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andyhb

Central/Western Medium-Long Range Discussion

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Pretty interesting GFS runs today with a moisture tap from the tropical system down there into Arizona and then again with the dying remnants of another system hitting the same area. Could be quite wet in some locations that traditionally get almost no rain in June.

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Just taking a brief glimpse at the models, it seems both the GFS and the EURO have a pretty significant trough entering the west CONUS around the 15-16th of June. Such an anomalous trough would be impressive for the time of year, and would obviously increase the chances of severe wx over the central/high plains, so we'll see if it continues in forthcoming runs!

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Just taking a brief glimpse at the models, it seems both the GFS and the EURO have a pretty significant trough entering the west CONUS around the 15-16th of June. Such an anomalous trough would be impressive for the time of year, and would obviously increase the chances of severe wx over the central/high plains, so we'll see if it continues in forthcoming runs!

00Z GFS definitely doesn't have a significant trough entering the W CONUS... But it does have a pretty significant trough across the far N CONUS (ND/SD/MT) with H5 flow progged at 50-70kts around June 14-15... And this is nearly the exact same scenario as shown by the 18Z GFS, with quite a difference in the 12Z run, and some similarities to the 06Z run... Overall though, the GFS has hinted for a few days at the possibility of some sort of MAJOR trough in mid to late June.

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Man 18z GFS has a trough with a 90 kt 500 mb and 120+ kt 300 mb speed max moving across the Northern Plains next week, that would be seriously impressive.

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Man 18z GFS has a trough with a 90 kt 500 mb and 120+ kt 300 mb speed max moving across the Northern Plains next week, that would be seriously impressive.

shows an incredible environment in place in S/SE SD and NC/NE Nebraska. 50-70knots of 0-6km shear juxtaposed to MUCAPE of 1000J/KG near the WF to 3000-4000J/KG across the Warm-sector. The environment is especially impressive along the WF in SE/E SD maxed out (500m2/s2) 0-3KM SRH across a large area... Looks as though one issue along the WF could be low-level winds.. Which are kinda meh, AOA 15-20kts along the surface warm front/ theta-E gradient. But further south they increase markedly by 00Z to 40kts at H85 and especially by 03Z to 50kts in C/NC Nebraska... But the LLJ is only slightly south of the front at this point, and this is still several days out so that's only if you take the run verbatim. Another very apparent issue on the soundings is a tremendous cap in place from about 900mb to 700mb, producing CIN around 150J/KG. Nevertheless mid level and upper level winds will not be an issue whatsoever if this were to verify.

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Details aside, there's at least some fair model support of some type of severe threat in the central/northern Plains to upper Midwest between June 16-20. The GFS, at varying degrees, has shown this threat in different capacities. Some runs showed a string of impressive days. The Euro has showed at least subtle signs, along with the ensembles. The latest Euro weeklies look a bit washed out in the mean, but the control run was a bit more dynamic up north.

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Like Quincy said, it seems that the rear end of next week seems to hold some good potential for some sig severe wx across the north central plains. still shows 40-60 knots at H5 along with pretty significant CAPE values. Euro is a little less excited as the GFS but of course it's still long range on both models. Definitely an encouraging sign for chasers such as myself. 

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Still have eyes on this period. Verbatim, the 12/10 Euro shows bonafide threats days 8, 9 and 10. Would like to see more model consistency, especially once we get inside of 7 days.

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Still have eyes on this period. Verbatim, the 12/10 Euro shows bonafide threats days 8, 9 and 10. Would like to see more model consistency, especially once we get inside of 7 days.

 

Some of these longer range GFS/ensemble runs as of late have really fallen into the "holy crap" category.

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Just a few thoughts about the 00z guidance (focusing on the operationals):

 

There are two camps in this set of model runs. One, consisting of the Euro and GGEM, is more progressive with the closed low that breaks off the main northern jet branch in the NW in a couple days (this is mainly due to it not retrograding west as far) and eventually leads to a rather messy, disjointed troughing across the N tier of the CONUS late next week since the aforementioned low does not phase very well with the incoming southern stream that undercuts the Aleutian ridging.

