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Central/Western Summer Medium/Long Range Discussions

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From April 4th on to the end of its cycle, the 17.00 Euro weeklies show ridging with above average heights across the central and southern Plains. Let's hope this comes to fruition!

 

Leading up to that, with a potential East Coast low/trough around the 26th, guidance suggests that there could be a temporary return to a Southeast ridge before the pattern shuffles a bit. We'll see how it plays it out.

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From April 4th on to the end of its cycle, the 17.00 Euro weeklies show ridging with above average heights across the central and southern Plains. Let's hope this comes to fruition!

 

Leading up to that, with a potential East Coast low/trough around the 26th, guidance suggests that there could be a temporary return to a Southeast ridge before the pattern shuffles a bit. We'll see how it plays it out.

Ridging across the Central/Southern Plains is what you don't want if you want severe, you need the ridging to be focused from the MS River and east otherwise you doing get enough of a moisture feed into the plains and the troughs would keep deflecting to the North. That would be a bad pattern for the Plains.

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Ridging across the Central/Southern Plains is what you don't want if you want severe, you need the ridging to be focused from the MS River and east otherwise you doing get enough of a moisture feed into the plains and the troughs would keep deflecting to the North. That would be a bad pattern for the Plains.

That's true. The ensemble mean is smoothed out and the main point is that instead of below average heights/troughiness across the eastern third of the U.S., we're at least projected to move toward a more "seasonable" pattern where the Polar jet lifts further north into Canada. How individual shortwaves flow through that pattern will be key, wrt moisture transport, as you mentioned, among other things.

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Don't waste your time...

 

Have to agree. I've been watching the 8-14 day range on both models and their ensembles for weeks, and we've been jerked around one too many times to keep me interested now. The "disappearing pattern change" that was supposed to happen 3/20-3/22 from as little as 8 days out was one of the worst model flips I've seen in awhile. Normally, when the ensembles so strongly support a large-scale pattern, you can trust them even 8-10 days out if you ignore the details. I'm going with persistence until a strong signal to the contrary emerges and holds firm into the 6-7 day range. Given the atrocious performance of the GEFS/ECMWF even at D7-10, I think the EPS control run and weeklies are just noise right now.

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Have to agree. I've been watching the 8-14 day range on both models and their ensembles for weeks, and we've been jerked around one too many times to keep me interested now. The "disappearing pattern change" that was supposed to happen 3/20-3/22 from as little as 8 days out was one of the worst model flips I've seen in awhile. Normally, when the ensembles so strongly support a large-scale pattern, you can trust them even 8-10 days out if you ignore the details. I'm going with persistence until a strong signal to the contrary emerges and holds firm into the 6-7 day range. Given the atrocious performance of the GEFS/ECMWF even at D7-10, I think the EPS control run and weeklies are just noise right now.

If we look toward the MJO, both the GFS and Euro push us into Phase 8/1/2, or in other words keep the NH into a cooler than average pattern with persistent troughiness across central/eastern Canada and at least portions of the eastern U.S.

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With regards to El Nino, it is traditionally seen as a severe weather inhibitor (as mentioned above), but we've been stuck in pretty much the same spring pattern going on two years now. At this point, I am welcoming any El Nino with hopes that it can at least shake things up a bit. Can't be much worse than the rubbish pattern we're currently in, right?

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New Euro weeklies show a consistently at to above average temperature pattern for the eastern half of the U.S. for the final days of March into mid-April. If that verifies, I think we'd see the severe season light up fairly quickly. With a tight gradient pattern and more ridging in the Southeast...

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Have to agree. I've been watching the 8-14 day range on both models and their ensembles for weeks, and we've been jerked around one too many times to keep me interested now. The "disappearing pattern change" that was supposed to happen 3/20-3/22 from as little as 8 days out was one of the worst model flips I've seen in awhile. Normally, when the ensembles so strongly support a large-scale pattern, you can trust them even 8-10 days out if you ignore the details. I'm going with persistence until a strong signal to the contrary emerges and holds firm into the 6-7 day range. Given the atrocious performance of the GEFS/ECMWF even at D7-10, I think the EPS control run and weeklies are just noise right now.

Yea, the 20-22nd potential change was a miss. Some guidance was even showing more western trough potential with the mid-week wave for next week, but it's clear that won't be happening either with the northern stream dominating things.

