After Delightful Monday, Showers, Surf and Rip Currents Arrive

New England’s weather in the days ahead remains largely removed from the major hurricanes in the tropics – but not entirely: our beaches will see large swell and rip currents building Tuesday onward, first on the north side of Hurricane Franklin as it passes between Bermuda and the East Coast, then from Idalia as it crosses northern Florida and re-emerges off the Carolina coast, moving south of New England at week’s end.  In the interim, New England enjoys a delightful Monday of sunshine and clouds with moderate humidity and a light southeast wind keeping the coast in the lower to middle 70s while inland communities near 80 by late day and a few isolated showers develop late in the day through the deep interior.  On the water, it’s one last day of quiet seas ahead of the building swell.  Overnight Monday night, clouds fill in and by early Tuesday, first showers will arrive to the South Coast.  Although the moisture generating these showers is arriving from the south, the energy that will ramp the intensity of the showers up approaches from the west, from Southern Canada, and showers will gradually develop north from the South Coast and west from the NY state line Tuesday afternoon, leading to passing showers and increased humidity Tuesday evening.  Overnight Tuesday night into Wednesday, expect a shot of rain and embedded thunder as the incoming disturbance crests over New England, dragging a cold front at the surface that will, by the end of Wednesday, shift rain off to the east and start a flow of less humid air.  In fact, the air Thursday onward looks delightful for New England, with sunshine and temperatures in the 70s to start and 80s by the end of the Labor Day weekend, with the chance of scattered afternoon thunder not returning to the forecast until Labor Day afternoon by the way it looks now.  That said, it’s quite possible the rip currents at our beaches will last into Saturday given the storms passing to our south, but likely subside during the day Saturday and especially Sunday into Labor Day, provided no new storms develop over the ocean.

Deep Heat To Remain West of New England

LKS_NEXT_WEEK_JET_ACTIVE (14)Amazingly, as a dome of exceptional heat becomes the nation’s main weather headline for the next few days, New England will remain entirely removed from hot temperatures.  The reason is the jet stream – the fast river of air, flowing at high altitudes, that steers storms and separates cool air to the north from hot to the south – taking a southern dip, called a “trough,” over the Northeast.  This allows cool air from Canada to pour south into New England, and cuts the heat off at the pass, keeping dangerous heat index values up to 115 degrees over the nation’s midsection and as far north as the Canada border, but west of New England.  Instead, Wednesday brings another day of low humidity and tons of sunshine, with a very high ultraviolet index about the only culprit to be aware of when it comes to sunburns – otherwise, with fresh, clean air and comfortable temperatures in a light onshore breeze, the weather remains very easy going.  The relaxed weather includes for beachgoers and mariners, with a one to two foot sea relaxing as the wind quiets even more late in the day.  Clear sky and dry air will contribute to another cool night Wednesday night with widespread lows in the 50s and some pockets of 40s in sheltered valleys.  Thursday will dawn with sunshine ahead of increasing clouds Thursday afternoon as a ribbon of showers – developing on the battle zone between cool and hot air nudging east through Upstate New York and into Western New England Thursday afternoon and Eastern New England by Thursday evening and night.  Once the showers arrive to New England, they’ll last awhile, with off and on showers and periods of rain expected Friday as noticeably more humid air arrives, concurrent with a jet stream disturbance aloft.  The humid feeling will very likely last into the weekend, with enough moisture in the air for a follow-up disturbance Saturday to touch off scattered showers and thunder at times, starting as soon as morning in Northern New England and mostly in the afternoon for the southern half of New England.  Even Sunday, as humidity lowers and disturbances aloft ease, a few showers still may pop up, particularly during the afternoon, though each day after Friday features noticeable improvement, leading into a nice start to next week.  The tropics will remain active, with now-Tropical Storm Franklin expected to intensify to a hurricane south of Bermuda by early next week, but as long as we continue seeing northern jet stream disturbances and surface cold fronts here in New England, the threat from tropical systems remains suppressed over the next several days.  Instead, we see the potential for some midweek showers next week then, perhaps a bit ironically, the potential for warmth to return as we start the new month of September.