 

The other, potentially more volatile scenario is shown by the GFS and likely an extrapolated UK. These two model retrograde the closed low far enough so that it is not picked up by the northern stream for a slightly longer period of time (both in a similar position at 144 hours). It then (on the GFS) is picked up by the northern stream afterwards and phases with the southern branch more effectively, eventually leading to a very potent shortwave trough ejecting across the Northern Plains around D8-9 with some extremely impressive wind fields for June (and likely higher end severe potential as it seems a large reservoir of seasonably high instability will be in place for whatever does come down the chute then).

 

In conclusion, while it seems all guidance would indicate at least some severe possibilities late next week (as they have for several days now), it's going to be crucial to monitor the evolution of this closed low off the West Coast over the next few days as it could have major implications downstream for the northern CONUS. Should also add that the northern stream shortwaves that eventually lead to the closed low being picked up are also highly important. Overall, a lot of moving parts and it should be awhile before anything is settled on.

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The next 7-10 days aren't looking too promising, at least anywhere in the Plains. The fat lady may have been warming up as the June 4-6 sequence concluded and we didn't even know it at the time.

 

After an exceptionally active April-May pattern wise, it's not too surprising. That said, it is still June, and there will still be tornadoes on various days. And "real" setups can't be ruled out north of I-80 even heading into late June and July.

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The next 7-10 days aren't looking too promising, at least anywhere in the Plains. The fat lady may have been warming up as the June 4-6 sequence concluded and we didn't even know it at the time.

 

After an exceptionally active April-May pattern wise, it's not too surprising. That said, it is still June, and there will still be tornadoes on various days. And "real" setups can't be ruled out north of I-80 even heading into late June and July.

 

Yeah that whole idea fell apart fast. Looks as if we'll go all of Spring and June without a high risk or PDS watch at this juncture.

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I would still expect at least one or two decent severe weather events between Thursday, June 18th and Sunday, June 21st. The Euro/GFS aren't in the best agreement with specifics, but both advertise some high CAPE/modest shear environments. Of course, the best kinematic support will likely remain displaced to the north. Still, with sizable areas of 3000+ J/kg MLCAPE progged for at least some of the period and decent winds upstairs, it's worth keeping an eye on.

 

Either way, as mentioned, nothing in the High Risk category should be expected. If anything, I'd suspect multiple SLGT/ENH risks in the period. The aerial coverage for such threats should remain on the smaller side, unless model guidance takes some sudden shift back into the "right" direction. 

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Seems to be the suggestion of a rather strong shortwave trough dropping SE out of the Gulf of Alaska towards the early part of next week via the deterministic guidance (supported a pronounced lowering of the heights across the Prairie Provinces and N Plains on the ensembles in this same timeframe). Northern stream has been quite active this summer so this doesn't seem to be too farfetched. Does seem that there may be some low latitude troughing that could cause problems with moisture availability though.

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Also, some model agreement is noted in the 11-15 day for a trough West ridge Midwest pattern. I'm talking end of August and first few days of September. Hints of both upper and low level jets responding is shown in the Plains some of the days. Northern stream staying active through the summer helps the case.

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I've been casually watching Sunday across the north-central states. A lot can change and there has been some model adjusting, but keeping an eye on a vigorous shortwave forecast to eject across the northern Plains Sunday into early Monday. There may be somewhat of a disconnect between the best forcing, strongest wind fields and the warm sector, but details can be ironed out in the coming days.

 

Based on model indications now, I'd peg the focus on the eastern Dakotas into the Upper Midwest as an area to keep an eye on. Nothing significant and not outbreak-material, but the way this year has gone, at least it's something on the radar.

 

I wonder how this fall will shape up, if it may try to pull a 2013 or keep the trend of generally lackluster severe threats. I'd tend to lean toward the latter.

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Expecting a 2013-like fall any year would be a tall order, considering that year had not one but two really significant severe events (10/4 and 11/17). However, I would lean more on the active side this fall given that previous ones heading into Ninos have featured some substantial fireworks and especially if this new regime that has taken over the E Pacific continues deeper into October/November (i.e. Gulf of Alaska/western N. America trough).

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So, the last few ECMWF runs have looked interesting about 6 days out.

 

Instability looks rather low, what was once looking like a solid warm sector has shrunk into almost nothing.

