02/04/08 FCST: AR,OK,MO,IL,TX,MS,LA,TN

[Brian Emfinger]

Surprised there wasn't a thread on this yet!

Temperatures around 70 and dew point's over 60 are forecast to make it all the way up into Missouri and the SPC already has a slight risk for the day 3 over much of Arkansas and Southern Missouri. Shear is nice and if the instability verifies then this should be a pretty nice setup for this time of year. I am definitely liking the large size of the warm sector. There doesn't seem to be too much that can mess this one up which is why I'll be chasing this one Monday and then east into MS/AL on Tuesday as well.

 

[Michael O'Keeffe]

I agree this looks to be like a nice setup across the S Plains. If the WRF is right I'd say NE OK/SE KS are the place to be right along the dryline. I like how sharp the dryline looks in this area and CAPE's are looking good. Winds are more SSE in this region as well. The SigTor parameters are showing up at 8 over NE OK/SE KS from Tulsa up through Coffeyville up to around Pittsburg, KS. So I think the SLGHT should be moved further west IMO. If the WRF DOES pan out my dad and I will be chasing this event.

 

[Bill Tabor]

Yes, NAM even seems to show a sliver of hope closer to home for me down here in TX - particularly eastern and extreme north east Tx from 21z to 03z though lower levels - 850mb seem to indicate a bit of veering weakening shear for sups / torns. Still there may be a small chance with likely a Slight risk for this area initially. Looks to be fairly juicy temps and dews for February! I'll have to take a better look further NE of there up toward MO/AR or even eastern OK as they may have some potential for better stuff.

 

[Mike Hollingshead]

http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=META&fcsthr=048&STATIONID=ksgf

Not bad for noon on Monday! Hope it can slow some/move west and get out of the trees. I hope I don't chase this one, but I'm starting to think I'd better get things setup.

Nice to see return flow already setup along the coast, with upper 50 dews onshore. Mid-upper 60 dews at the two central/western gulf bouys out there...on the move north too.

Freezing drizzle or rain Sunday night may keep me home Monday morning. That's usually the problem with chasing in WINTER, lol.....winter.

Edit: Hell it may not need to slow at all. Just leave *some* room to be able to chase in se KS.

 

[Chris Wilburn]

I agree with Michael that the slight may need to move a bit further west to include sections of SE KS/NE OK. Here is to hoping that the NAM verifies. Dewpoints near 60 with CAPE forecasted to be near 1,000 J/kg should be interesting. Surface temps. should be near 70 as well along with southerly surface winds and very nice 0-1 and 0-3km helicity values. I too like how the dryline looks in SE KS into NE OK. I also noticed the Significant Tornado Parameters that you are talking about Michael and they are very impressive to say the least. It will be interesting to see if things actually verify, but it is hard not to get excited for early February. I will probably jinx everything, but this looks very similar to January 7th. I am with you Mike in hoping that it gets moved back west a tad to stay out of the less than favorable terrain. I guess only time will tell. SPC day 2 has mostly SE OK and most of Arkansas in the slight risk along with southern Missouri. I am guessing they are going off the GFS which has the system moving through faster or maybe they are expecting convection well east of the dryline. I mention this because the NAM breaks out precip. well east of the dryline into western Arkansas and southern Missouri. After reading the SPC day 2 text it appears they think the CAP may be too strong to overcome in the Eastern OK area which is why the NAM has no precip. breaking out in this area. This is reflected in the lid strength index I just looked at. Hopefully this will change.

After looking things over more and looking at the 06z forecast (midnight Monday) shows parameters increasing in Eastern Oklahoma into Western Arkansas which could pose a serious threat after dark for these areas. The CAP should erode later in the evening and CAPE, helicity, moisture and Significant Tornado Parameters actually increase near midnight as opposed to 6pm. I know night chasing isn't the best, but late late night Monday into Tuesday morning could get very interesting.

