POTENTIALLY PARALYZING STORM FOR SOME CENTRAL U.S. CITIES TO HEAD INTO NEW ENGLAND ON FRIDAY
AS ONE MESS CLEARS NEW ENGLAND ON A WINDY NOTE THIS WEEKEND, I CONTINUE TO EYE SUNDAY NIGHT/MONDAY STORM POTENTIAL

AFTER MILD THURSDAY, WINTRY MIX TO AFFECT NORTH COUNTRY...HEAVY RAINS AND WIND FARTHER SOUTH

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 [email protected].  This blog is for you, so I hope you enjoy it!  -Matt Noyes

General Weather Summary:

A huge swing in temperature along a sharp cold front in the nation's midsection is separating air producing high temperatures around zero in the Northern Plains from air warming to near 90 in Texas.  Sure enough, this clash of airmasses has created a major storm that will paralyze parts of the Central U.S. before drawing northeast and eventually serving as the impetus for heavy rain, damaging wind, and heavy snow for some of New England by the time Friday night is done.

For now, however, New England weather remains comparitively quiet.  After a slow start in most areas with clouds and some fog Thursday morning, sunshine has continued to break through the cloud deck.  In fact, Thursday's sunny breaks will be far more evenly distributed across New England than Wednesday's were, as most of the dense, cold air has been displaced, lessening the clash of airmasses taking place.  Still, an influx of warm and moist air will provide for plenty of clouds to mix in with the sun, and a few scattered showers will continue to pop up through the day and into the evening.  Nonetheless, an active southwest wind - the result of being sandwiched between the clockwise wind flow of a departing high pressure cell and the counter-clockwise flow of an incoming storm center - will transport enough mild air into New England to bring Southern New England temperatures to over 60 degrees, with 50s spreading across much of the North.

Meanwhile, the strong storm to our west is already evident on the weather map, moving northeast across Oklahoma.  This storm is sandwiched between air that produced a difference in high temperatures of 97 degrees from Northern Plains to Southern Plains on Tuesday, and 87 degrees yesterday.  This tremendous difference in high temperatures was the perfect recipe for a mega-storm to develop, and the storm will continue to travel along this clash of airmasses, making its way through the Ohio Valley and eventually across Northern New England, straddling the battlezone between the mild air across most of New England and the cold air sitting across Quebec.

But on it's trip northeast, this storm will continue to be a powerhouse, and will leave what will be paralyzing impacts from Oklahoma City and Tulsa to St. Louis due to the ferocity of the wraparound snows, and a heavy snow continuing on a stripe northeast across Chicago, Detroit and Toronto, as cold air is drawn south toward the storm center, only to clash with deep tropical warmth and moisture feeding north Thursday (OK), Thursday night (through Detroit) and Friday (Toronto).  Farther south, this storm will make headlines for its severe weather, which should produce multiple tornadoes from Arkansas and Louisiana eastward through the Lower Mississippi River Valley, Tennessee Valley and lower Ohio Valley Thursday night.  This severe weather will continue to roar northeast on Friday, ripping through the Mid-Atlantic and perhaps as far north as extreme Southern New England.  Meanwhile, the wind feeding this system will be tremendous both ahead of the storm in the warm air, and behind it where blizzard conditions will likely verify in the Central U.S. areas described for heavy snow above.

Here in New England, we will wait until Friday for any direct effects from this storm.  The energy aloft that is associated with this storm is quite impressive, and the storm will still yank a slug of fast winds across New England on Friday as south winds just a few thousand feet off the ground are forecasted to blow at over 80 mph.  Though I don't think we'll see 80 mph gusts at all, mild air that's in place and a well-mixed atmosphere will mean favorable conditions for allowing winds to transport toward the ground later in the day, especially as downpours and thunderstorms move through.  This will produce locally damaging winds across New England late Friday into Friday night. 

It appears as though the push of cold air from the north will be sufficient enough to push a cold front out of Quebec, across Northern New England on Friday morning, and settle that front near the Route 2 corridor of Northern Massachusetts.  North of this front, cool air will come spilling south, and this will ensure quite a bit of snow for parts of Northern Maine on Friday.  South of the front, mild air will continue to pour into Southern New England, and along the front itself - through Southern Vermont, Southern New Hampshire and Northern Massachusetts - heavy rains will fall with up to two inches of rainfall.  Through the day, the reinforcement of Canadian cool air to the North Country will continue through Friday evening, and this means an area of sleet and freezing rain will continue to push southward, as well.  So what about snow?  Yesterday I'd mentioned that a brief period of whiteout conditions would impact the North Country...the track of the upper level energy driving the impending storm appears to be moving a bit farther northwest, and this means that temperatures aloft will be warm enough to melt snowflakes upon descent for an extended period of time through much of Northern Vermont and New Hampshire.  Still, by the end of the storm later Friday night into Saturday morning, cold air will come sweeping in from the west and this will turn raindrops to snowflakes across most of Northern New England.

