Lexington, Massachusetts, USA
000 FXUS61 KBOX 081753 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 153 PM EDT Thu Jun 8 2023 .SYNOPSIS... Similar conditions expected today, Friday and Saturday, not a washout, but scattered afternoon showers each day, perhaps most numerous Friday. Temperatures will continue to run slightly cooler than normal. There will also be some near ground level smoke at times, as a result of the ongoing Canadian wildfires. A brief pattern change occurs Sunday and possibly lingering into Monday, bringing drier and warmer conditions to the region. Then the next frontal system may bring widespread rain to the region around Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 925 AM Update... * Rather Cloudy/Cool Today with scattered showers with bulk of any sunshine confined to the south coast, Cape & Islands Persistent closed upper level low pressure system will continue to spin today along the northern New England/Quebec border. Some additional shortwave energy rotating southward from this main upper level low will result in forcing for ascent. The result will be scattered showers...especially this afternoon during max heating. Perhaps we muster a few hundred J/KG of MUCape...but thinking if we do see any thunder it would be rather isolated. Therefore...kept the current forecast with just scattered showers. An abundance of clouds with cyclonic flow will keep highs mainly in the 60s. The exception to this will be areas near the south coast, Cape/Islands where they are just far enough removed from the upper level low. This will keep most of the showers to their north and also allow for some sunshine...especially during the first part of the day. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... 345 AM update... * Showers may become more widespread Friday Tonight... Any diurnal early evening scattered showers diminish with or shortly after sunset. Given cold pool aloft, light winds and decreasing diurnal clouds, another chilly night. Lows 45-50 with low 50s along the coast, including the city of Boston. Normal low, 52-57. Friday... Vertically stacked low remains over northern New England, but some short wave energy dives into the backside of the trough and backs the mid level flow to more SW over New England. This results in more cyclonic flow aloft and greater moisture & instability advection into SNE. PWATs rising to near 1 inch and surface dew pts climb into the 50s. This combined with steep mid level lapse rates will provide sufficient instability for scattered showers and and isolated thunderstorms. Given the increased instability coupled with weak forcing for ascent, showers could be more widespread Friday than Thursday. Cold pool aloft (-21C at 500 mb) limits highs to the mid and upper 60s Friday, perhaps a few 70 deg readings in the CT River Valley. Winds light and variable except locally onshore. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... 345 AM update... Highlights * Warmer this weekend with more showers on Saturday and drier weather on Sunday * Unsettled weather returns early next week as a new area of low- pressure moves over The Northeast Saturday The upper low that's been sitting over The Northeast this week will finally lift out and fill during the first half of this weekend. This will allow warmer air to advect in from the west as a mid-level ridge builds east. Despite the upper-low ejecting away from the region, cold air aloft will continue to support steep lapse rates through the column. Additionally, there will remain sufficient moisture in the column to support more diurnal showers and thunderstorms on Saturday afternoon. With 925 hPa temps warming to 12 to 13 Celsius on Saturday, we're currently expecting surface temperatures to top out in the low to mid 70s. This combined with steep lapse rates will support modest diurnal instability with CAPE values getting as high 500 J/Kg across southeastern MA and RI. Wind fields are forecast to be very week, thus no organized severe convection is a concern at this point. Nonetheless, a few isolated to scattered thunderstorms capable of producing small hail will be possible on Saturday afternoon. Sunday Sunday looks to be the pick of the weekend as a mid-level ridge building in from the west will result in the lowest precipitation chances we've experienced since last week. A drier low-level air mass will support sunshine for most of the day, but we may see increasing cloudiness during the mid to late afternoon hours as a new system approaches from The Great Lakes. 925 hPa temps climbing to 15 Celsius should support highs in the upper 70s to low 80s across southern New England Sunday afternoon. Next Week After a nice taste of summer weather on Sunday we'll return to another wet/unsettled pattern early next week. Low-level wind fields will turn south ahead of a robust upper-level low that will bring the region its next opportunity for substantial rainfall. Southerly flow will bring increasing moisture and cloud cover on Monday as well as the opportunity for some diurnal showers and thunderstorms. At this point guidance is not insistent on forcing strong enough to support a wash out on Monday, but Tuesday is a different story. As the upper-low advances further east Monday into Tuesday, continued southerly flow is forecast to support PWATs rising to near 1.5 inches across southern New England. As the surface low and associated cold front push through the region during the day Tuesday, southern New England should experience a more widespread rainfall event. Guidance suggests this would be followed up by more rainfall on Wednesday as a secondary area of low-pressure moves over The Northeast. Details are vague at the 7 day time range, but the signal is for a wet/unsettled first half of next week. Despite the wet/unsettled pattern, there is also a strong signal that more seasonable temperatures will prevail next week with daily high/low temps in upper 70s/low 60s respectively. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 18z TAF Update... Through Tonight...High Confidence. Mainly VFR outside briefly lower conditions possible in any scattered showers into the first part of the evening. We will need to watch for some lower ceilings possibly working into mainly northern MA toward daybreak. We may also see some haze tonight near the south coast from the lingering wildfire smoke that has been impacting our region the last several days. Light/Calm winds. Friday...Moderate Confidence. A period of generally MVFR ceilings will be possible Friday morning mainly across northern MA. We will also need to watch for some lower vsbys from haze near the south coast Friday from the lingering wildfire smoke. Otherwise...VFR outside briefly lower conditions in the expected scattered showers and a few t-storms that are expected to develop by Friday afternoon. Light NE winds except SE towards the Cape & Islands. Friday night...Moderate Confidence. The scattered showers and a few t-storms should wind down Friday evening. It does appear that MVFR-IFR ceilings/vsbys may develop across the region Friday night as a result of the cooling boundary layer and lingering low level moisture. Areal extent/coverage of these potential low clouds and fog patches is somewhat uncertain...but greatest risk will be across central and eastern sections of our region. Winds will be light/calm. KBOS Terminal...High Confidence in TAF. Main concern will be a period of MVFR ceilings that are possible Friday morning and perhaps a few t-storms within the vicinity of the terminal Friday afternoon/early evening. KBDL Terminal...High confidence in TAF. Main concern will be the potential for a few t-storms within the vicinity of the terminal Friday afternoon/early evening. Outlook /Friday Night through Monday/... Friday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Saturday: Mainly VFR, with local MVFR possible. Chance SHRA, isolated TSRA. Saturday Night through Sunday: VFR. Sunday Night: VFR. Slight chance SHRA. Monday: VFR. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 345 AM update... Weak low pressure over Maine remains nearly stationary through Friday. Scattered showers and patchy fog will reduce vsby at times. Outlook /Friday Night through Monday/... Friday Night through Saturday: Winds less than 25 kt. Chance of rain showers. Saturday Night through Sunday: Winds less than 25 kt. Sunday Night: Winds less than 25 kt. Slight chance of rain showers. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. && .FIRE WEATHER... 345 AM update... Latest model simulations have the smoke conditions improving somewhat Thursday, with highest concentrations of smoke along and near the south coast. Nonetheless, Air Quality Alerts remain posted for western MA, and all of CT/RI. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert until midnight EDT tonight for CTZ002>004. MA...Air Quality Alert until midnight EDT tonight for MAZ002-003- 008>011. RI...Air Quality Alert until midnight EDT tonight for RIZ001>008. MARINE...None. && $$ SYNOPSIS...Nocera/RM NEAR TERM...Frank SHORT TERM...Nocera LONG TERM...RM AVIATION...Frank/RM MARINE...Nocera/RM FIRE WEATHER...