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Mid to Long Term Discussion 2017


buckeyefan1

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Discussion from GSP

The medium range
guidance is having some trouble with these individual pockets of
energy, and this is resulting in some disagreement on the forecast
details for our area. A weak wave is progged to develop along a
strong baroclinic zone off the East Coast on Friday, in response to
the height falls. As the wave develops, mid-lvl frontogenesis and upper
divergence will increase over the Carolinas and up the Mid-Atlantic
coast. This will likely result in a precip shield expanding north
and west of the sfc front, into the colder air inland. However, how
far inland the forcing and available moisture sets up is the main
question. The 12z GFS (and in general the GEFS) has trended a little
further east overall, and results in a dry fcst for entire area. The
12z ECMWF and CMC have trended west and would result in likely to
possibly categorical PoPs across the I-85 corridor and east with up
to a quarter inch of QPF. Low-level thicknesses support some snow or
rain/snow mix on the northwest edge of this precip shield, which may
include the I-85 corridor. So this could result in some trace or
light snow accums on grassy sfcs with temps in the 30s to mid 40s.
With competing trends in the guidance, confidence is still below
average. I went close to the WPC PoPs and the Superblend temps
(which are on the cool side), which keeps a slgt chc to low-end chc
from NW to SE across the CWFA on Friday, with some snow and
rain/snow wording. The sfc-based warm layer is expected to increase
enough to change precip over to rain across the Piedmont. So snow
accums are not expected to be enough for any big impacts.

As the sfc wave zips off to the NE Friday night thru Saturday, the
precip shield should exit the area. Temps will be about 10-15 deg
below normal, as the upper trough axis pivots east over the area.
Another vigorous vort max will round the base of the trough on
Saturday and bring a brief shot of moisture to the area. A quick
inch or two of snow may be possible in the west-facing slopes of the
NC mountains. An isolated band of showers cannot be ruled out east
of the mountains, due to the very strong forcing, but pinning that
down is impossible this far out.

Temps begin to slowly rebound Sunday and Monday, but another
reinforcing shortwave will dive into the eastern CONUS longwave
trough by the end of the period. This may bring another quick NW
flow snow shower event to the mountains by late Monday
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GSP and RAH must not have had much of a conference call.

 

Discussion from RAH

The final s/w will cross the region late Friday-early Saturday. This
system may trigger or few rain showers mixed with some wet
snowflakes near or north of the Triad early Friday evening. More
appreciable cold air advection will occur in the wake of this
system. This will result in afternoon temperatures a solid 10-15
degrees colder than normal, and overnight temperatures well into the
20s Saturday night and Sunday night.
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5 minutes ago, WarmNose said:

I'll take a blend of E49 and E51 and call it a winter. 

Question for the weather veterans on here. What variable is causing big numbers on frames 49 and 51?

They likely have a more consolidated wave that kicks out at the base of the trough > stronger surface low that isn't strung out > more precip back inland

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Everyone's talking about the Greenland block being in place. If that's the case then why does that 1032 HP scoot off the east coast when the low pressure system shoots out of the gulf and up the east coast on December 15th? (Per 12z GFS) 

edit: I'm no meteorologist but I see potential for a phaser if we can keep HP in place. I'm just here to learn. What am I missing?

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31 minutes ago, WarmNose said:

Everyone's talking about the Greenland block being in place. If that's the case then why does that 1032 HP scoot off the east coast when the low pressure system shoots out of the gulf and up the east coast on December 15th? (Per 12z GFS) 

edit: I'm no meteorologist but I see potential for a phaser if we can keep HP in place. I'm just here to learn. What am I missing?

You said the magic words...... GFS, 10 days away. Enough said

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26 minutes ago, WarmNose said:

Everyone's talking about the Greenland block being in place. If that's the case then why does that 1032 HP scoot off the east coast when the low pressure system shoots out of the gulf and up the east coast on December 15th? (Per 12z GFS) 

edit: I'm no meteorologist but I see potential for a phaser if we can keep HP in place. I'm just here to learn. What am I missing?

It's the Burrel Hudson Bay vortex pattern.  As northern stream energy keeps dropping down thru the north central states and into the eastern trough, surface high pressure is kicked off the east coast.  So, we have to rely on timing where an arctic front moves through, but a storm wave quickly follows and digs far enough south to give us wintry precip.  It's not a good pattern for locking in strong cold highs over the Great Lakes.  During that timeframe, the AO is negative, but the NAO is neutral.  There's no big Greenland block in place at that time.  A week or 2 ago, there was probably more model support for -NAO, but that has waned.

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Looking at the 3 ensemble means (GFS, CMC, Euro), the CMC is actually the farthest east with the late week storm, with the least amount of precip inland (though it's Op run had precip well inland).  

18z GFS Ens Mean was a little stronger with the coastal low with a jog northwest with the precip compared to 12z

Looking ahead, the pattern looks pretty good for chilly conditions and possible storm threats thru at least Dec 18-19

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1 minute ago, mackerel_sky said:

JC on 4, said absolutely no snow outside of the mtns! :(  But CJ saying looking more likely! That's what happens when you have an old coot and a weenie at the same station!

Ya... I saw that, I moved to WSOC, they mentioned that one model said maybe snow and one had the low further east.

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WPC Model Diagnostics Discussion...

THE 12Z ECMWF AND 12Z CMC HAVE TRENDED TOWARD THE UKMET (THE 12Z UKMET IS FAIRLY CONSISTENT WITH ITS PREVIOUS RUN) IN SHOWING A MORE AMPLIFIED AND SLOWER WAVE ACROSS THE FOUR CORNERS REGION. THIS SETS UP QUITE A BIT OF MODEL SPREAD. THE 12Z GFS IS NOW AN OUTLIER FROM THE OTHER OPERATIONAL GLOBAL MODELS...SO WOULD PREFER TO TREND THINGS TOWARD THE SLOWER AND MORE AMPLIFIED SOLUTION. HOWEVER...GIVEN THE NUMBER OF GEFS...CMC...AND ECMWF ENSEMBLE MEMBERS STILL FASTER THAN THE OPERATIONAL ECMWF...UKMET...CMC...WOULD ALSO PREFER NOT TO GO WITH A SOLUTION THAT AMPLIFIED YET. THE SOLUTION IN THE MIDDLE AT THE MOMENT IS THE 00Z ECMWF ENSEMBLE MEAN...WHICH ACTUALLY CAPTURES THE SPREAD WELL (SOME ECMWF ENSEMBLE MEMBERS EVEN MATCH CLOSER TO THE GFS).

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1 minute ago, mackerel_sky said:

JC on 4, said absolutely no snow outside of the mtns! :(  But CJ saying looking more likely! That's what happens when you have an old coot and a weenie at the same station!

JC is the semi-old coot,  DG is the real old coot and won't forecast snow may be coming until it has started or has finished accumulating.  

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Just now, NorthernUpstateSC said:

JC is the semi-old coot,  DG is the real old coot and won't forecast snow may be coming until it has started or has finished accumulating.  

Very true!! KK wouldn't call for snow if it was pelting her in the face and was so deep she couldn't get out of the Fox parking lot!!

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