3/31/05 FCST: Southern Plains

[Ben Prusia]

ETA is forecasting CAPES of 1500-2000 J/Kg over an area of eastern Oklahoma and eastern Texas, extending eastward to the Mississippi River. Td's progged to be in the lower 60's, along with LI's of -6 from the Texas/Arkansas border southward to the Gulf of Mexico. SPC has slight risk out for the area, but say they may upgrade to moderate risk.

LATEST INDICATIONS ARE THAT WIDESPREAD CONVECTION WILL ALSO DEVELOP EWD ALONG THE WARM FRONT WHERE SHEAR PROFILES WILL LIKELY SUPPORT SUPERCELLS...SOME POTENTIALLY LONG TRACK.

http://www.rap.ucar.edu/weather/model/eta7...hr_sfc_mslp.gif
72 Hour ETA shows Low developing along the Red River valley just NE of Dallas.

Will wait until 12Z ETA for further discussion from me.

 

[Jeff Snyder]

As much as I want this to happen, I seriously doubt we will get this moisture as far west as most plains chasers would like. I'm seeing a slow model trend to shove the moisture farther south and east, much like what the NAM did for tomorrow (Wednesday). The 12z NAM shows the low into AR by 0z with strong northerly winds across OK and all but the far past of eastern TX. So, I think the greatest risk will be in southern AR and LA. For whatever reason, the models just can't bring the moisture westward enough to engage me! UGH! The NAM, as I mentioned aa couple sentences back, did the same thing between the 72hr and 84hr forecast for Wednesday... I suppose we have climo working against us... For what it's worth, it looks like the we're going to get another Gulf washer / scourer again out of this low.

 

[Karen Politte]

Well.....I don't chase the Kiamichis ! Seriously......it's a great shame that we couldn't get some of these early systems further west......but alas that's just inherent to the time of year. I have high hopes that much of April's activity will finally make the pilgrimage westwards to an area from Abilene TX to Buffalo, OK to Clinton, OK.......but that's wishcasting right now.

Seriously - I think I've pretty much discarded thoughts of chasing anything this week - I'm really not interested. Let's let this next system's front plunge through, bring us winter again, clear the atmosphere down to Mexico and middle-America, and start over, OK?

Honestly, I'd be beginning to pin my sights on the 2nd week in April...

KR

 

[Jeff Snyder]

Honestly, I'd be beginning to pin my sights on the 2nd week in April...

KR

I agree Karen... The cold front will plow through the area soon, which will push the moisture well east of the plains by Thursday. The strong northerly winds behind this system (models indicating 40-60kts northerly flow all the way to the Yucatan!) guarantees that we won't see any plains chases for a while. This is highly reminiscient of 2002, a year in which we had continual intrusions of continental/modified polar air into the Gulf. As we all remember, we had cap bustola's like crazy that year, many of which were likely aided by some moisture issues. At any rate, this is deviating from the 3/31 FCST timeframe, so I will end just as the severe weather threat has...

 

[Jeff Snyder]

LOL, well, I'm going to post this based on the 18z NAM forecast... It seems that the NAM has been incredibly poor in terms of run-to-run consistency, as each model run seems to be markedly different than previous runs. This has continued for the 12z and 18z runs, which are trending AGAINST the trends from previous runs yesterday in bring the moisture back westward tomorrow. Instead of having the low in AR tomorrow, the new 18z run shows the low out near Childress! This brings southerly flow across all of northern TX, and appears to bring the warm front to the Red River by 18z. I'm only able to see the 18z run over at NCEP, so the fields I looked at were few in number. At any rate, Gulf moisture is currently locked up just inland along the TX Gulf coast, so I'm not sure how far north the >60 Tds can get tonight and tomorrow morning... Otherwise, with strong flow in the mid-upper levels, supercell appear possible. In addition, while 850mb flow isn't very strong, favorable veering, especially invof the Red River, may provide enough srhelicity for a tornado threat. Then again, this could all be a crapcast in a few hours when the 0z comes out, seeing how poorly the NAM has been performing lately.

EDIT: UGH! We need another 12-24 hours of southerly flow here... The low is hanging back a little more, though we just don't have enough time to advect some good moisture into the area before the dryline/front sweeps through.

 

[Bill Schintler]

Chase target for today, March 31

Chase target:
Greenville, TX

Timing:
Storm initiation 4 PM

Storm type/intensity:
Stronger storms that organize and develop rotating updrafts will produce hail to 1”.

Discussion:
At 00Z, moisture was still quite limited in the target area… SHV sounding indicated a 250mb deep “moist” layer – with surface T/Td = 84/47F. FWD was even drier with the “moist” layer, largely because of WRLY LLVL winds in response to the surface wave passed through the area today. LCH was much more promising – showing a well-mixed layer nearly 200mb deep with a surface T/Td = 73/68F, along with SSWRLY 5-10 kt winds in the lower levels advecting this moisture to the north. Slow BL recovery is in place.

Eta/NAM, GFS, and NGM were all consistent with the 00Z initialization to UA fields in the SRN CONUS – basically that of a 500mb 70kt streak traversing the ArkLaTex, along with initialization of temperature, dewpoint, and wind fields at 850 and 700 mb. The Eta/NAM was somewhat more aggressive as to the WWRD extent of current surface moisture, otherwise Eta and GFS have initialized well to the surface fields.

Tomorrow, between 18Z and 00Z, all models generally agree to bring a 70kt, 500mb streak exit region into the target area. At 850mb, guidance is consistent with a narrow moist tongue focusing into ERN TX by 18Z, and veering into the target area by 00Z, while advecting healthy moisture (60F+ Td’s at the surface / 10C at 850) into the target area. Surface low pressure will form in the Waco area in response to UA forcing, associated with this will be an inverted trough that will push EWRD during the afternoon hours. While thermodynamics will be marginal even with the moisture return (MLCAPE’s to 800 J/k g per Eta), 0-6km shear will approach 60 kts, along with a narrow N/S band of 200 m2/s2 1km SRH’s. This will allow for good storm organization between the peak heating hours of 4PM and 6PM.

- bill