As Cool & Dry Air Arrives, Some To Hit 40s Tuesday Overnight

LKS_FCST_LOWS_TONIGHT_NEWENG (22)New, delightful air has arrived to New England!  A Monday night cold frontal passage shifted the wind to blow from the north, opening the door to a chunk of cooler, drier Canadian air thrust southward in the clockwise flow of air around a dome of high pressure, or fair weather, building southeast through Ontario.  The north and northeast wind will remain fresh at 10-20 mph Monday afternoon, creating a two to four foot chop on the ocean waters.  Meanwhile, while our exclusive, First Alert 10-day forecast averages about 5-6 degrees cooler than normal for the upcoming stretch, a massive dome of heat is developing in the nation’s midsection, with Excessive Heat Warnings owing to dangerous heat index values up to 115 degrees from Texas and Louisiana all the way north to Minnesota and Wisconsin!  Not only is our flow of cool air from Canada protecting New England from that heat, but also from an increasingly busy Tropical Atlantic – at least for now.  The biggest concern for New England during this annual peak in tropical activity is if a southerly wind flow develops through the atmosphere, opening the door for storms to move north from the Atlantic, but that doesn’t appear to be the setup for us over the next 10 days, thanks to recurring cold fronts that are the product of northern jet stream disturbances.  So, instead, New England will see showers when each of these jet stream disturbances passes, with our next round of showers arriving to the Northern and Western mountains Thursday afternoon, then to the remainder of New England Thursday night, lasting as periodic rain with embedded thunder into Friday, infused with a piece of moisture that was once the Western U.S. Hurricane Hilary.  Depending on the intensity and timing of the rain, a First Alert may be needed for impact from the rain Friday – there’s also the chance thunderstorms could grow strong in Southern New England as humid air makes a brief comeback on an increasing southerly wind.  Even Saturday enough moisture will linger in the air – evident by a continued humid feeling – for passing disturbances aloft to touch off scattered showers or thunder, especially during the afternoon.  The chance of showers drops Sunday though isn’t zero – it’s still possible a shower sneaks back into the forecast, though that isn’t our expectation at this point – then the chance of showers looks low next week, even as what is likely to be Hurricane Franklin passes near or over Bermuda, trucking north but likely to turn northeast while still safely to our southeast.

Sharp Cold Front to Reset New England Air For Midweek

LKS_SATRAD_ANALYSIS (3)Summer warmth and humidity starts the week, but Monday is expected to be the warmest day of our First Alert 10-day forecast, with a sharp cold front set to move in from Canada Monday afternoon and evening, delivering some cooler, fresh air for the midweek.  For now, an increasing southwest, then west wind is transporting some haze, some wildfire smoke, and steadily increasing humidity to New England Monday with highs into the 80s, even under increasing and thickening clouds.  The clouds will make it a tough day for sunbathing, but it’s not a bad beach day with a nearly calm sea and water temperatures in the 60s and 70s.  Scattered showers and thunder will develop during the middle and late afternoon ahead of the approaching cold front, but aren’t expected to reach severe or damaging strength for most.  That said, any amount of cloud-to-ground lightning can pose a danger to those outside, so remember the phrase, “When thunder roars, go indoors” – if you can hear thunder, lightning is close enough to be a threat.  Showers will end gradually from northwest to southeast, clearing VT and NH by late day, Northern MA by dinner and taking deeper into the evening farther south, with the Cape seeing a few showers at times all the way into predawn Tuesday.  That said, Tuesday brings fresh, delightful air for all of New England with plenty of sunshine and comfortable highs in the 70s, with a repeat performance expected Wednesday. As a dome of heat builds across the Central and Western United States later this week, New England will lay east of that hot air dome, instead seeing multiple jet stream disturbances dropping across the Northeast for returning rounds of showers from later Thursday through Friday and into Saturday.  Although precise timing becomes more difficult to pin down the farther out in time a forecast is, right now the showers look to arrive from west to east midday to late day Thursday, respectively, and remain off and on in New England at least through Saturday morning, though it’s possible at least some showers linger longer than that.  Of course, a steady feed of northern jet stream disturbances means New England stays out of the deeper warmth and humidity, but also tends to protect our region from an increasingly active Tropical Atlantic.  While Hilary has been the headline maker in California, multiple numbered and named disturbances in the Atlantic have developed, with Tropical Storm Franklin set to cross the Dominican Republic Thursday, Gert and Emily out at sea and a new, developing system in the Gulf expected to move into Texas Tuesday into Wednesday.  For all that said, as long as Canadian cold fronts keep diving across New England, that provides multiple opportunities to sweep the tropical systems and their moisture out to sea before ever making it this far north.  That said, a pattern like always leaves us on guard, as the brief windows between disturbances often are accompanied by increasing southerly atmospheric wind flow, which can open the door to the tropics – we just don’t see that happening imminently with the current series of tropical systems.

