7/3/2009 FCST: CO/NE/KS

[Stan Rose]

Heavent seen any discussion of what could be an unusually active early July, so might as well kick things off.

Given the poor track record of the NAM at 60 h, SPC is rightfully wording it conservative, but if everything lines up i can see a couple TORs coming out of this setup;

Zonal flow, shortwave moves through E CO and the NE panhandle Fri afternoon. Surface low sets up probably over SE CO, with stationary front eastward through Central KS. Dews should be low 60s N of the front. There should be sufficient forcing for inititation, looks best near the tripple point somewhere N of a line from GCK to Pratt. Bulk shears 40-50 kts and CAPE 1500-2000 will be sufficient for supercells. Another potential target could be NE of the surface low in the AKO-LIC-ITR region in Ern CO. Certainly worth watching how this evolves.

Not worth a thread of its own, but its interesting to note the "armageddon" prog in the GFS for July 7 over NE KS and W NE. The GFS is almost certainly overdoing the deepness of the Pacific trough, but even in model-land the crazy May-like paramaters it's spitting out over that area are hard to ignore!

 

[Matthew Piechota]

the new WRF develops a nice meso low in northern KS with nicely backed sfc winds and a good CAPE axis to the immediate east of that. this could be an interesting little set up.

this model run is showing some CIN in that area for the time period...but breaking out precip on the northeast side of the meso low along the NE/KS border. there is nice 500 flow out of the west at around 35kts with 850s being out of the ssw at 20kts.

there is a descent wave on the KS/NE border at 18z but kicks outs east of the area by 0z. MLCAPE values look to be AOA 2000 j/kg with dews in the mid 60's to near 70 with the theta-e axis running right into the low. it bullseyes the KS/NE border where it breaks precip out by 0z with 0-1 helicty between 150 and 200 and EHI values near 4. sups do look possible this day and wouldn't be suprised to see a few T0Rs.

will be interesting to see how this plays out. anyone going to be chasing?


Matt

 

[Stan Rose]

Still looks good for tomorrow. 12Z NAM shifts things to the east, now the tripple pt looks to be somewhere between Salina and Marysville, where the NAM also progs a 50kt mid level jet in the afternoon. I will probably head out to Limon if things still look good in E CO tomorrow, a short drive for me, looks like the area N and E of the Palmer Divide should see some action by late afternoon. Looks like 4th of July also could provide some severe fireworks.

 

[Bill Schintler]

Storm Chasing Target for Friday, July 3

Chase target:
Belleville, KS.

Timing and storm mode:
Aa area of elevated storms will be ongoing in extreme northeastern KS through the early afternoon. Surface-based storms will develop in the target area after 7 PM CDT. Supercell storms with a minor attendant tornado threat will be possible through mid-evening. Storm motion will be towards the NE at 20 mph.

Synopsis:
A broad ULVL ridge axis was centered over WRN TX at 00Z. The persistent Great Lakes trough will begin to deamplify and shift E over the next 24-48 hours. Further W, WV loop and 00Z H5 analysis indicates a compact disturbance over UT. This disturbance will round the ridge and dive towards NE, KS, and then IA and MO on Friday.

Discussion: Tonight through tomorrow morning…
Overnight, isentropic lift will increase along the 305-310 K SFCS as the LLJ strengthens out of the S late in the evening and then later veering into NERN KS by 12Z. WAA will increase, with elevated convection firing from NCNTRL into ECNTRL KS after 5Z as 15C H85 dewpoints currently over the SRN TX panhandle are advected towards the N. Modest instability is noted with MUCAPE AOB 1000J/kg, so any SVR threat will be minimal and limited to moderate hail. During the morning hours, this area of convection will be ongoing from SWRN MO, ERN KS, and north into CNTRL NEB. This will shift E during the day, with clearing over the S half of KS. CI will remain over the N half of KS, resulting in differential heating. An E/W-oriented outflow boundary is likely to exist along I-70 in KS, reinforcing the developing synoptic boundary.

