South Yarmouth, MA Weather

What Has Changed

No meaningful changes to the forecast, with an extended stretch of quiet and dry weather ahead.

Key Messages

- Prolonged stretch of dry weather through the first half of the upcoming weekend. Seasonably cool temperatures Tuesday through midweek followed by period of warmer temperatures later in the work week.

Discussion

KEY MESSAGE 1...Prolonged stretch of dry weather through the first half of the upcoming weekend. Seasonably cool temperatures Tuesday through midweek followed by period of warmer temperatures later in the work week.

A cold front pushes southward into southern New England tonight. This front will be fairly moisture-starved limiting it's impacts to a period of breezy northerly winds overnight accompanied by advection of a cooler airmass.

Upper ridging and surface high pressure will dominate through the upcoming weekend favoring dry weather. Southern New England will be in a cooler post-frontal airmass Tuesday with 925mb temperatures ranging +1C to +4C. This will support high temperatures in the mid to upper 50s. Locations along the Cape/Islands and even portions of the east coast may be limited to the low 50s given the N/NNE onshore wind component. The cool airmass in place combined with light winds and clear skies will favor efficient radiational cooling Tuesday night into Wednesday. Temperatures are likely to fall into the upper 20s and 30s. The higher terrain, valleys, and other radiator spots have potential to see mid 20s with even a some spots in the low 20s!

Similar conditions prevail Wednesday. Temperatures trend slightly warmer as a mid level ridge shifts further east into the region accompanied by warmer temperatures aloft. The warming trend in temperatures continues into late-week resulting in 925mb temperatures warming to +10 to +13C. This will yield high temperatures in the mid-60s on Thursday which is seasonably warm for this time of year. Despite the mid-level pattern becoming more zonal Friday (ahead of our next weak wave), the westerly flow will support efficient mixing in the boundary. This will result in a breezy, but likely the warmest day of the week with high temperatures in the upper 60s and even low 70s in portions of southern New England. NBM highlights moderate to high probabilities(60%-80%+) for 70F or greater across the valleys, CT, and I-95 corridor. Therefore a larger portion of southern New England, with the exception of the higher elevations and Cape/Islands, will have a good shot at hitting the 70 degree mark on Friday.

Another moisture-starved shortwave and cold front moves overnight Friday. This will bring back temperatures into the low 60s for the weekend which is seasonable for late-October. Looking further ahead to the latter half of the weekend and next week, ensemble guidance shows agreement with a transition to a generally unsettled pattern which may feature periodic chances for showers. Confidence decreases with respect to the details such as timing.

Aviation

Forecaster Confidence Levels...

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

18Z TAF Update:

Today and Tonight...High confidence.

VFR conditions. W to WNW winds this afternoon at 6-12 kts. Occasional gusts of 18-20 kts possible for Cape/Islands. A cold front pushes through the region between 00-04Z. No rain expected; however, this will bring a windshift to the NW/NNW with gusts 18-25 kts. Highest gusts for Cape and Islands. SCT to BKN cloud decks accompany the front, but likely to be mid-level (050-100).

Tuesday...High confidence.