Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 191400 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1000 AM EDT Sat May 19 2018 .SYNOPSIS... An approaching warm front will bring a steady widespread light rainfall today, becoming more showery late this afternoon into tonight. Chilly conditions today transition to warm and humid later tonight into Sunday with hit or miss showers/thunderstorms. Dry on Monday with passing showers during the mid-week. Cooler, drier air follows for Thursday into Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 10 AM Update... Previous forecast verifying very nicely especially with arrival time for onset of rain. Thus not much change if any needed with this forecast update. Latest radar imagery has leading edge of rainfall from about Springfield MA extending southeast into northeast CT then to the PVD area, making steady progress to the northeast. Heaviest rain today falls across western portions of CT/MA westward into NY as strongest wind fields and associated WAA occurs across this region. Therefore most of CT/MA and especially rain will see light rain. Mid level dry air moves across the region later this afternoon and should transition rain to more showery and drizzle into this evening. Thus steadies rain from late morning into early afternoon. Given dew pts are in the upper 30s to mid 40s expect temps to drop a few degs as the rain commences, resulting in a chilly afternoon. Earlier discussion below. =============================================================== High pressure has slide eastward over the Maritimes as rain from the southwest begins to approach the region. This high pressure has slowed the timing down so expect precip to overspread between 9am-noon. Heaviest of the rainfall will remain north and west of the I-95 corridor, closer to the better dynamics. Could see some enhancement in the rainfall across the Worcester Hills and east slope of the Berks thanks to upslope flow. Temperatures will slowly continue to rise today, as WAA begins with approaching warm front to the south. However, it still will be chilly thanks to easterly flow as high temps remain in the 50s. Made some minor adjustments to account for current trends. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... Tonight...Warm front lifts north across our region this evening. Increasing low level jet will advect higher precipitable water values and some elevated instability. Expecting at least a risk for showers, with a thunderstorm or two not out of the question. Temperatures should slowly rise overnight behind the warm front. As temperatures rise, so will dewpoints. This should lead to patchy fog formation. Sunday...A cold front should cross our region by evening. Given the modest instability and forcing, not expecting severe weather at this time, just scattered showers with a few thunderstorms. More summer-like temperatures and humidity, with highs in the 70s away from the south coast Cape and islands. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Dry weather returns by Monday * Passing showers Tuesday and Wednesday * Potential for dry weather but below avg temps for the end of the week Details... Sunday night into Monday...High confidence. Conditions should be improving as upper level trough pushes cold front through the region Sunday night/early Monday. Surface high pressure from Canada will move into the region resulting in dry weather. Westerly flow aloft will result in downslope flow allowing temps to remain in the mid to upper 70s away from the coast. Tuesday into Wednesday...Moderate confidence. Increasing chances for showers on Tuesday as weak disturbances moves through the flow and south of the region. Still some spread on timing and location of where precip will fall. Highest confidence is south of the Pike. Behind this disturbance, an approaching cold front will move in from the northwest. Could see some showers along this front but moisture is a bit marginal. Temperatures will be more seasonable with highs in the low to mid 70s. Thursday and Beyond...Moderate confidence. Drier but breezy conditions looks to be in store for the end of the week due to a northwest flow pattern. Will have to watch for a possible disturbance or two passing through the flow. For now trended the temperatures below avg and kept with a dry forecast. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. 14z update... Not much change from previous TAFs. Steadiest rain falls from late morning into early this afternoon then becomes more showery late day and drizzle overnight as warm front approaches and then lifts north of the area. Earlier discussion below. =================================================================== Today...Lowering IFR-LIFR with -RA/RA and BR/FG spreading NE this morning through afternoon, especially over N/W MA and CT. Meanwhile, rain becomes SCT S/E. However LIFR-VLIFR with FG is anticipated in these areas. E winds continuing, diminishing slightly, turning SE towards evening. Tonight...Widespread IFR/LIFR with areas of BR/FG, locally dense, especially over S/E New England. SCT SHRA activity continuing through roughly around midnight before drying out. Sunday...Mainly VFR, with local IFR possible during the morning. Breezy. Chance SHRA and TSRA. KBOS Terminal...Rain moving in closer to 15z, will see conditions deteriorate through the day into this evening. KBDL Terminal..Rain, moving in around roughly 12z. Lower conditions with SCT SHRA activity persisting during this afternoon. Outlook /Sunday Night through Wednesday/...Moderate confidence. Sunday Night through Monday: VFR. Monday Night through Tuesday: VFR. Slight chance SHRA. Tuesday Night: VFR. Chance SHRA. Wednesday: VFR. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...Moderate confidence. E flow gradually becomes SE this evening as a warm front crosses the waters from S to N. Steady rainfall likely. Increasing S winds tonight, shifting SW Sunday. Building seas across the outer coastal waters tonight into Sunday. Vsbys reduced in rain and fog today, with areas of dense fog developing tonight. Risk for scattered showers and isolated thunderstorms Sunday. Outlook /Sunday Night through Wednesday/...Moderate confidence. Sunday Night: Winds less than 25 kt. Local rough seas. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday Night through Tuesday: Winds less than 25 kt. Slight chance of rain showers. Tuesday Night: Winds less than 25 kt. Chance of rain showers. Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from midnight tonight to 6 PM EDT Sunday for ANZ231>235-237-250-254-255. Small Craft Advisory from 4 AM to noon EDT Sunday for ANZ230. Small Craft Advisory from midnight tonight to 3 PM EDT Sunday for ANZ236. Small Craft Advisory from midnight tonight to noon EDT Sunday for ANZ251. Small Craft Advisory until 2 PM EDT this afternoon for ANZ256. && $$ SYNOPSIS...Belk/Dunten NEAR TERM...Belk/Nocera/Dunten SHORT TERM...Belk LONG TERM...Dunten AVIATION...Belk/Nocera/Dunten MARINE...Belk/Dunten

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