Chase Case #4

[Scott Weberpal]

Here it is, the long-awaited chase case #4. It is up to you to determine whether or not there will actually be chaseable storms (there will be storms somewhere), their severity, storm mode, whether or not you believe there will be tornadoes or if it's a non-tornado event. Large hail? Straight line winds?

Name your target and discuss why you picked that target and what mode of severe weather you believe will take place. 12z maps are included with this post. I will post 18-20z data in the next 20-24 hours (Wednesday evening), and 00z data/results the following evening.

I have added the SPC Day 1 Outlook as any chaser would likely have access to it if they have access to data.

12z UPPER AIR MAPS

300 mb
500 mb
700 mb
850 mb

12z SURFACE MAPS

Central High Plains
Central Plains and Ozark Region
Upper Midwest
CONUS Surface with Fronts
Dewpoint Contours

12z SOUNDINGS

Dodge City
Denver
Davenport
North Platte
Little Rock
Minneapolis
Omaha
Springfield
Topeka

SATELLITE & RADAR

Satellite
Radar

SPC 13z DAY 1 OUTLOOK

...NRN INTERMOUNTAIN REGION...

ONGOING ACTIVE THUNDERSTORMS MOVING INTO SWRN ID AHEAD OF THE
VIGOROUS S/WV TROUGH REFLECTS THE AVAILABLE MOISTURE/INSTABILITY
COUPLED WITH LARGE SCALE ASCENT. ISOLATED SEVERE STORMS CURRENTLY
INTO SWRN ID...EXPECTED TO INCREASE IN NUMBER AND INTENSIFY FURTHER
WITH AFTERNOON HEATING EWD ACROSS SRN ID INTO SWRN MT/WRN WY. WITH
MUCAPES CLIMBING TO 1500 J/KG AND 50 KT DEEP LAYER
SHEAR...SUPERCELLS LIKELY WHICH WILL ENHANCE LARGE HAIL AND
DAMAGING WIND THREAT ALONG WITH POTENTIAL FOR ISOLATED TORNADOES
VICINITY SNAKE RIVER VALLEY.

...MIDWEST/GREAT LAKES...

THE STRONG DIGGING TROUGH NRN MN VALLEY WILL PROVIDE VIGOROUS
UPWARD MOTION AHEAD OF THE RATHER DEEP SURFACE LOW WHICH IS
CURRENTLY MOVING SEWD FROM NRN MN INTO WI. INSTABILITY AND
MOISTURE INITIALLY AHEAD OF THIS SYSTEM IS MARGINAL...HOWEVER BY
LATER THIS AFTERNOON...THE SYSTEM WILL BE ENCOUNTERING INCREASINGLY
MOIST/UNSTABLE AIR AS IT MOVES SEWD INTO WRN PORTIONS OF OH VALLEY.

12Z ETA BY LATE THIS AFTERNOON HAS A STRONG CONVECTIVE SIGNAL AS
COLD FRONT MOVES ACROSS SRN WI INTO SWRN MI AND NRN IN. GIVEN THE
STRONG DEEP LAYER SHEAR AS 80-90 KT NWLY WIND MAX DROPS SEWD
ACROSS IA INTO WRN OH VALLEY...ORGANIZED THUNDERSTORMS WITH
POTENTIAL FOR PRIMARILY WIND DAMAGE AND LARGE HAIL WILL INCREASE
INTO THE EVENING HOURS. SEVERE POTENTIAL SHOULD CONTINUE WELL AFTER
DARK EWD ACROSS OH VALLEY GIVEN THE VIGOROUS UPPER SUPPORT AND
CONTINUED INTENSIFICATION OF SURFACE LOW.

...CENTRAL HIGH PLAINS...

SURFACE RIDGE PUSHES SWD THRU NRN PLAINS IN WAKE OF THE UPPER MS
VALLEY SYSTEM. RESULT WILL BE INCREASING UPSLOPE FLOW INTO ERN
WY/NERN CO DURING AFTERNOON WITH DEWPOINTS INTO LOW 50S PUSHING WWD
TO E SLOPES OF MOUNTAINS.

STRONG HEATING WILL INITIATE THUNDERSTORMS VICINITY HIGHER TERRAIN
ERN WY/NRN CO THIS AFTERNOON. WITH SURFACE CAPES TO 1500
J/KG...AND VEERING SHEAR PROFILES...A FEW SUPERCELLS ARE LIKELY.
PRIMARY THREAT WILL BE LARGE HAIL AS STORMS DEVELOP E/SEWD INTO
HIGH PLAINS. POTENTIAL EXISTS FOR OVERNIGHT MCS INTO WRN KS WITH
SEVERE THREAT DECREASING A FEW HOURS AFTER SS.

 

[Dennis Dennison]

Thanks in advance!!!!!!!!!

 

[Dick McGowan]

Thanks for putting this up! Maybe for future ones, someone can dig up GFS, ETA/WRF/NAM, then maybe RUC maps for 18-03z of the event and we can compare maps and decide. I just hate going off of 12z data and not being able to look/compare into the future. It would be more like the "real thing."


