Lexington, Massachusetts, USA
000 FXUS61 KBOX 142335 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 735 PM EDT Sun Apr 14 2024 .SYNOPSIS... Showers end overnight, along with gradual clearing. Dry and seasonably mild Monday through Wednesday. Another unsettled pattern develops late this week, with near normal temperatures a few chances for rain Thursday into next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Made some changes to the forecast this evening. First, removed thunderstorms from the forecast north of the northern border of CT and RI. The latest SPC mesoanalysis showed an increasingly unfavorable environment to support thunderstorms. That said, mid level lapse rates should remain about 6-6.5 C/km for a few hours yet. Thus, there is the remote possibility for an isolated thunderstorm to develop towards the south coast of New England overnight. Thinking all showers end by about 4-5 AM, but even earlier for most of interior southern New England. Gradual clearing from west to east overnight. Also tweaked temperatures to reflect observed trends. Previous Discussion... A disorganized frontal wave will traverse over the Northeast this afternoon and evening with scattered showers and a perhaps a few thunderstorms. Latest SPC meso-analysis reveals no significant surface based CAPE over southern New England within the warm sector of the wave of low pressure moving through the region. However, steep mid-level lapse rates are contributing to elevated instability that could support a few rumbles of thunder across western MA/CT and possibly over some locations near the south coast this evening. Areas along and north of I-90 are forecast to be in the cool sector, thus not expecting any thunderstorm activity north of that mark. Any remaining showers and thunderstorms are forecast to clear to the south and east around or just before midnight. Thereafter we can expect gradual clearing with winds shifting to the west/northwest. Low temps bottom out in the low 40s across northwestern MA and mi to upper 40s elsewhere. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Tomorrow A dry surface cold front pushes through the region during the day tomorrow. This will support dry conditions and west/northwest winds throughout the day. Skies will be clear to start which will allow surface temps to warm to the upper 60s to near 70 in some locations by the mid-afternoon hours. After a sunny start, we will begin to see increasing diurnal cu during the afternoon thanks to steep low- level lapse rates from cooler air aloft. Overall a warm/dry afternoon. Warmest temps will be focused in the CT River Valley and over southeastern MA where downsloping from WNW winds should help temps over achieve. Tomorrow Night Very quiet tomorrow night. Clear skies and light west/northwest winds. There is some question as to whether or not the atmosphere decouples overnight. This will govern how far temperatures are able to fall with radiational cooling. Will have a better idea by tomorrow, but for now have leaned on a blend of CONSMOS and NBM for low temps in the low to mid 40s on Tuesday morning. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights: * Broad trough settled over the region for much of the upcoming week, with a brief period of mid level ridging in the Tuesday- Wednesday timeframe * Near to above normal temperatures, with an unsettled pattern developing late this week Based on the latest guidance suite, still have the greatest confidence in the forecast details into early Wednesday. After then, there is little consistency with the timing and amplitude of some synoptic features, leading to low confidence in the forecast details. Kept a broad period of unsettled weather from late Wednesday into Saturday, but not expecting this to be a total washout this entire time. Expecting it will be a couple more days before these details come into better focus. All that said, there has been a consistent signal for near to above normal temperatures through this portion of the forecast. High pressure dominates our weather Tuesday into Wednesday. Thinking we could get through most of Wednesday dry, especially across the eastern half of southern New England. Just a low risk for some showers during the afternoon farther west. More likely to see rainfall arrive some time Wednesday night into Thursday as a low pressure moves into the Great Lakes, with a secondary low pressure possibly developing toward the Mid Atlantic coast. This should move offshore Friday, with a lingering cold front into Saturday. A large high pressure over the northern Plains states should become more of a factor in our weather some time Sunday. Moisture is not particularly impressive, so not expecting a lot of rainfall during the second half of this week. This should be a good thing, by permitting area waterways a chance to drain further. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High- greater than 60 percent. Tonight...High Confidence. VFR. Any remaining SHRA diminish after 03Z across most of the region. Some SHRA may linger near the south coast of RI/MA through about 08Z. This will be followed by some gradual clearing from west to east through 12Z. Southwest winds becoming northwest from 5 to 10 knots. Tomorrow...High Confidence. VFR. W/WNW winds around 10 knots. Some gusts up to 20 knots possible. Tomorrow Night...High Confidence. VFR. Steady WNW winds continue. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday through Friday/... Tuesday: VFR. Breezy. Tuesday Night: VFR. Wednesday: VFR. Slight chance SHRA. Wednesday Night: VFR. Chance SHRA. Thursday: VFR. Breezy. Chance SHRA. Thursday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA. Friday: Mainly VFR, with areas MVFR possible. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight Some showers and possible a rumble of thunder possible over the south coastal waters before midnight tonight. Otherwise, expect gusty southwest winds to diminish as winds shift to the west/northwest overnight. Sustained speeds fall to 5 to 10 knots by tomorrow morning with gusts less than 20 knots. Seas begin to subside but remain high enough to warrant Small Craft Advisory headlines for the outer marine zones. Tomorrow and Tomorrow Night Seas continue to subside to sub-Small Craft Advisory criteria by tomorrow evening. Otherwise, expect relatively quiet conditions over the coastal waters with modest 10-15 knot west/northwest winds. Outlook /Tuesday through Friday/... Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday Night through Wednesday: Winds less than 25 kt. Wednesday Night: Winds less than 25 kt. Slight chance of rain showers. Thursday through Friday: 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 until 2 PM EDT Monday for ANZ232>235-237- 250. Small Craft Advisory until 8 PM EDT Monday for ANZ254>256. && $$ SYNOPSIS...Belk/RM NEAR TERM...Belk/RM SHORT TERM...RM LONG TERM...Belk AVIATION...Belk/RM MARINE...Belk/RM
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