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Mid to Long Term Discussion 2020

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Buyer beware of the Pivot precip type map on the Euro.  The map says rain for Raleigh, but the sounding says snow (very, very shallow above freezing layer at the surface which is likely too warm)...and the sounding output at the bottom right says snow...granted, precip is light

jscC49O.png

dTpcnNF.png

 

 

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Bottom line after today's runs is that a coastal low appears to be our best chance now and coastal lows do have a tendency to trend NW. Modeling will bounce around for the next few days but the players have entered the field from all camps and we are finally able to track something inside 4 days. Not every run is going to be better than the last one but I'd say overall the trends today have been encouraging. Obviously the CMC, which had a beautiful run last night, wasn't as good but it still had the same idea. Starting to see agreement 4 days out which to me is as good as we could ask for in this timeframe. 

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8 minutes ago, griteater said:

3 days prior to go time, this is what storms that hit us look like.  It's far from perfect, but we're in the game here.

Man, I don't know grit.  I'd understand if we were on the fringes of the juice, but no model has significant precip near us that I can tell (maybe the nam long range).  You expecting a powerful NW trend here? Storms that are legitimate usually have some models in our court.  I'm just not seeing anything close. 

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8 minutes ago, griteater said:

Buyer beware of the Pivot precip type map on the Euro.  The map says rain for Raleigh, but the sounding says snow (very, very shallow above freezing layer at the surface which is likely too warm)...and the sounding output at the bottom right says snow...granted, precip is light

jscC49O.png

dTpcnNF.png

 

 

I feel like this will be the case with a lot of locations in central NC, NW SC, and NA GA. The rain/snow simulated radar mostly takes into account the modeled surface temperatures as being between 36-42, which translates to rain. But looking at the thermal profiles, you can clearly see an incredibly shallow warm layer at the surface that can easily be tweaked a few degrees between now and Thursday. This is a tricky setup and I do not think we get a real idea of what to expect temp wise until the hi-res models get into range. Right now we should be focusing on how the globals handle the energy transfer to our west and not expect the lower res sims to accurately depict surface conditions 84 hours out. 

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Man, I don't know grit.  I'd understand if we were on the fringes of the juice, but no model has significant precip near us that I can tell (maybe the nam long range).  You expecting a powerful NW trend here? Storms that are legitimate usually have some models in our court.  I'm just not seeing anything close. 
NAM handles the extremely short range better than the globles (look at the last couple events), granted the hr84 NAM is to be taken only for verbatem from its track record but there is a lot of time to move pieces.

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8 minutes ago, griteater said:

Buyer beware of the Pivot precip type map on the Euro.  The map says rain for Raleigh, but the sounding says snow (very, very shallow above freezing layer at the surface which is likely too warm)...and the sounding output at the bottom right says snow...granted, precip is light

jscC49O.png

dTpcnNF.png

 

 

That is a snow sounding all day. Hi-res models will sniff that out when they get in range. Key is seeing a N/W expansion of precip trending over time. 

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11 minutes ago, SnowNiner said:

Man, I don't know grit.  I'd understand if we were on the fringes of the juice, but no model has significant precip near us that I can tell (maybe the nam long range).  You expecting a powerful NW trend here? Storms that are legitimate usually have some models in our court.  I'm just not seeing anything close. 

 I mean, it depends on where your expectations are.  Yes, I think a light to moderate event with some surprises is possible....it all has to come together though.  Still 3 days out.

 

The Euro has trended better at 500mb.  At a timeframe of Wed aftn, the western ridge is taller...the wave out west is has trended west...and the flow across the south is better....all good trends.

5cIywvM.gif

 

Then by Thursday morning, the wave over the Great Lakes that is acting to keep everything suppressed to the south has trended farther north - again, good trend for precip to climb north as long as temps work out.

kZUa1S4.gif

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19 minutes ago, griteater said:

 I mean, it depends on where your expectations are.  Yes, I think a light to moderate event with some surprises is possible....it all has to come together though.  Still 3 days out.