 

[Bill Schintler]

Chase target for Monday, February 4

Chase target:
Texarkana, AR.

Timing and storm characteristics:
Strong to severe storms should develop along a line from Texarkana to Pine Bluff, AR by 4 PM CST. A localized outbreak with a full spectrum of severe weather is possible, including a few tornadoes within supercells embedded in this line.

Synopsis:
Looking at the big picture, a 120kt H5 ULJ was rounding the base of the broad ULVL trough, with strongest height falls concentrated over the Four Corners area. Upstream soundings (AMA, ABQ) indicated steep lapse rates from the SFC through H6. Closer to the target area, the axis of deepest moisture was located generally E of the OK/AR border on a veering LLJ. This moisture plum showed up well on the visible satellite as ST while local soundings (SGF, LZK, and SHV) each indicated a 150mb-deep moist layer along with SFC dewpoints ranging from 50F to 65F from north to south. MDLS initialized well on LLVL moisture, and the latest runs place tomorrows 00Z DL further E as was anticipated due to the veering LLJ resulting in mixing out of the moisture in OK and TX.

Discussion:
During the afternoon hours, a subtropical 70kt H5 jet will strengthen S of the main trough and polar front jet. An associated vorticity ribbon will be maximized along the left side of the SRN jet. Attendant with these features will be a CI shield, which should be located along and S of an Ardmore, OK to Fort Smith, AR axis by 22Z. The primary synoptic SFC features will remain well N and W of the target region where moisture is limited. Further SE in the moist sector, a line of storms should form within the left-exit region of the subtropical jet, on a developing SFC convergent axis well E of the DL. Capping, with H7 temperatures in the 5C range, should aid in keeping convection isolated except were forcing is strongest. There are also some indications that a meso-low may form along the convergent axis resulting in localized backing of the SFC flow.

Modest instability will be juxtaposed with impressive shear parameters. Differential advection of the aforementioned moderate mid-level lapse rates of 7C/km over a deep moist layer should result in MLCAPE’s to 1000J/kg, especially NW of the CI shield where modest insolation takes place. A 45kt SWRLY LLJ will surge over SRLY or slightly backed 15kt SFC flow, resulting in SRHs (SFC to 3km) in excess of 300 m2/s2. Deep-layer shear will also increase to 60kts. Supercells should be embedded along the SRN periphery of the convection, and tornadoes are possible given forecasted hodograph curvatures along with LCL levels in the 800m AGL range.

- bill
8:30 PM CST, 02/03/08

 

[Brian Emfinger]

Yeah I agree Texarkana and SW ARK looks best for the earlier storm chances (right now). That Special 0z WRF run does break out very isolated storms (well, one) just north of there by around 3z. The 3z SREF shows a small little corridor (near but north of I-30) of CAPE approaching 1000 from around Dallas into Central AR. The 0z runs of the GFS and NAM also show this as well. We'll see. The more certain storm chances are further NW as the cold front dives down in Oklahoma but everything I looked at shows everything developing here after 6z. As it stands right now, I will head down into SW Ark BUT I also will have a go at the frontal storms in OK later.

 

[Wesley Luginbyhl]

Just went through SPC forecast tools and the RUC analysis was showing Supercell composite of 20 in OK right now, not to mention a Sig Tor of 2 already. The new WRF seems to hold the dryline further west in OK this afternoon as well. This afternoon could get interesting, though it willl be likely well after dark as the new WRF shows no precip till well after 0z.

 

[Billy Griffin]

Not to put a damper on folks hoping for an Oklahoma chase, but per Mesonet data, looks like you can chalk off much of Oklahoma for any major severe threat. The dryline is now SURGING east with TDs already 30F in OKC! Perhaps the CF will still yield a chance for some lightning shots later this evening?

My money is for tomorrow being a significant Mississippi and Ohio Valley event. Good luck to all who chase tomorrow, and be safe!

