6/1/08 FCST: CO/KS/NE/WY/OK

[Andrew Stoller]

Sunday is shaping up for eastern CO. Other severe looks marginally possible to points south and east, but I'll focus on CO and points north where the best dynamics will be.

First and foremost, very pronounced dryline through CO with 60 degree dewpoints possible. 2500 J/KG CAPE by 00z. 995 mb surface low over south central CO by 00z. Small wave/impulse coming through the westerly flow. Speed shear won't be too strong, but directional shear will be doable.

Cap doesn't look to be much of an issue.

:edit: After looking things over a bit more, cap could be a serious issue actually. NAM shows little to no CINH at 00zz, but 700 mb temps are potentially 16 to 18 to 20 degrees C. Ouch! If something could break through on the palmer divide though and move east northeast, mid level temps cool way off. So perhaps the cap could aid in more isolated, explosive discrete convection very late in the afternoon.

 

[Mark Farnik]

A localized outbreak of tornadoes/extremely large hail appears to be taking shape for portions of southwestern SD, far eastern WY, the NE Panhandle and northeastern CO on Sunday afternoon. Forecast soundings for 00z tomorrow show 0-6 km shear values of 50-70 knots, which will be more than sufficient for supercells. A low pressure center will develop over central Colorado, advecting a tongue of moisture north/northwestward from western Kansas, with dewpoints reaching the mid 50's as far north as Torrington, WY by 00z tomorrow. Given the high dewpoints, combined with directional shear in excess of 45 knots below 700 mb across the area and the strongly backed surface-850 mb winds, and high lapse rates, intense supercells with a few tornadoes and gorilla hail are a strong possibility in a northwest/southeast oriented polygon bounded by Douglas, WY/ Pine Ridge, SD/Colorado Springs, CO/ Goodland, KS, with the most favored area for tornadic storms to be just north and east of the low from Elbert, CO to Scottsbluff, NE. The stout cap is of concern, but cells that fire in orographically favored areas (Palmer Divide/Cheyenne Ridge/Black Hills) and then move farther east, where mid level temps are significantly cooler (as Andrew noted) could put on quite a show. On the plus side, the cap will also help keep any convection that does fire very isolated and discrete in nature, which would be a refreshing change of pace, given the utter lack of such storms to this point in the chase season.
Given that I'm smack in the middle of the target area, I'll start from home tomorrow afternoon and adjust north or south as necessary.
All in all, it's looking to be a potentially excellent little backyard chase.

EDIT: Just looked at the forecast Skew-T's at KAKO, KITR and KLIC for tomorrow afternoon. Strong cap is present at 21z but is gone by 0z at all three stations, with between 2000-2500 j/kg of CAPE, very nice turning with height with SE surface winds, S/SW 850 winds and due W 500 mb winds, with decently curved hodographs.
The 03z soundings are even more impressive, with surface winds veering to E/SE at all stations, SRH values soaring to well over 300 and a nearly perfectly curved hodograph at KLIC.
I also glanced at some forecast Skew-T's for KSNY and KTOR, and they aren't nearly as impressive as those further south, with much less CAPE and semi-linear hodographs through the afternoon and evening.
If those Skew-T's come even close to fruition, eastern Colorado is going to be in for a VERY active late afternoon and evening tomorrow...

 

[Bill Schintler]

Chase Target for Sunday, June 1

Chase target:
10 miles east of Enid, OK.

Timing and storm mode:
Elevated convection will persist throughout much of the day in northeastern OK. Storms will back build late in the day and become surface-based at 6 PM CDT. Parameters will support a few supercell storms, and a transition to a multicell cluster will take place during the early evening.

Synopsis:
Little change in the UA flow over the last 24 hours, with slow height falls noted over the WRN CONUS. The Great Lakes/Hudson Bay low has kept the upper Midwest in NWRLY ULVL flow. Two disturbances of note here today, the first of which was a S/WV over SERN IA into IL; and the second over MN. Both of those brought mainly diurnal convection with some low-end SVR noted, and this activity will die off with loss of daytime heating. Further S, activity has fired in response to forcing provided by a mid-level disturbance, along with convergence along boundaries left over from earlier convection. This activity will expand in coverage and intensity as a LLJ strengthens and transports 15C H85 dewpoints into the area. Over the next 48 hours, low-amplitude ULVL ridging will build into the SRN plains while a parade of compact impulses traverse though this flow.