 

The Euro has trended better at 500mb.  At a timeframe of Wed aftn, the western ridge is taller...the wave out west is has trended west...and the flow across the south is better....all good trends.

5cIywvM.gif

 

Then by Thursday morning, the wave over the Great Lakes that is acting to keep everything suppressed to the south has trended farther north - again, good trend for precip to climb north as long as temps work out.

kZUa1S4.gif

Thanks Grit.  A couple inches of accumulation and I'd be happy.  Hope you're right!

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Being that this is basically an over running event, no Miller a or Miller b or ULL, which model historically handles this the best. I would think the higher resolution 3km Nam and Rgem would really be the 2 to watch after today?

I know the Nam did really well with the last wave and marginal temps but I dont think we get that much precip here in the upstate and ne ga this time...hopefully wrong.

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5 minutes ago, TARHEELPROGRAMMER88 said:

ECMWF ensemble members are around 28 of the 50 with hits on central NC. A few others outside of those hit ENC. A few hit both Carolinas. That is a good spread. A little above 50% is good at this range.

Agreed and will be interesting to see if the count tics up in next couple of runs. Hopefully not down that’s for sure

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Some things I’m seeing;

Starting with the bad:
- I don’t know how much of a northwest trend is really *possible* given that the shortwave is coming from the northwest. A shift north could mean a flatter system overall and could mean less precip.
- Euro + UK combo saying no is a tough hand to bet against
- Betting in a late blooming coastal always scares me, a lot can go wrong with transporting moisture that far away from the LP

Now the good:
- Hi-Res models haven’t gotten a good crack at this yet. They’re not just good for thermals, they’re *much* better at rendering topography. Can’t emphasis enough how much of a night and day difference a mountain range looks on the gfs compared to the nam 3k. I mention that because any shortwave gets stretched and contracted in the mountain west and that has implications downstream. Our shortwave is being held back in dang Utah may look a little different in the hi-res stuff
- We have a wildcard I haven’t seen mentioned yet: this shortwave. It’s currently between Oregon and Hawaii and flies into Cali in 3 days like a bat out of hell. Pay attention to this storm; if it holds on some more of its integrity it could be a nice little boost to our Rockies shortwave 869791961b0ad346f051fe9b0a32eca6.jpg594eb6deb6c20c73899ba7adfc20bbd6.jpg

I’m pretty neutral on this storm, I’m not completely optimistic but it still has a lot of upside.

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FWIW, probably not much. But the 15z SREF mean trended a good bit further north and west with the higher qpf totals, comparing to 9z.

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Some things I’m seeing;

Starting with the bad:
- I don’t know how much of a northwest trend is really *possible* given that the shortwave is coming from the northwest. A shift north could mean a flatter system overall and could mean less precip.
- Euro + UK combo saying no is a tough hand to bet against
- Betting in a late blooming coastal always scares me, a lot can go wrong with transporting moisture that far away from the LP

Now the good:
- Hi-Res models haven’t gotten a good crack at this yet. They’re not just good for thermals, they’re *much* better at rendering topography. Can’t emphasis enough how much of a night and day difference a mountain range looks on the gfs compared to the nam 3k. I mention that because any shortwave gets stretched and contracted in the mountain west and that has implications downstream. Our shortwave is being held back in dang Utah may look a little different in the hi-res stuff
- We have a wildcard I haven’t seen mentioned yet: this shortwave. It’s currently between Oregon and Hawaii and flies into Cali in 3 days like a bat out of hell. Pay attention to this storm; if it holds on some more of its integrity it could be a nice little boost to our Rockies shortwave 869791961b0ad346f051fe9b0a32eca6.jpg&key=4402403d10286b9c80cf5542bdf808e414621ff4c52eb471ffe5ceb6ec8999b7594eb6deb6c20c73899ba7adfc20bbd6.jpg&key=84cecf67866ecf617b22f4109856da4a27beae9cc7ac7492904b18f9d35a4ca2

I’m pretty neutral on this storm, I’m not completely optimistic but it still has a lot of upside.

