Tallis Rockwell

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About Tallis Rockwell

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  • Four Letter Airport Code For Weather Obs (Such as KDCA)
  • Location:
    Houston TX

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  1. Decent weekend ahead. ...Synopsis... A progressive shortwave trough will move from the southern Plains into the lower MS Valley during the day, and will continue to the GA/SC/NC coast by Monday morning. The entire southeastern region will be under the influence of strong westerly winds aloft which will strengthen as the upper trough approaches. Southwesterly 850 mb winds will increase in response to the wave, reaching 50+ kt by 00Z from MS eastward to the coast. At the surface, low pressure will develop near the ArkLaTex by late afternoon as a warm front lifts north across the southeastern states, oriented roughly from southern AR into northern MS, AL, and GA at 18Z. Meanwhile, a cold front/dryline will develop over east TX. Across the warm sector, rich moisture with 65-70 F dewpoints will result in moderate instability. The low, likely associated with widespread convection, will translate eastward along the synoptic front overnight, reaching NC by 12Z Monday. ...Southeastern states... Substantial instability will already be in place Sunday morning from TX into the lower MS Valley, with rapid destabilization expected behind the warm front farther east into GA. Midlevel lapse rates aloft will be modestly steep, averaging 6.5 to 7.0 C/km. Early day storms related to warm advection will be present over AL and GA, and they will likely be elevated with perhaps a hail threat initially. As the air mass warms, a wind or tornado threat could develop in the vicinity of this activity as it continues east. To the west, storms are likely to be severe by 18Z near the Sabine Valley/ArkLaTex. Here, long hodographs but modest low-level SRH may result in cells capable of very large hail, and perhaps an eventual MCS with damaging-wind threat. A severe wind corridor may thus develop during the day across northern MS, AL, and GA. There is also a threat of daytime supercells, possibly tornadic, as the small capping inversion is eroded by early afternoon. During the evening and overnight, low-level shear will increase further, and models suggest southern AL into GA may be a favored area for tornadoes. Bows or isolated supercells are possible into SC early Monday morning as the relatively cooler air mass is destroyed by the warm front.
  2. A pretty sound for southeast TX from 12z NAM
  3. 18z NAM is showing a more some good helicity over East TX.
  4. Decent stuff this week. Waiting for a watch in central Texas
  5. ...DISCUSSION... An upper trough should impact the western CONUS this upcoming weekend, eventually closing off over parts of the Southwest and adjacent northern Mexico around Day 5/Sunday. Medium-range guidance is in reasonably good agreement that this upper trough/low will eject east-northeastward across the Plains early next week. However, there are still differences regarding the degree of low-level moisture return and resultant instability that will develop ahead of this feature over the Plains and lower/mid MS Valley. Some severe threat may exist from late Day 6/Monday into Day 7/Tuesday, mainly across parts of the southern Plains into the lower MS Valley. This threat could continue into parts of the Southeast on Day 8/Wednesday. Inclusion of 15% severe probabilities in this extended time frame appears imprudent given the differences in both how and when the upper trough/low ejects over the Plains (positive versus negative tilt), and uncertainty regarding the low-level moisture return across these regions.
  6. NAM is really showing something here...Could this be the first high risk of the year? The NAM model are starting to show more discrete cells ahead of the cold front, not a whole lot but a decent bit.
  7. Low level winds for Friday is looking impressive!
  8. E EDIT: The new outlook has a better picture ...DISCUSSION... The latest runs of the GFS and ECMWF appear to be in reasonable agreement with respect to synoptic-scale features through Day 4 and into the first half of the Day 5 period. After this, differences in the evolution of the large trough progged to crossing the Plains states Day 4 and then the Mississippi Day 5 begin to become fairly substantial. As such, confidence in the predictability of the pattern beyond day 5 is quite limited. In the mean time, some potential for the evolution of scattered to isolated severe storms remains apparent over the eastern Oklahoma and Arklatex region and surrounding areas Day 4 (Sunday 10-20), as a deepening surface low shifts out of the central and northern High Plains and eventually reaches the Minnesota vicinity. Correspondingly, a trailing cold front is shown crossing eastern Kansas/Oklahoma/western Texas during the afternoon, as warm-sector destabilization becomes diurnally maximized. As favorably strong flow aloft overspreads the region in tandem with the advancing surface front, at least isolated cells -- developing as residual capping is locally breached -- will evolve within a sheared environment likely supportive of rotating updrafts. Storms may diminish somewhat in intensity overnight, but it appears that reintensification of convection -- and regeneration of accompanying severe risk -- should occur across portions of the central Gulf Coast region, as the front continues its eastward advance through an amply moist/destabilizing low-level airmass. Again, potential for supercells, and all severe hazards, appears possible. By Day 6, model differences -- including with location of the surface frontal position -- have become substantial enough to preclude continuation of severe risk into the eastern Gulf Coast/southern Atlantic Coast states.
  9. The short range models are starting to agree with 20+ inch totals
  10. GFS NAM RAP hasn't reached to this time yet...either way this looks to be interesting