Area Forecast Discussion
Issued by NWS Boston, MA

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102 FXUS61 KBOX 301056 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 656 AM EDT MON MAY 30 2016 .SYNOPSIS... Bands of heavy rain showers are expected this morning. The bulk of the rain will be over by early afternoon, but a few thunderstorms may develop late this afternoon/early this evening across interior southern New England. Mainly dry weather expected tonight except for another batch of showers that may graze the south coast and Islands. Dry conditions with warm afternoons follow Tuesday into Wednesday. Unsettled weather may return by the end of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ***Bands of heavy showers/isolated thunderstorms this morning may result in localized poor drainage street flooding*** ***A few thunderstorms are possible across the interior late this afternoon/early evening*** 7 AM Update...Forecast this morning is generally on track. Made a few minor updates to the temperatures and the PoPs to bring more in line with current trends. There are bands of heavy rain across southern New England. There are two areas that are seeing this heavy rain. The first is in the northwestern part of Massachusetts. The second is across eastern CT/RI and eastern MA. Rainfall rates over an inch per hour have been observed at times in this heavy rain. Despite the heavy rain, mainly looking at poor drainage/street flooding only. Tropical plume of moisture is lifting northward into southern New England early this morning, despite shallow cool marine layer in place. PWATs near 2 inches combined with a southwesterly low level jet of 25 to 35 knots will result in bands of heavy rain showers and perhaps a few embedded thunderstorms this morning. Bulk of our mesoscale guidance brings the heaviest swath across CT and then across central and northeast MA. There are also some hints of a secondary heavier band developing across the south coast or it may remain just offshore. The rain this morning may result in localized poor drainage street flooding issues in the heaviest bands, but do not expect these problems to be widespread. The bulk of the rain will occur this morning. Drier mid level air working into the region will bring an end to most of the precipitation by early afternoon, except perhaps the immediate south coast. While an abundance of clouds will remain in place, some peeks of sun will likely develop at least across the interior this afternoon. This will allow for some destabilization out ahead of the approaching pre-frontal trough/cold front. This will result in a few thunderstorms developing across eastern NY. It`s uncertain if they will survive the trip into our western zones, but its possible we may see a few t-storms late this afternoon/early evening with the highest risk in northwest MA. The combination of instability/shear appear too low for severe weather, although we can not rule out an isolated strong storm or two. As for temperatures, they remain quite cool early this morning along with areas of fog. While it will take some time to mix out the marine layer, expect temperatures to shoot up well into the 70s to around 80 in most locations by late afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... ***Patchy dense fog may develop late tonight*** Tonight... If a few thunderstorms are able to develop across interior southern New England, they will weaken this evening with the loss of instability. Otherwise, much of the night will be dry but can not rule out a few brief showers as the actual cold front crosses the region. The one exception to this is along the south coast and particularly Martha`s Vineyard/Nantucket, where a weak surface trough will combined with still relatively high PWATs. This will likely result in another period of rain showers overnight. Low temperatures tonight will mainly be in the upper 50s to the lower 60s. Breaks in the clouds overnight may allow for some patchy dense fog to develop given the wet ground, so something will have to watch closely. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Mainly dry with above normal temperatures Tue/Wed * Unsettled weather may return toward next weekend Medium range models are in good agreement on the overall synoptic pattern. A mid-level ridge will move over southern New England Tuesday and then move offshore Wednesday. Mid-level troughing then moves into Quebec towards the end of the work week and starts influencing our weather with several shortwaves working around the base of the trough. This will result in more unsettled weather towards the end of the week. Tuesday and Wednesday...Mid-level ridge moves over southern New England. This will bring dry weather to much of the area. A dry cold front will move through southern New England Tuesday, resulting in a wind shift to the north. This is followed by another back door cold front on Wednesday. Temperatures will be above normal through both days, especially across the western zones. Onshore flow will result in more seasonable temperatures along the east coast. Thursday through Sunday...Mid-level trough moves into Quebec allowing several shortwaves rotating through the base of the trough to move through southern New England. This will result in periods of showers, particularly Friday and Saturday. Due to the difficulty in pinpointing when and where these showers will occur, have kept chance PoPs in the forecast for much of this period. However, not expecting rain to be widespread, nor for the entire period. Temperatures will be around normal for much of the time. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Today...Moderate confidence. Marine layer will remain in place through mid to late morning, resulting in mainly IFR-LIFR conditions in locally heavy rain showers and fog patches. Timing uncertain, but improvement from west to east to mainly MVFR conditions should occur during the afternoon. The exception might be the south coast, Cape and Islands where low clouds and fog may hang tough. Bulk of rain ends by early afternoon, but a few thunderstorms may affect the interior late this afternoon/early evening. Tonight...Moderate confidence. Mainly MVFR to even VFR conditions this evening, except the Cape and Islands where IFR conditions persist. Localized IFR to even LIFR conditions may develop late across other areas in patchy dense ground fog. KBOS TAF...Moderate confidence in TAF. KBDL TAF...Moderate confidence in TAF. Outlook /Tuesday through Friday/... Tuesday and Wednesday...Moderate confidence. VFR. Thursday...Moderate confidence. Mainly VFR conditions expected. Increasing clouds with diminishing conditions through the night, particularly along the south coast. Friday...Moderate confidence. Mainly VFR conditions expected. Brief MVFR conditions are possible in SCT -SHRA at times. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...High confidence. Biggest concern through tonight will be areas of fog, mainly near the south coast where it could be locally dense at times. A period of southwest wind gusts in the lower 20 knots may affect the near shore waters of the south coast this afternoon, but kept them just below small craft advisory thresholds. Some very marginal 5 foot swell may arrive into our extreme southern outer-waters overnight, but they look to cover such small area will let the next shift assess. Outlook /Tuesday through Friday/... Tuesday...Moderate confidence. Some uncertainty on wave heights with swell from Tropical Depression Bonnie potentially moving up into the coastal waters. At this point there is potential for 5 foot seas, especially on the outer waters. Southwesterly winds remain below 20 kts, shifting to the north Tuesday night. Wednesday...Moderate confidence. Northeasterly winds and seas will remain below Small Craft Advisory criteria. Thursday...Moderate confidence. Easterly winds and seas increase. Seas may rise above 5 feet, especially on the outer waters. Friday...Moderate confidence. Easterly winds are expected to remain below 15 kts. Seas decrease through the period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/RLG NEAR TERM...Frank/RLG SHORT TERM...Frank LONG TERM...RLG AVIATION...Frank/RLG MARINE...Frank/RLG is the U.S. government's official web portal to all federal, state and local government web resources and services.