You raise a good point, this storm hasn't even been sampled yet. Way too much time left to get on one model over another

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Question, are we referring to a northward expansion of the precip shield and a NW trend as the same thing? As was said, a significant NW trend seems unlikely because of the energy dropping in from the NW. But I feel what a lot of us really want is the wave to dig more SW and simply have better moisture transport northward during the over running portion of the event. I know globals are often terrible for QPF on the northern fringes of over running events, so that's what I'm pinning my hopes on IMBY. 

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RAH not biting:

Mid and high level moisture will increase rapidly on Thursday ahead
of a positively tilted trough digging through the Midwest.  Precip
will spread along the stalled frontal zone over the SE US, with
cyclogenesis induced off the SE coast.  Models continue to trend a a
bit closer to the coast with the surface low bringing more moisture
inland.  The low is still relatively weak, however, and moves east
with the digging trough.  The bigger question is whether or not the
arctic air associated with a 1045+ mb high over the central US will
spill across the mountains in time to cause a mix of rain and snow
or changeover to rain.  The high is not in a favorable location for
the dense cold air to make it into NC very quickly...likely having
to filter across the central Appalachians and south through VA...and
so the probability of probability more than a rain/snow mix appears
very low at this time.  If there is an opportunity for phasing of
sufficiently deep moisture/omega and cold air, it would be north and
east of the Triangle, which is where the outlier EPS solutions
lie..while the the GFS and GEFS appear to be too aggressive with
with cold air.

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Just now, ragtop50 said:

RAH not biting:

Mid and high level moisture will increase rapidly on Thursday ahead
of a positively tilted trough digging through the Midwest.  Precip
will spread along the stalled frontal zone over the SE US, with
cyclogenesis induced off the SE coast.  Models continue to trend a a
bit closer to the coast with the surface low bringing more moisture
inland.  The low is still relatively weak, however, and moves east
with the digging trough.  The bigger question is whether or not the
arctic air associated with a 1045+ mb high over the central US will
spill across the mountains in time to cause a mix of rain and snow
or changeover to rain.  The high is not in a favorable location for
the dense cold air to make it into NC very quickly...likely having
to filter across the central Appalachians and south through VA...and
so the probability of probability more than a rain/snow mix appears
very low at this time.  If there is an opportunity for phasing of
sufficiently deep moisture/omega and cold air, it would be north and
east of the Triangle, which is where the outlier EPS solutions
lie..while the the GFS and GEFS appear to be too aggressive with
with cold air.

GSP says kinda sorta, hey maybe, remember last week?  

There now looks to be a brief break in the precip Wednesday night as
the first wave of forcing moves east and some drier air moves in. Of
course, this sets the stage for the potential for some wintry precip
as moisture moves back in Thursday ahead of the surface wave moving
along the front and some upper divergence associated with a coupled
jet streak. The guidance still doesn`t agree on how far north the
moisture moves or just how cold the air will be. That said, it is
now looking like there will be precip at least as far north as the I-
85 corridor and likely the NC mountains. Precip tapers off quickly
Thursday night as the wave moves east of the area. The thermal
profiles and partial thickness progs show the precip to be rain or
snow with no significant warm nose. I`m beginning to become wary of
the snowfall potential given the previous 2 snow events where the
thermal profile and thickness values were quite similar. I suspect
this event could be similar where precip begins as snow over the
western CWFA along and north of the I-85 corridor with accumulations
developing where precip can fall for the longest period of time.
That said, have followed the national guidance for now which keeps
the accumulating snow across the higher elevations and mainly rain
outside of the mountains. Of course, this forecast could go either
way, so interested parties will need to stay abreast of the latest
updates.
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6 minutes ago, SnowDawg said:

Question, are we referring to a northward expansion of the precip shield and a NW trend as the same thing? As was said, a significant NW trend seems unlikely because of the energy dropping in from the NW. But I feel what a lot of us really want is the wave to dig more SW and simply have better moisture transport northward during the over running portion of the event. I know globals are often terrible for QPF on the northern fringes of over running events, so that's what I'm pinning my hopes on IMBY. 

Reminds me of the heavy snow rates in Chattanooga with the last storm

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