885 FXUS61 KBOX 280148 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 948 PM EDT Mon Apr 27 2020 .SYNOPSIS... Low pressure east of Cape Cod slowly moves seaward tonight but remaining unseasonably cool, brisk with rain showers possibly changing over to snow showers overnight. Dry weather finally returns Tuesday along with moderating temperatures. Dry weather continues Wednesday as high pressure builds into the area. The next big storm arrives later Thursday into early Friday with heavy rain and strong winds. As this storm exits later Friday dry weather returns for the weekend along with temperatures at or warmer than normal! && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 1000 PM Update... There are no major changes from our previous update. We have increased our POPs across much of eastern Massachusetts, Rhode Island, and eastern Connecticut - we did this based on latest radar and satellite guidance. The area of low pressure is still on track to depart the eastern waters of Southern New England early Tuesday morning. As previously discussed a few wrap around snow flurries are possible. We aren't expecting much of anything to stick to the ground, except across the highest terrain in central and western Massachusetts. Strong northeast winds up to 40 mph over Cape Cod and the Islands will slowly relax overnight into Tuesday morning. Wind direction will become more northerly. PREVIOUS DISCUSSION BELOW: Rest of today and tonight... Overlaying the GOES-16 satellite imagery with SPC mesoanalysis shows the low pressure that has brought us this brutally cold and dreary weather for late April standards in Southern New England slowly moving east from the 70W/40N benchmark. This is in response to the upper level blocking pattern over northern Quebec finally weakening a little, allowing the deep closed 500mb trough to move east. With a surface high pressure over Southern/Central Quebec, and the surface low pressure strengthening a bit, winds have shifted to the north over the interior areas except for NNE near the coast. SPC mesoanalysis also shows good 925-850mb moisture transport into Eastern MA, which is consistent with a 30-40 kt 850mb jet and saturation up to 850mb this evening. And talking about the cold air, with 850mb temperatures at -5C, there will be decent cold air advection and so have gone with the 10th to 25th percentile of low temperature guidance for tonight which yield lows in the low to mid 30s areawide. Because of the cyclonic curvature, as the colder air makes its way into the lower elevation, expect lingering rain showers to mix with or change to snow showers. The omega is lacking in the Dendritic Growth Zone for anything more than decorative snow and with the marginal temperatures, any coating or marginal accumulations will be on grassy surfaces. Expect a drying trend towards daybreak. Immediate coastal areas including the Cape and Islands should see mostly rain thanks to the northerly flow advecting in warmer ocean air, which keeps the lower levels too warm to see snow. So in general, expecting no more than a coating to a few tenths of an inch of decorative snow for Monday night into Tuesday morning. No road impacts are expected. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Tuesday ... In a nutshell, Tuesday will be a huge improvement compared to Monday, especially for interior MA/CT which should see more sunshine than Eastern MA/RI. Looking at NAM Nest Bufkit soundings, with good mixing up to 800-850mb for areas west of Worcester, and with 850mb temperatures at 0C in the afternoon, this will support highs in the low 60s where there could be a few hours of sunshine. Even with a light northwest flow, the late April sun will overcome that easily. For areas along the coast, it could be hard to get rid of the clouds initially but as the northwest flow becomes more established, Eastern MA should see some peeks of sunshine towards the late afternoon hours. So have generally gone with the 90th percentile of high temperature guidance, yielding low 60s across the CT River Valley and low 50s across Eastern MA. Tuesday night... With clearing skies and light winds, conditions are ripe for a good radiational cooling night. Have gone with the 10th percentile of low temperature guidance which yield lows in the low to mid 30s away from the coast and upper 30s near the coast. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... 415 pm update ... Highlights ... * Dry weather Wednesday * Heavy rain & strong winds Thu into Fri * Drier and warmer this weekend Wednesday ... Short wave ridging provides dry weather along with near seasonable temperatures. Model soundings suggest mixing to about 850 mb or so and with temps around zero at the top of the blyr, this should support highs of 55-60 inland. Given light winds and sunshine (especially in the morning) it will feel even milder. Cooler closer to the coast with afternoon seabreezes. Looks like morning sunshine will give way to increasing afternoon clouds as warm front approaches from the west. Longest duration of sunshine should be over eastern MA and RI. Low risk for some light rain/sprinkles late in the day western MA/CT in response to WAA. Otherwise dry weather prevails. Thursday/Friday ... Full latitude trough impacts the east coast with PWATs +2 to +3 standard deviations as GOM and Atlantic moisture stream northward into New England. Wind anomalies more impressive with southerly low level jet +4 standard deviations. Thus strong jet dynamics acting on copious deep layer moisture will result in periods of heavy rain and strong to perhaps damaging winds Thu into Fri. Preliminary rainfall expected 1-2 inches with possibly up to 3 inches given upslope southerly component and if and where convective elements develop. As for flood potential, given a few days of dry weather (Tue & Wed) leading up to this event combined with Thu/Fri system fairly progressive, this should preclude significant flooding with worst case scenario to be minor poor drainage flooding along with rivers and streams. As for temps, given strong low level WAA temps Thu should be in the 50s, then rise Thu night with 60s possible Fri after the rain moves offshore. Weekend ... Showers possible Saturday depending how progressive mid/upper trough becomes, otherwise trend should be for dry and warmer weather as deep trough ejects into the Maritimes. Low risk for scattered showers late Sun ahead of a cold front. Overall many hours of dry weather this weekend with highs in the 60s Saturday, 65-70 Sunday. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 2300Z Update... There are no changes to our previous forecast. Expect improving conditions overnight as an area of low pressure moves away from Southern New England. This includes rain showers coming to an end from southwest to northeast. Additionally, this will lead to improving visibility and ceiling heights. PREVIOUS DISCUSSION BELOW: Rest of today and tonight...Moderate confidence. Areas of MVFR-IFR CIGS/VSBYS lingering across most areas with scattered -RASH/-SNSH. Lowest conditions across E coastal areas through around midnight. Conditions should slowly improve to VFR across central and western areas after 08Z and across Eastern terminals after 18z. VSBYS improve to VFR across central and western areas after 08Z and across Eastern terminals after 12z. Winds back to N-NW 10-15 kt across most areas, except up to 20-25 kt gusting to around 30 kt along E coastal areas. Tuesday...Moderate to high confidence. Any leftover MVFR CIGS across most areas should improve to VFR by around midday. Leftover scattered -RASH should taper off by mid to late morning. N-NW winds 5-10 kt inland, up to around 15 kt across Cape Cod and the islands. Good visibility. Tuesday night...High confidence. VFR conditions expected with light and variable winds. KBOS Terminal...Moderate confidence in the TAF through Tue 12z, then high confidence. KBDL Terminal...Moderate confidence in the TAF through Tue 12z, then high confidence.. Outlook /Wednesday through Saturday/... Wednesday: Mainly VFR, with local MVFR possible. Slight chance SHRA. Wednesday Night: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. Thursday: Mainly MVFR, with local IFR possible. Windy with areas of gusts up to 30 kt. SHRA likely. Thursday Night: Mainly MVFR, with local IFR possible. Windy with gusts up to 30 kt. SHRA. Friday: Mainly MVFR, with local IFR possible. Windy with local gusts up to 30 kt. Chance SHRA. Friday Night through Saturday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. && .MARINE... 0200Z Update... Since our last update we've decided to allow the Gale Warning on Boston Harbor to expire and be replaced by a Small Craft Advisory. From our previous update we increased the seas across the waters of eastern Massachusetts. An adjustment to the forecast was made after buoy 4429 reported 20 foot seas. North to northeast will fall below Gale force towards morning. PREVIOUS DISCUSSION BELOW: Gale warnings remain in effect for most open waters and Boston Harbor, and Small Craft Advisories along the southern near shore waters and Narragansett Bay. Rest of today and tonight... N-NW winds 15-30 kt gusting to 35 kt across the open waters through most of the night, then slowly diminish, Seas up to 8 to 12 ft on the eastern waters and 5 to 8 ft on the southern waters, slowly subsiding overnight but remaining well above 5 ft. Visibility 1-3 nm across the eastern waters through improve to 3-5 nm by around 06Z, and over 6 nm on the southern waters. Tuesday... N-NW winds 15-25 kt gusting to around 30 kt early, diminishing 10-15 kt by around midday or early afternoon. Seas generally 5 to 10 feet, highest across the eastern waters continuing to slowly subside through the day but remaining at or above 5 feet on the eastern waters. Good visibility. Tuesday night... Light and variable winds 5-10 kt. Eastern outer waters diminishing from 5 to 7 feet to below 5 feet overnight. Good visibility. Outlook /Wednesday through Saturday/... Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers. Thursday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 9 ft. Chance of rain showers. Thursday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 13 ft. Rain showers. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 13 ft. Chance of rain showers. Friday Night: Winds less than 25 kt. Rough seas up to 11 ft. Chance of rain showers. Saturday: Winds less than 25 kt. Rough seas up to 9 ft. Chance of rain showers. && .TIDES/COASTAL FLOODING... 415 pm update ... Persist NNE gales may yield a 1.25-1.50 storm surge with tonight's high tide cycle. This may result in very minor/nuisance coastal flooding at Nantucket and across Cape Cod. ESTOFS and ETSS were running too low given current observations so followed the Stevens Institute ensemble surge guidance. Time of high tide around 3 am, so risk for minor/spotty flooding from about 1 am to 5 am. && .CLIMATE... Temperatures today will feel more like early March rather than late April. Expect the highs across the region to run from 15 to around 20 degrees below seasonal normals. Record low maximum temperature records will be challenged. Here are the record low max temperatures for today, April 27 for our four long term climate sites... Boston: 41F set in 1882 Hartford/Bradley: 46F set in 1917 Providence: 44F set in 1917 Worcester: 41F set in 1973 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Warning until 6 AM EDT Tuesday for ANZ231-232-250-251- 254>256. Small Craft Advisory until 8 PM EDT Tuesday for ANZ233>237. Small Craft Advisory until 8 AM EDT Tuesday for ANZ230. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera/Chai/Gaucher SHORT TERM...Chai LONG TERM...Nocera AVIATION...Nocera/Chai/Gaucher MARINE...Nocera/Chai/Gaucher TIDES/COASTAL FLOODING... CLIMATE...