Quick Tuesday Early Afternoon Update: Radar Indicated Tornado Touchdown, Widespread flash flooding, scattered additional storms expected

Have been live with coverage most of the morning and midday but with things quieting at 1:20 PM, here's where we stand:
* Radar indicated tornado touchdown in the Rochester/Acushnet, MA area.
* Widespread flash flood damage and stranded cars across the area
* The most widespread and worst storms have passed
* New scattered storms will develop this afternoon and evening
* Tornado threat is NOT a significant concern with remaining scattered storms
* Widespread severe weather is unlikely, but scattered severe storms can still develop with a few damaging straight-line wind gusts.

Two Unsettled Days Start the Week, About-Face Expected at Midweek

LKS_MATTS_MEMO (92) LKS_MATTS_MEMO (92) LKS_MATTS_MEMO (92)Two unsettled days start the week for New England but will give way to the return of comfortable air and great weather for midweek onward.  Right now, however, New England sits east of a large and powerful storm system over the Great Lakes that is slowly moving east, inducing a strengthening southerly wind over the next couple of days, returning a flow of humid air to New England.  Monday started with relatively cool and dry air, so the incoming warmth and humidity, arriving aloft first, has been colliding with the outgoing cooler air to create areas of showers, pockets of rain and embedded downpours.  Expect these showers to continue moving across New England from southwest to northeast throughout much of the day, heaviest during the midday to afternoon, then breaking into scattered showers Monday evening, but with a decidedly new feeling of humidity.  A muggy night overnight Monday night will see decreasing showers for a time, but a new round of showers and thunder will arrive in the predawn hours Tuesday morning, likely impacting at least part of the morning commute.  Tuesday will be an unsettled day: with muggy air all day and a series of disturbances at the jet stream level, morning showers and thunder won’t be the only round of disturbed weather, with more scattered downpours and thunder likely to erupt over the course of the day.  Both the early morning round and scattered afternoon storms will hold the potential to turn damaging for some communities, plus heavy rain will cause isolated spots of flooding, so our weather team continues a First Alert to keep our viewers alert for the potential of impactful weather.  Tuesday afternoon’s storms will be the result of a passing cold front that will open the door to a steady west-northwest wind Wednesday, ushering in comfortable air with a fair sky and high temperatures in the 80s.  A jet stream disturbance aloft and its attendant cold front at ground level will arrive late Thursday for some scattered showers or a thunderstorm, opening the door to reinforced comfortable summer air for Friday into the start of the weekend.  None of this comfortable air looks to be very cool by nature, so we’re likely to still rise into the 80s most days, with some rebound of humidity Sunday with a chance of late day storms, then another cold front Monday renews the chance of scattered thunder with a similar disturbance every two days or so in the forecast next week in our exclusive First Alert 10-day forecast.

