306 FXUS61 KBOX 102319 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 719 PM EDT Sun Mar 10 2024 .SYNOPSIS... A strong upper level disturbance will bring a period of showers to the southern coastal waters tonight. Seasonable and drier Monday with gusty to strong northwest winds Monday into Monday night. Mainly dry conditions Tuesday through Thursday with a warming trend. Then the weather pattern turns unsettled for Friday through Sunday with multiple chances of showers. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 7PM Update Light showers have popped up on the south coast in response to the base of the upper level trough and weak cold front now swinging through. Rain accumulation with these showers will be light and likely less then a tenth of inch. hi-res guidance continues to pick up on isolated rain/snow showers inland overnight. However, with dew point depressions over 10C, chances are precip will struggle to reach the ground. If any precip, esspically snow, reaches the ground, impacts would be little to none. 430 PM Update: Surface low pressure which brought downpours and gusty SE winds to Southern New England last night into early this morning has now moved into southeastern ME. This has brought weak subsidence to our area now, reflected in decreased cloud cover that continues as of mid afternoon. Winds have shifted to WSW/W with gusts in the 20-25 mph range for most. However the pattern is more complex aloft, with a potent closed low over northern PA embedded within a broader cyclonic mid level flow. This is associated with pool of colder air that will be working its way into Southern New England later tonight and especially into Monday. So for tonight, the robust closed low over northern PA is expected to move into the southern coastal waters through the late-evening hours. As this feature moves eastward, expect an increase/fill-back- in of cloud cover towards a mostly cloudy look. In addition there looks to be a pretty concentrated area of convective showers that mainly projects to affect the southern waters by sundown thru late evening, but could extend as far north as the Hartford-Providence- southeastern MA area. Because of the cold air aloft, steep low-level lapse rates could bring some convective enhancement with a narrow ribbon of 50-100 J/kg of MUCAPE in the NAM guidance; that may including the potential for graupel or perhaps a flash or two of lightning. Day Cloud Phase RGB imagery over PA was indicating some mixed phase glaciation to the current field of convective clouds, which could lend credence to this potential. Higher-res convective- permitting solutions really do blossom this region of heavier showers during the 22-04z timeframe, though most of it is over the southern coastal waters. Otherwise, dry weather is expected elsewhere through midnight. After midnight, the potent upper low will have pulled eastward well east of Nantucket, with broader cyclonic flow then developing over SNE. It is less focused and poorly agreed upon, but there's some low- chance indication of rain or snow showers/flurries that may develop after midnight into the predawn hrs in central and eastern MA and into northern RI; I wouldn't bank of this area of rain or snow showers adding up to much at all. The bigger story though will be the increase in NW wind speeds/gusts, and while the stronger gusts take place on Monday (see below), should see wind gusts of 25-40 mph by daybreak. Despite the colder air coming in, still have a fair amt of cloud cover and increasing winds which will help keep air temps from falling too far down. Lows tonight to range between the mid/upper 20s in the interior hills, with readings in the lower to middle 30s for the valleys and coastal plain. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... 430 PM Update: Monday to Monday Night: Key Points: * Very Gusty to Strong NW Winds Expected, Peaking Monday Late Morning to Early Monday Evening. * Wind Advisories expanded eastward into eastern MA and RI. Pretty strong NW gradient sets up on Monday between a 980 mb low over Atlantic Canada and a 1028 mb high pressure over the OH/TN Valleys. In addition, Monday features a strong shot of cold advection which combined with daytime heating should promote pretty deep mixing, potentially as high as 850 mb. NW wind fields from 950 to 850 mb, which were already increasing early Monday, stand to increase further with GFS winds at 850 mb increasing to 55-60 kt. We expect a period of very gusty to strong NW winds Monday into Monday evening, especially as cloud cover decreases. We expect the strongest gusts to take place in and around the interior higher terrain (Berkshires, northern Worcester and Tolland Hills), with the highest gusts up to 55 mph over the Berkshires. After coordination with NWS New York and NWS Portland/Gray, we did expand the existing Wind Advisory further eastward to include the entirety of Southern New England; however as one moves into the Boston-Providence I-95 corridor, the low-level jet isn't as strong and gusts probably reach into the borderline Advisory level (45-50 mph). Otherwise, we are expecting a dry but windy Monday, conditions which continue into Monday evening. While there may still be gusts into the 45-50 mph range after midnight in the Berkshires, we should see gradually decreasing gust speeds as the low level jet slackens and mixing becomes slightly less deep. Outside of the Berkshires, after midnight, speeds should fall into the 30-40 mph gust range. Highs on Monday range between the mid 30s to lower-mid 40s, though it will feel chilly with the NW gusts. Lows in the mid 20s to around freezing, but it will feel like the upper teens to the upper 20s. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Key Points... * Dry and mild Tue-Thu with temps into 60s Thu * Pattern turns unsettled Fri through the weekend Overall a quiet stretch of weather Tue through Thu with increasingly mild temps. Starts out blustery Tue then winds diminish in the afternoon as weak ridging builds in from the west. Temps in the 50s Tue eventually warming into the 60s Thu as warm sector airmass sneaks in ahead of low pres to the west. Still some uncertainty with where the boundary sets up which could impact temps on Thu if it ends up to the south. Low risk a few showers could spill into northern MA late in the day Thu but more than likely it remains dry. Active northern stream develops Friday through Sunday as a series of shortwaves rotate through the flow. Lots of uncertainty with timing and amplitude of individual waves which will impact temps and sensible weather and expected timing. Right now we have chance showers for the entire Fri-Sun period but it won't be raining all the time. Friday's weather and temps will be dependent on track of low pres which is very much uncertain at this time. A track to the north would lead to 60s again with mostly dry weather but a south track would result in 40s and rain. GEFS and ECMWF ensembles indicate 60s are an outlier solution closer to 90th percentile of the guidance so it will probably trend cooler on Fri. We may get a temporary break between systems on Sat before next system arrives Sunday. But again, timing is very much uncertain. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z TAF Update: Tonight: High confidence in trends, but moderate on timing. Increasing/filling cloud cover to BKN/OVC mainly VFR levels. Passing showers 00-03z mainly for HFD-PVD-MVY-ACK south. A brief period of lighter rain showers or snow showers/flurries 06-10z possible but still uncertain on coverage. W winds around 10-15 kt with gusts in the mid 20s kt range, then becoming NW after midnight with a marked increase in gusts to around 25-30 kt by daybreak. Monday and Monday Night: High confidence. Mainly VFR. NW gusts increase to 35-45 kt, on the stronger end of that range over the higher terrain. Gusts decrease a bit to around 25-35 kt. KBOS TAF...High confidence in TAF. VFR. There is an outside chance at light rain or snow showers/flurries 05-10z but not expected to produce any impact. W gusts to around 25 kt this aftn and tonight. A more marked increase in W/WNW gusts pre- dawn Mon into Mon aftn, with gusts 35-45kt. KBDL TAF...High confidence. BKN MVFR-VFR bases tonight, trending VFR bases on Monday. Continued W/WNW winds around 10-12 kt with gusts 20-25 rest of today into early tonight. A more marked increase in W/WNW gusts pre-dawn Mon into Mon aftn, with gusts 30-40 kt. Outlook /Tuesday through Friday/... Tuesday: VFR. Windy with gusts up to 35 kt. Tuesday Night: VFR. Breezy. Wednesday through Thursday: VFR. Thursday Night: VFR. Breezy. Slight chance SHRA. Friday: VFR. Breezy. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 430 PM Update: Made several changes to existing marine headlines. Seas on most waters are already into the Small Craft Advisory range, but we expect northwest winds to increase significantly overnight and into Monday night into the Gale force range. For ease of messaging, we cancelled the existing small craft advisory and Gale Watches, while upgrading to Gale Warnings. Although these start immediately, we expect NW gusts to be steadily increasing, and reach into the Gale range after midnight into Monday morning, then remain at solid Gale criteria gusts (35 to 45 kt) for much of Monday evening. We do also want to message a period of heavy convective showers for tonight til midnight over the southern waters. This occurs preceding the marked increase in NW gusts. Graupel and perhaps a rogue lightning strike are possible before shifting offshore. Outlook /Tuesday through Friday/... Tuesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Wednesday through Thursday: Winds less than 25 kt. Thursday Night: Winds less than 25 kt. Slight chance of rain showers. Friday: Winds less than 25 kt. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Wind Advisory from 8 AM to noon EDT Monday for CTZ002>004. MA...Wind Advisory from 8 AM to noon EDT Monday for MAZ003-004- 010>012-026. Wind Advisory from 8 AM Monday to 8 AM EDT Tuesday for MAZ002- 008-009. Wind Advisory from 8 AM Monday to 1 AM EDT Tuesday for MAZ005>007-013>024. RI...Wind Advisory from 8 AM Monday to 1 AM EDT Tuesday for RIZ001>008. MARINE...Gale Warning until 2 AM EDT Tuesday for ANZ230-233>237. Gale Warning until 11 AM EDT Tuesday for ANZ231-232-250-251- 254>256. && $$ SYNOPSIS...KJC/Loconto NEAR TERM...Loconto/KP SHORT TERM...Loconto LONG TERM...KJC AVIATION...KJC/Loconto/KP MARINE...KJC/Loconto