ECMWF screaming MAJOR overrunning event (CAD) on Day 7

[jpp5862]

I was just reading the latest NWS discussion from GSP, which covers the Charlotte area, they have finally acknowledged what you guys have been talking about all week on here:

Main concern for the medium range is the latest developments in the
medium range models...which continue to show surface low development
along the western Gulf Coast Saturday. All models show cold air
damming configuration on Sunday with large surface high in favorable
spot over northern middle Atlantic or southern New England coast. That supports
lowering maximum temperature another five degrees or so...which keeps temperatures in
the 30s across most of the forecast area that day.


The differences continue to be in the handling of the surface
low...which is of major importance given the potential for cool dry
air at low levels. The european model (ecmwf) keeps a weaker surface low in the Ohio
Valley...while the operational 00z GFS moves the low across the
southeast to the Carolina coast by late Sunday in Miller type a
fashion. The latter scenario would hold the potential for
significant snow in the mountains and icing in the
foothills/Piedmont.


The 12z GFS continues to support keeping primary low to the south.
Will go with the hpc solution which is similar to the GFS...but for
the time being...think it best to only nudge precipitation type forecast
toward the wintry GFS. That means I plan to go with rain/snow in the
mountains and rain/freezing rain in the foothills/Piedmont for late
Saturday night and Sunday.


The models move the timing up another 6 hours...so precipitation will be
introduced in the Saturday night period...but ended by the Monday
period across all but the western side of the mountains will hold pop to 50
percent for time being. Remainder of forecast for Monday and Tuesday
looks quiet with high pressure building in and will stick close to
hpc guidance. GFS shows potential for next system arriving late
Tuesday...but will not put pop in at this time.
&&


Up until today the weekend forecast has been for rain on Sunday with highs in the 50s. They now say a potential for freezing rain exists with the cold air damming in place.

Looking forward to seeing how this unfolds, clearly a lot of uncertainty and a lot of things that have to come together, but good job guys on here for getting a head start on this.

[donsutherland1]

John,

I'll elaborate to a greater extent tonight, but I believe that interior sections of the Mid-Atlantic and Northeast have a real possibility of being plastered by a heavy wet snowfall. The big cities from Philadelphia to Boston will probably start with accumulating snow changing to rain and then end with more snow possibly with some additional accumulation.

The 500 mb evolution does not support all or mostly rain for the interior sections of the Mid-Atlantic and Northeastern regions. Moreover, given the weak ridging likely over the Atlantic, I do not believe the system will be suppressed to the south.

There are also intriguing hints in the 500 mb evolution that suggest that a shot of very cold air might lie ahead in the longer-term (perhaps arriving in the next 8-14 days--the latter part of that timeframe looks better). For now, the potential for an Arctic outbreak, possibly preceded by a storm or at least some snowfall, down the road seems to be growing. Consequently, it would not be far-fetched to argue that the northern Mid-Atlantic region, as well as the Northeast, has a good chance of having snow on the ground for Christmas Day. The same holds true with regard to the Ohio Valley.

[DCmetroraleigh]

Don, how about central North Carolina, southern Virginia?

[nystate]

Any chance that we could get some snow out of this in Watertown/Syracuse, NY? We're in a little bit of a defecit right now, we've only had a few dustings the whole season so far. Last year I think we had about 30 inches by now...could this give us our first significant snowfall?

[donsutherland1]

It's still a close call. With some cold air damming likely, I believe at least a brief period of frozen precipitation (ice or snow) is likely over central and western North Carolina and southwestern Virginia. A significant period of frozen precipitation cannot be ruled out, but there is considerable uncertainty at this time.

[RNS]

Don...disregard tonight/s EC the solution is exactly the same as last night...(w/ reagrd to the H5 set-up...the pushing out of the 1030mb or more high...little CAD signature...its CRAP and big load of it...the GFS and the ETA (out to 60hrs so far) are beginning to come into line. I dont like the way it just shunts the high out of there like that in 24 hours...no coastal development (in spite of the fact that it finds the inverted/coastal trough)...just as last night/s run...its a big fresh pile of BULLSH!T.

[RNS]

All the other models keep the high in place (which IMO is correct)...and recall how the EC shifted its track of the SFC low 24 hrs prior to the start of the previous event...its not often one will find me agreeing (to a pont albeit) with the GFS but this one of those times.

[Stormsfury]

Amazing how I said that 99% of the time, I go with the EURO, but this is one of those times (the 1%) that I don't ...

For some reason or another, it's NOT handling the split flow worth a damn and the placements of 500mb/surface is all wrong ...

SF

[RNS]

Amazing how I said that 99% of the time, I go with the EURO, but this is one of those times (the 1%) that I don't ...

For some reason or another, it's NOT handling the split flow worth a damn and the placements of 500mb/surface is all wrong ...

SF

Thats the problem here...i think its correct with regard to the strength of the high...but the kicker is that the the energy coming through is almost purely STJ based. Which means the EC will have a harder time handling it (STJ energy + bias=EC crash...lol). But what really floors me that it pushes that high pressure center out into the northwest atlantic in 24 hours...

[RNS]

Now dont get me wrong here...I/m not fully in bed w/ the GFS YET but i think it has a better handle on the situation than the EC by far. b/c we have ridging going up near spain...it will NOT just get sheared out...but at the same rate im doubtful that the teleconnection will be strong enough to force the development of a southeast ridge sufficient to force the track of the low inland from the coast.

