05/10/05 FCST: Central/Southern Plains

[Tony Laubach]

The first day of my 3 week venture and it holds potential! NWS Denver mentioning a potent system kicking through and potential for storms. Glancing out 156 hrs at the GFS, I'm thinking it holds potential...

At 500mb, a trough kicks through with some divergence over Western Kansas/Oklahoma and the Panhandles. Speeds in these areas range from about 30 to 45 knts. 850 TDs have a moisture tounge surging up through the Western and Central parts of KS/OK, as well as the far Eastern Panhandles with a decent tounge of theta-E along those same areas. It also hints at a dryline setting up along a line from the Central TX Panhandle north along the KS/CO border (just a bit east) and south through Lubbuck and pulling southwest. Winds at 850 are straight out of the south at that time with 700 winds out of the SW and 500mb winds from the WSW... good directional sheer looks forecasted, speed shear not bad, either..

Still a ways out, but something I'm keeping an eye on over the weekend as it will be the first chance I get to play after I'm done with all work and school at 9pm Monday night. I'll be watching to see if some consistancy builds in the coming runs and as it gets closer, start looking at finer details to see exactly what the chances are...

 

[Ben Prusia]

This appears to be a very potent system, and looks like a very good severe weather producer.

What I see is a really deep upper level system at 998mb centered along the KS/CO border, consistent with the 0Z GFS run from last night. Of course it is very far out to pinpoint exact parameters including moisture and instability, but it looks like the upper level winds in western Kansas and south into the northern Texas Panhandle will be enough to sustain severe thunderstorm/supercell development. GFS shows some precip breaking to the east of the low in Kansas, southward into the panhandle of Texas.

There is another system in northern Wyoming that could also be worth watching. Still far out, but I think that western Kansas along with the Panhandles better watch!

 

[Mikey Gribble]

I was wondering how long it was going to take someone to get this started. The 12Z run isn't quite as good as last nights run. I think one of the little question marks is going to be how quick moisture will get back North in the wake of this weekends system. I am very optimistic on this setup though. SE surface winds, >60 dewpoints, great directional shear especially in the lower levels, and 500mb winds at 40-50kts is good enough to get the job done. Upper level winds could be better and I still have a couple other concerns with Tuesday, but I am thinking tornadic supercells would be likely if the GFS verifies.

 

[Rodney Price]

Next week's system

It's definitely a long way out but things are finally looking a bit more promising! The long range guidance has been consistent with getting the pesky, eastern trof out of the way and get a more favorable SW flow aloft developing across the western and central parts of the U.S.

It will be interesting to see how the activity slated for the weekend will possibly impact things early next week. I won't be too surprised if the models shifted the activity +/- day or so.

To quote Tim Marshall (from an old StormTrack issue): "May, oh unpredictable May!!"

Rodney

 

[Tony Laubach]

Looking over the 144 hour, it looks as if the GFS shifts things a tad bit to the east. The theta-E tounge noted in the previous dicussion has been shifted more into Central Kansas as opposed to just east of the CO/KS border. Everything else still looks pretty good with good divergence and directional shear. The 500mb winds actually looked a bit stronger in Eastern Colorado/Western Kansas... still watching...

 

[Mikey Gribble]

If we could just get the mid and upper level winds to come up a little Tuesday would be great. 12Z is showing SE surface winds throughout the warm sector with great directional shear. It looks like we might have good moisture to work with for the first time this year with dewpoints >65. It is still a long way out, but it is looking good so far.

 

[nickgrillo]

Almost everything is supporting a outbreak for the 10th. I just took a look at the GFS and everything seems to be in place, except we could definitely do better with the upper level winds. We'll have >65F dew points across the central/southern plains and we'll have VERY strong shear which will support supercells and tornadoes. It's still 5 days out, but considering it's May, I'm betting on this...

 

[Gabe Garfield]

Judging from tonight's GFS, it looks like the big day will probably be Wednesday and not Tuesday (though Laubach et al. could still cash in on Tuesday). It still looks incredibly impressive...definitely outbreak material, if it verifies (negative tilt s/w trough, deep moisture, strong low-level jet, etc).

What impresses me most is that trajectories at 850 mb are directly from the Carribean. The biggest juice (by far) of the year looks like it will juxtapose quite nicely with one of the most potent systems (kinematically speaking) of the year.

Things could get quite interesting...

