As far as summertime goes, today will feature some fairly active weather as a cold front approaches from the north. We’ll deal with oppressive heat and humidity for much of the first half of the day, before strong to potentially severe thunderstorms develop later in the afternoon. Because of the active weather, this blog entry might be a little longer than usual, but I’ll try to stick to just the info you need to know.
A warm front is crossing the area this morning, and some showers are being observed ahead of it, mostly in northeastern areas. A couple of thunderstorm cells are noted along the front this morning, crossing the NH/ME border north of Bethel as of 6:50 AM. These cells are moving towards Augusta, and will bring a brief period of heavy rain and thunder to areas between Bethel and Augusta, such as Rumford.
Behind the warm front, west-southwesterly winds will develop and strengthen this morning. Near the coast, the influence of the cool Gulf of Maine will bend these winds to a more southwesterly direction, which will offer relief from the heat for Midcoast areas especially. For the rest of the area, especially SW of a Brunswick – Lewiston – Bethel line, those WSW winds will be downsloping off the hills of Southern NH. This downsloping will help to mix very warm temps down from aloft, and will also contribute to developing patchy sunshine. The result will be temps soaring into the low-mid 90’s in the favored SW warm spots, while areas farther north and east see highs in the low to mid 80’s. Meanwhile, these winds will also be transporting very moist air in our direction, and dew points will rise accordingly. The mugginess combined with the high temperatures will result in heat indexes approaching or exceeding 100 degrees. Heat advisories have been issued as a result for southwestern areas.
This heat will help fuel thunderstorm activity once the cold front begins to approach this afternoon. Look for storms to develop in two waves, one along a pre-frontal trough, and one along the front itself. The pre-frontal storms will get going in the mountains early this afternoon, before moving southeast towards the coast. Storms along the front itself won’t arrive in the mountains until early this evening, before moving towards the coast around sundown. Storms will pose primarily a damaging wind threat in terms of severe weather, while flash flooding and frequent lightning will be dangerous with any storms, even non-severe ones.
Storms will weaken after dark, and skies will clear from north to south by tomorrow morning.
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