Activity to increase through the rest of the week The region can expect to see increasing heat and humidity on Thursday, which will linger along the coast through Friday. An upper-level trough, accompanied by a cold front, will build into the region on Friday afternoon and evening, bringing the risk of strong to severe thunderstorms. Behind the front, high pressure builds in for the weekend, bringing seasonable temperatures, drier air, and breezy northwest winds on Saturday, which shift southwest by Sunday. The early part of next week appears quiet, with near-normal temperatures and mostly dry conditions, except for a few shortwave troughs that may bring a chance of showers and storms. The heat returns on Thursday A warm and humid air mass will continue to build into the region Thursday afternoon as high pressure shifts offshore and a cold front approaches from the northwest. Southwesterly flow around the departing high is drawing in moisture and heat, pushing dew points into the 60s and sending heat indices into the upper 80s to near 90° across central and southern Maine. Northern areas will see more clouds through the afternoon, and a few showers or an isolated thunderstorm may develop late in the day as the front nears. Showers and storms on the way on Friday A Marginal Risk for severe storms is in place for Maine on Friday as a cold front drops south into a warm, humid air mass. Moderate instability, fueled by daytime heating and seasonably high moisture, may support isolated strong to severe storms. Westerly mid-level winds (30–50 kts) will provide sufficient shear for organized convection, including the potential for damaging wind gusts and possibly some hail, especially across northern areas where mid-level lapse rates (the rate at which temperature decreases with height) may be stronger. While confidence in storm coverage remains uncertain, future updates may increase the probabilities if the trends persist.  The Weather Prediction Center in their Day 3 outlook has much of the region in a Marginal Risk area for excessive rainfall on Friday, as a cold front slowly crosses the region. This front will interact with a very moist air mass already in place, particularly across eastern Maine, where precipitable water values (PWATs) are expected to exceed 2 inches, well above average for the region. These high moisture levels, combined with daytime heating and modest instability (CAPE values exceeding 1,500 J/kg in some areas), will support the development of scattered showers and thunderstorms, some of which may produce heavy downpours. The concern is there for localized flash flooding, especially in areas where storms repeatedly move over the exact locations or where drainage is poor.  Friday 5 AM (09z) to Friday 9 PM (01z Saturday) - Rainfall in Maine is expected to begin early Friday morning, mainly in the north around 5 to 6 AM. Activity will remain light and scattered at first, but coverage and intensity will increase by the afternoon as a cold front moves in. The most significant risk for heavy downpours and isolated flash flooding will be during the afternoon and early evening, especially in central and eastern areas. Showers will gradually taper off Friday night as the front exits. It is important to note that this model idea should be interpreted for a general idea for timing purposes only. Please stay updated on the forecast for more details. Comfortable conditions return on Saturday A refreshing change is on the way for Saturday as a cold front clears the region, ushering in drier and more comfortable air. High pressure will build in behind the front, mainly delivering sunny skies and seasonable heat indices in the upper 70s to low 80s across much of Maine. A light northwest breeze and noticeably lower dew points will help ease the humidity, making it feel much more pleasant compared to earlier in the week. The most comfortable conditions will be felt across the north and interior, with slightly warmer temperatures lingering near Bangor and the DownEast coast. Extended outlook and temperatures through TuesdayA series of shortwave troughs moving in from the northwest will bring a few chances for showers and thunderstorms from Sunday through Tuesday. While timing remains uncertain, each disturbance could spark afternoon and evening convection, mainly across central and southern areas. Brief downpours and gusty winds are possible with any storms.  Today's update prepared by NC State student intern |
Mike Haggett
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