970 FXUS61 KBOX 280004 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 704 PM EST Fri Nov 27 2020 .SYNOPSIS... High pressure will bring mainly dry and quiet weather through Sunday. Strong low pressure lifts through New York State Monday. This will bring the potential for strong winds and heavy rain. Above normal temperatures early in the week trend seasonably cold midweek, then above normal again late week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 7 PM Update... Broad area of strato-cu covering New England, New York, and PA. Expect these clouds to linger through the night. A few breaks are noted over eastern NY, so we may see some breaks in Srn New England as well. Radar shows sprinkles over Eastern NY extending into the Berkshires, and which are trending to Western MA. No significant changes to the forecast. Previous discussion... Abundant low level humidity remains in place tonight. Expecting the clouds to linger overnight, although there should be some fleeting breaks. A mid level shortwave is projected to pass us by to our southeast overnight, which could lead to a stray shower or sprinkle across portions of southeast MA, and also possibly across Cape Ann. Most of southern New England will remain dry, however. The arrival of colder air should lead to slightly lower overnight temperatures than this past morning, but still some 5-10 degrees above normal. Light winds should also lead to patchy fog once more, but not quite as widespread or thick as this morning. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Colder air continues to move across our region. Still looking at one more mid level shortwave to pass us by with the cold pool aloft. The humidity associated with this feature is limited, so just expecting mainly clouds. Trend in the guidance has been for less of a risk for showers, but it will not be zero. Expecting clearing to develop during the afternoon into the evening behind this shortwave. This clearing continues into Saturday night. High pressure becomes more of a factor Saturday night. Above normal temperatures continue Saturday. how much above normal will depend upon how quickly the clouds break up. Thinking max temperatures about 5 degrees lower than today. Low temperatures Sunday morning should be near normal as colder air continues to overspread our region. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Big Picture... Upper flow starts with seperate northern and southern jet streams going into the weekend. Shortwaves, one in each stream, merge over the Mississippi Valley Sunday night and Monday. This creates a closed low over the Midwest Monday that ejects through NY into Canada Tuesday and Wednesday. Upper contours are above normal values over the weekend and on Monday, then crash below normal Tuesday and Wednesday as the upper low passes to our west. Contours then build to normal Thursday and Friday. This suggests above normal temps early with a below normal period during midweek, then a return to normal late week. Mass fields and thermal fields are similar among the models through midweek, then greatly diverge next Thursday and Friday. Forecast confidence is good through midweek, then turns poor late next week. Details... Sunday and Monday... High pressure over the Eastern USA Sunday morning moves offshore by evening. This maintains subsidence over New England Sunday and resulting mostly sunny, fair weather. Warm advection aloft will limit the depth of mixing Sunday. Temperatures at 950-mb support max sfc temps in the upper 40s and lower 50s. If mixing reaches to 925- mb, max temps would climb into the 50s. Fair skies Sunday night, although expect increasing mid/high clouds especially late at night. With dew points in the 30s, expect min temps before the arrival of clouds will be in the 30s. Southern stream shortwave directly supports a surface low over LA/MS, and the digging northern stream shortwave will turn the Eastern USA flow from the southwest and eventually from the south. This will draw the weather system and its moisture up the Appalachians and over the Northeast USA. This pulls the surface low up through PA/NY with a broad south flow over Srn New England. The south flow draws higher than normal PW values...1 inch to 1.3 inches...into our area for Monday, suggesting wet weather with occasional downpours. Increasing surface pressure gradient supports increasing wind on Monday with sustained winds 25-35 mph. Low level jet reaches 60-70 kt at 2000 feet above the surface, which suggests potential wind gusts reaching 40-45 kt especially along the coastal plain. Will continue with the rainy/windy forecast for Monday. With 950-mb temps around 10C, forecast has max sfc temps in the 50s, possibly low 60s in a few spots. Tuesday-Wednesday... Surface cold front sweeps east of Srn New England by Tuesday morning. The passage of the upper flow will bring cold advection aloft Tuesday, destabilizing the airmass and generating scattered showers. Cold advection extends to the surface Wednesday with mixing to 850-mb...that will only support max sfc temps in the 40s. Mixing will draw southwest gusts of 30 kt to the surface. Thursday-Friday... Upper trough pulls out through Eastern Canada. Global models show another trough sweeping east from the Plains, but with differences on its evolution. Offshore high pressure will provide dry weather Thursday and much of Friday, but with increasing potential of precipitation during Friday night. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight...High confidence. VFR conditions expected across much of the region. Radar shows some light showers/sprinkles over Eastern NY moving into Western MA. These may continue to affect Srn New England before midnight. Localized MVFR to IFR conditions possible across the CT River Valley and typically prone areas. Light to calm winds. Saturday...High confidence. VFR conditions expected as high pressure begins to arrive. May have brief MVFR ceilings across the interior during the morning. Winds W to WNW with speeds of 5-10 kts. The higher elevations may see some gusts of 15-20 kts. Saturday Night...High confidence. VFR with diminishing wind. KBOS...High confidence in TAF. KBDL...High confidence in TAF. Outlook /Sunday through Wednesday/... Sunday: VFR. Sunday Night: Mainly VFR, with local MVFR possible. Chance SHRA. Monday: Mainly MVFR, with local IFR possible. Strong winds with local gusts up to 40 kt. SHRA. Monday Night: Mainly MVFR, with areas IFR possible. Strong winds with gusts up to 40 kt. SHRA. Tuesday: Mainly MVFR, with areas VFR possible. Windy with local gusts up to 35 kt. Slight chance SHRA. Tuesday Night: Mainly VFR, with areas MVFR possible. Breezy. Slight chance SHRA. Wednesday: Breezy. && .MARINE... Winds will briefly diminish tonight into Saturday, before picking up again late Saturday and Saturday night as colder air moves over the waters. Thinking gusts up to 20 kt, with seas approaching 5 ft across the outer coastal waters during that time. Later shifts may consider Small Craft Advisories if winds are forecast to be stronger. Small Craft Advisories should be able to expire later this afternoon across the southern outer coastal waters, where rough seas continue to subside into this evening. Outlook /Sunday through Wednesday/... Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night: Winds less than 25 kt. Monday: Low risk for gale force winds with gusts up to 40 kt. Local rough seas. Rain showers. Monday Night: Moderate risk for gale force winds with local gusts up to 45 kt. Rough seas up to 16 ft. Rain showers. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 12 ft. Chance of rain showers. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 13 ft. Chance of rain showers. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 11 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/Belk NEAR TERM...WTB/Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk