Central/Western Medium-Long Range Discussion

[bjc0303]

Although the trends are encouraging one thing to watch is early/midday convection. Looks like a lead impulse is leading to pretty widespread convection/rainfall over the central OK warm sector by morning/midday which would put a huge dent in potential for Sunday. Obviously things can and will probably change but as we enter realm of better predictability, this is a growing concern. 

[CheeselandSkies]

Well in any case the Plains especially along and west of I-35 need all the rain they can get between now and May.

[WhiteoutWX]

6 hours ago, bjc0303 said:

Although the trends are encouraging one thing to watch is early/midday convection. Looks like a lead impulse is leading to pretty widespread convection/rainfall over the central OK warm sector by morning/midday which would put a huge dent in potential for Sunday. Obviously things can and will probably change but as we enter realm of better predictability, this is a growing concern. 

At least for now, the GFS and Euro seem to be keeping areas west of 35 relatively rain free during the afternoon before CI which could leave at least some area of potential open over western/west-central OK.

[bjc0303]

4 hours ago, WhiteoutWX said:

At least for now, the GFS and Euro seem to be keeping areas west of 35 relatively rain free during the afternoon before CI which could leave at least some area of potential open over western/west-central OK.

Perhaps. 12z Euro keeps precip in the picture but as you said, it’s confined to the east. The euro does destabilize the dry line quite a bit, and has a solid shear profile. Would be potential for supercells I imagine, but the effects of mid morning precipitation still has me concerned. Hopefully the NAM can bring clarity. Doubting the lead wave just disappears at this range of modeling, but maybe we can get more favorable timing. 

[rolltide_130]

Oof, the NAM has a potentially isolated but significant event near Enid on the 12z run for Sunday evening. Dryline bulge close to the triple point.. that can spell trouble. 

 

[jojo762]

Personally really like the setup on Sunday near the triple point in NW OK all three models show a conditionally volatile setup (pending mature supercells that break the cap)... The euro shows some convection, GFS shows very little, and the NAM currently shows none (albeit, it's the very end of the NAM's range). If anything does go in the progged environment it is likely to be significant severe, and given the wind profile should be supercellular and isolated. 

Monday presents a very tricky forecast, but there will almost certainly be severe storms, and possibly several tornadoes. 

[Quincy]

Sunday is very conditional and I don't like to pick apart soundings this far out, but just a few notes:

Convective temperatures in the vicinity of the dryline bulge are in the mid-80s, while models show temperatures in the low to mid-70s. (Areas that do reach 80+ are on the dry side of the dryline) Forecast soundings show very little CAPE in the lowest 2km AGL, indicative of a capping inversion. Also, large scale forcing appears limited, with only very modest 12-hour 500mb height falls, in the ballpark of 10-20 meters.

Regardless, we do appear to be rounding the bend and thunderstorm threats are increasing across the southern Plains. We should see several days with at least spotty severe reports over the next 5-7 days. At the very least, much-needed rainfall across the area should help ease some drought concerns, although there are signs that the bulk of the rainfall will stay closer to I-35 and points east, but we'll see. As some recent years have shown us, a pattern change can knock out a drought pretty darn quick.

[bjc0303]

Euro has trended towards a pretty decent severe threat on Monday I would imagine. Surface winds go from SE to S/SSE at 850 to SW aloft. The euro has exhibited quite a trend in SW flow, what used to be SSW @ 500 has trended to SW. The euro also seems to have dialed back on widespread QPF, potentially allowing greater instability to develop and better storm organization to take place. 

 

With the change in modeled wind fields, deep layer shear vectors now exhibit a large component orthogonal to the dry line, suggesting a better opportunity to remain discrete. 

[AfewUniversesBelowNormal]

This is some pretty awesome cold for April. Wonder if it verifies.

[Quincy]

Severe prospects for Sunday through Tuesday are muddled, as neither day stands out, despite having a slow-moving trough moving from the Southwest into the southern Rockies. 

Sunday remains fairly conditional, but there does appear to be a narrow corridor, somewhere near the Red River Valley across the southern Plains, that could support an isolated supercell threat. Forcing remains the largest concern, but model forecast soundings are a little bit more aggressive with boundary layer heating in the afternoon. This may be enough to erode surface-based convective inhibition.

