000 FXUS61 KBOX 051109 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 609 AM EST Mon Dec 5 2022 .SYNOPSIS... Dry and pleasant weather continues today and tonight. Milder temperatures along with some rain at times are expected mainly late Tuesday into Wednesday. Dry weather returns Thursday. We then will have to watch the track of a potential low pressure system to our south sometime Friday into the weekend, but whether it brings much precipitation to our region is uncertain. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 630 AM update... Coldest morning in quite a while ongoing this morning with readings across the region in the teens and low 20s. Minimal changes to the forecast with this update. Previous Discussion... Highlights... * Plenty of sunshine today with highs between 45-50 Details... High pressure currently overhead will move northeast of the region today. This will allow a southwest flow of milder air to work in aloft. We expect plenty of sunshine today; other than some high thin cloudiness this afternoon. However...given the cold start and the low December sun angle the recovery will be somewhat limited at the surface. Nonetheless, we expect afternoon highs to reach between 45 and 50. We may see some southwest wind gusts of 15 to 20 mph this afternoon, but overall not a bad day for early December standards. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Highlights... * Clouds increase overnight with temps mainly in the upper 20s/30s * Milder Tue with a few showers in the afternoon across the interior Details... Tonight... High pressure to the northeast of our region coupled with a frontal boundary across the Great Lakes will result in a light southerly flow of air across the region. Upper level ridging over the Atlantic will keep the stronger warm advection/forcing to the west of our region. So while we expect to see an increase in clouds overnight, dry weather will prevail. Temps probably drop quickly with sunset given an initial dry airmass in place, but should level off or even rise a bit near daybreak especially on the immediate south coast. Overall...temps much of tonight will be in the upper 20s and 30s. Tuesday... A weak wave of low pressure over the Ohio Valley will lift northeast into the eastern Great Lakes Tuesday. In response...a southerly LLJ of 25 to 35 knots develop across interior southern New England. However...high pressure over the Maritimes will tend result in southeast surface winds and actually advect a pocket of low level dry air into eastern New England. Model cross sections indicate a lot of dry air at 850 mb across eastern MA & RI. Given the above...mainly dry weather should persist across eastern MA/RI during the daylight hours of Tuesday. A few warm advection showers are expected across western MA/CT mainly during the afternoon hours, but even in these locales rainfall amounts should be light during the daylight hours. High temps should reach between 45 and 50 across the interior high terrain with readings well into the 50s southeast of the I-95 corridor. Inverted soundings will keep winds generally in the 5 to 15 mph range from a southeast direction. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Rain, moderate to heavy at times, overspreads the region Tuesday night and continues into Wednesday before drier weather returns Thursday * Low confidence forecast Friday and beyond when it comes to precipitation chances but unsettled weather is possible * Anomalous warmth through mid week, peaking on Wednesday before cooling again through the weekend Details... High confidence in a wet stretch of weather Tuesday night through Wednesday thanks to a reinforcing mid level shortwave which moves the Great Lakes into Quebec during the same period. At the surface a high pressure center remains over Nova Scotia while low pressure builds to our east, with southern New England in between. This induces a strong 35 to 45 kt low level jet overhead late Tuesday and Wednesday which along with warm frontal isentropic lift will provide forcing for ascent of a very moist airmass (PWATs over an inch). That equals a prolonged period of rain, amounting to between 0.5 and 1.5 inches of rain by Thursday morning when rain tapers off behind a cold front. The previously mentioned low level jet might cause concern for some damaging winds if it weren't for a stout inversion which should keep the strong winds aloft for the duration of the event. Thursday then becomes, perhaps briefly, drier under a colder NW post frontal flow. Besides lack of rain, this will bring about an end to the anomalous warmth we saw on Wednesday when temperatures are expected to reach well into the upper 50s. Thursday begins a slow but steady reset back toward normal. Though it will still be quite warm on Thursday in the low to mid 50s, by the end of the week and next weekend high temperatures back in the 40s are likely. Overall, though, the forecast beyond Thursday relied on the NBM (a blend of guidance) owing to the great deal of discrepancy amongst global guidance as to how the pattern breaks down. While there is agreement that a mid level shortwave will approach from the midwest, there is disagreement as to how deep it is and how far south the surface low goes (either over southern New England or suppressed to our south). This will determine if the Friday-Saturday period is wet or dry. For now the forecast indicates a slight chance of rain and high elevation snow. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 12Z TAF Update... Today...High Confidence. VFR with winds becoming SSW at 5 to 15 knots by afternoon. Tonight...High Confidence. Mainly VFR conditions expected, but some MVFR ceilings may develop generally northwest of I-95 between 8z and 12z. Light S winds. Tuesday...Moderate Confidence. MVFR conditions should gradually become dominant across the interior, but mainly VFR conditions should prevail for most of the day across eastern MA/RI. A few showers are expected across the interior...mainly during the afternoon. SE winds 5-10 knots. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday Night: Mainly VFR, with local IFR possible. Breezy. RA. Wednesday: Mainly VFR, with areas IFR possible. Breezy. RA. Wednesday Night: Mainly VFR, with areas IFR possible. Breezy. Chance RA. Thursday through Thursday Night: VFR. Breezy. Friday: VFR. Windy with areas of gusts up to 30 kt. Slight chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Tuesday...High Confidence. A ridge of high pressure will move northeast of our region into the Canadian Maritimes today and persist into Tuesday. This will result in southerly flow developing today and continuing into Tuesday...but the pressure gradient will remain weak enough to keep winds and seas below small craft advisory thresholds. Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain. Wednesday through Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Rain. Thursday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain. Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 12 ft. Slight chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/BW NEAR TERM...Frank/BW SHORT TERM...Frank LONG TERM...BW AVIATION...Frank/BW MARINE...Frank/BW