. Areas from the central interior to the foothills will feel the most heat, with heat indices of 90 to 92° over those areas. Locations right along the coast will remain cooler due to the sea breeze, with heat indices in the 70s to low 80s. Wednesday appears to be the warmest of the stretch High pressure will remain in control on Wednesday, allowing for intense diurnal heating and limited cloud cover. Temperatures are expected to climb into the upper 80s to low 90s across interior Maine, with the warmest readings from Millinocket southward. Southwest flow will draw in higher dew points, approaching 70° in the valleys, leading to heat index values in the mid-90s. These conditions may reach Heat Advisory thresholds, especially away from the coast. Cooler conditions are expected along the immediate coastline due to onshore winds, but the combination of heat and humidity inland will make for a hot and uncomfortable day. Cold front approaches Thursday The ECMWF model shown above hints at high instability on Thursday afternoon, with CAPE values modeled at over 2000 J/kg in parts of New Hampshire and western Maine. This signals a strong potential for thunderstorms as warm, moist air combines with an approaching front to add lift to the atmosphere. Surface dew points in the 70s, along with hot temperatures, will fuel storms capable of heavy rain, gusty winds, and possibly hail. The strong instability and slow-moving nature of storms could lead to localized flash flooding, especially where storms train over the same areas. Thursday afternoon looks active, particularly for inland areas. Showers possible to end the week Friday's weather will be influenced by a frontal system moving through the region, allowing drier and more stable air to take hold gradually. However, some lingering moisture and energy in the atmosphere could still spark scattered showers or an isolated thunderstorm, mainly during the afternoon (timing could still change since we're still a little ways out). While activity is expected to be spotty and short-lived, the Weather Prediction Center has issued a Marginal Risk for excessive rainfall across most of the state, meaning localized downpours and minor flooding can't be ruled out. Stay tuned for updated on any changes in the forecast. Weekend outlook & temperatures through SundayHigh pressure builds in behind Friday’s cold front, bringing a more stable and drier pattern for the weekend. The atmosphere will be less supportive of widespread convection, though a weak disturbance could still trigger an isolated shower Saturday, mainly in the mountains. Overall, the setup favors quieter weather with limited precipitation chances and more sunshine as the weekend progresses.  Today's update prepared by NC State student intern |
Mike Haggett
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