Today will feature another day of warm and humid weather as well as another round of afternoon showers and thunderstorms. As I write this shortly after 8 AM, cloudy skies are being observed across the mountains and the coastline northeast of Portland. Meanwhile, a thin wedge of sunshine extends from southeastern NH into southwestern ME. With an upper-level low approaching from the west, I think this pattern will generally hold through the rest of the morning hours, though I think at least a few breaks of sun are possible up in the mountains and along parts of the Midcoast.
That sunshine will help push temps into the upper 80s to low 90s for southern NH and the foothills/coastal plain of Maine. Cooler temps (low/mid 80s) are expected in the mountains and along the Midcoast. Dew points will once again linger near 70 which will push heat index values towards 95 in southern NH and interior SW ME.
The combination of hot temperatures, high humidity, and an approaching upper-level low will prove favorable for thunderstorm activity this afternoon.
Model guidance shown here indicates that scattered showers and storms will pop up starting around 12-1 PM. As per usual, the mountains will be the first to see shower activity before storms move east towards the coastline. The biggest threat with this afternoon’s storms will be damaging winds in addition to heavy rain and lightning. Storms will fade after sunset.
As a quick aside, yesterday’s round of storms was admittedly much stronger than anticipated across the Sebago Lake region. While activity was expected to be focused in NH, a few strong cells strayed across the border. The strongest of these was a classic supercell that ended up producing an EF-0 tornado near Hiram. I happened to be out chasing that cell and got a neat timelapse showing the vigorous low-level rotation associated with that cell. The tornado itself is hard to spot in the video because it never produced a coherent “condensation funnel” connecting the circulation on the ground with the parent cloud.
The photo below was taken while the tornado was on the ground and shows a short condensation funnel dropping down from the cloud above as well as a plume of water being sucked upward from Barker Pond.
The plume of water is just to the right of the tallest pine tree above the yellow flowers. The condensation funnel is near the left edge of the ragged wall cloud extending from below the thunderstorm’s base. Both features are small and hard to spot, but are very rare to see here in Maine! Usually we get 1-2 tornadoes each year, but often they occur in remote northern parts of the state where only the observers are moose.
I’m quite confident we won’t see any tornadoes today, but then again, that’s what I said yesterday. We still have a lot to learn about tornadoes and how/when they form!