Behind Friday Night cold front, the weekend air will feel great - though there still may be an isolated shower Saturday for some

LKS_FCST_HIGHS_D1_NEWENG (85) LKS_FCST_HIGHS_D1_NEWENG (85) LKS_FCST_HIGHS_D1_NEWENG (85) LKS_FCST_HIGHS_D1_NEWENG (85)Although pleasant air will take over for the weekend, it won't be a sudden shift into the new air with the passage of the cold front Friday night.  In fact, showers will still linger on someplace like Nantucket until dawn, and with a light wind, there will still be a twinge of humidity Saturday morning for much of New England (especially Southern New England).  By midday into afternoon, however, a light northwest breeze will do the trick on mixing down less humid air from aloft.  That said, there will be just enough lingering moisture that a weak afternoon disturbance has a 20% chance of touching off an afternoon shower from puffy, fair weather clouds in Eastern MA, and a 40% chance from Southeastern MA to the Cape.  Nonetheless, most will remember Saturday as a lovely day.  Sunday there's no chance of rain and the air will feel great, though some cirrus clouds (high altitude clouds) will mute the sun at times.

"Old School" meteorology helps on a day like Friday, where computer guidance stumbles

WaterVapor WaterVapor WaterVaporThunderstorms Friday will tend to be clustered during the afternoon, owing to the presence of a few subtle wind shift boundaries that help to focus the storms as a jet stream disturbance tracks overhead.  It's been interesting to see how poorly computer weather guidance has handled this event thus far, stumbling even an hour or two out, but "old school meteorology" does the trick today.  The jet stream level disturbance is evident on water vapor imagery and has already touched off a cluster of storms in Central New York, headed east.  These should continue on their current trajectory, arriving from west to east across New England from noon to 3 PM, respectively.  This morning, early downpours tended to "train," or develop along a line, following one another, as a steady southwest wind in the lowest levels of the atmosphere carries warmer and more humid air north, colliding with cooling air aloft from the north, ahead of an approaching cold front.  The result may be that clusters will tend to do the same thing as they arrive Friday afternoon, causing prolonged downpours for some and that's the concern for some pockets of flash flooding.  The greatest chance of isolated damaging wind gusts in stronger storms will come both this afternoon in VT/NH/ME, then again this evening for more of us as a cold front arrives from the northwest, eventually overturning the air for a pleasant feeling this weekend.

Friday Storms Mark Cold Front To Bring Pleasant Weekend Air

LKS_FIRSTALERT_MAP_BOSDMA (8)Our First Alert continues for Friday, expecting a number of showers, downpours and thunderstorms to develop over the course of the day, particularly during the afternoon to evening.  What’s unusual is the amount of uncertainty lingering, even on this day of the event, as to exactly where and when storms will hit – so our best forecast is to continue expecting scattered showers and downpours to crop up until they expand during the afternoon, converge into pockets of downpours and thunder, raising the potential for localized flash flooding where downpours linger, and a few spots of damaging wind gusts where storms grow strongest.  The culprit – both regarding storm development and uncertainty in the details surrounding it – is the convergence of warmth and humidity arriving on a breezy southwest wind and the destabilization of the atmosphere ahead of a cold front pressing southeast out of Ontario and Quebec.  The cold front won’t press through Southern New England until predawn Saturday, which is why even after the worst of the storms weaken heading into Friday night, at least some showers will continue to float through, still falling on Nantucket at sunrise Saturday, clearing out quickly thereafter.  At the beaches, Friday doesn’t bring much sun and beachgoers will not only have to occasionally duck inside when showers and thunder move through (though very few, if any, showers are expected Friday on Cape Cod, with more breaks of sun), but rip currents will be a possibility through the day.  Although Friday night will still be a bit humid, Saturday may start with a twinge of humidity but that will be swept away for comfortable air and a fair sky for the day, though building puffy, cumulus clouds may yield an isolated shower in the afternoon, particularly in Southeast MA.  Sunday most assuredly will stay dry, regionwide, with comfortable air, though high-altitude clouds will mute the sun through most of the day.  At this point, it looks like all of next week into next weekend will reach the 80s for high temperatures, daily.  The best chance of scattered showers and thunder is Monday night and especially Tuesday, then perhaps again late in the week around Friday in our exclusive, First Alert 10-day forecast.