4/12/07 FCST: TX / OK / KS

[Dal Archer]

Wow! What a difference 24 hours makes. I was pretty pessimistic yesterday evening, but now I don't know.

I had not checked the GFS since yesterday afternoon and I was shocked with the difference in projected dewpoints over such a short period after just checking it again. What a major difference from yesterday. If (a big IF) the moisture does manage to return we could be in for a great day on Thursday.

Here's hoping a secondary shot of cold air doesn't wipe out our moisture return over the next few days.........

 

[SteveCarter]

Grrrrrrr, seeing a diminishing chance here for the entire week ahead. Looks like Wednesday's little system will run into dry air and do about nothing. Thinking this may also lead to a boundary of sorts setting up that inhibits any moisture from moving up into the plains. Just not confident..at all, that the system Friday can crank up to much being this mositure-starved. It's still early tho.(Sun PM) Had started clearing my schedule out for Thu-Sun...just in case. Think I may start filling it back in. I hope I'm wrong.

 

[Ray Walker]

I'm excited and yet worried at the same time. This system looks as though it is either going to be a bust, or a pretty nasty outbreak. This system looks as though Oklahoma and Texas could be in for a wild ride Thursday and or possibly Friday. If the moisture return is strong the I think we could be dealing with a pretty sizable severe weather event.

 

[Kevin Polston]

I just took a quick glance at the 00Z GFS. If the GFS is correct (and it is been showing from last nights 00Z run through the 12Z today and now the 00Z tonite).....moisture doesn't look to be a problem for late in the week. By 00Z Fri there are 60 deg dewpoints to the KS/OK border with a well pronounced dryline in western OK south into TX. By 18Z Fri 60 deg dewpoints are in ern KS with mid/upper 60 dewpoints into ern OK/TX. Seems to me with the dynamic system coming out into the plains and well pronounced boundaries and a decent sfc low.....things should be good to go. Assuming the GFS is correct of course.

 

[Tom Tackett]

Kinda slightly off subject, but guess what huge event will be underway here in North Texas this upcoming weekend, April 12-15??? NASCAR---Texas Motor Speedway (18 miles north of Downtown Fort Worth on I-35W) with 40,000 to 50,000 people in campers and RV's alone with an estimated 180,000 to 200,000 others in for the races. Might need to hope that this possible Friday severe weather event does not materialize. Will consider starting another thread elsewhere by midweek, to cover this aspect, if this forecast scenerio appears to possibly verify. TT in FW.

 

[Stan Rose]

SPC believes the cap will be too strong for anything thu afternoon. WRF soundings for thu do show the cap weakening by mid-day over the panhandles, so im not sure i agree, particualarly given how strong the dynamics are with this system.

 

[Chris C Sanner]

Thursday looks like it could be a sleeper type of day before the day event. However I'm not sure how much lift we will be getting along the dryline at the key point of the day. Winds are backed though, and the wind fields would support severe weather. I'm favoring SW Oklahoma if the chase comes to fruition. Moisture return is a definite negative for Thursday as I'm not sure it'll be all that deep but the further S you go the better your chances of a better moisture fetch. Either way, looks like Spring is coming back after old man Winter decided to return for a weekend

 

[Doug Mitchell]

I don't know exactly where to post this but I'm going to drive down to Oklahoma on Wednesday night and if anyone in the OKC/Norman area can house me for the night, I'd reimburse you for your troubles. Just PM me.

Otherwise, looking decent for Thursday. NAM/GFS are in general agreement of modest moisture return for NW TX/W OK area ahead of a strong system. I agree with the assessment as a "sleeper" event before a big day on Friday. I think initiation will occur along the TX Panhandle/W OK border...this all, of course, assuming the last few runs are correct (which they won't be). As with March 28th event, this system is probably progged to fast and we could be facing some more Caprock chasing later this week.

