South Portland, ME Weather

What Has Changed

No significant changes to the forecast with this update.

Key Messages

1. High pressure will dominate the weather for the week. Expect dry conditions and no significant weather impacts.

Discussion

KEY MESSAGE 1 DESCRIPTION... High pressure builds back into the region today in the wake of a cold front that has ushered in a slightly cooler airmass, so expect temperatures to only max out in the mid to upper 40s for the mountains and foothills, and in the low 50s to the south. High pressure then becomes centered directly overhead tonight which is going to lead to another night of strong radiational cooling. This pattern has been so persistent lately that the NBM (which usually doesn't handle radiational cooling all that well) actually looks pretty reasonable, but MOS has still been incorporated into some of the better radiating locations to add some value there. The result is likely one of the colder nights we have seen so far with widespread 20s and upper teens (low teens at the better radiators) expected by early Wednesday morning.

High pressure than moves its way offshore Wednesday with return flow starting a warming trend that will last through the end of the work week. Wednesday is likely going to see temperatures top out in the 50s and rising dewpoints making for a warmer night in the 30s. High astrotides are going to push this morning's and Wednesday morning's high tides close to minor flood stage, but calm conditions and off shore winds are expected to result in little to no surge meaning they should stay below. By Thursday temperatures should be able to mix in to the 70s across the area. Dewpoints also continue to rise, so Thursday night looks to end up relatively mild with temperatures likely only being able to fall into the mid to upper 40s. Clouds and a few showers are possible Thursday night ahead of the next frontal passage and while global models have been consistently showing a signal for more widespread shower chances, as this event moves into the hi- res window the suggestion is for more widely scattered showers. So, while this does technically mean many locations will see a higher chance for rain then they have seen over the last week or so, that chance is still going to be quite low. In fact the latest NBM, still doesn't even really want to bring PoPs south of the mountains, but again as more hi- res model data gets ingested low chances will likely begin expanding southward.

The front likely begins crossing early Friday morning with the colder air filling in north of the mountains by the afternoon and limiting the temperatures in those locations to the mid to upper 50s. South of the mountains should be able to see temperatures warm into the mid to upper 60s (maybe even 70 on the coastal plain) before the front crosses. High pressure then moves back overhead for Halloweekend which looks decent as this frontal passage doesn't quite pack the punch of the current one, so daytime temperatures look to end up in the upper 50s and low 60s. For Saturday night temperatures look to generally be in the 40s and 50s during trick or treat time. For what it's worth global models have been showing a pretty consistent signal for November to begin wet, so that will be the window to watch for our next chance of potentially appreciable rainfall.

Aviation

Through 06Z Wednesday: VFR conditions anticipated with a NW breeze continuing through the morning. Some gusts arrive in the afternoon, but winds become calm for tonight.

Outlook... Wednesday-Thursday...VFR conditions expected. There may be brief period of IFR or lower in valley fog at LEB, CON, and MHT prior to sunrise.

Friday: Another front approaches the region and some MVFR CIGs may be possible north of the mtns, including HIE.

Saturday: VFR conditions expected.