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Srain

Central/Western Summer Medium/Long Range Discussions

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A lot of bust potential with temperatures early next week in Oklahoma with the frontal passage. We'll see how far southwest that airmass can penetrate, before getting shoved eastward. NWS forecast high for Norman on Tuesday is 70. MEX guidance is 59.

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The GFS has been very insistent of driving a good old fashion 'Blue Norther' down the Plains into Texas for the last week. While there is some question regarding the placement of the Western Ridge, the signals are beginning to increase that the first legitimate Fall Polar Front may drop very far S pushing the sub tropical jet well S of Brownsville and even Key West. If the trends continue as advertised, the first real Southern Rockies snow storm of the season may spread as far S as ABQ and possibly into the Panhandles of Texas and Oklahoma.

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ECMWF and GFS currently agree on carving out a broad but positive-tilt trough over the Rockies early next week. Severe weather looks possible for the central and southern Plains, particularly Monday. As per the autumn usual, impressive kinematics but questionable thermo. Might be the last hurrah for anything worth paying attention to out here until Feb/Mar.

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Looks like the 12z Euro wants to morph the trough into a large closed low and slowly migrate it across the southern portion of the country on the days following Monday.

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ECMWF and GFS currently agree on carving out a broad but positive-tilt trough over the Rockies early next week. Severe weather looks possible for the central and southern Plains, particularly Monday. As per the autumn usual, impressive kinematics but questionable thermo. Might be the last hurrah for anything worth paying attention to out here until Feb/Mar.

 

Also potential for an E CO snowstorm, if anyone is interested (besides Howie)

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12z Euro offered quite an imposing-looking solution (with good support from its ensemble mean) regarding the trough diving into the west next week, as it loses the influence from the cutoff to the west, swings neutrally tilted and initiates some impressive low level cyclogenesis moving into MO and a very strong LLJ by 192 hrs.

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There appears to be a string of positive anomalies at 500mb/250mb going all the way from Africa to the Yukon, shifting the jet stream farther north into the Pacific, and allowing troughs to drop into the West USA. Much weaker 250mb wind speeds in mid-latitudes of the Pacific.  Do any of you guys have an explanation for such a consistent pattern of anomalies (Like MJO or something?) October 1-20 anomalies at 250mb. 
 

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post-1182-0-32585600-1382564039_thumb.gi

 

 

 

 

 

 

 

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A lot of uncertainty with that trough next week. (See the thread in the main forum). But GFS and Euro both have shifted to the south-southeast with the trough axis and low track, tilting the trough axis neutral over Oklahoma. I mentioned the snow possibilities for eastern Colorado, but this could get interesting for the central Plains too.

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Just as a quick look, using the free ECMWF graphics, 850 mb jet near/in excess of 60 knots ahead of a ~986 mb low in Minnesota, Halloween severe over a big chunk of the Eastern part of the Plains into the Mississippi Valley would seem possible.

 

Haven't delved deep, but over a day of return flow off a GOMEX still aoa 26º

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Medium range guidance still points toward a potential Plains severe threat with the trough ejection; there's just a wide temporal discrepancy in when that happens. GFS strongly favors Tuesday, while the ECMWF has consistently been slow enough to make it Wednesday, and potentially on the late side even for that. Last night's GGEM was a compromise. The SPC D4-8 outlook this morning favors Wednesday as the more significant of the two.

 

The most significant takeaway from current guidance is that BL moisture should be sufficient for a decent event, should other factors fall into line.

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Yeah it's becoming more evident to me that this will be more of a Plains focused event with the current progs, the 12z Euro strings out the trough following 132 hrs and the suite of models suggest that instability will be hard to come by east of the region. I will also say that the last few systems have grown more impressive synoptically as we have gotten closer to the event (not that it will happen this time, but something to keep in mind). Both the Euro and GFS have fairly expansive warm sectors on their respective days in the Plains.

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Judging by the ejection of the trough continuing to slow on the GFS with the 00z run, it definitely looks like Wednesday may end up having the most substantial potential of the days next week, with perhaps some threat on Tuesday in the High Plains as mentioned by the most recent D4-8.

 

One thing of note, both the GFS and GGEM show a lead impulse triggering a sfc cyclone on Tuesday that affects the wind fields and may lead to a lot of junk convection.

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Actually the 12z GFS doesn't look so bad in West-Central KS on Tuesday with the lead edge of 50-60 kt H5 flow (50+ kts of 0-6 km shear) nosing into the area, 25-30+ kts of 0-1 km shear and an adequate amount of instability (@ 00z).

 

There's holes in the Wundermap data, but the Euro at 108 is potentially intriguing with the progs at both 96 and 117 hrs actually showing rather expansive areas of 1000+ J/kg CAPE. I really hate these model differences and not being able to delve into this more precisely, but I'd tend to think that one of these days could still end up being a decent event, with my money more on Wednesday considering the continued slowing trend.

 

Pretty solid sounding @ Pratt valid 84 hrs from the 12z GFS.
 