Gabe

 

[Glen Romine]

Guess this is probably a sign that the last time this thread saw an update was 3 days ago..... but I've been interested to see how this day might pan out as a trip out west generally requires more than one 'chaseable' day in a row if conditions are only marginal. Certainly, marginal is a fair descriptor - but it is at least possible for tomorrow and the following day to have pockets of quality activity. Let's cover tomorrow first.

Disappointed this morning making rounds through soundings on the plains. Most notably, despite several days of flow off the gulf, moisture depth is still rather shallow even down at the coastline. This is probably partly owing to the much cooler than usual GoM temperatures. Nevertheless, adequate moisture for at least high based convection appears to settle into the MO River valley according to NAM/GFS guidance, with modest wraparound moisture feeding back to northeast CO. No real distinct dryline push ever develops, and most of frontal "push" is dominated by cold air from the strong high ressure building toward the Great Lakes, with surface deformation setting up near Davenport. Odds are reasonable for storms to develop out over the high country of Wyoming on Tuesday, tracking out along the boundary with backed flow and cell motions favoring tracking along the front. Weak shortwave also forecast to emerge into this region during the evening hours, so storms are at least likely in the Nebraska panhandle area. Very high-based nature will probably limit tornado threat - but it doesn't take much that far west. Further east, persistent convergence leads to a convective cluster developing in the rough vicinity of Omaha to Fort Dodge. GFS more stubborn with development, despite a slightly weaker cap forecast than the NAM. Shear drops off markedly south of the boundary, and is nearly aligned with the southern edge. So, the GFS rendition of the boundary slightly further north helps in the shear department, but a modest shift the other way could lead to all storms being elevated well behind the front where lift and cap weakness contribute to storms initiating during the early evening. Some of the WRF runs has the boundary further south, or further north, so not much help there. Assuming the cluster does develop, odds of early mode being discrete and supercells is appearing to be at least possible, particularly if cells can build back into Nebraska - where cell motions would potentially favor cell interaction/boundary entrainment. With LCL's in the 1.2-1.5 km range - might need some extra help. I might give this a go if tonight's runs favorably reinforce this scenario.

Glen

 

[Mike Hollingshead]

Fairly excited about Tueday's prospects. Perhaps that is largely due to not having to go anywhere by the looks of it. Target would therefor be eastern NE/western IA near Omaha. 18z eta tries to get something going in western IA at 0z and by 6z it is going to town in eastern IA. So at least it is wanting convection to fire on the warm front. The shear looks fine to me with w at 500 at 35-40 knots over ese at 10-15 knots at the surface with the front lined up rather nicely for things to latch onto it. It is possible there may be too much turning with height and lead to things really wanting to backbuild west. I haven't looked above 500 but I imagine it is pretty sad(just looked and yeah sad). It is always nice to see an area go under a rapid change and that looks to be a good bet in this area(TD in w IA of <50 at 12z to 65 by 0z...not that I know that will actually happen and get that high). Tornado will be 15 miles sw of Ft. Dodge IA at 7:22. Now that I said that I will be heading far west into NE away from that area.

 

[Tony Laubach]

Time to chime...

My preliminary target is Western Nebraska... not too convinced of the forecasting in Eastern Nebraska and Iowa and not sure my time would allow for such a eastward haul out that way anyway...

Glancing over things, the upper level winds still look pretty sad; 50/55kts over Western Nebraska at 250mb and 35 to 45kts at 500mb. The 700mb is actually backing the winds over SW Nebraska along with the 850mb; so directional shear looks to be decent..

There's a tounge of several factors pulling through Central Nebraska and into my target area. Theta-E at 850mb and at the SFC noses right over the frontal boundry and into Western Nebraska. SBCAPE does about the same with values approaching 2500J/kg along and north of I-80. Best SRH values remain away, though... two areas of higher values exist to our north/northwest and well off to our East over the northern portions of SPC's current 25%. However, at that same time, the ETA progs a lot of CINH over those same areas. The ETA also has an area of precip over the NE Panhandle as well as those CINH'd areas, so its hard to say...

In any case, I think we'll play on the nose near the boundry and see what happens... I'll be anxious to see how things evolve over the next 12 to 18 hours to see if this can look better/worse! :lol: In any case, we'll be on the road by 9:30a from Denver!

