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Central/Western Summer Medium/Long Range Discussions


Srain

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Uggg... I'm so torn on tomorrow.  The 4 km CONUS NAM Nest run shows big cells developing in SE/E Nebraska, but some other models aren't really showing the cap breaking very easily.  I'm also worried the storms won't become surface based and may just be elevated HP hailers.  But, the low level directional shear is impressive if things can become surface based and cells can stay isolated.  00z NAM appears like the best convective potential looks greatest in NW Iowa but it looks displaced from the best instability... however, the helicity values and LCLs in that area are fantastic.  I'm probably going to give it a go no matter what.  This is my last chance to chase before my baby comes and its really not THAT far, but I'm worried about it.  I think there is potential, but I feel like there are tons of question marks.

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The afternoon AFD out of Sioux Falls at least mentioned the T word:

 

 

 

STORMS WOULD INITIALLY BE SUPERCELLS BEFORE PROBABLY BECOMING MORE OF
A CLUSTER...WITH LARGE HAIL AND STRONG WINDS THE MAIN THREAT...BUT
GIVEN LOW LEVEL WIND FIELDS AN ISOLATED TORNADO WOULD ALSO BE
POSSIBLE IF STORMS GET INTO OUR AREA EARLY ENOUGH. FURTHER NORTH THE
THREAT SEEMS LOWER. HOWEVER WILL HAVE TO KEEP AN EYE ON THINGS...AS
IF AN ISOLATED STORM IS ABLE TO FORM ALONG THE FRONT NEAR THE JAMES
RIVER...IT WOULD LIKELY BECOME SUPERCELLUAR WITH CAPE AROUND 2000
J/KG AND DEEP LAYER SHEAR OF 40 OR MORE KTS.

 

Meanwhile, Omaha's AFD only gave the threat a glancing mention.

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Columbus, NE at 21z tomorrow:

 

SKT_NAM__KOLU.png

 

0-1 km SRH of 143 m2/s2, 0-3 km SRH of 313.

 

0-1 km EHI of 4.8, 0-3 km EHI of 10.5.  

 

Though one of the AFDs (I think Hastings?) did mention that they preferred ECMWF over NAM for surface Dew Points, expecting that the NAM is too moist and blowing up CAPEs that are too big.

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We bagged Nebraska for high-based stuff in Colorado due to concerns over driving distance (and the very real threat that we wouldn't even get there before initiation, since we stayed in Belle Fourche last night).

 

The vote was 18-1 in favor of Colorado.  I was the 1.

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Columbus, NE at 21z tomorrow:

 

 

 

0-1 km SRH of 143 m2/s2, 0-3 km SRH of 313.

 

0-1 km EHI of 4.8, 0-3 km EHI of 10.5.  

 

Though one of the AFDs (I think Hastings?) did mention that they preferred ECMWF over NAM for surface Dew Points, expecting that the NAM is too moist and blowing up CAPEs that are too big.

 

It could be that this image is the 21 hour forecast from 12z, which would put it at nighttime, 09z.  That would help explain the capping, inversion at the surface.

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We bagged Nebraska for high-based stuff in Colorado due to concerns over driving distance (and the very real threat that we wouldn't even get there before initiation, since we stayed in Belle Fourche last night).

 

The vote was 18-1 in favor of Colorado.  I was the 1.

 

Damn. You guys could've made it even leaving at 11am most likely. Hopefully the upslope play provides some photogenic storms. The warm front play is fairly risky for a mess (perhaps even going linear quickly as a worst-case scenario), but I'm en route and hoping for the best, since the ceiling still impresses me .

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This is kind of an exciting supercell index in Iowa (6 hour RAP forecast)

 

So you guys think storms will fire in east Colorado? The slight risk only touches a tiny bit of Colorado, although it does seem like CAPE could briefly get above 1500 J/kg in east Colorado.

