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 linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
General Weather Summary:
Reminder: The podcast and written discussion are now being posted separately, for those of you who subscribe to either or both of the feeds to easily decipher between podcasts, issued relatively early in the morning, and the written discussion, which comes around late-morning most days.
Keep in mind that with respect to ice jams, you can follow river levels in these areas on your own through this National Weather Service Link.
It's an amazing setup when the morning immediately preceding a storm still features a rising barometer. A barometer, afterall, is the meteorology world's tool to measure atmospheric pressure - in fair weather, air is usually sinking and pressure is rising, while in stormy weather, air is rising and atmospheric pressure is low. So, with a storm approaching, weather enthusiasts would expect to find falling pressure, not rising. But the cold air moving in is dense, and is offsetting the normal change in barometric pressure, but rest assured, the pressure will fall rapidly through the afternoon and evening as our powerhouse storm moves closer.
Most of New England begain the day with a cold northeast wind draining a chunk of winter air southward during a dry break in the action. The lull was well timed for morning travelers, and marked the space between one wave of low pressure departing, while another grows legs through the Southeastern United States, heading for the Mid-Atlantic coastline. This wasn't the case for all areas, though, with light snow through the pre-dawn hours along the South Coast, and moving northward, en route to the remainder of New England by later Friday.
To give you a sense of how dynamic the upcoming system is, consider where each piece of the storm is coming from: cold air from Eastern Canada (the coldest air this side of the Northern Hemisphere) now spilling into New England, tropical air and moisture from the Gulf of Mexico surging up the Eastern Seaboard with an energetic disturbance moving north from the Gulf of Mexico coast, where it's been producing severe weather and heavy rain for most of the week, and additional energy feeding in Friday morning from the Midwest. All of these components bring a different amount of moisture, energy, and differing airmass origins to the table, and the recipe is one for a major storm to develop as the disturbances "phase," or merge.
As snow continues to race northward through the day Friday, follow it through the radar links at right on my homepage. Steady light snow will be falling along the Massachusetts Turnpike by noon, with light snow and flurries all the way into Southern New Hampshire and heavy snow from Hartford to Providence to Cape Cod points south. Between 2 PM and 5 PM, this heavy snow will march steadily northward, all the way to Concord and Manchester, NH, creating an absolutely horrendous evening commute for the entire Southern half of New England. It's rare for me to advise folks simply not to travel, but late this afternoon into this evening is one of those times where widespread treacherous conditions are anticipated in one to two inch per hour snows during the late afternoon and early evening Friday.
Remember, though, that this storm will be carrying a formidable
chunk of tropical moisture with it, which means not only lots of juice
to wring out as precipitation, but also warm air at several levels of
the atmosphere. Aloft, about 10,000 feet above our heads, warm air
will begin to move over New England, and this will allow sleet to mix
in with snow. Not only does this mean accumulations of snow will be
cut down significantly where a mix occurs, but it also marks the
beginning of a transition to a warmer second half of the storm for
especially eastern New England. At this point, I'd expect to see a
sleet mix beginning at somewhere around 2-4 PM at the South Coast of
Connecticut and Cape Cod (most of the storm will be sleet on Nantucket after brief snow), around 6 PM Plymouth, MA to Hartford, CT, around 8 PM Hingham, MA, to Springfield, MA, and by midnight as far north as Southern Vermont, Central New Hampshire and Southern/Donweast Maine. In the far North Country - from Montpelier to Berlin to the Maine Mountains points north - I expect little in
the way of a mix with or change to sleet, with a mostly snow event producing impressive snow
totals around two feet in some locales. In the areas that do see a
mix, while this will cut down on snowfall totals, the snow should fall
so heavily prior to the changeover - thanks to the dramatic clash of
warm and cold air, and the available moisture - that we'll be looking
at amounts between half a foot and a foot in much of Massachusetts,
with amounts dropping the farther south one is. It's important to realize that even in those locations that change from snow, a messy storm will continue Friday night with prolonged sleet from interior Southern New Hampshire through the White Mountains and through interior Maine - ensuring terrible road conditions Friday night will continue into Saturday morning. The only area I foresee a bit of freezing rain is for a few hours Friday late evening and night in the Pioneer Valley, though at this point I'm hopeful amounts will be below damaging ice accumulation criteria. Where precipitation does turn to rain, a couple of inches of rain will fall, and the result will be flooding of streets, streams, poor drainage areas and - by the time this all runs into rivers on Saturday - small rivers, as well. Below are maps for precipitation type and snowfall amount forecast:
Meanwhile, the strengthening storm center will be poised to move
across Southeastern Massachusetts on Saturday morning, bringing some
fierce winds with it, as winds will kick out of the northeast at 50 mph
gusts all along the eastern coastline of Southern New England Friday
evening and night, churning seas 12-18 feet! These winds will snake up
the New England coastline Friday night into Saturday, shifting to blow
from the northeast and then from the southeast along and east of the
storm track from Southeastern MA to the Midcoast of Maine. These winds
will penetrate far enough inland that blizzard conditions are possible
with heavy snow across Northern New England Friday night into Saturday
morning, from eastern Vermont through the White Mountains and into the
mountains of Maine!