A larger area is expected to see favorable deep layer shear and instability on Monday from Texas to eastern Kansas, but the issue here is that wind profiles show veer-back-veer signatures. Hodographs are somewhat elongated, but very messy looking. Mesoscale details may determine the scope and magnitude of any severe threat, although it does not look like a big day, any way you slice it.

A sagging frontal boundary becomes increasingly parallel to the deep layer shear vectors by Tuesday, suggesting the potential for more of a squall line type feature, from the southern Plains into the Arklatex and lower Mississippi Valley region. 

While severe weather may not be widespread, as mentioned earlier, heavy rain will probably be the biggest story. There is not much hope for substantial rainfall over the High Plains, but areas from I-35 and points east have the highest probability of seeing above to well above average rainfall over the next 3-5 days.

[jojo762]

After these few nondescript Slight/Marginal Risk days we've had across the plains with what once looked like a conditionally promising system, we appear to be headed for an incredibly boring period of unremarkable weather systems and below average temps, followed by possibly above average temps for a brief period and more unremarkable systems. There seems to be no real chances for S/W flow across the Central or Southern plains for the foreseeable future, likely well into April. 

[Weatherdemon]

11 hours ago, jojo762 said:

After these few nondescript Slight/Marginal Risk days we've had across the plains with what once looked like a conditionally promising system, we appear to be headed for an incredibly boring period of unremarkable weather systems and below average temps, followed by possibly above average temps for a brief period and more unremarkable systems. There seems to be no real chances for S/W flow across the Central or Southern plains for the foreseeable future, likely well into April. 

Ugh... just took a look at the models and this simply sucks.

[Quincy]

Severe thunderstorm prospects for the foreseeable future are quite bleak. The CFS has had a consistently quiet signal for the first two weeks of April, while this is supported by yesterday's Euro weeklies. 

The weeklies try to improve a bit around mid-April, only to reload the eastern U.S. trough around April week 3. A more favorable pattern is advertised for the last week of April, but model confidence decreases into this range. At the very least, climo favors increased activity around the end of April, even commonly in most years that were otherwise quiet. 

[CheeselandSkies]

I despise eastern trough dominated springs, which seem to be the rule rather than the exception. Although, I remember April 2011 as being raw, gray and convectively uneventful as we were stuck on the cool side of most of the systems after the April 10th one (which, maddeningly, produced most of its tornadoes NORTH of southern Wisconsin). Even had snow showers on the 18th.

I just realized something, going back and rereading the April 9th, 2011 Day 2 outlooksvalid for April 10th. It always seemed to me like that event underperformed its potential based on the wording of those Day 2 outlooks, even though by Wisconsin standards it was fairly significant (16 tornadoes, 1 EF3 and 3 EF2), the wording  -particularly in the initial one- made it sound like it would be April 27 for the upper Midwest (2 1/2 weeks before anyone knew what "April 27" meant). Now I know why that is...IT WAS BROYLES!!!

[Sydney Claridge]

That said, the GFS has been trying to show an active period around the beginning of April.  Don't know what this means for severe potential though, but if the GFS verifies on delivering storm systems and we can have sufficiently high parameters for severe thunderstorms perhaps we'll at least get something out of it.

[Chinook]

The last time we saw a decent amount of severe weather was March 19th and 20th. Considering prospects for tornadoes are not too high over the next few days, this means we have gone through another dorky March with respect to severe weather. Not that I want anyone to have damage/fatalities from these things, it's just that cool weather patterns prevailed in March 2013, 2014, 2015, and 2018 for sure.

[bjc0303]

It seems like a near certainty as described by several others that the first week or two of April will be quite dull. Anything after that - even considering the euro weeklies - is probably a crapshoot. Hope is that activity begins picking up April 15th and onward.

[jojo762]

1 hour ago, bjc0303 said:

It seems like a near certainty as described by several others that the first week or two of April will be quite dull. Anything after that - even considering the euro weeklies - is probably a crapshoot. Hope is that activity begins picking up April 15th and onward.

Quite sad. Gives us lots and lots of time to focus on course work and regular work. ha... Generally like what late April/early May has been advertised as in almost all the long-range models, but as Quincy noted that is typically an active period anyways.

Meanwhile on the CFSv2, if only this wasn't 4 weeks away in CFS fantasy land LOL... #LockItIn.

