Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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644 FXUS61 KBOX 280243 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1043 PM EDT Thu Jun 27 2024 .SYNOPSIS... Dry and pleasant conditions through Friday as a high pressure briefly builds in. Still looking to be an active weekend in store as a slow moving frontal system brings showers and t-storms with localized downpours, especially Saturday afternoon into Sunday night. Drier weather then returns for early next week with seasonable temperatures. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 1030 PM Update... Have increased wind speeds and gusts across southern New England tonight as they are coming in a bit higher than previously anticipated. Latest guidance indicates roughly a 20-30+ kt NNW to NW jet pushing in. This should not be too difficult to mix down given the colder air advection. Rest of forecast remains on track. 735 PM Update: Cold frontal trough extends from the North Shore SW through east-central CT. Its passage over the next couple hours into the southeast waters will usher in increasing NW breezes as well as a rapid decrease in dewpoints. While current dewpoints are in the mid 50s to mid 60s, dewpoints should fall some 10 degrees through the balance of the overnight. Other than northerly breezes, it adds up to a pretty tranquil, open-the-windows kind of evenings. Lows upper 40s in northern/northwest MA, with mid to upper 50s for the remainder of Southern New England. Previous discussion: Post cold front air mass settles into the region with breezy conditions overnight from the northwest. A rouge spot shower is possible this afternoon, but not anticipated to be anything more than light and brief. Diurnal cu cloud cover will dissipate overnight, but winds are likely to remain strong enough to preclude any radiational cooling. Never the less, a great night for sleeping with windows open as the low temperature drops into the low 50s and upper 40s away from the coastal plain. Near the coast a few degrees warmer in the middle to upper 50s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Surface high pressure and mid-level height rises will lead to a wonderful day across southern New England. One challenge will be how strong the winds become, building surface high could lead to weaker winds and potentially a sea breeze, which have lower confidence in, if it were to happen, it would occur by early afternoon. Otherwise a dry and comfortable day with low humidity and highs in the middle and upper 70s with the lower CT River Valley near 80F. Mostly sunny with scattered diurnal cu developing the late morning through the afternoon hours. Mainly dry overnight into early Saturday morning, though a few spot showers are possible with the passage of the mid-level shortwave. As for lows, slightly warmer than tonight, mid 50s to low 60s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highlights: * Periods of showers and t-storms associated with a slow moving frontal system starting late in the day Sat and into Sun. Heavy downpours capable of producing street flooding are possible, although the risk for severe storms appears low. * Gradually improving conditions Mon. * Dry and seasonable weather for Tue and Wed with high pressure in control. Details: Saturday and Sunday: Still looks to be an active period of weather for the weekend as today`s models and ensembles continue to advertise a frontal system moving in from the Great Lakes region later Sat aftn and continuing into Sunday. This frontal system looks to interact with an anomalous plume of moisture (PWATs 2-2.25"!) and favor several chances for showers and t-storms. Seems to be a slower trend in the guidance as far as timing goes, so think there is a decent chance the morning to early-aftn Sat is dry, but with increasing cloud cover. PoPs then steadily increase during the 2nd half of the daytime hrs into the Chance/lower Likely range, with Categorical PoPs (70-90%) Sat evening and continuing into Sunday, with the best chances on Sunday in southeast New England with indications for a stalling cold front. There are some signals that showers could linger into early on Mon in eastern and southeast New England, consistent with a slowing frontal boundary. While there may be some stronger storms at times, it is looking as though given an unfavorable time of day for destabilization, the main potential hazard is primarily heavy rainfall capable of street flooding. It`s still too uncertain which area(s) are most at risk to see flooding; hydrologically, more urbanized areas are typically more vulnerable, and portions of the CT Valley and along the reach of the Massachusetts Turnpike have seen significant rainfall in recent days. We also want to emphasize it won`t be raining everywhere at all times, but the potential exists for heavy rainfall this weekend, mainly Sat evening into Sunday. Temps are seasonable with readings in the upper 70s to mid 80s, but both Sat and Sun look to be quite muggy with dewpoints rising into the upper 60s to mid 70s. Monday: Gradually improving conditions on Mon as surface ridge tries to build in from the northwest. Still looks as though eastern MA could see more hit-or-miss scattered showers as upper trough moves through during the morning hrs in vicinity to a slow-moving surface front. However improving conditions into Mon aftn and also turning MUCH less humid. Highs mid 70s to low 80s and lows mid 50s/around 60. Tuesday through Wednesday: Sprawling high pressure settles over New England for Tue and Wed, favoring dry weather and temps around or slightly above normal. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: Tonight: High confidence. VFR, dry weather. A dry cold front is working through Southern New England and should make it to the southeast coast by 03z Fri. NW winds around 10-15 kt with gusts in the low-20s kt range behind the front, with initial SW winds around 10 kt shifting to NW for the Cape and Islands. Friday... Moderate confidence. VFR, scattered cu around 5-7 all though dry. High pressure settles in with variable wind conditions while the flow is out of the west, there is a chance for winds to become south during the late morning with low confidence in sea breeze development. Will reassess this afternoon/evening update. Friday Night... High confidence. VFR. Perhaps a spot shower across western MA/CT prior to sunrise with southwest winds less than 10 knots. KBOS TAF...High confidence in TAF, though some uncertainty on sea breeze potential Friday. VFR tonight into at least 15z Fri, with NW winds around 12-15 kt with gusts in the low 20s kt range. Winds then slacken into the aftn and that could allow a seabreeze to develop but would be late in the day (after 18z?) if it develops. Winds to shift to light SSW for Fri evening. KBDL TAF...High confidence in TAF. VFR. NW winds around 10-12 kt tonight, easing trends for Fri. Outlook /Saturday through Tuesday/... Sunday: Mainly MVFR, with local IFR possible. Breezy. SHRA, slight chance TSRA. Sunday Night: VFR. Breezy. Chance SHRA, slight chance TSRA. Monday: VFR. Breezy. Slight chance SHRA. Monday Night through Tuesday Night: VFR. Wednesday: && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight through Saturday morning... Cold front moves off shore and high pressure moves in from the west which will ease seas and wind gusts. Dry conditions prevail during this time with patchy areas of marine fog possible southeast of Nantucket. West to northwest winds between 10 to 20 knots overnight, becoming lighter from the north by daybreak. Friday, there is a low chance of onshore winds developing during the afternoon along the south coast, eventually going south to southwest overnight into Saturday morning. Residual seas at 5 ft for the outer southern waters this afternoon and settles around 2-3 ft off shore and 1-2 ft near shore Friday into Saturday morning. Outlook /Saturday through Tuesday/... Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Rain showers, chance of thunderstorms. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday Night through Wednesday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ231-232-250- 251-254-255. && $$ SYNOPSIS...Loconto/Dooley NEAR TERM...Loconto/BL/Dooley SHORT TERM...Dooley LONG TERM...Loconto AVIATION...Loconto/Dooley MARINE...Loconto/Dooley