Tricky Weather Pattern Leads New England into the Weekend After Quiet "Hump Day" Wednesday
Isolated Wind Damage Friday...Plowable Snow for Many on Saturday...Blustery and Cold Sunday in Store

Emerging Snow Squalls to Pose Travel Hazards Thursday...Plowable Snow For Some Saturday Night

Welcome to the weather blog - a regular Monday through Friday discussion of the weather!  While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants.  I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible.  You'll find a quick weather synopsis and a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. My email is [email protected].  This blog is for you, so I hope you enjoy it!  -Matt Noyes

For latest radar imagery, to check for watches and warnings, and for links to sites in the world of weather, feel free to click over to my website: www.mattnoyes.net

Matt's Quick Weather Synopsis:  A strong upper level disturbance will cross New England today, and will push a weak disturbance, called a "trough", through at ground level.  This trough, in conjunction with the approaching disturbance, will continue to spark showers of snow and rain across New England today, under mostly cloudy skies.  With high temperatures approaching 40 degrees in Southern New England, and in the middle 30's north, some rain showers will certainly mix in, but the concern is that temperatures will fall just enough around the time of evening commute in Southern New England - and will be cold enough through the day across hilly terrain and VT, NH and ME - that roads may become slippery and covered with snow and ice in some communities.  A key to understanding today's forecast is the realization that *localized bands* of heavier precipitation will cause the problems - not all communities will be hit hard - but you can monitor where these areas of rain and snow are today via radar imagery on my main page, www.mattnoyes.net.  Overnight, snow and rain showers will end between 9 PM (most areas) and midnight (eastern ME), but with partial clearing and light winds, black ice will become a problem in many communities.  Another disturbance raises chances for snow squalls just in time for the morning commute on Friday, then a blustery day with scattered snow showers between breaks of sunshine.  Saturday dawns with limited sunshine, but clouds thicken and snow is likely by late Saturday afternoon, lasting through Saturday night.  This won't be a blockbuster storm, but a few inches and therefore a plowable snow does appear likely.  Behind this storm, bitter winds usher in very cold air for both Sunday and Monday, with a blend of sun and clouds interspersed with occasional flurries.  Take it easy!  -Matt

General Weather Summary:  The overall weather pattern has been consistent this week - keeping the northern (polar) and southern (subtropical) jet streams separate - thereby keeping the significant cold and energy separate from southern moisture.  These streams have been phasing to our east, across the Western Atlantic, and that's where larger storm centers have been taking shape.  Thursday, the merger of northern energy and southern moisture will occur closer to New England, at the same time a strong northern stream disturbance drops across the six-state region. 

This combination of factors will serve to produce plenty of clouds for all areas, with morning mountain snow squalls expanding in areal coverage to envelope most of New England by Thursday afternoon.  With a light wind but limited daytime heating through the clouds, temperatures will still be able to climb to around 40 degrees in Southern New England and this will be warm enough for a mix of rain and snow showers, or even just rain in some locales as precipitation blossoms later Thursday.  With cold air aloft, however, hilly terrain across Southern New England will likely find mainly snow showers, and as the afternoon progresses, this cold air will allow for a change to snow squalls for most valleys and the coastal plain, as well.  Road crews will need to be on standby across Southern New England today as a result, because while bursts of snow will be found in *localized* heavy bands, communities under these bands of snow late this afternoon and this evening will see a quick ice/snow coating on roadways as temperatures fall to near freezing.  Farther north in New England, most of Vermont, New Hampshire and Maine will be cold enough for mostly snow, and therefore a few inches of accumulation are possible in only a few hours in some of these heavier squalls Thursday afternoon and evening.  By 9 or 10 PM Thursday evening, after what will obviously be a difficult commute for some areas, snow squalls will diminish and skies will partially clear - though this will be delayed until around midnight in Central and Eastern Maine as the disturbance sparking these squalls moves east across New England.  For more on how this disturbance is coming together...an explanation of the "Norlun Trough" that will set up across New England today...please refer to yesterday's summary (found in the archives at left, and found below today's post).

Friday will dawn wtih widespread black ice after clearing skies allow temperatures to drop into the 20s through most of New England by Friday morning, and leftover moisture on New England roadways freezes.  On top of this black ice, it appears as though at least some communities will find a fresh coating of snow coming through Friday morning - right around the time of the morning drive - as yet another disturbance moves through and sparks a new round of snow showers and squalls for some communities of both Northern and Southern New England.  For a few unlucky souls, we certainly may see back-to-back aggravating commutes.  The passage of this Friday morning disturbance marks the leading edge to a new installment of cold air, and blustery conditions will prevail with emerging breaks of sunshine amidst leftover flurries for most of us, and lingering heavier squalls in the Northern Mountains.