 

[Jeff Snyder]

Interesting possibilities for Thursday as more of a "day before the day" event. With strong flow at all levels, shear profiles will be quite significant. Fortunately, midlevel flow appears as though it'll be very manageable, which should provide for a relatively chaser-friendly storm motion. The primary concern that I have at this time is the quality (magnitude and depth) of moisture. Tonights 0z NAM shows respectable 850mb Tds, indicating that depth may not be a big problem. However, I don't like the meteoric rise in dewpoints in the NAM forecast between 12z and 0z. I assume much of that is attributable to the downward mixing of higher moisture that is advected northward on the LLJ Wednesday night and Thursday morning, but we'll have to wait to see if that really happens. I'm very much not a fan of "last-minute" moisture return, since it seems that few "big" days occur when substantial moisture is not in place the day before the event (3-28-07 being the obvious, most recent example). I can name what seems like a million examples of busts that occurred when the forecast last-minute moisture did not materialize... But hey, it's still April, so I can't be too picky about moisture yet.

The moisture forecasts remind me of the Feb 23rd 2007 "event" in the eastern TX panhandle in that dewpoints, IIRC, were overforecast, and we never saw the last-second advection of 60F tds. In this regard, Friday rings a few more bells than Thursday, since >60F tds should be in place in the warm sector by Friday morning. Alas, that's a different thread.

 

[Jim Tang]

Interesting possibilities for Thursday as more of a "day before the day" event. With strong flow at all levels, shear profiles will be quite significant. Fortunately, midlevel flow appears as though it'll be very manageable, which should provide for a relatively chaser-friendly storm motion. The primary concern that I have at this time is the quality (magnitude and depth) of moisture. Tonights 0z NAM shows respectable 850mb Tds, indicating that depth may not be a big problem. However, I don't like the meteoric rise in dewpoints in the NAM forecast between 12z and 0z. I assume much of that is attributable to the downward mixing of higher moisture that is advected northward on the LLJ Wednesday night and Thursday morning, but we'll have to wait to see if that really happens. I'm very much not a fan of "last-minute" moisture return, since it seems that few "big" days occur when substantial moisture is not in place the day before the event (3-28-07 being the obvious, most recent example). I can name what seems like a million examples of busts that occurred when the forecast last-minute moisture did not materialize... But hey, it's still April, so I can't be too picky about moisture yet.

The moisture forecasts remind me of the Feb 23rd 2007 "event" in the eastern TX panhandle in that dewpoints, IIRC, were overforecast, and we never saw the last-second advection of 60F tds. In this regard, Friday rings a few more bells than Thursday, since >60F tds should be in place in the warm sector by Friday morning. Alas, that's a different thread.

The models were pretty consistent in developing 50's dewpoints the days before the event on the 23rd, I believe.

Many big outbreaks do occur after last minute rapid moisture advection. Nevertheless I do agree that moisture could be a problem on Thursday. The models vary on the degree of how an initial trough will close off over the Northeast. If that thing bombs like the NAM shows, it will leave behind a continental air mass that will delay moisture return initially, until the LLJ picks up Thursday night.

As of right now, an initial target would be in southern OK near the Red River. I think the cap could remain an issue further south affording a nice tail-end charlie in that area. Great directional and speed shear and steep lapse rates should allow for some nice sups and possible tornadoes.

 

[Stan Rose]

Well yeah the 00z NAM is very optimisitic, but ill run win its optimisim and take the risk of a bust. Im not gonna ignore parameters that are off the charts from sw KS all the way thru OK (and if you believe the 00z, even E CO) I sure aint sittin home with the dynamics of this storm! If i gotta go south, south ill go.

 

[Jason Boggs]

With all the talk about moisture return, here is my scoop on things. After this last cold snap that took Td's down to the 30's in the gulf, significant moisture return is already occuring. Td's in the low to mid 40's are in place in the TX panhandle and western OK while Td's are in the low 50's in the Abilene area. A slight cool front on Wed. will damper the moisture return a bit, but the front is not that strong, and moisture will definitely be on the increase when the LLJ gets cranking bigtime early Thursday morning. I think Td's in the mid to upper 50's will be in place when the dryline sets up along the TX-OK border (possibly a little further west) on Thursday. I think SW OK and the Red River area will see Td's in the low 60's.