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Instability looks rather low, what was once looking like a solid warm sector has shrunk into almost nothing.

 

I'll be honest and say I haven't really looked much at anything other than the standard height plots up to this point, but I can see how that could be an issue. Having the current system shear out and leave some junk behind for a few days certainly doesn't help things at the surface with return flow. I'll still be watching it though, and if the models don't shift anything around with the timing, I'm actually probably good to go Wednesday if things look good at that point.

 

*EDIT: Just looked at the 12Z ECMWF CAPE for Wednesday. Ick, I can see what you mean...

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I wouldn't be surprised if this thing peaks severe wise on Wed from 12-18z over the E Plains and Lower MO Valley. Both the Euro and GFS are showing some appreciable instability there closer to the triple point where colder 500 mb temps will result in steeper mid level lapse rates on the nose of the LLJ.

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You often see hints of higher instability on the DGEX, but even that isn't much different than the GFS when comparing theta-e values.

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I wouldn't be surprised if this thing peaks severe wise on Wed from 12-18z over the E Plains and Lower MO Valley. Both the Euro and GFS are showing some appreciable instability there closer to the triple point where colder 500 mb temps will result in steeper mid level lapse rates on the nose of the LLJ.

Based on the GFS/Euro (12z), certainly have to agree with this.

 

The Euro actually shows the best instability in the east-central Plains at 12z on Wed, lessening with time with movement into Iowa and Missouri. Likewise, the GFS forecast soundings for eastern Missouri and southeastern Iowa are not as impressive as further west/earlier.

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FWIW, the message I'm getting from basically every AFD I've read (OAX, EAX, TOP, LSX, SGF, ILX, DMX, etc.) is concern for just how dynamically impressive this system is, as I've stressed from the beginning with this thing. Troughs like this can and often do pull a lot out of very little thermodynamic wise. Then you start concerning with areas that actually have appreciable buoyancy like closer to the 500 mb low. I also noticed that the Euro was showing some better 700-500 mb lapse rates further south on Wed, although still very little CAPE.

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From Broyles... Day 4 OTLK:

 


 DAY 4-8 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0342 AM CST SUN NOV 08 2015   VALID 111200Z - 161200Z   ...DISCUSSION...   THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH AN   IMPRESSIVE UPPER-LEVEL SYSTEM OVER THE SRN AND CNTRL PLAINS. STRONG   TO POTENTIALLY SEVERE THUNDERSTORMS MAY BE ONGOING AT THE START OF   THE PERIOD IN THE CNTRL PLAINS NEAR THE EXIT REGION OF A POWERFUL 85   TO 100 KT MID-LEVEL JET. THIS JET MAX IS FORECAST TO MOVE ENEWD INTO   THE MID MS VALLEY DURING THE DAY ON WEDNESDAY/DAY 4 AS A COLD FRONT   ADVANCES QUICKLY EWD ACROSS THE REGION. THUNDERSTORM COVERAGE IS   EXPECTED TO EXPAND FROM THE LOWER MO VALLEY SWD INTO THE OZARKS   EARLY IN THE DAY AS SFC DEWPOINTS INCREASE INTO THE 60S F ALONG THE   FRONT. THIS COMBINED WITH ENHANCED LARGE-SCALE ASCENT ASSOCIATED   WITH THE FAST MOVING UPPER-LEVEL SYSTEM AND VERY STRONG DEEP-LAYER   SHEAR SHOULD BE FAVORABLE FOR SUPERCELLS WITH WIND DAMAGE AND SOME   TORNADOES. AN ENHANCED SEVERE THREAT MAY DEVELOP ACROSS PARTS OF THE   MID MS VALLEY WEDNESDAY AFTERNOON AND EVENING WITH THE SEVERE THREAT   EVENTUALLY REACHING THE OH AND TN VALLEYS. 

 

post-397-0-66969900-1446983742_thumb.gif

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I agree with Andy. Models are probably too pessimistic due to clouds etc. However the system is very dynamic. It should over achieve. Look at the wind fields. SPC is right to go ENH for sure.

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The GFS/Euro show another dynamic system in the Plains about a week from now. Not quite as impressive as this current system and a bit further south, but worth watching later forecasts and trends.