Saturday will dawn with rain in Eastern
and Coastal Maine, sleet for Central Maine and Central New Hampshire, and snow in far Northwestern Maine and Northern
New Hampshire, while the remainder of Eastern New England sees mostly
rain, falling heavily through the first part of St. Paddy's Day before
diminishing. Winds will shift to blow from the northwest - a drier
direction - during the afternoon, which will allow some late-day
sunshine in all but the State of Maine where our winter mess continues, but also will mean cool and windy conditions set in. With our
storm center winding up northeast of New England, we'll stay cool and
windy on Sunday, though much drier with bubbling cumulus clouds and
scattered mountain and hilly terrain snow showers.
By early next week, expect sunshine early Monday, then a chance of light snow late as milder air attempts to make a return to New England, but is cut off at the pass with light snow and perhaps a mix with raindrops in some of Southern New England overnight Monday night, but light accumulations are probable for many areas into Tuesday morning.
Technical Discussion: Issued last evening. See below.
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, March 15 at 5:45 PM
A late discussion today thanks to burning the candle at both ends but I figure better late than not at all, and I'll try to make this applicable for those of you reading it on Friday, as well, since I'm sure Friday will prove plenty busy.
Cold front made steady southward progress southward though the area of snow behind the front shrunk rapidly over Upstate NY. This was well forecasted by the guidance - especially the NMM - as moisture feed outran the cold air and the slow pace of cold advection simply couldn't keep up. This wasn't a surprising way for it all to play out considering the lack of broad height falls today - falling, but only gradually - not supporting a real thrust of cold, and the sfc anticyclone not yet strong enough and close enough to do the job on its own. Both of those factors remedy themselves Thu Ngt, however, as anticyclone will be on the move and expanding while heights will fall in response to shortwaves ejecting E from main trof to our west. The southward sag of moisture does slow later Thu Ngt and this will enable cold air to catch up, resulting in areas of snow across Srn NewEng Thu Ngt. Oddly enuf, the best intersection of moisture and cold appears to set up over far SE areas, where the tropical moisture feed never really breaks entirely, but cold air overtakes. This will result in a general coating to two inches for Srn NewEng, with most 1-2" amounts found on grassy surfaces and cartops as a wet, sloppy snow thanks to warm ground and boundary layer. It's this warm ground that will make any snow a non-event on Srn NewEng roadways, as most will melt on contact.