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Elsewhere, the weekend will begin a bit brisk, but bright on Saturday with a blend of sun and clouds.  The problem we face in the atmosphere by the end of the weekend into early next week is that the pattern still isn't comfortably settled.  That is, cold air will have been tugged into the North and plenty of energy will linger across both the Great Lakes and the Central Plains.  This sets the stage for another possible interaction of northern and southern stream energy - weaker than the first time around, but still with an available feed of tropical moisture off the U.S. East Coast.  If the two systems were to interact, and they could tap some of the available moisture, we'd be looking at a snowstorm for New England and some rain and snow farther south.  That said, at this point the pattern seems to favor limited - but still evident - interaction between the northern and southern disturbances.  This would produce increasing Sunday clouds, then a period of possible light snow Sunday night into Monday, but the heaviest of the precipitation falling over the fish as the storm takes off just east of New England.  It's, of course, still early, and I'll continue to keep you posted on the setup.

Nonetheless, the pattern for the upcoming couple of weeks - the first half of December - will feature a fast flowing jet stream with numerous disturbances embedded in it, thanks largely to the weak El Nino flow and therefore the steady stream of disturbances racing across the Pacific and through the Western United States.  This will mean repeated tugs of cold air at the surface into New England, with plenty of availability to tap additional moisture from the tropical Pacific and Gulf of Mexico if any of these disturbances can grow strong enough, which they'll have a better chance of doing after the first week of December, when Pacific input strengthens even a bit more.

Have a good Thursday!

Technical Discussion:  Barely got the summary out!  None today, my friends.

Matt

Matt's Technical Meteorological Discussion:  Updated Wednesday, November 29 at 2:40 PM

Cold is eroding where you'd expect it to today - that is, south and west with winds shifting from that direction, and southeast where warmer ocean waters have also assisted.  Otherwise, shallow cool dome is doing its part in creating clouds and areas of fog that have been migrating gradually northeast in response to the wind shift.  I'd expect Essex County, MA, points N and E to remain mostly cloudy until sunset with breaks of sun most other locales farther S and W and responding temps.  Clouds and fog will fill back in overnight as temps cool briefly until they meet the rising dewpoint.  This slow start on Thu will give way to emerging breaks of sun as mixing gets underway with increasing boundary layer flow from the SW.

Tried to go into as much detail as possible on the upcoming storm in the General Wx summary, but my technical reasoning on such a paralyzing potential for OK City to St. Louis comes from the combination of tremendous dynamics with...more importantly...extreme baroclinicity.  I would venture that the rate of deepening will be deeper than progged, the wind will be more fierce than progged in the Central US, and the wraparound precip will be just as fierce as progged with heavier banding resulting from the combo of differential advection as warm air wraps around the north side of the circulation and into the falling midlevel temps.  This will be a fun show to watch from afar on Thu and then also on Thu night as the snow band carries NE while severe weather breaks out from the MS Valley to the OH/TN valleys as tropical air streams north and intersects strong PVA.

Here in NewEng, as mentioned already, boundary layer flow increases Thu.  This, of course, increases low level WAA and with breaks of sun likely at times, that will only help to boost sfc temps with airmass supporting around or just above 60 in Southern NewEng and 50s north.  Various levels of the atmosphere showing high RH on Thu and with continuous WAA bringing bursts of isentropic lift, scattered showers possible at just about any time as is being witnessed on radar scopes to the west of NewEng today, so will hold the forecast to that regard.

Fri storm is extremely dynamic.  Yesterday I mentioned to Tim Kelley that the vort max itself reminds me a bit of the December 9 storm of last year, and in fact the dynamic low level setup is quite similar, as well.  There are, of course, some major differences that will make this a very different scenario - for example the storm is going to track hundreds of miles farther north and west, it's reaching its peak intensity aloft while it crosses the Ohio Valley, and the fact that it's removed from the ocean takes away a great deal of additional baroclinicity and moisture input.  So how are they similar?  The strength of the 500 mb vorticity maximum is quite similar, the system is closed aloft, and it's taking on a negative tilt as it crosses NewEng.  Track across Nrn NewEng puts Nrn VT, NH and ME in the bullseye of this storm for dynamically forced precip.  At first there is enuf mild air that this will mean heavy rain Fri for Central and esp Nrn NewEng.  FFG values are running around 2-2.75" in 6 hours, and that may be exceeded, so small rivers and streams may flood far North Country Fri night.  The dynamic cooling should be so intense, however, that we will tug cold air southward faster than progged by guidance and this will mean a quicker changeover to snow in the far North Country - esp north of the 500 mb circulation - with white-out conditions likely for a time overnight Fri Ngt and snow falling at the rate of a couple of inches per hour for a brief time.

