South Yarmouth, MA Weather

What Has Changed

Extended the time of the Small Craft Advisory for the eastern waters to 18z today. Otherwise, the forecast remains on track.

Key Messages

- Stretch of dry weather with cold nights continues for the first part of the week. A moderating temperature trend arrives later in the week.

Discussion

KEY MESSAGE 1...Stretch of dry weather with cold nights continues for the first part of the week. A moderating temperature trend arrives later in the week.

Upper ridging and surface high pressure will dominate through the upcoming week and weekend resulting in a prolonged stretch of dry weather. Southern New England will be in a cooler post-frontal airmass today 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. Even cooler conditions arrive overnight with ideal radiational cooling. The combination of mostly clear skies and boundary layer decoupling allows lows to fall into the 30s across urban/coastal areas and the lower to mid 20s further inland. Guidance even hints at lows approaching either side of 20 degrees across areas of northern Franklin and Worcester counties by Wednesday morning. Less cooling may be realized further west as mid and high clouds filter in from the west through the overnight.

The theme of dry and cooler weather continues 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 layer. 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.

12z TAF Update...

Today and Tonight...High confidence.

VFR conditions continue through tonight. N-NE winds of 6 to 13 knots today strongest of which through mid-afternoon for the Cape/Islands where brief 20+ knot gusts are expected. A more traditional E sea breeze probably will develop during the afternoon along parts of the immediate eastern MA coast. Winds diminish to very light/calm levels shortly after sunset tonight.

KBOS Terminal... High confidence in TAF.