 

As for the ECMWF weeklies and the CFS...They once showed change occuring for mid-late March several weeks back, but then quickly backed off...And as we can see now no change occured. They're once again looking encouraging...Both agree on a more zonal flow/west trough pattern developing during the first few days of April and continuing into at least mid-April. They have been fairly consistent in showing this, so we'll see if it sticks or it's another failed attempt at a large scale change. I've been hitting the "See you in April" thing on FB since February, so we'll see that indeed works out.

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Yea, the 20-22nd potential change was a miss. Some guidance was even showing more western trough potential with the mid-week wave for next week, but it's clear that won't be happening either with the northern stream dominating things.

 

As for the ECMWF weeklies and the CFS...They once showed change occuring for mid-late March several weeks back, but then quickly backed off...And as we can see now no change occured. They're once again looking encouraging...Both agree on a more zonal flow/west trough pattern developing during the first few days of April and continuing into at least mid-April. They have been fairly consistent in showing this, so we'll see if it sticks or it's another failed attempt at a large scale change. I've been hitting the "See you in April" thing on FB since February, so we'll see that indeed works out.

 

Yeah even if some of these things end up working out, March will have likely passed on by then. Cyclone made a good point in GL/OV that, for our sakes, it's probably better if we get these unfavorable regimes out of the way now rather than later.

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That period around next Thursday looks a bit intriguing despite rather low moisture content (still a surprising amount given the passage of the eastern trough earlier in the week). The further east the shortwave that traverses area gets (somewhat like the 00z Euro's idea) without running away from the moisture return, I would tend to think the better chance for any severe weather, given that capping will likely be a problem further west (as highlighted by the 00z/06z GFS). Areas potentially affected look to be somewhere in the Southern Plains into the Ozarks (anywhere further east is going to be hard-pressed to have an effective warm sector).

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That period around next Thursday looks a bit intriguing despite rather low moisture content (still a surprising amount given the passage of the eastern trough earlier in the week). The further east the shortwave that traverses area gets (somewhat like the 00z Euro's idea) without running away from the moisture return, I would tend to think the better chance for any severe weather, given that capping will likely be a problem further west (as highlighted by the 00z/06z GFS). Areas potentially affected look to be somewhere in the Southern Plains into the Ozarks (anywhere further east is going to be hard-pressed to have an effective warm sector).

Obviously 5 days out, but guidance is showing it being an ana-front situation as well...

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Any shot at getting something worthwhile late next week will be closely tied to the lead system being a fish storm, instead of a coast-hugging nor'easter. Couldn't be rooting harder for that, especially after the winter they've had already. ;)

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Obviously 5 days out, but guidance is showing it being an ana-front situation as well...

 

It's not exactly the classic anafrontal setup that we saw last year, it helps that the s/w trough upon ejection is neutral/negatively tilted. The 12z Euro had quite a vigorous system with a 988 mb low in northern KS at 129 hrs with the warm sector expanding into western AR with what appear to be pre-frontal confluence bands. There must be rather cold mid level temperatures given the rather cool temperatures at the surface and yet still yielding 800-1200 J/kg of CAPE over that area. These low amplitude, strong shortwaves have yielded "cold season" events in the past (I say in quotation marks because the thermos are reminiscent more of a winter event currently).

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It's not exactly the classic anafrontal setup that we saw last year, it helps that the s/w trough upon ejection is neutral/negatively tilted. The 12z Euro had quite a vigorous system with a 988 mb low in northern KS at 129 hrs with the warm sector expanding into western AR with what appear to be pre-frontal confluence bands. There must be rather cold mid level temperatures given the rather cool temperatures at the surface and yet still yielding 800-1200 J/kg of CAPE over that area. These low amplitude, strong shortwaves have yielded "cold season" events in the past (I say in quotation marks because the thermos are reminiscent more of a winter event currently).

 

Yeah, the 12z EC is on the cusp of a moderately interesting Plains/Ozarks setup Thursday. Both the 2m temps and dews are marginal across OK/KS, but SBCAPE still exceeds 1000 J/kg along most of the dryline. I'm also interested in parts of N TX (including DFW), where the low-level thermodynamics are more impressive. Tough to say how big an issue the cap would be down there without detailed point soundings, though. The downstream pattern would suggest a relatively modest ceiling on this setup for now, but it's much better than nothing.

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Definitely some differences emerging in the 00z suite tonight regarding the amplitude of the trough that moves across the Plains, with the Euro showing a much more robust and well defined mid level orientation with an accordingly stronger surface low. TX does hold some interest there as a wider warm sector with moistening low levels will be in place along with still favorable low level winds/hodographs. In addition, the Euro places central/eastern TX under a very favorable upper level jet configuration (the left entrance region of the incoming + RRQ of the departing), which would likely enhance the chances for storm development.