Of course, that's only for the Nrn NewEng part of a storm that will bring widespread effects.  Though there is some excitement for snow lovers of any prospect of snow - and that means some getting giddy about next Monday's potential (more on that below) - it's critical that meteorologists and the public remain focused not on what plays better to emotion but what will have the most immediate impact on life, which will be the potential for damaging wind on Fri.  Southerly winds in advance of the storm are progged to blow to 85 knots at 850 mb and though the core of the 925 mb winds stays immediately south of NewEng in the latest NMM prediction, even those winds are blowing at 75-80 kts!  This may be somewhat mitigated in extreme Srn NewEng where mixing will be a bit limited due to flow off ocean waters that will be cooler than the air aloft, but Richardson Numbers indicate mixing all the way to 850 mb farther north and over the interior!  The combination of this southerly llvl jet prior to arrival of the front, convection likely to develop along and immediately ahead of the front, and CAA with assoc downward momentum transport behind the front gives plenty of cause for concern over damaging winds later Fri in NewEng.  As for the convective threat, there is no question the deepest instability is found to our south, from the Mid-Atlantic to the Southeastern US where I would expect a squall line to sweep east later Fri ahead of the front.  But while the same llvl instability is not present in NewEng, mid-lvl lapse rates are moderate over Srn NewEng where slug of warmth and moisture above 800 mb is just as impressive as it is farther S.  Combined with available dynamics and low level jet structure, there certainly appears to be a slight chance of that squall line extending/expanding north into Srn NewEng late Fri.

Though Sat looks fairly quiet for most of us, winds will still be 40-50 kts at 850 mb with cold advection from the NW and this favors upslope snows until the dry air can overcome those processes, and would expect these upslope snows in the favored locales of the Greens, Whites and mountains of Maine first half of Sat.  Elsewhere, downsloping flow and removal from rather channeled vorticity will leave most areas dry with sunshine between cold Cu.  Additionally, with the trof axis still well to our west, the deep cold will not carry all the way thru NewEng and we should find a rather pronounced temp difference from N to S by Sat afternoon.

Of course, this failure to move the trof axis farther east is what leaves such an interesting setup for late Sun into Mon.  That is, the jet stream will be laid over Srn NewEng with a baroclinic zone similarly ribboned across the region, and with two vorticity lobes to our west - one over the Upper Great Lakes holding back arctic air, and the other dipping thru the Rockies and Central Plains - the intriguing questions of potential phasing come back to give NewEng meteorologists and weather enthusiasts alike something to scratch our heads over.  I have to be completely honest that my thoughts this morning were that phasing would happen farther east than NewEng, and I held this thought largely because of the progressive nature of the flow over the Northeastern US, leading into the confluent flow locked east of NewEng, which, of course, will also serve to hold in the cold.  This idea of progressive disturbance and later phasing found good agreement among both Canadian and GFS Ensemble products, along with most operational runs, though one overwhelming feature was the presence of a rather well-defined inverted trof between the northern and southern disturbances that swings thru NewEng later Sun into Mon.  This, in combination with shortwave energy sheared out in the upper flow and running ahead of the main southern disturbance, was among my primary reasons for increasing Sunday clouds and putting at least light snow in the fcst late Sun into Mon.  This also set off an alarm, however, as I've seen cases in the past where a well-defined inverted trof is the precursor that the guidance is picking up on more interaction than it would appear, and the 12Z model guidance certainly has trended in this direction, at least in the case of the GFS and GGEM.  I should make it clear that I don't think storm track is a huge question here, contrary to what the instinct is to worry about (ie: will it come close enough?).  I don't think there's any question it will come close enough to affect New England - the baroclinicity is laid over us at 850 mb, the jet is over us at 300 mb and 500 mb flow is just south of the coast.  In fact, I think the track of any surface reflection would be farther north and west than currently progged.  What the question revolves around here is simply over how quickly the interaction and phasing takes place, and exactly where that happens.  12Z GFS started looking too progressive but then retrogrades the system, which is not only possible but in fact likely to happen when in fact phasing does occur.  With 12Z Canadian phasing early, but hot-off-the-presses ECMWF phasing late, this really doesn't help much, does it?!  So, for now will hold the line with the public forecast in expressing likelihood of light snow Sun Ngt/Mon and explain potential of earlier strengthening.

But again, very important to note that this won't be the highlight of the public forecast for now - while it entices meteorologists and weather enthusiasts, the major primary concern is Friday's blow of damaging winds, and must not be overshadowed by a storm potential at 5 days out.

Have a good day!

