487 FXUS61 KBOX 240810 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 410 AM EDT Sun May 24 2020 .SYNOPSIS... High pressure builds southeast into New England promoting a trend back to drier but cool weather today. Cloudy conditions with seasonable temperatures for Memorial Day. Pattern change toward warmer and more summer-like conditions for the rest of the upcoming workweek. Increasing threat for showers and thunderstorms associated with a slow-moving cold front late in the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Highlights... * Expect plenty of sunshine across the majority of southern New England today. The exception will be across the Islands where clouds will linger. The rest of southeast MA and RI will see increasing cloud cover as the day progresses. Ridge axis building into and through much of New England today. A surface high will build into the region from Nova Scotia. Will also see low pressure linger well to the south of the region. High pressure will keep much of the region sunny today, but will have modest ENE to E flow. With decent onshore flow expect cool temperatures roughly from central MA to RI eastward. Highs range from the low 50s to the low 60s in this corridor. West of the line temperatures range from the low 60s to the low 70s. With the current setup in mind anticipating a decent pressure gradient, which will keep it gusty across the south coast. This includes Cape Cod and the Islands. Still some uncertainty on the back edge of cloud cover with the high nudging in from the north, but based on high resolution guidance am anticipating it to remain cloudy across the Islands. The clouds will increase toward southeast MA and RI once flow becomes more ESE/SE. There is some weak convergence and in combination with the clouds in place there could be some light showers or drizzle across Cape Cod and the Islands today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Highlights... * Clouds moving in across southern New England as flow becomes ESE tonight. Fog and spotty rain showers/drizzle possible. * Cloudy start to Memorial Day with spotty rain showers/drizzle ending, but may linger across Cape Cod and the Islands. May see some peaks of sunshine across western and central portions of the CWA during the afternoon. Tonight... A weak shortwave trough will lift into Quebec from eastern Ontario, while the ridge axis slides offshore. Low level flow will be southeasterly, which will advect moisture in from the system well to the south of the region. This should bring some stratus onshore and with some weak convergence anticipating there will be spotty showers/drizzle along with fog. Best shot of precipitation is across Cape Cod and the Islands along with eastern coastal MA. Leaned toward HREF/NAMNest guidance for increasing cloud cover across the region tonight. Should be a good stratus deck in place across much of the coastal plain and into southeast MA. With the weak shortwave swinging through to the north, could have enough moisture in place for spotty showers/drizzle. With the cloud cover in place across the region, do expect low temperatures to be milder in comparison to this morning. Low temperatures will generally be in the 40s, but a few locations along the south coast could see readings in the low 50s. This is a result of warmer air advection due to southeast winds. Memorial Day... Shortwave trough to the north lifts into northern New England from Quebec. A ridge axis will build into the Mid Atlantic and eastern Great Lakes. Could see the spotty showers linger across the east coast, but with the ridge sliding in will see decreasing cloud cover from west to east. Have some uncertainty of high temperatures especially across eastern areas. Some high resolution guidance such as the ARW/NAM and HREF are much cooler than the current forecast. This is due to the easterly onshore flow, but do have winds shifting to the southeast. If winds shift slower than currently anticipated then temperatures will need to be reduced significantly. Should be mild across the CT River Valley. Temperatures range from the mid to upper 50s across eastern coastal areas to the low to mid 70s across the CT River Valley. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Trend toward more summer-like temperatures by midweek, with humidity levels on the rise as well. Highs across the interior in the mid/upper 80s with plenty of sun and scant rain/thunder chances. * Unsettled Thursday into Friday, turning more humid. Cold front late in the week may bring showers and thunderstorms with downpours, though timing and location remain uncertain at this range. * Somewhat cooler and drier weather for Saturday. Details... Monday Night through Wednesday: Building mid level ridge along the Eastern Seaboard, with a large surface ridge associated with a high pressure across the North Atlantic. Once rainfall chances across southeast MA diminish Monday evening, expecting dry weather to dominate this period. Temperatures and humidity will be on the rise through this time as well. While much of the region will see summer-like warmth, the immediate south coast will stay on the cooler side due to the onshore south to southwest winds. Thursday through Friday: Expecting a period of more convective weather sometime towards the end of next week. Timing remains an issue. More ingredients for showers and thunderstorms look to be in place on Friday than Thursday. However, cannot dismiss the idea of some active weather on Thursday due to the diminishing influence of a surface high pressure. The main ingredients will be the heat and humidity ahead of an approaching cold front. The current timing takes this cold front past southern New England Friday night into Saturday. Not entirely confident in this timing given the forecast range and the pattern of a retreating high pressure. Above normal temperatures continue. Saturday: Trends favor a drier day with lower temperatures as high pressure arrives from the Great Lakes region. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Thru 12Z...High confidence VFR for all terminals except for Cape Cod and the Islands where MVFR ceilings linger. Winds remaining NE to ENE overnight. Speeds generally less than 10 kts as high pressure builds in from the northeast. The only exception is along coastal locations where speeds will be around 10 kts. Remaining gusty at ACK. The latest RAP has a good handle on the MVFR ceilings across Cape Cod and the Islands with RH values at 975 hPa. Will need to keep an eye on satellite to see if this activity spreads into eastern RI. Today...High confidence VFR at all locations, except for ACK. Expect MVFR ceilings to linger at ACK. Will see a surge of moisture from the southeast, which will bring MVFR ceilings back into Cape Cod terminals during the afternoon. Could see IFR develop at ACK, but have only hinted at this point in time. This is per Bufkit forecast soundings of the NAM/RAP guidance. Winds out of the ENE to E and gusty across Cape Cod and the Islands. Expecting gusts up to 20-25 kts. Tonight...High confidence Moisture will surge from the southeast, but winds remain out of the ENE/E. Expect MVFR ceilings to spread in and potentially some IFR ceilings as well. Best shot for IFR is across Cape Cod, the Islands, northeast CT, northern RI and central MA. Could see some light showers or drizzle spreading in as well. Memorial Day...High confidence MVFR conditions initially with IFR across Cape Cod and the Islands with spotty showers/drizzle and fog. Will see improvement to VFR as the day progresses as winds shift from the ENE/E to the SE/S. KBOS Terminal...High confidence in the TAF. KBDL Terminal...High confidence in the TAF. Outlook /Monday Night through Thursday/... Monday Night through Tuesday Night: VFR. Wednesday: VFR. Breezy. Wednesday Night: VFR. Thursday: VFR. Breezy. Slight chance SHRA. && .MARINE... High confidence in heightened seas across the south coast and just east of Cape Cod into tonight and Monday. Have extended the SCA as 5 ft waves linger. Should see Ipswich/Mass Bay and the outer water zone next to this area have seas fall below 5 ft by this evening. Fog and showers/drizzle moving in this afternoon into early Memorial Day. May see some low visibilities tonight across the south coast as a stratus layer moves in. Outlook /Monday Night through Thursday/... Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Tuesday through Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ235- 237. Small Craft Advisory until 8 PM EDT this evening for ANZ250- 251. Small Craft Advisory until noon EDT Monday for ANZ254>256. && $$ SYNOPSIS...Belk/BL NEAR TERM...BL SHORT TERM...BL LONG TERM...Belk AVIATION...Belk/BL MARINE...Belk/BL