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12z GFS actually brings two systems across the central/eastern US (one on Thursday and the other on Friday/Saturday), the second one, as expected, has a much more expansive warm sector to work with thanks to the lead system pulling a modified air mass northwards.

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It's not exactly the classic anafrontal setup that we saw last year...

No doubt, I was just stating it because, well...it's ana-front season.

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12z Euro looks pretty interesting late Thursday into Friday as the warm sector expands eastward into the Lower MS Valley.

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12z Euro looks pretty interesting late Thursday into Friday as the warm sector expands eastward into the Lower MS Valley.

It continues to be slower than the GFS with Thursday.

 

The problem is it has the warm/moist sector clouded over with showers during the day.

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GFS is a good 12 hours too fast with the shortwave for Thursday, and it's only 96 hrs out. Quite doubtful that things will fall into place, although assuming a 75/25 ECMWF/GFS split might give a slim shot to the Ozarks and Arklatex. After that, a significant height weakness centered around FL looks to hose Gulf moisture for a time. I think we're headed for a nearly-tornadoless March, and a first part of Spring 2014 that's deja vu from last year.

 

Several veteran chasers mentioning this looks to be their first chaseless March ever, some dating back to the 80s.

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Considering the rest of model suite has a more vigorous (and slower moving) trough at 500 mb on Thursday (in addition to less emphasis on the FL vort), I'll reserve my judgment until the rest of the 00z runs are in.

 

And to be quite honest, it's not like March usually yields a ton for the Plains (years like 2007 and 1990 are the exception). This actually isn't the least active March on record, increase in tornado detection notwithstanding, 1969 and 1951 both had fewer than we do so far (although that's attempting to put a model's face on a troll obviously).

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Slight risk for Thursday.

Both the GFS and the ECMWF have ditched what was looking like a potentially favorable period after this weekend. Flow stays too progressive...Still a change from what has been seen though.

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This still looks like a change towards the more favorable to me.

There still a general pattern change...From a mean trough in the east and ridge in the west, to now what will be a progressive flow with fast moving west/east troughs.

 

Mostly what I was stating is guidance ditched the multi-day potential for next week...Sort of like they once did with what was once the 3/20-22 potential.

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There still a general pattern change...From a mean trough in the east and ridge in the west, to now what will be a progressive flow with fast moving west/east troughs.

 

Mostly what I was stating is guidance ditched the multi-day potential for next week...Sort of like they once did with what was once the 3/20-22 potential.

 

Well I'm not going to jump on any OP runs showing multi-day threats for now at that range, the main thing is that the ensembles largely kept with things changing towards the better.

 

The key thing will be development of troughing in the Gulf of Alaska.

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Guidance has been slowing coming back around the the idea of a multi-day event next week. OP wise...Both the ECMWF/GFS show a Tue-Thur threat, but obviously are much different in placement/evolution this far out. ECMWF is much more interesting.

 

A mention by the SPC as well...

 

A MORE EXTENSIVE/SLOWER-MOVING UPPER TROUGH IS EXPECTED TO EVOLVE
OVER THE WESTERN STATES EARLY NEXT WEEK...WITH LOW-LEVEL MOISTURE
STEADILY INCREASING ACROSS THE SOUTH-CENTRAL CONUS WITH 60S F
SURFACE DEWPOINTS BECOMING MORE PREVALENT BY MID-WEEK. CURRENT
INDICATIONS ARE THAT THE SEVERE RISK MAY APPRECIABLY INCREASE AS
EARLY AS DAY 6/TUESDAY ACROSS THE SOUTHERN HIGH PLAINS...BUT MORE
SO...INTO DAYS 7-8/WEDNESDAY AND THURSDAY FROM PARTS OF OK/NORTH TX
TO THE ARKLATEX/OZARKS AND MIDDLE MS RIVER VALLEY. LARGE
HAIL/TORNADOES WOULD BE POSSIBLE IN THIS SCENARIO. PENDING GUIDANCE
TRENDS...ONE OR MORE 30 PERCENT SEVERE RISK AREAS MAY BE WARRANTED
IN SUBSEQUENT OUTLOOKS FOR THE MIDDLE PART OF NEXT WEEK /WEDNESDAY
AND/OR THURSDAY/. 

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