My quick analysis notes this is a NW flow event, probably late June/early July. I'm staying in Kirksville, MO northeast of the surface low, and in position for the shortwave progged to arrive later today. I'll most likely be heading east at around 15z into Western Illinois depending on my 18z data. But, I don't want to commit anywhere without a better idea of where any outflow boundaries may lay down from the decaying MCS to my east/northeast...but feel that this is a good spot to start waking up.

I'm not too hyped about tornadoes today under NW flow, and see perhaps (by SPC's standards) a 2-5 percent risk my area and a bit further south of me, then pointing north-and eastward. I'm more of a structure guy anyways, so I'll still be chasing it.

 

[Brian Stertz]

Wow this one looks like a C.Illinois event to me. I am going to set up shop at the NWS Lincoln and make some adjustments from there. Tornado potential looks at about a 5% with a major bow echo looming if that wave can hit just right. It's a slight risk but could go moderate if the moisture advection could be a little stronger. Thats my first guess...

 

[Danny Neal]

Since it is going to be a nearby event.... I am going catch up on some sleep and talk to y'all in a few hours

I will be out the door at 930 AM for La Salle, IL , going to do some fishing at Starved Rock before the show begins and if it doesn't happen? Gone Fishin'

 

[Bob Hartig]

Cedar Rapids, IA, please. The surface low is well to the north, and the dewpoints aren't particularly impressive right now, but I think they'll increase as the system works its way eastward. After all, it's only 7 a.m. CST. And I've gotta love how the 300 and 500 mb jet maxes are aimed right at me.

 

[John Farley]

Hard to tell, with only analysis and no model runs, but I would say this - do not discount the possibilities of tornadoes with northwest flow situations - if the low-level winds are such that there is directional shear, tornadoes can and do happen with northwest flow. Look at the SGF sounding!

Having said this, I am sitting at home in Edwardsville, IL waiting for the morning model runs before making any decisions.

 

[Adam Lucio]

Its 12z and Im sleeping off the night before. Gonna wake up in about 3-4hrs and take a look at things. Before going to bed and taking a glance [perhaps a tad buzzed] I was thinking my home state may be the place to play, or not too far. Preliminary plans will be to head down I-80 to around I-39 by Peru

But first...sleep.

 

[Chris Allington]

Based on the current information, I especially like the SGF sounding. I am leaving for Rolla, MO and should be there between 17-18z. I'll check data on the road as I might end up wanting to head farther E or S.

 

[Scott Weberpal]

Thanks for putting this up! Maybe for future ones, someone can dig up GFS, ETA/WRF/NAM, then maybe RUC maps for 18-03z of the event and we can compare maps and decide. I just hate going off of 12z data and not being able to look/compare into the future. It would be more like the "real thing."

Unfortunately I have no idea where to get archived forecast model data. I could post everything all at once, but that would take away from the point of the exercise. I'd be more than happy to add any additional information if someone tells me where to find it. All the data I currently have on here is from SPC, UCAR, and Plymouth State.

 

[Tim Segraves]

Based on what I'm seeing I don't think I'd leave CO to chase this. Being this is a virtual chase or if I was based somewhere closer, I think think the best tornado potential will be in the IA, MN, WI area so I'll start out in Rochester, MN.

 

[Mike Peregrine]

Thanks for another case, Scott ... I'll definitely look forward to taking a look in the a.m., after a long, peaceful night's sleep here.

 

[Jeff Duda]

This looks to be a marginal, widely spread event. If anything can get going, it's going to be marginal in intensity, but I did a brief calculation of BRNs and got some low numbers, so I could imagine some rare, widely scattered HP supercells occurring. However, I think the rest would be multicellular or ordinary.

Surface winds are all veered way too much for anything to happen in WI, MN, and all but SW IA. Tds are kinda low there (< 60 F and some < 50 F), too.

There will be a nix of activity in KS, OK, TX due to the cap there at 700 mb. Since this is a northwest flow event, I'm guessing it's a dead-of-summer time period, meaning 13-14 F at 700 mb is unbreakable, which is being met or exceeded over those states.

I don't really believe the stationary front in the southcentral US, but the SGF sounding looked impressive for shear and looked decent thermodynamically. With a little afternoon mixing, I could see up to 2500 J/kg of CAPE there as long as minimal WAA occurs at 700 there (looks like some is). The column is very moist there, though...odd. Doubt there will be much damaging wind.

I probably wouldn't chase this in real life, but I'll put my money on a strip extending from SW MO near SGF NNEward towards Lamoni, IA and extending that about 75 miles northeast. I'll head towards Cameron, MO and be ready to slide up and down I-35 or head east on Hwy 24. I would be surprised if more than one or two tornadoes occurred, and I'd bet between 25 and 50 hail reports could occur. I predict damaging wind reports to be at a minimum, too (say < 10 reports).

 

[Dann Cianca]

TARGET: Twin Falls, Idaho.

Good surface moisture, divergent flow aloft, and I like the turning with height. With temps as they are that early in the morning, I know it's going to be a warm day ... should give us some good CAPE to work with.

Will be looking for a few supercells out in front of a line of storms that will probably form and blow east along the Snake River Plain.

Where's Gerrit at? Want to get lunch, buddy?

 

[Doug Mitchell]

Gah, NW flow event. These things are always a pain. Due to the high level of uncertainty, I'm going to stay close to home and play the southern target. I'm going to choose my initial target as Sedalia, MO and just watch the shortwave eject.