 

[Chad Cowan]

Not to put a damper on folks hoping for an Oklahoma chase, but per Mesonet data, looks like you can chalk off much of Oklahoma for any major severe threat.

I wouldn't write off Oklahoma quite yet. The models have hinted at a secondary sfc low developing in the panhandles, and with the depth of the moisture (per 12z SHV sounding), I would expect the dryline to hold firm if not retreat a bit. The significant cap will most likely hold off convection until after 0z, but even without insolation the svr parameters all crank up between then and 6z.


EDIT: New SWODY1 is thinking the same: "AS LOW LEVEL FLOW BACKS THIS EVENING ACROSS SRN PLAINS...LOW LEVEL MOISTURE WILL SPREAD BACK INTO NWRN TX AND CENTRAL OK OVERNIGHT."

 

[John Farley]

Well, I am a little more bullish now on daytime chasable storms in eastern MO or southwestern IL. SPC expects initiation mid or late afternoon, and the RUC does indeed show precip breaking out. With CAPE around 1000 and good shear, the potential for supercells is certainly there if the storms get going. Sig tor already is around 2 in southeast MO. Here in Edwardsville we went from dense fog and temperatures in the 40s to sun and 70s in a short time, with nearly all the snow melted off now.

 

[Ilya Neyman]

Unbelievable temp is 80 degrees right now here in Norman! This morning felt more like a late March-April Plains severe wx day, not February 4th!

Anyway, latest mesonet data shows the dryline now stalling over the Pottawatomie/Seminole county line with winds beginning to back over the moist sector. This goes well with latest forecast data of developing secondary sfc low ivof TX p.h. as upper jet and associated system strengthen/approach.

This AM's RUC started picking up on the retreating dryline, but latest runs don't fire anything along it just yet. Cap could hold fairly firm unless enough forcing acts to overcome it.

Not quite sure yet if this is something to be concerned about as far as central OK goes just yet, but obviously is interesting given time of year.

Gotta be fascinated by those retreating drylines. Case in point - the infamous May 11, 1970 Lubbock F-5 developed along a dryline that had cleared the Lubbock area to the east that afternoon...and then surged westward during the evening firing off the tornadic storm that would devastate the city that night.

 

[Jeff Piotrowski]

Dryline Eastern Ok

A Storm just developed on the dryline over Wagoner county OK. This is about 30 miles east of Tulsa.

The dryline on the TUL radar is starting to back up.

 

[Brian Emfinger]

A Storm just developed on the dryline over Wagoner county OK. This is about 30 miles east of Tulsa.

The dryline on the TUL radar is starting to back up.

Yeah I have actually been watching this enhanced cu for a couple hours and it definitely tried for awhile but not so much anymore. Some of this afternoons ruc runs have been showing some stuff breaking out here but it still looks like its going to hold of till later (although maybe not as late as Ive been thinking all day...hopefully!).

Here it was as it was earlier (415ish) http://www.realclearwx.com/02040801.jpg

 

[Wayne Hlinicky]

Oklahoma is out

I wouldn't write off Oklahoma quite yet. The models have hinted at a secondary sfc low developing in the panhandles, and with the depth of the moisture (per 12z SHV sounding), I would expect the dryline to hold firm if not retreat a bit. The significant cap will most likely hold off convection until after 0z, but even without insolation the svr parameters all crank up between then and 6z.


EDIT: New SWODY1 is thinking the same: "AS LOW LEVEL FLOW BACKS THIS EVENING ACROSS SRN PLAINS...LOW LEVEL MOISTURE WILL SPREAD BACK INTO NWRN TX AND CENTRAL OK OVERNIGHT."

I don't think anything is going to happen in central Oklahoma. We are expecting rain changing over to snow with no accumilations. After a 76 temp today the ground will be too warm. Should any bad storms go they will be in far eastern Oklahoma but so far the storms that are there have "behaved" themselves.