Lexington, Massachusetts, USA
000 FXUS61 KBOX 041058 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 658 AM EDT Sun Jun 4 2023 .SYNOPSIS... Unseasonably cool weather will continue today with gusty northeast winds. A few showers this morning, then more widespread rain is expected later this afternoon into tonight, especially in eastern Massachusetts. Scattered showers will linger into Monday in eastern New England with some temperature moderation, but still well below normal. Warmer Tuesday with more seasonable temperatures for early June, then turning cooler for the rest of the week. Unsettled weather pattern will persist through the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 7AM Update... Decreased pops across western MA and CT this morning to bring in line with current radar trends. Otherwise the current forecast remains on track. Steady showers are currently working their way south along the eastern coast line and will fill in throughout the day. Previous Discussion... Main weather feature will continue to be the anomalous upper low just east of New Eng which is forecast to rotate westward into SNE. Multiple shortwaves pinwheeling around the low will bring occasional showers/light rain, mainly eastern MA. Main focus for showers through daybreak will be across SE MA, otherwise occasional showers are expected to rotate southward from northern to eastern MA today. Most of the rain should be east of CT valley although can't rule out a few showers making it this far west. Increasing coverage of rain is expected later this afternoon in eastern MA as inverted trough rotates westward toward SNE with nose of increasing low level jet increasing convergence. This LLJ will bring increasing N winds this afternoon along the eastern MA coast with gusts to 25-35 mph. Unseasonably cold temperatures will continue today and we have the potential to get close to record cold highs (see records below). Core of cold air aloft will be over SNE today with 850 temps near zero and 925 mb temps 2-4C across central and eastern New Eng. Highs will only reach lower 50s in these areas and some locations may struggle to 50. A bit milder in the CT valley with highs upper 50s, and possibly near 60. Normal highs for today are low to mid 70s. High Surf Advisory was extended through Monday for eastern MA as rough seas and surf will continue. Obviously very poor beach days but dangerous conditions for anyone observing the rough surf from jetties given large breaking waves onto rocks and other nearshore structures. Always observe from a distance! && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Tonight... Low pres will set up east of New Eng and will eventually become captured by the upper low which moves off the coast late tonight. Low level jet axis will be focused across eastern MA while deepening moisture plume moves in from the north and NE. This will result in periods of rain tonight across eastern MA, with showers possibly extending to the west across central MA and eastern CT. Some areas along the eastern MA coast may receive around 0.50" of rain through tonight. Winds will remain gusty along the coast where gusts to 30 mph are expected. Very little change in temps with lows 45-50. Monday... The upper low slowly moves eastward away from New Eng. However, deeper moisture plume will remain across eastern half SNE with closed cyclonic flow aloft which will continue the risk of showers in the east. Improving conditions in the CT valley where some sunshine may develop in the afternoon. Low level temps moderate so it will be milder with highs ranging from lower 60s eastern MA to lower 70s CT valley. Less wind Monday as gradient relaxes with north winds 10-20 mph, higher gusts Cape/Islands. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Tuesday Night: The closed low that has been stalled over the region for the past several days continues NE into Nova Scotia while the next closed low drops south from Quebec. How cold we get will likely depend on if there are lingering clouds or if we can clear out. If it remains cloudy lows will like hang around normal in the low 50s, while a clearing could drop lows in the mid 40s. Tuesday: Models have been in good agreement over the last 24 hours that the closed low dropping south from Quebec will bring another back door cold front with it. The recent deterministic and ensemble guidance have also been trending higher on instability with a 50% chance for 500 J/kg of CAPE. CSU machine learning probs for severe also highlight some of the region in a 5% prob for hail. This makes sense considering the cold pool aloft and mid level lapse rates between 6- 8 C/km will be favorable for hail growth. Like our last severe event, shear looks very meager. The big question will be if we can get enough sun to generate the instability considering the cold pool aloft could mean lingering overcast skies. Given this is still a few days out and outside hi-res guidance range, things