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12z model suite continues a strong signal for the lower Mississippi Valley and surrounding subforums to the east. Too soon for details, but this easily looks more impressive than what's going on today.

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12z model suite continues a strong signal for the lower Mississippi Valley and surrounding subforums to the east. Too soon for details, but this easily looks more impressive than what's going on today.

 

Trend over the past 24 h since your post has been toward focusing the most interesting period on Monday over OK/TX, before the system becomes more barotropic thereafter. Right now it looks a bit too positive-tilt to get me excited about the hodo shape (particularly given that instability is likely to be seasonably modest), but it's nice to see the above-average November severe activity continue.

 

http://www.pivotalweather.com/model.php?m=GFS&p=03ehi&rh=2015111212&fh=108&r=sc&lat=33.5000&lon=-98.3780&metar=

 

ECMWF looks relatively similar this afternoon, with 1000 J/kg SBCAPE nosing into SW OK by Monday afternoon.

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HGX had quite the discussion for Mon/Tues in their most recent AFD.

 

THE PATTERN WILL BEGIN CHANGE SUNDAY INTO MONDAY AS A DEEP PACIFIC
NORTHWEST TROUGH DIGS SOUTH INTO THE GREAT BASIN...SURFACE PRESSURE
GRADIENT TO ORIENT MORE ONSHORE EARLY NEXT WORK WEEK. STRENGTHENING
SOUTHERLIES THROUGH MID NEXT WEEK AHEAD OF WHAT IS PROGGED TO BE
A FAIRLY PROGRESSIVE STORM SYSTEM. THIS SYSTEM IS CURRENTLY MODELED
TO BE QUITE IMPRESSIVE...ESPECIALLY FROM A DYNAMIC STANDPOINT. THE
TROUGH IS FORECAST TO EVOLVE INTO A DEEP CLOSED-OFF LOW THAT WILL
BARREL OUT OF THE LOWER ROCKIES EARLY TUESDAY AND BE EAST OF US
BY MID TO LATE WEDNESDAY. UNLIKE RECENT SYSTEMS WHOSE ENERGY
TRAVELED OFF TO THE NORTHEAST...THIS LATEST TROUGH IS FORECAST TO
DIG WELL INTO NORTH CENTRAL TEXAS AND PROVIDE VERY ROBUST MID TO
UPPER LEVEL SUPPORT FOR VERY ACTIVE WEATHER. A 40-60 PLUS KNOT LOW
LEVEL JET WILL COME ACROSS THE FORECAST AREA EARLY TUESDAY...GENERATING
AN HIGHLY-SHEARED WIND PROFILE (RIGHT CURVED HODOGRAPH WITH 0-1KM
PLUS 200 SRH) THAT...IF THESE DETERMINISTIC MODELS GET IT RIGHT...
EQUATE TO A SEVERE WEATHER OUTBREAK MID-MONDAY THROUGH TUESDAY.
OTHER INGREDIENTS THAT ARE WORTH MENTIONING ARE COLUMN MOISTURE
AT...OR SLIGHTLY UNDER...2 INCH PWATS THAT IS NEAR MAXIMUM CLIMO
VALUES FOR MID- NOVEMBER...NEAR 1K TO 1.5K J/KG SB CAPE VALUES
(MID-UPPER 30 K INDICES)...AND A SIGNIFICANT SPLIT JET STRUCTURE
TUESDAY MORNING TO PROVIDE THE NEEDED UPPER LEVEL EXHAUST. ALL
TOLD...IF RUN-TO- RUN NWP CONSISTENCY HOLDS UP THROUGH THE WEEKEND
...THIS WILL BE ANOTHER IN A STRING OF SEVERE WEATHER OUTBREAKS
FOR US HERE IN SE TX. OF COURSE...WE ARE DISCUSSING DAYS 5 AND 6
SO CERTAINLY THERE IS MUCH TIME TO TUNE THE FINER DETAILS.
CONSIDERING WHAT THE 12/12Z DETERMINISTIC MODELS ARE OUTPUTTING...
THIS SYSTEM WOULD POSE A MORE OF A DAMAGING STORM WIND AND TORNADO
THREAT...VERSUS THAT OF FLASH FLOODING...STRICTLY DUE TO ITS VERY
PROGRESSIVE NATURE.

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