This weekend, with multiple energetic disturbances still dropping in from the north, and moisture beginning to finally ride northward to meet the energy, we will be very close to phasing the streams over or near New England.  It continues to appear as though later Saturday, energy slides through quickly, passing through Saturday night and then ushering in cold air as the storm strengthens once passing to our east.  The end result should be as follows:  Saturday morning sunshine fades behind thickening clouds in advance of the approaching storm.  Snow will develop later Saturday afternoon as moisture and warmth aloft is ushered northward in the south winds ahead of this counter-clockwise circulation, and snow will become heavier Saturday night.  As the storm circulation moves over New England, a big part of the forecast hinges on how strong the storm center becomes.  If it strengthens quickly enough - and I think it will - an east wind will develop through the lower few thousand feet of the atmosphere and this will mean we tap moisture from the Atlantic Ocean.  My expectation is for relatively light snow late Saturday afternoon to find embedded bursts of heavier snow Saturday evening, then an overnight gasp of steady snow as this easterly wind develops at the very same time the storm gets ready to pull away.  This means a short-duration event that will be winding down Sunday morning, with a few inches that falls in most of at least Central and Southern New England (Northern New England likely to get into some of this, too) but areas that see this ocean influence may come closer to 4"-6" of snow.  It's still early to pinpoint whether those higher amounts fall - but likely somewhere between Northeast MA and the Central Coast of ME - certainly in eastern New England.

Behind this storm, cold and blustery conditions come pouring in on Sunday with scattered snow showers between sun and clouds, and a reinforcing shot of cold air with possible snow squalls swings through on Monday.  Don't be expecting the cold air to go very far!  Indications are we'll remain chilly through next week.

Have a wonderful Thursday.

Matt

Matt's Technical Meteorological Discussion:  Updated Thursday, February 23 at 2:45 PM

Today's convective activity is firing nicely as of this writing and visibility to 1/2 mile in snow has already been reported under numerous locales in the northern band and also in HFD under the southern activity.  Details on today's event were laid out here yesterday and I won't bother to rehash - suffice to say the bridging of convection between northern energy/front and southern moist inflow has begun and will continue, bringing heavy squalls of rain and snow to Southern NewEng, and of snow to areas N of the MA State line and in the hills of Southern NewEng as well.  Of course, the challenges won't stop there - while surface wet bulb temps have risen above zero in most of Southern NewEng, still well below zero just off ground level and this will allow snow to make it to ground level.  Dynamic cooling is likely to bring some of this colder and drier air toward the surface and heavier convective bursts will feature changeover to snow even in the valleys and coastal plain during the afternoon.  Approaching sunset, the combo of this factor and waning diurnal heating will help road surfaces to cool enough for snow and ice to accumulate in some areas, which is the reason for concern on roadways of both northern and southern NewEng Thu afternoon and evening.  Snowwfall rates of 2" per hour will be found in the White Mountains, Mountains of Maine, and perhaps in the Berkshires.  Anywhere from Berkshires to hilly terrain of MA to MA/NH border points north will be susceptible to a few inches of snow in just a few hours in the more intense convective bands and bursts.

Overnight, skies will clear in area of subsidence and wedge of dry air between shortwaves as next vorticity maximum shoots east from current position over MI and across the Great Lakes into NewEng by morning.  In the interim, widespread black ice will result thanks to light winds, high ambient RH in the boundary layer, and widespread precip of various forms during the day leaving plenty of moisture on the roadways.  Next shortwave will be driving a cold front with it as it charges thru Fri AM, and the trof moving thru NewEng will also whip southward, providing multiple lines of convergence for what will likely be another round of snow squalls for Fri AM commute.  Once this shortwave whips thru, expect strong subsidence combined with downslope flow to bring the sun out most areas, tho upslope areas will capitalize on cold air aloft and associated instability to keep squalls going thru most of the day.

Two trends for Sat system: faster and farther N.  The farther north trend is the one that should be a bit concerning for snow lovers across Southern NewEng - I'd say we're still guaranteed to get the snow in here, but it's going to mean any easterly flow on the north side of the low level circulation is mostly going to be focused along the Maine coastline and into Northern New England.  But while this news may bring some frowns to Southern New England snow lovers, it brings smiles to the faces of Northerners, who are undoubtedly leaning forward into your monitors right now, waiting for more info!  Here's the deal:  As the northern stream shortwave races east on Saturday, the reason I'm so confident we'll see a shield of snow moving into New England from the south is owing to the intense speed convergence and isentropic lift associated with strong warm and moist advection at 850 mb ahead of the circulation.  With a faster eastward progression of the low, this convergence and warm/moist advection spreads into far SW NewEng as soon as Sat morning, then overspreads the remainder of NewEng during the day Sat, and snow is certain to develop with this southerly thrust of air.  The downside to this is that while it can snow exceptionally hard in situations like these, it will also even further shorten the duration of an already short-lived event.  The result is likely to be a burst of about 6 hours of steady and at times heavy snow for Southern NewEng on Saturday, then the areas to see extended snowfall will be found where easterly or southeasterly flow can set up on the north side of especially the 850 mb circulation.  In fact, given the baroclinicity, the low level jet max, and the available ocean moisture, I'm a big believer that this event will be strongly driven by what unfolds in the low levels, and this means a burst of warm advection snow to start for everyone, then lingering snow where easterly flow establishes.  Ratios will likely be somewhere around 16:1 as an early rough estimate, but I'll dig into this a bit more tomorrow.

Still looks like real cold stuff in store for Sun and reinforcing arctic front with wave possible Monday.  NAO stays negative and cold air looks to stay locked in with trough over Northeastern US and Greenland block developing.  While this keeps in the cold, it still leaves us on the fence for storms, favoring a continued storm maximization to our east, but close enough that we'll be watching each strong shortwave like a hawk.

Enjoy your day.

Matt