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Starting to get that "too late for D1, too early for D2" feeling with the latest data. The GFS still gives Tuesday a shot, but it's trending toward the slower Euro.

 

Meanwhile, the Euro looks really solid synoptically and kinematically for Wednesday. Trouble is, it's an all-day washout that completely hoses some great potential, exactly like we saw about 2-2.5 weeks ago.

 

Leaning slightly in favor of Tuesday as being the better day, but a cap bust is quite possible.

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Actually the 18z GFS looks really good IMO for Tuesday along a GBD-WWR-CDS line as winds back slightly along the DL and you get discrete convection along it with 60-65 dews.

 

 

 

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Actually the 18z GFS looks really good IMO for Tuesday along a GBD-WWR-CDS line as winds back slightly along the DL and you get discrete convection along it with 60-65 dews.

 

attachicon.gifgfsSGP_con_scp_078.gif

 

18z GFS was basically a step up in every parameter on Tuesday compared to 12z...and over a larger area. Will pull some soundings momentarily.

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No doubt this run is impressive, but I don't like that it requires an even greater deviation from the fairly steadfast slow ECMWF timing. Unlikely as it is, hopefully a more progressive trend will start with tonight's suite.

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No doubt this run is impressive, but I don't like that it requires an even greater deviation from the fairly steadfast slow ECMWF timing. Unlikely as it is, hopefully a more progressive trend will start with tonight's suite.

 

I love it when models are more than a day apart in timing <5 days out... :axe:

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Monday is worth watching too on the southern High Plains, as illustrated by the 00z NAM. In fact, verbatim, I believe Monday would be the only shot at something noteworthy. It's too slow for Tuesday, with height rises through the afternoon and no QPF signal anywhere. No doubt Wednesday will be at least somewhat junky too when extrapolating.

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Yeah Monday on the new NAM looks like a good day in the eastern TX panhandle for sure if that were to verify. Over 90 degrees of turning to work with along the dryline with good shear vectors

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06z NAM has some pretty crazy soundings in Western OK around 00z and 03z Monday evening, and also has precip signatures that strongly suggest discrete convection. Also, despite it being in its fuzzy range, it has quite the warm sector in place on Tuesday with less height rises than 00z...and more than enough shear (although the questions regarding initiation still exist).

 

It is interesting to see that with either the NAM or GFS, there is a day that looks to provide a more reliable chance at a more notable event, Monday for the former, Tuesday for the latter.

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Once again we are facing a very complex and complicated pattern where a deep Western trough that appears to be slow moving and abundant Gulf moisture heads inland into the Southern Plains as well as deep tropical moisture associated with yet another EPAC tropical cyclone (future TS Sonia) combine to bring another heavy rainfall event for portions of Texas/Oklahoma/Kansas/Arkansas and Louisiana. What complicates the forecast this time is the guidance is suggesting a stronger SE Ridge that would tend to block the forward progression of the trough lending to another multi day heavy rainfall event that extends mid to late week time frame of the first full week of November. It is noteworthy that portions of the Hill County in Central Texas received nearly 15 inches of rainfall on October 30-31 and general amounts in the 4-8 inch range fell across the Eastern half of Texas into Louisiana with isolated higher amounts near 10 to 11 inches. Any additional heavy rainfall return in a short period would lead to additional flooding threat across a Region that has received above normal amounts of rainfall for the month of October.

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Steve, it is a complicated situation and far enough out that the details could still change.  Right now it looks like the heaviest would be north and west of you but it is still early. 

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The pattern certainly looks wet for the middle of the country as systems keep digging into the west in the long range. I noticed the 300hr GEFS ens mean still has higher than normal heights over the east and lower over the west   That is cause for concern though the euro digs one of the trough so far west it might give TX somewhat of a break.  Of course that's just a quick look with little deep thinking.  

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Steve, it is a complicated situation and far enough out that the details could still change.  Right now it looks like the heaviest would be north and west of you but it is still early.

I hope it hits north of the last two, north texas got missed with both of the last two big storms, could really use the rain in the DFW area and points west.

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An interesting pattern may develop in the medium range. The operational and ensemble guidance has been very insistent that an anomalously large blocking ridge will develop close to the Aleutian Islands allowing for the potential of a sharp and shallow Arctic air mass to develop across Canada. While there remains a lot of uncertainty via the ensembles, it is noteworthy that an early season chill may drop rather far S into the Plains extending to the Gulf Coast and the Eastern US next week.

 

11062013 12Z:

 

 

11072013 00Z:

 

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That's a major pattern reversal, and as is usually the case, LR model forecasts were a little too quick with communicating it downstream (hence the chillier start to November in the east). But anyway by day 2 we have the massive Aleutian ridge, by day 4 the ridge breaks, and by day 6 huge full latitude trough in the west, and ridge in the east.

What LR models are agreeing on now is a decent arctic intrusion into the western trough, and one heck of a temperature discontinuity in the central and southern Plains by around day 8-9. Looks like a classic Plains cold front.

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