could change so keep an eye on the forecast. High temps Tuesday will also depend on lingering cloud cover and the timing of the back door front. If we can get some sun, 850mb temps ahead of the front around +8C could allow temps to jump into the low to mid 70s, while more cloud cover will keep highs in the mid to upper 60s. Wednesday - Friday: The closed low stalls again over the North East leaving the region under consistent cyclonic flow. This will allow for daily pop up shower chances. No day is looking like a sure washout with ensemble probs for greater then 0.25 inches less them 40% each day. Blended ensemble guidance keeps highs in the upper 60s to low 70s this week while deterministic guidance such as the GFS and EURO have trended cooler with highs in the low to mid 60s. I think highs this week will be highly dependent on cloud cover considering the strong June sun angle will be able to heat the surface quickly while mostly cloudy skies combined with the northerly flow could keep temps lower. Saturday - Monday: The closed low begins to break down and push NE with a short wave ridge building over the region. This will allow temps to become more summer like again. Another closed low drops down from Canada late in the weekend towards early next week. Considering this is still a week out, wont speculate on details as the model forecasts are likely to change over the next week. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Tonight...Moderate confidence. Mainly MVFR cigs expected to deteriorate to IFR later this afternoon and especially tonight across eastern MA as areas of rain move in from the N and NE. Mainly VFR cigs in the CT valley. N wind gusts 20-25 kt along the eastern MA coast increasing to 25-30 kt late afternoon and tonight. Monday...Moderate confidence. Mainly VFR CT valley. MVFR elsewhere should improve to VFR during the afternoon, except IFR SE MA improving to MVFR. Scattered showers, mainly across eastern MA. N winds 10-20 kt, gusts to 25 kt Cape/Islands. KBOS Terminal...Moderate confidence in TAF. Mainly MVFR cigs, but may lower to IFR later afternoon and tonight as areas of rain develop. KBDL Terminal...High confidence in TAF. Outlook /Monday Night through Thursday/... Monday Night: VFR. Breezy. Slight chance SHRA. Tuesday: Mainly VFR, with local MVFR possible. SHRA likely, isolated TSRA. Tuesday Night: VFR. Breezy. Chance SHRA, isolated TSRA. Wednesday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA. Wednesday Night: VFR. Chance SHRA. Thursday: Mainly VFR, with local MVFR possible. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Monday...High confidence. Persistent northerly wind gusts 25-30 kt will continue through tonight. Another surge of wind is expected late Sun into Sun night with an increasing low level jet. There may be a few gusts approaching 35 kt over eastern MA waters but duration and areal coverage not enough to upgrade to Gale Warnings. Winds gradually diminish Monday afternoon. Strong N winds will continue to produce rough seas on coastal waters which may make conditions difficult to navigate for less experienced boaters. Periods of rain becoming more widespread later this afternoon and tonight, especially on eastern MA waters. Outlook /Monday Night through Thursday/... Monday Night: Winds less than 25 kt. Local rough seas. Slight chance of rain showers. Tuesday through Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. Wednesday: Winds less than 25 kt. Chance of rain showers. Wednesday Night through Thursday: Winds less than 25 kt. Slight chance of rain showers. && .TIDES/COASTAL FLOODING... Key Points: * Areas of minor coastal flooding along the eastern MA coast during the high tide tonight and possibly again Monday night A storm surge around 1+ ft combined with 7-10 ft seas offshore will be enough for minor coastal flooding along the eastern MA coast during the high tide near midnight tonight. A coastal flood advisory was issued. Similar conditions and tides are expected during the Monday night high tide so another round of minor coastal flooding is possible along the eastern MA coast. Along the South Coast, surge values will be lower due to offshore flow (N winds). Locations such as Providence are forecast to remain well below flood stage. && .CLIMATE... Record Low Max Temps for Sunday June 4th. BOS...52/1891 PVD...55/2012 BDL...59/2018 ORH...51/2018 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...High Surf Advisory until 8 PM EDT Monday for MAZ007-015-016- 019-022-024. Coastal Flood Advisory from 10 PM this evening to 2 AM EDT Monday for MAZ007-015-016-019-022>024. RI...None. MARINE...Small Craft Advisory until 2 PM EDT Monday for ANZ230-233>235- 237. Small Craft Advisory until 8 PM EDT Monday for ANZ231-232-250- 251-254>256. Small Craft Advisory until 8 AM EDT Monday for ANZ236. && $$ SYNOPSIS...KJC/KP NEAR TERM...KJC/KP SHORT TERM...KJC LONG TERM...KP AVIATION...KJC/KP MARINE...KJC/KP TIDES/COASTAL FLOODING... CLIMATE...