 

[Nic Wilson]

Tuesday will see the next upper-level low and associated trof move on shore from the Pacific which will be the focus of potential severe weather throughout the week.

Tuesday's Target: Avoca, IA

By 00z, lee cyclogenesis will see low pressure set-up near the intersection of CO, KS and NE. An associated warm front will be draped northeastward across central NE, near Blair, NE and further eastward near Ames, IA. 15 kt southerly winds at the surface will nudge the boundary northward through the afternoon. Temperatures south of the boundary will be in the mid-80's with Td's recovering to the low 60's by late in the day. Increased baroclinicity along the boundary will enhance 500 mb winds to 35 kts or greater late in the day allowing for marginal support of supercells. The focus of backed surface winds will be in western Iowa with peak moisture convergence and initiation likely near Avoca and points northward. NAM forecast soundings prog. in excess of 4300 J/Kg surface based CAPE and 0-3 km SRH of 177 m^2/s^2. Storm motion will be ENE ~20 kts.

Factors to be concerned about include the likelihood of overdone moisture return in the NAM which could significantly raise LCL heights in this area. My main concern is meager 250 mb winds of 35-40 kts. Better upper-level support is available north of the warm front, so if a storm can get rooted to the surface and interact with the boundary, a chaseable storm void of HP-qualities may be possible. It would be nice for the 850 mb winds to strengthen as well. Good luck to everyone that plays this set-up tomorrow, I plan on staying in Norman and waiting for the improved dryline (cross your fingers the cirrus stays away) in the TX panhandle on Wednesday.

 

[Mike Peregrine]

After yet another bustacious weekend for me, hoping to be able to head out over the next couple. Wind profiles (OAX) generally look weak throughout the day - with slightly improving upper level by 0z ... unfortunately llvl looks like it's shifting around to unidirectional by then - at the same time lifted indices also make a good jump. Biggest concern in my mind: fcst LCLs at 2020m and LFCs at 2039m. Chasing is useless under high bases. We need surface-based convection that is well supported in the upper levels! I will probably be forced to target further north, along the WF, wherever that might end up. Probably North Dakota the way things have been going. If the WF isn't chaseable, then it will probably be yet another day of looking at a pathetic radar screen for me.

 

[Glen Romine]

Well, time for a day 1 review. The fact that I'm here doing this is evidence that I'm not on the road. After more careful analysis - kinda wish I was, as I think there is still a chance for a good storm within my range - which I had more or less written off as of last night. Anyway, let's get to it.

Upper low continues to slowly dig southward along the California coast, while upper ridge amplifies downstream over the central plains. Subsidence is evident in water vapor imagery along a line from New Orleans to near Denver, slowly expanding northward. Jet stream level winds are westerly across w NE to wnw in e NE from 50-55 knts, and wsw at 30-35 knts across w TX. 500 mb ridge from CDS-ICT-PIR. 850 mb deformation near 9V9 this morning, sliding eastward, along with a secondary front from near DEN to just north of SGF, with trailing temps over 20C. Surface shows weak 1002 mb low over eastern CO, with warm front extending along the KS/NE state line this morning. Mid to upper 60 dewpoints were already into central OK this morning, and OUN sounding shows this moisture should be well preserved despite being shallow across the eastern portions of the state, whereas behind southern 850 front expect mixing to erode moisture and veer winds across n TX panhandle into w KS. Vis sat shows expanding sheild of low stratus across e WY and the w half of NE, and also shows pocket of deeper moisture sliding into eastern KS and tendril connecting back to southcentral NE.

Todays target/forecast: Encouraged to see tendril of moisture feeding back to central/western NE, which should provide a narrow axis of favorable conditions there if convection can get going despite overcast conditions. On the positive, the front should stall out near the I-80 corridor, which improves chaseability. For this area I'm struggling to decide where storms might form, but might prefer the Cozad area until it becomes obvious somewhere else is better. Additional potential exists further east really anywhere along the front, but I'm still fond of early evening just east of the OMA area, as abundant sunshine and increasing low-level moisture, along with healthy deep layer shear, could provide the best chance for a substantial tornado if convection can indeed form during daylight hours. Would probably need to wait until late afternoon to try and pinpoint a favorable initiation point. RUC model decimates surface moisture under the subsidence - probably way overdone. Other region with potential is extreme se NM area, where if convection can form, they could be rather impressive storms. Good luck to all chasing today.

Glen