 

I actually took a drive over by Greeley (eastward to Ft. Morgan) yesterday to look at a storm. It was more of a drive than a storm chase. I think I was seeing the NW side of a weakening cell. I only saw a couple of lightning bolts the whole time. It looked sort of generic.

 

post-1182-0-43957700-1371228006_thumb.pn

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So you guys think storms will fire in east Colorado? The slight risk only touches a tiny bit of Colorado, although it does seem like CAPE could briefly get above 1500 J/kg in east Colorado.

 

Most hi-res guidance shows something going, but I'm really bitter about the decision.  Everyone else on the trip is on board apparently.  They say it would have been too long a drive tomorrow if we did the NE play today, but imo nothing tomorrow in CO/KS/NE looks better than today in NE.

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You could go down to Lamar CO, and take pictures of the thermometers!

 

Just keep in mind that eastern Colorado seems to be the place for landspout-type tornadoes and also dry microbursts. Also 1500 J/kg can do wonders at this elevation.

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You could go down to Lamar CO, and take pictures of the thermometers!

 

Just keep in mind that eastern Colorado seems to be the place for landspout-type tornadoes and also dry microbursts. Also 1500 J/kg can do wonders at this elevation.

 

I've done Denver cyclone days plenty already but I've been watching northeastern NE for about 7 days now so it was a disappointment to bag.

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In addition to the current threat, medium range guidance appears to be suggesting a fairly volatile pattern setting up in the West towards the middle of next week, with troughing becoming established and a strong vort max ejecting into the Northern Plains, the 12z GFS/ensemble suite appears to be more aggressive in developing this feature and resulting cyclogenesis as a possible catalyst for severe weather. On the other hand, the Euro and GGEM appear to be less bullish and instead sacrifice this anomaly to break down/buffet the ridge somewhat. However, the Euro and GGEM also show a very large ULL/trough setting up off the Pacific NW coast by the end of their respective runs, so this trough around this time next week would likely not be the last ejecting out into the Plains. The differences are pretty clear between the Euro and GFS suites when looking at the 8-10 day means for their respective ensemble suites (although they both appear to suggest +AO/+NAO combos and the Euro suggests a relatively strong -PNA developing, which would increasingly favor western troughing). Some of the 12z GFS ensemble members also suggest a trend towards the Euro/GGEM in terms of Western troughing later in their runs as well. Another interesting thing is that several of the Euro and GFS suites show the MJO again slowing in Phase 5 (in the rather near term as well). Should this type of pattern verify, severe potential would likely increase somewhere in the CONUS towards the last week in June.

 

teu.gif

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Why does this thread have "tropical cyclones" as a tag? 

Last time I checked, The Central/Western sub included the tropics from the EPAC to the Western Atlantic Basin (Mexico/Texas/Louisiana) ;)

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It looks like a very active week ahead on the Canadian Prairies. Alberta, Saskatchewan, and Manitoba may all be under the gun at some point. Closer to home (southern MB), I am intrigued by Thursday and Friday. A ways to go yet but it looks promising. Cap may be an issue, though!

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South east North Dakota, north west South Dakota, and west central Minnesota look to also be active on Friday / Saturday (6/22). The shear parameters look marginal, but it is something to watch five days out given the amount of moisture available.

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Thursday in eastern ND is what I'm interested in.  Although, my wife's due date is this coming Sunday, so it would have to basically be right on me or in a 20 mile radius for me to chase anything.  Still, northeast NN into SE Manitoba, and southeast ND look to have decent parameters in place for at least a mean MCS or some big hailers.

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18z GFS continues to suggest a robust threat in the Eastern Dakotas through MN and IA perhaps into WI around the end of this weekend as a strong vort max and near 70 kt 500 mb jet streak kicks the ejecting s/w trough negatively tilted and rapidly enhances LLJ dynamics, leading to 0-3 km SRH of 250-400 m2/s2 in addition to already strong instability of 3000+ J/kg SBCAPE. Rather impressive looking setup.

 

You don't see dynamic troughs like that everyday this time of year...

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