During the afternoon…
At the SFC, weak low-pressure will track along I-70 in WRN KS between 18Z and 06Z, 07/04/09, with a nearly stationary boundary extending E and NE from this feature. Meanwhile, a N/S-oriented DL will mix E through CNTRL KS. The intersection of the DL and WF should be the focus for redevelopment of storms late in the afternoon, especially if residual boundaries exist from earlier storms.

Models seem to be handling subtle details relating to phasing between the S/WV over UT and the main NRN stream flow. Model performance is once again horrible with convective feedback issues as has been the case for the last few months with the American models. The GFS seems to have the best handle on LLVL moisture, with the WRF appearing too bullish. Neither model can be relied on for reliable QPF output, as it appears as though convective energy release is interfering with kinematic fields. The UKMET appears not to be suffering from feedback to this degree and has been used for QPF evaluation.

Capping for SFC-based convection will remain strong through 02Z owing to the EML, with H7 temperatures in the 12C range noted. This EML will also contribute towards steep mid-level lapse rates of around 8C/km, with strong instability resulting with MLCAPE’s locally increasing to 3000J/kg along and immediately S of the boundary. Shear will remain modest but sufficient for storm organization, as the strongest H5 flow associated with the aforementioned short wave will remain N and E of the area. LLVL directional shear will increase after 00Z as a SWLY LLJ strengthens to 50 kts over weak but backed SFC flow. During the evening into the overnight hours, storms will increase in coverage while evolving into a squall line and tracking S and E as the strengthening LLJ.

- Bill

10:56 PM CDT, 07/02/09

 

[jshields]

tomorrow looks like it could be a low cape/high shear day especially once the LLJ kicks in. the 0Z NAM at 03Z 7/4, shows 850 winds screaming at over 50 kts, resulting in 0-1km SRH of 570 near York, NE!! i even saw effective shear values up to almost 80 kts!! but again the lack of CAPE really worries me. the forecast sounding even show 0 j/kg of 0-3km CAPE it's too bad we couldn't get about 3000 CAPE tomorrow evening! i'm not able to go out due to the holiday, family, etc, so i'm sure there'll be a group of tornadoes right around sunset in SE Nebraska

http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=NAM&STATIONID=kjyr

 

[Mark Blue]

My wife and I will be heading out from Denver this morning to chase this event. South Central NE is where I was born, so I love it whenever severe weather sets up in this region! The GRI AFD is talking about MLCAPES of 2000 J/kg later today along and near the warm front moving north from Kansas, so if that pans out I think there will be sufficient instability to work with in addition to the bulk shear mentioned above. The mid level lapse rates could kick up a notch or two from the current 7 C/Km, but I'm not belly aching about the current projections by any stretch. I will be studying the forecast as we drive, but will plan to play right along the warm front where the winds will be backed out of the east. I would expect this to be somewhere between I-80 and the KS/NE border in a box bounded by Alma to Kearney to Lincoln to Beatrice and perhaps just a bit further east later (if that makes any sense). I fully expect this to be a chase that lasts all the way up until dusk and since the LLJ is progged to go nuts around that time, I'm hoping for this to be a diamond in the rough. The hodographs appear to have nice curvature all along select stations I mentioned in the boxed area above (i.e. GRI, UEX, JYR, BIE, HJH). We'll be in a Black on Black Nissan Murano with Colorado license plates "DRYLINE", so if you see us stop and say hello. We are tentatively planning on setting up either in Grand Island or the Wal Mart parking lot in York. That Wal Mart in York has become quite the gathering place for chasers over the last couple of years from what I've noticed. Enjoy your 4th of July weekend everyone and stay safe.

 

[Matthew Piechota]

sfc winds already backed in northern KS at 20kts with an 83/67. the low is currently in western KS. sfc heating taking place with complete sunshine in the area.

http://weather.cod.edu/loops/Southcentral-VIS.loop.html

will be interesting to see how things play out later.

 

[Mark Blue]

We are adjusting our target to the south and west of my earlier forecast based on the lack of eastward and northward progress by the low and warm front. We will probably drop south from Lexington, NE and go down to Hill City, KS where we can easily move any direction, but most likely to the east on Highway 24 later. Conditions are cloudy on I-80 around North Platte so it will be nice to see some sunshine and insolation further to the south. The next hour or two will tell the eventual tale as to where we wind up, but for now that is our plan.