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Feb Long Range Discussion (Day 3 and beyond) - MERGED


WinterWxLuvr
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7 hours ago, psuhoffman said:

I remembered years ago in the fall of an impending Nina (I think it was 2016-17) I did some seasonal research and was shocked to find that what makes a Nina so terrible isn’t that it mutes an NAO. It’s that we suck monkey nuts and get NO snow unless we get a -NAO and since those are exceedingly rare since the 80s... 

So I went back and found my files and updated them with the last few years. These are the actual splits for every -NAO month since 1990 at BWI.  I hate using DCA.  It’s depressing and I do think BWI is more representative of most in the 95 corridor.  

December 

La Niña -NAO avg snow 2.2”  17% above avg

Non Nina -NAO Avg snow 6.1. 40% above avg 

so yes in December a Nina mutes the NAO. So this years challenged start despite a -NAO in hindsight should have been expected 

but get a load of this...

January

Nina -NAO avg 15.9” 67% above avg

Non Nina -NAO AVG 5.6” 50% above avg

February 

nina -NAO avg 16.1” 100% above avg

non Nina -NAO avg 11.5” 50% above avg

March 

nina -NAO avg 3.6” 50% above avg

non Nina -NAO avg 1.0” 25% above avg

So in January to March our mean snowfall with a -NAO is actually HIGHER in a Nina then non Nina months and our chances of having an above avg snowfall month is higher in a -NAO Nina. 

The reason Nina’s suck is actually because a -NAO is pretty rare and they are horrid without one.  When I did my warning event snowfall study I don’t think there was a single Nina one in the whole 70 year study without a -NAO!  We simply do not snow much without a -NAO in a Nina. But the truth is a -NAO seems to have the same effect, and maybe even better, in a Nina as in other enso states. 

All good info and we have discussed this before, but the OP said something to the effect that it would be depressing or a fail if we didn't get a big storm with the persistent blocking we have had this winter. Sure a -AO/NAO favors more snow than average regardless of ENSO state, that should be evident to every weenie here by now lol, but in my replies to that post I simply stated that it is more likely to come in multiple "smaller" events rather than a KU for the MA in a Nina. I just find the "bar setting" thing to be a little silly, especially given the climo for much of this region tends to be hostile for snow.

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morning AFD from LWX

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...

Tranquil conditions Tue night as high pressure builds again. Not
as cold as this morning with thick clouds overhead.

Overrunning wintry precip is expected to break out across the
region Wed in response to a shortwave-trough and increasing
upper level divergence from an approaching right entrance jet
streak dynamics. This area of organized precip is expected to
expand east Wed night into Thu. It should be mostly snow, but
may start as rain in the south Wed afternoon before changing to
snow everywhere Wed night as freezing levels drop. Several
inches of snow accumulation appear likely Wed night with the
event continuing into Fri morning with some transition to mixed
precip across southern areas Thursday. Refer to long term
section below.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...

Arctic high pressure will remain wedged in along the eastern slopes
of the Appalachains. Meanwhile, low pressure will be sliding by to
our south. Wintry weather is expected to continue into Thursday.
Still some uncertainty in regards to precipitation type for the
duration of the event. Guidance overnight, which now includes
the NAM, have started to trend cooler aloft, leading to a
snowier solution across the region, especially the northern
half. Do expect some mixing of sleet, snow, and freezing rain to
occur across the southern half of the CWA. Will be tough, as
usual, to pin point that mixing line at this point. This system
continues into Friday morning as well, which will make this a
fairly long-duration event.

For the weekend, the pattern remains quite unsettled. An even colder
arctic air mass will become wedged into the region Saturday, setting
the stage for yet another winter weather event. First part of the
day could be dry, though there is some spread there, so will
maintain some chance POPs during the day. The bigger event comes
late Saturday night into Sunday. Details are still fuzzy concerning
temperatures aloft, thus not really sure of precip types at this
point, but am growing increasingly confident in another winter
storm. At this point, would certainly favor our northwestern zones,
given climatology. However, plenty of time for things to change, so
will continue to monitor in the coming days.

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3 minutes ago, yoda said:

morning AFD from LWX

 

 

And here is the AM AFD from Mount Holly-

As the languishing midlevel vortex remains nearly stationary in south-central Canada, fast quasi-zonal flow will remain across the U.S. with periodic low-amplitude perturbations zipping eastward. Models have trended in two distinct ways the past 24 hours. First, the northern-stream vort max amplifying the late- week system for our area is noticeably weaker compared to simulations yesterday. Second, the progression of the midlevel Canada low allows for more troughing in eastern Canada. The result has been for a reduction in strength (suppression) of the system affecting the area Wednesday through Friday, and a steadily colder solution as well. Deterministic guidance exhibits, to varying degrees, an extended period of wintry weather late this week. The gist of the first portion of the event seems agreeable. Warm-advection precipitation will spread rapidly eastward to the northern Mid- Atlantic by Wednesday night, promoting a round of snow for the area as cold air advecting from the retreating surface high keeps surface temperatures below freezing for much of the area. The weaker nature of the upper-level shortwave trough suggests the strength and advance of the warm nose will be on the weak side, certainly weaker than that predicted by the models yesterday. A lengthy period of light snow is likely in this regime then for much of our area, with the main questions being how far south the potential for snow exists..

A second wave looks to move through the eastern U.S. Thursday night and Friday, which may bring a second round of wintry precipitation to the area. Questions abound regarding this potential, though, with the GFS quite suppressed (keeping most precipitation to our south) versus the more amplified ECMWF. The CMC seems more agreeable with the ECMWF, and the GFS fast-bias may be playing a role in its equatorward shift. However, in either scenario, any precipitation for the area would increasingly favor snow. Thus, felt confident moving precipitation types in that direction and lowering temperatures markedly in the Thursday through Friday time frame. The bottom line for the Wednesday through Friday period is that one or more periods of wintry weather seem likely, with meaningful impacts possible for much of the CWA.

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6 hours ago, Bob Chill said:

I'm not sure we'll get full agreement on being on the good side for bit. One or more models will likely irritate everyone every 6 hours. Should be a blast in here as time ticks and nerves twitch. 

Bumping this. I will take the euro and the trends and invite people not to freak out over the occasional hiccup . 

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25 minutes ago, Wentzadelphia said:

Icon being somewhat similar to the euro is a great sign. Model is seriously underrated would love to see verification stats. ATM I would rather be in N VA and Md compared to me up in Philly for this one. 

I remember those famous words recently...........

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2 hours ago, Weather Will said:

WB 6Z GFS thru Friday am,  6 inch snow line ticked south 30 miles or so this run compared to 0Z.

Nice trends overnight into this morning.  Colder scenario gaining more traction. 

I like this too

32E1077B-5176-4E21-9A65-3BF5696A1F6D.gif.f770484f49362a447a0ae5f34228d208.gif

 

Also notice snow cover over the mid center of country expanding South,  and fringes around the great Lakes starting to freeze over .  

 

ims2021038_usa.gif

 

 

Arctic press evolving towards mid month extremes. 

This is yet again the coldest 10 day mean look yet. Are you kidding me a - 9.4 mean :pepsi: Sources regions getting colder and colder and areas Northeast of the Great Lakes getting colder as well. 

 

 

479948084_tenday(3).thumb.gif.edc23540896c4a6af5d40331a1b3f1cf.gif

 

 

 

 

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