[Jim Martin]

Looking like an active severe weather day possible for Tuesday. The Storm Prediction Center mentioning a fairly good risk for discrete supercells.

[Chinook]

For this data, I have looked at 2010-2017, 8-year climatology of severe weather reports per day. All numbers come from http://www.spc.noaa.gov/climo/online/monthly/newm.html

March tornadoes have been relatively low in this 8-year time period, compared to April. This is probably due to weak severe weather setups in March, over a period of years.

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Edit: a longer-term climatology of tornadoes/month is posted here: http://www.ustornadoes.com/2016/04/06/annual-and-monthly-tornado-averages-across-the-united-states/

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[rolltide_130]

3 hours ago, Chinook said:

For this data, I have looked at 2010-2017, 8-year climatology of severe weather reports per day. All numbers come from http://www.spc.noaa.gov/climo/online/monthly/newm.html

March tornadoes have been relatively low in this 8-year time period, compared to April. This is probably due to weak severe weather setups in March, over a period of years.

--

Edit: a longer-term climatology of tornadoes/month is posted here: http://www.ustornadoes.com/2016/04/06/annual-and-monthly-tornado-averages-across-the-united-states/

--

 

What would happen to the data if you removed April 2011 from the dataset? I noticed that April averaged more tornado reports per day than May but that seems to be heavily skewed by 2011. 

[Chinook]

This is the new graph, with the new value for April at about 5.99 tornadoes/day. This is very close to the value from UStornadoes.com web site, which is 5.93 tornadoes/day, if you just divide their number by 30.  Also, their value for June is 7.6 tornadoes/day, vs. my calculation at 6.8 tornadoes/day. So that is a kind of interesting deviation from the long-term dataset.

[bjc0303]

Am a fan of the euro/EPS mean for mid-late next week. 

[WhiteoutWX]

34 minutes ago, bjc0303 said:

Am a fan of the euro/EPS mean for mid-late next week. 

Will be nice if we can actually get some decent ridging for an extended period in the east. The general pattern since November, with a few exceptions, doesn’t lend much confidence to that. 

[andyhb]

38 minutes ago, WhiteoutWX said:

Will be nice if we can actually get some decent ridging for an extended period in the east. The general pattern since November, with a few exceptions, doesn’t lend much confidence to that. 

The idea shown on the Euro/EPS mean is a more low amplitude pattern that doesn't necessarily mean a big SE ridge.

[WhiteoutWX]

2 hours ago, andyhb said:

The idea shown on the Euro/EPS mean is a more low amplitude pattern that doesn't necessarily mean a big SE ridge.

Low amplitude can work but I’d be worried about moisture return this early in the season if systems are spaced too closely. 

[cheese007]

In addition to today's threat, SPC out with a 15% contour for Day 4 that includes a good chunk of the northeastern parts of the state stretching into central TX, including DFW and Austin 

[bjc0303]

1 hour ago, WhiteoutWX said:

Low amplitude can work but I’d be worried about moisture return this early in the season if systems are spaced too closely. 

Agreed, but (though, extended range) spacing looks pretty solid on GFS/Euro...for now 

[bjc0303]

Lots will change - but the way the GFS has shifted ridge axis about 100 miles east is allowing for pretty impressive moisture return forecast next week, with return flow undisturbed. Scenario would suggest upper 60s dewpoints within reach, especially with anomalous gulf water temps we’ve seen in recent years. 

 

Plenty can change - that lead wave with a few changes could amplify to hell and send all of our moisture back into the gulf. However ensembles expand the ridge in the east which should mitigate any opportunities for the lead wave to blow up on us. So low-mid 60s just chill, capped under a stout EML, in the RR area waiting for the arrival of the next system. 

 

The euro and CMC show a similar evolution but show a storm track that could leave the plains out of it. Most of all I’m a fan of the ensemble consensus for perhaps a persistent east coast ridge. 

[Chinook]

SPC day-3 (Friday) outlook includes northeast Texas and southwest Arkansas. Tonight's 3km NAM shows this impressive sounding near Texarkana, AR. This is some nifty eye-candy. It is In the warm sector, before scattered storms develop in Oklahoma/Arkansas. The only weakness here would be winds that are weaker at 300mb-250mb, compared to 500mb.