Good dynamics will be in place with a trough in the west. Good upper level diffluence will aid in lift, along with high lapse rates with the cold, dry air in the upper levels. Speed and directional shear will be quite favorable for rotating storms with surface based storms forming in the richer moisture environment. CAPE values should be over 2000 with the presence of good moisture and adequate daytime heating.

Going out on a limb, a favorable target area in my opinion is going to be in the Sayre, OK area because of the good road network and WIFI access.

 

[Adam Atkins]

I agree with the previous posters in regards to moisture return mechanisms...due to downward mixing and daytime advection. While this is of concern, I'm optimistic due to the presence of a warm frontal boundary and storm motions perpendicular to the dryline, while nearly parallel to the WF. The greatest theta-e ridge and moisture advection will be east of the dryline boundary meaning there might be significant forcing necessary for initiation off the dryline, because of poor moisture depth. Fortunately, the storm motions will quickly get developing storms off the dryline and into better moisture to the east. (NAM has trended to lower Td's since yesterday's 12 UTC run)

So the #1 issue is initiation potential, while the #2 issue is how plentiful the instability will be east of the dryline. These warm advection "day before the day" events usually have a low stratus deck over the bulk of the warm sector. The presence of the warm front will offeset this concern, slightly, but thin CAPE axis days are historically unsuccessful for me.

Large target area as of now, mesoscale features (mainly thermodynamic) will play a role in defining eventual location to head out.

 

[Jeff Snyder]

The moisture forecasts remind me of the Feb 23rd 2007 "event" in the eastern TX panhandle in that dewpoints, IIRC, were overforecast, and we never saw the last-second advection of 60F tds. In this regard, Friday rings a few more bells than Thursday, since >60F tds should be in place in the warm sector by Friday morning. Alas, that's a different thread.

The latest NWP guidance now suggests that areas north of I20 will not see Tds >55F, as I had feared. With a slower solution, the 12z NAM makes me a little more optimistic for a northern TX and OK chase on Friday, but it makes me much less optimistic about a Thursday chase... Unfortunately, Friday will see extremely strong 500mb jet streak moving across the risk area (80-90+kts at 500mb!), leading to 50-60kt storm motion per 12z NAM.

Back to Thursday... shear profiles look very good in the warm sector, particularly north of the Red River, and this morning's NAM indicates 65-85kts 0-6km shear (see HERE) across the eastern TX panhandle, southwestern Kansas, western OK, and northwestern Texas by evening. Given Tds only in the low-to-mid 50s, CAPE will likely only be 500-1250 j/kg across the area, which, I fear, will be much too weak in face that the very, very strong deep-layer shear. Of course, relatively low CAPE wasn't enought to prevent a violent tornadic supercell on Feb. 28th in southeastern Kansas...

Each new model run should shed more light onto the availability of significant (sufficient) moisture by Thursday afternoon, so I hope that this changes. Given the beating the Gulf has taken the past 10 days, however, I won't be holding my breath. Actually, looking at Td progs, it looks like the biggest problem for moisture return Thursday will be the cold front that will traverse the southern US today and tomorrow. This morning's models suggest that the cold front will hang up in the northern Gulf and extreme southern Texas Wednesday night, with Gulf moisture making headway north of BRO and CRP Thursday morning (way too late it to make it to western OK I fear... I'm not sure about moisture advecting 600-700 miles in 8-10 hours).

 

[Stan Rose]

Im afraid you're right, Jeff. I haven't thrown in the towel yet, but may have to just hope the system stays slow enough that i can have a shot at friday. On the other hand, the blizzard odds look good, so maybe ill just stay close to home and play in the snow!