Discussion:
Key to timing and location of convection will be evolution of overnight elevated MCS and location of attendant OFBs. During the day, low-pressure will strengthen between AMA and LBB. At 20Z, a WF will extend E, parallel to and about 30 miles N of I-40 in WRN OK; and then it turns slightly ESE in ERN OK with outflow enhancement. Thick SC will persist N of this boundary for much of the day with differential heating and elevated convection continuing most of the day. Strong capping will persist until late in the afternoon when omegas increase with a mid-level wave and temperatures rise to convective temperatures in the low-90s. Convection will backbuild and become SFC-based. W of I-35, warm mid-levels and weaker convergence should suppress convection there. Strong instability will couple with impressive turning of winds with height with 30kt H8-H7 flow above ERLY SFC winds.

Please feel free to PM me for nowcasting.

- bill
9:30 PM CDT, 05/31/08

 

[Warren Faidley]

Looks like a classic set-up for eastern Colorado later this afternoon. I'm sure the SPC would have spotlighted this area more... but they have a large area to deal with today. Regardless, it's the target for today, especially with all the boundaries, 50k deep shear in the region and DP's at or above 55 by late afternoon. I would not be surprised to see the risk percentages go up by 16:30z.

W.

 

[Mark Blue]

We're going to play the upper air disturbance that crested the ridge in Eastern Colorado earlier this morning that is currently setting off convection in SC KS right now for later today in Arkansas. We holed up in Siloam Springs AR last night and will basically be waiting for the upper air support to arrive in NW AR around mid day or so and hope to follow anything that fires up along outflow boundaries being laid down from this morning's convection that is moving this way. Seems like a large area is depicted for possible severe weather today according to the SPC. Being from Denver I wish we were closer to home based on the other posts about Eastern CO, but I think we'll make out fine with the cards we've been dealt for today.

Mark & Jane

 

[Andrew Stoller]

After looking at forecast NAM skew Ts for northeastern and southeastern CO (Akron and La Juanta), I'm inclined to think northeastern CO would be the better setup. 700 mb temps are still very warm, but CINH is less today and the forecast skew Ts show no cap remaining by 00z.

Akron 00z: 2600 J/KG CAPE, supercell potential 70% (goes to 85% by 03z), no cap remaining, hodograph isn't the prettiest thing a storm chaser's seen, but directional shear is decent 0-6 KM of 60 knots, low level shear is lacking at 20 knots.

All in all, with boundaries left from last night, looks decent. WRF and RUC seems to keep precip confined to northeast CO. Will likely start out in Limon with a gut feeling that the Cheyenne Ridge will pop a decent supercell by 01z. The NCEP WRF model does pop a monster on the Palmer Divide around 03z so will have to watch for that as well.

:edit: southeast CO has low clouds as well - northeast CO is much more clear.

 

[Steve Miller TX]

Western OK

Sitting here in Weatherford, OK after chasing the spectacular supercell here yesterday evening. The big MCS in NE OK has left a nice OFB across the west half of OK. Things are still kind of a mess at the surface, but the OFB is pretty apparent on satellite and careful surface analysis. It appears to have slowed quite abit and should do so with continued afternoon heating. The question is if it remain intact enough to be a factor late this afternoon. I believe it will with it being noon and still pretty evident.

The RUC updates seemed to have stopped this morning for some reason, so that certainly doesn't help matters. However, I am liking anywhere from around Vernon, TX to just south of Woodward, OK...picking Clinton OK as my target. If something can pop the cap and latch onto the OFB, another spectacular supercell is pretty likely moving SE along aforementioned boundary.

Latest SPC mesoanalysis is starting to increase favorable values towards Clinton, OK. I hope this trend continues.

 

[Andrew Stoller]

After looking at the satellite, there is an outflow boundary in eastern CO from about Denver International airport to Cheyenne Wells, with another boundary moving southwest through northwest KS/southwest NB. Excellent Excellent. OFB backed into the palmer divide =

Limon dewpoint is only 52 though - need to get that pumped up some more. Burlington is 56. Just hope the moisture mixes out well to the east.

 

[Andrew Stoller]

700 mb temps are still 16-18 degrees but cool off into NE, WY, and SD. Today is looking like a cap bust until later this evening as MCS evolution looks to unfold off the higher terrain of WY/SD.

Moisture has mixed out a bit as well.