As cold air becomes better established and break in parade of shortwaves moves into most of NewEng on Fri morning, I expect a lull in the action asthe atmosphere reloads with more tropical moisture poised to move north, but impressive low level cold capitalizing on the opportunity to advance south and become quite well established. Helping its cause is the northeast wind that sets up Thu Ngt on the south side of the Canadian anticyclone progged to exceed 1040 mb in strength, and the strengthening of this wind due to gradient and eventually ageostrophic flow that will make the cold impenetrable for a time. In fact, don't see how we're going to get daytime temps much out of the 20s for most spots with a pegged NE wind and cold/dry advection continuing in the lower levels. This also sets up a great coastal front from Merrimack Valley to 495 belt of Ern MA first part of Fri Ngt that really cranks snow before warm air aloft gets the best of the entire situation and results in sleet changeover. Tried to nail down timing of change to sleet in general wx summary above - never easy but basically what I did to determine was use GFS thermal fields adjusted for consensus track of model guidance, which would be over SE MA. Before this changeover even occurs, though, we're talking about a period of snow Fri afternoon and eve that will come with intense positive Theta-E advection across a tight baroclinic zone and tightly packed isodrosotherms at 850 mb (dewpoint) which will bring very impressive isentropic lift capable of producing 1"-2" per hour snows thru the afternoon and evening, likely as S to N propagating bands until coastal front begins to focus more banding on the cold side of the boundary. Later Fri Ngt, can't really stop the warmth from penetrating far inland given storm track and good phasing that implies lots of warmth to be entrained into the system. Interesting to see guidance agreeing on slower passage of low and more intense precip on immediate west side of track on Saturday that will keep cold driving rain in Ern NewEng but also has the potential to drop significant sleet/freezing rain on interior areas...tho confidence too low on this to hit it hard at this time. This is something I will re-evaluate on Friday morning before going up with forecast. In the meantime, snowfall amount forecast actually was fairly straight-forward based on changeover times mentioned in general wx summary and ratios that ranged from 5 or 6 to 1 at the south coast, to 12 to 1 Boston to 14 to 1 interior to 17 to 1 North Country. Given NE llvl flow, not expecting the kind of downsloping snow shadow we saw north and northwest of the Presidentials last time, so this should be a good dumping for snowmobile country, too. Amounts will be limited in ME where warm air penetrates in from the Gulf of ME, and extended sleet is possible away from the coast given cold air well in place but warm air sure to spill in aloft - therefore I've gone with lower snowfall totals but this should be made up for by sleet accumulation.
Thereafter, forecast is fairly straight-forward with shot of wind and cold followed by warm advection clouds and light snow later Monday after early sun.
Enjoy the storm! Should be a hum-dinger!
Matt
Monday's Discussion
4:50 PM: Though the short range is fairly straight-forward, there are a few tricky points to it, focused especially upon cloud cover Tue that will limit strength of insolation, but question is by how much. H7 to H5 moisture is solid across Srn NewEng late in the day but this comes after decent insolation that will promote mixing to about 900 mb, and this supports highs near 60 in many areas. Exceptions will be found at all south coast facing locales and penetrating quite a way inland where ocean cools the airmass thanks to S flow. In circumstances like this, cooler influence usually makes it all the way to HFD/PVD/PYM from the south, tho certainly not as pronounced as closer to the coast. SE sfc flow expected in ME and that will also keep things cool for areas within 30-40 miles of the coast.
The end of the week brings a delicate but critical interaction between Canadian cold that builds south with strengthening anticyclone sliding E across Ontario and into Quebec, and warm SW flow. At this point, I still expect front to be over Nrn NewEng to start Wed, then begin to press S as anticyclone moves E. Ahead of the front, tho, good dry slot evident thru most lvls and with continuous and strengthening SW flow temps can really soar with Srn NewEng possibly achieving first 70 of the season? Setup looks favorable. Farther N, Central NewEng shud see convection firing with front on N periphery of dry slot, and periodic showers/rain in Nrn NewEng, then srn stream shortwave comes into Srn NewEng late or at night Wed ngt. The situation becomes more dynamic on Thu as shortwave parade continues with another wave of low pressure passing s of NewEng while CAA continues from the N and this raises potential for snow in Nrn NewEng, esp Thu afternoon as cold air continues to become better established.
Main show comes Fri with strengthening storm center ahead of trof, moving NE and across NewEng. The ingredients are there for a good snow in Nrn NewEng if the baroclinic zone can be tight enuf, tho Central and Srn NewEng look vulnerable to the surge of warmth and moisture ahead of the cyclone that should ensure mostly rain in Srn NewEng. GFS sfc low track certainly raises eyebrows passing S of NewEng, tho it does appear even in that cold solution that there's enuf warm air envelope to penetrate north across Srn half of NewEng. Will keep a close eye on this.
Matt