Matt

Monday's Discussion

1:30 PM:  30 degree spread across NewEng as of this writing from snow and 32 in Caribou, ME, to 62 and sun through Ci in OWD, SFZ, PVD, FIT.  Not bad for peak diurnal heating on what some would consider a quiet weather day!  Shortwave prompting rain and snow across Nrn ME will remain progressive, but so will the next shortwave upstream over Ontario as of this writing, which has been well-evidenced on radar and now shows good cloud top cooling on infrared imagery.  This shortwave will regenerate the swath of rain and snow across Nrn ME, and will a cooling boundary layer this should go to mostly snow with the I-95 corridor valleys starting as rain then changing to snow.  The shield of precip will drop south across Central ME and Bangor area may see a dusting by AM with temps around freezing which means black ice/icy spots a possibility, and accums of 2" possible higher terrain north of BGR area, esp from Millinocket points north.  Elsewhere, periods of clouds with shortwave passage seem rather innocuous but come prior to surge of shallow but meaningful cold that will migrate south behind Mon night's shortwave.  This cold has been brewing in Quebec and is a breakaway from gargantuan anticyclone in Central and Western Canada - therefore, this breakaway nature of the airmass means the cold is not overly deep but instead is a rather typical Eastern Canada surface dome that will be marked by a shift of winds to the northeast and brief gusts to over 20 mph with the wind shift.  Timing is 04-06Z in Portland and by 12Z most of NewEng has seen frontal passage.  Temps behind the front today are verifying in the 30s and NMM will verify best with this airmass thanks to its higher low level resolution.  Some areas in Srn NewEng will see falling temps after morning highs thanks to this cold advection.

Cold airmass remains locked in thru Tue Ngt, and areas of drizzle and light showers will be likely thanks to substantial low level instability.  Inversion present aloft, however, will strengthen Wednesday as warm advection commences above the boundary layer, but contrary to guidance forecasts I don't think the cold, dense air is going to give way to warm advection and mixing will be little if any, meaning low level deck remains locked in, isolated to scattered showers are possible thanks to warm advection aloft and temps remain cool.  Next system winds up enough to increase gradient and move air at the surface, so I do expect some warm advection in the boundary layer on Thu, though was looking at GFSX Ensemble members mostly in the middle 60s for Lawrence, MA, area Thu and I have a very hard time believing this with limited insolation and a stronger tendency for the cold to be rather begrudging in its departure.

In fact, as explained in the General Weather Summary above, I'd be surprised to find this cold air losing any meaningful battles in the next couple of weeks, and that includes Friday night, which is a critical battle in the world of meteorology, as nearly everything in the forecast will ride upon it.  I do mean quite literally "ride upon it" as the cold front will serve to be the path of the next incoming low.  I made my mind up which way to go with this for now when I reviewed the 00Z suite early today, and I have seen the warmer GFS solution even in its more recent 12Z run.  That said, I also see that the 00Z to 12Z has shown a rather substantial displacement to the southeast in the track of the low center - not yet where I'd expect it, but getting there.  So where would I expect the track?  Given the passage of a Thursday night shortwave similar to this coming night's wave, there's no reason to doubt whether the cold is capable of pushing thru NewEng.  It would appear as though the cruxt of the argument is the speed at which it sinks southward, to which we find good agreement among the Canadian Ensemble members and operational GGEM of a quick progression, GFS Ensemble mean position east and south of NewEng, and an ECMWF solution that is a bit more sluggish tho not nearly as sluggish as the GFS.  One could say that given the tendency for cold air to win the battles this time of the year, and the agreement among the Canadian Ensembles on the progression of this Canadian air - along with an NMM that also appears to be trending in a quicker cold direction, this certainly seems like the best forecast for the time-being.  Of course, in our discussions that's not quite enough, as I like to see synoptic reasoning to support guidance, and that synoptic reasoning is founded in the presence of confluent flow east of Maine, indicating the cold will come pouring in, then will hold.

Perhaps an equally challenging question is how the incoming Pacific vort will track and whether it will hold its identity as it encounters the confluent flow.  Thus far, the trend is only stronger with this Pacific energy as it lifts northeast across the OH/TN valleys, tho logic would say it should weaken as it approaches confluence.  I do think the guidance in general are still too far west with the vort max given the confluence east of NewEng and the colder surge as described above.  All of these factors raises my awareness of the potential for carrying accumulating snow farther south through New Eng than we've done so far this year, tho exactly where that is still remains up for grabs at 5 days out.  Heck, at 5 days out we know the whole thing remains up for grabs as described above, but of the solutions I prefer it would make the most sense to carry a moist Pacific-moisture loaded system either south of NewEng or over Southern NewEng Fri Ngt into early Sat, and this would mean the potential for accumulating snow even in Central NewEng.  It's also important to remember that shallow but strong cold can mean freezing precip, which wouldn't be impossible for interior locales if enuf cold air weren't present for snow.

So...plenty to work thru in the next couple of days.  In the meantime, enjoy the mild Monday (south) and the following chill Tuesday.

Matt