My take remains unchanded...one center develops in th western gulf and moves northeast to Pikeville KY thwen transfers energy to the coast...and the system comes up. the high will provide the cold air for a significant ice event in the piedmont of NC/VA/WV...and possibly the major cities (especially DCA/BWI/PHL)...for inland areas its all snow and the axis of heaviest snow (IMO right now) is 50-75 miles either side of a line from hagerstown MD to Scranton PA to Concord NH.

A colder version of xmas 02.

[RNS]

But one thing that i am sure of is that the Southern plains are about to get basted by heavy snowfall from the STJ s/w...

[RNS]

and yes the GFS at 84hrs IS showing a partial phase...

[donsutherland1]

Over the next several days, the storm that will bring heavy rain to parts of the eastern U.S. will move into eastern Canada and very slowly northeastward from there. Afterward, high pressure will likely build from the upper Midwest to upstate New York/northern New England and slowly east-northeastward from there. It will probably have a central pressure of 1035 mb to 1040 mb, perhaps a little stronger.

In the meantime, a weak ridge of high pressure should build into Spain, though by the weekend it should be centered over eastern Spain. Consequently, one can look for a weak ridge out over the Atlantic Ocean. In its position, it should:

1) ensure that the storm does not escape out to sea (suppressed track) as shown on the 12/10 0Z run of the GFS
2) ensure that the storm turns northward.

Given high pressure over upstate New York or northern New England by Sunday, along with what the ensembles show will likely be a neutral to somewhat negative NAO, I do not believe that this system will cut to the west of the Appalachians.

Rather, one center will probably move northeastward along the Appalachians sparking secondary cyclogenesis east of Cape Hatteras. This secondary system will eventually become the primary system as it tracks east-northeastward offshore but not far from the Coast (perhaps by the time it reaches the Delmarva?).

I do not believe that the high pressure over eastern Canada will race off to the northeast as quickly as depicted on the latest 12Z run of the ECMWF. Rather, I expect a slower drift of the high. Thus, the exit of cold air should be delayed sufficiently to afford the big cities at least a period of accumulating snow. How much? That remains the question.

At this time, I believe that interior sections of the Mid-Atlantic and Northeast i.e. Harrisburg, Albany, etc., have a real possibility of being plastered by a heavy wet snowfall. Local amounts could exceed a foot. The big cities from Philadelphia to Boston will probably start with accumulating snow changing to rain and then end with more snow possibly with some additional accumulation. All said, these cities will probably see at least a few inches of snow and possibly more especially if the high largely holds in place.

Finally, since 12/4, there have been several days in which the above normal height anomalies have linked up across North America. Such a linking-up, especially when it is sustained, has sometimes been a precursor of significant Arctic outbreaks in the past. With some signs that the pool of coldest air may be starting to expand to our side of the North Pole, this is a situation that will bear watching, especially as there are also hints that a strong low could take residence near the Aleutian Islands in the near-term.

Should such an Arctic outbreak occur--and it's not yet a certainty--it appears that it could begin to overspread the eastern U.S. sometime between 12/19-23 perhaps preceded by an important storm (between 12/18 and 22?) that could lead to the Ohio Valley, northern Mid-Atlantic and Northeast enjoying snowcover for Christmas.

[donsutherland1]

RNS,

I agree with you. The ECMWF appears to be doing a poor job with regard to the 12/15 system. BTW, as you make the comparison with the Christmas Day nor'easter, if I recall correctly, the Euro also had difficulty handling that system.

[RNS]

RNS,

I agree with you. The ECMWF appears to be doing a poor job with regard to the 12/15 system. BTW, as you make the comparison with the Christmas Day nor'easter, if I recall correctly, the Euro also had difficulty handling that system.

personally...all the model output aside...if one looks at the evolution of the pattern the system looks alot like Xmas 02 or the early jan noreaster...but the only difference is the high to the north which leads me to think that the system (though running up along or west of the mountains initially)...will transfer energy to the coast further south than xmas or jan 03 (due to the supressive high) and will be a rapid deepener. (I.E... bomb cyclogenesis.) So right now i see this as an ice problem for DC and BWI...perhaps PHL (though prob biased more toward snow there as well as in NYC and BOX).

in these situations you cant take the model output seriously...this is where an understanding of the trend of the pattern becomes HIGHLY important. So if one can find a mean between the EC and GFS...IMO thats your storm.

[RNS]

New 0z GGEM:

I want folks to notice something here...and it aruges strongly against the EC...



Notice that while we have ridging over spain at 108 hours...the flow is still somewhat split across the central ATL w/ neg tilted H5 trough...this would help to pump the ridge to the north of it and strengthen the blocking in eastern greenland (notice the height rises taking place along the easten shore). this would help to hold the trough over quebec and newfoundland. therefore the high would be forced to move slower...and the teleconnection between the ridge over spain will be mitigated enough so that the system is not an inland runner...but the effect of the teleconnection is still indirectly present (helping to turn the system up instead of shearing it out).



as we can see here...the canadian has aclassic miller B scenario...w/ the reack of low pressure from the outerbanks to just southeast of nova scotia.

[JCT777]

RNS & donsutherland - Great posts, and I am anxious to see how the models trend over the next few days.

[donsutherland1]

RNS,

Your comparison to the XMAS 2002 nor'easter with colder air is a good one. I expect the modeling to begin to trend in that direction over the next day or two. The mean you suggest between the GFS and ECMWF looks like as good an idea as is possible at this time.

[Stephanie]

So far the forecast for Sunday is a mixture of rain/snow/ice. Rob Guarino from Fox Philadelphia is still suggesting another winter storm but later next week? Actually, up until yesterday, Sunday was supposed to be nice.

[CaptinCrunch]

All of our local news channels for Dallas/Ft Worth are calling for the chance of snow mix with sleet friday night thru saturday afternon, lets hope they are right.....