NOAA SPC Day 1 OUTLOOK - 13z/March 18th (spc.noaa.gov)

KDR media streamers will be out the next two days as the first widespread, appreciable SVR weather event appears poised to unfold for the southern Plains into the mid-Mississippi Valley regions today and tomorrow as an upper-level trough, currently located over the Great Basin/Sierra Nevada regions, gyrates E/NE, with the eastern belt of stronger mid-level flow approaching the southern and central Plains this afternoon.  Ongoing convection is expected to clear out, allowing for rapid destabilization later this afternoon.  A dryline, expected to lie from the Caprock region of TX northward into W KS and NE, will be juxtaposed with seasonably ample moisture profiles that, combined with surface heating and favorable shear profiles as surface winds back relative to the forcing, will likely facilitate the outbreak of convection late this afternoon or early this evening.  An initial warm layer aloft will probably inhibit convection early on, though greater forcing for ascent and/or convergence along the dryline are expected to ignite convection after 21z.

If storms can maintain a discrete mode, a tornadic threat appears likely, as SRH profiles improve this evening when the low-level (850 mb) jet strengthens and LCLs improve, though large hail and damaging winds are also threats; storms are expected to take on a more linear mode, moving eastward into the Red River Valley, OK/KS and perhaps parts of S NE.

NOAA SPC Day 2 PROBABILISTIC OUTLOOK - 6z/March 18th (spc.noaa.gov)

By Monday afternoon, the trough will have moved into the four corners region and points northward, with stronger winds aloft, taking a more meridional flow, moving from the central Red River Valley northward into C/E OK, EC KS, E NE and parts of MO, AR and W IA.  This greater forcing for ascent is expected to overrun a region of moderate instability, though the greatest surface-based instability parameters look to be centered over E OK, the eastern one-third of Texas, and the ARKLATEX region, with slightly less magnanimous instability over the lower Missouri River Valley.  SFC-500 mb bulk shear profiles of 40-60 kts, coupled with ample instability profiles, will again favor the evolution of severe weather, with the primary threats located over the southern portion of the aforementioned area.

Please stay tuned to KDR media for further updates, and check back for links to live streams and video from stringers as this event unfolds Sunday and Monday.

JLR

Based on 00z/15 (ECMWF and GFS) and 12z/15 (NAM) model runs, there appear to be two severe weather events poised to impact parts of the southern Plains this weekend, with the best chances coming on Friday, March 16th over parts of the Red River Valley region and Sunday, March 18th over parts of the southern Plains.  Additional chances are likely into early next week, though it’s still a bit far out to pin down anything more exact at this juncture.

For  Friday, March 16th, the major model runs are depicting a mid-level impulse with an area of enhanced vorticity, with mid-level flow of 30-40kts, gyrating out of NW Mexico and into western Texas by early Friday (note a difference between the NAM (first) and ECMWF (second) in placement of the impulse by 18z FRI).

500 mb profile at 18z/FRI per 12z/15 NAM

ECMWF 500mb profile at 18z/FRI

This impulse will be co-located with ample surface heating, return moisture flow, and moisture pooling along a dryline that extends from near Pecos, TX into western Kansas.  Surface temperatures are progged to warm well into the mid-80s, with dewpoints likely reaching the upper 50s by late afternoon.  MUCAPE values are progged to be very ambient, AOA 2000 J/KG, favoring the evolution of steep lapse rates and LI values AOB -8C ahead of the dryline.

MUCAPE at 18z/FRI per 12z/15 NAM

Tds and LI values at 18z/FRI per 12z/15 NAM

The environment will be characterized by mediocre SFC-500 mb shear values of 30-40 kts, though favor unfavorable direction shear profiles and less than stellar T/Td profiles will promote surface LCL indices > 1000m, so the tornadic threat appears rather nill, with large hail being the primary threat, though damaging winds are also possible with any cells that do develop.

Forecast Skew-T profile at 18z/15 west of Wichita Falls, TX

It should be noted that there are some timing differences with respect to the NAM, GFS and ECMWF regarding the placement of the impulse and greatest DPVA, though the convective simulations appear to be initiating convection off the caprock between 20z and 22z, with evolution to a more quasi-linear or MCS structure after 00z, either moving into WC OK or staying proximal to the Red River valley and points eastward (see below).

Saturday’s potential looks more limited and localized due to a lack of major upper-air forcing for ascent, but Sunday could prove interesting as well, though it’s still a bit too far out to make a more detailed forecast for Sunday, as conditions will be easier to forecast as the weekend approaches.  For now, it appears that a trough will slowly make its way onshore over the weekend, with stronger mid-level flow (>80 kts) approaching the western Plains by mid-day Sunday, with a 996 mb surface low sitting in NE CO, with a dryline extending down into W KS and the TX panhandle.  As of right now, shear and instability profiles appear to favor SVR weather invo the dryline from parts of KS S/SW into the TX panhandle, and the 00z/15 GFS and ECMWF are hinting at convective potential along southern portions of the dryline late Sunday evening in a favorably sheared environment that may hold some better tornadic potential as well.  More on this setup will be forthcoming as the convective evolution becomes more certain in the next 48 hours.

GFS 550 mb profile at 00z/SUN 19th

JLR

The next chance for SVR weather may arrive tomorrow afternoon courtesy of a closed low that is currently situated over the four corners region of the SW CONUS, which is forecast to gyrate eastward int the central Plains by late tomorrow.  A pseudo-warm front is poised to lie across the ARKLATEX region, lifting into the I-40 corridor by late tomorrow afternoon.

This cutoff low with a coterminous 85 kt 500 mb jet core will place portions of AR, NW LA, E OK and SW MO to the right of the jet core in an enhanced region of dynamic lifting as a strong S/SW LLJ strengthens to 60 kts between 21z/11 and 00z/12.  Suffice to say that dynamic lifting will be proximal to ample WAA/moisture flow at the surface, though the amount of instability to be realized continues to be the one factor threatening to impugn on tomorrow’s otherwise favorable parameters, as surface flow backs to AOA 25kts behind the surface boundary, promulgating 0-km shear values of 40-80 kts across the region.

NAM/WRF - MUCAPE at 00z/12

GFS Skew-T: 21z/11 forecast at Camden, AR

NAM Skew-T: 21z/11 forecast at Camden, AR

The models have been consistently showing a rather obstinate throng of precipitation ongoing throughout the day, which could shunt the most favorable instability parameters south of the most favorable shear parameters, yielding a fairly doltish, shear-driven event that lacks the robust CAPE values necessary for a more substantial SVR weather threat.  Nonetheless, interested parties will want to monitor the situation tomorrow in the event that more robust instability parameters do materialize.  Keep an eye on KDR media for further updates, as live streams are possible with affiliate chasers who may be active in the region tomorrow afternoon and evening.

JLR