SPC Mar 18, 2018 1630 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 18 Mar 2018

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1156 AM CDT Sun Mar 18 2018 Valid 181630Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN PLAINS TO THE SOUTHEAST STATES... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL/SOUTHERN PLAINS TO THE SOUTHEAST STATES... ...SUMMARY... Thunderstorms with large hail and a tornado risk are possible especially across North and East Texas late this afternoon into evening, with additional severe thunderstorms possible across other parts of the south-central Plains to Southeast States. ...North/East Texas and far Southern Oklahoma to ArkLaTex... The potential exists for locally intense storm development later this afternoon/early evening, but a number of questions remain regarding the likelihood and locations/coverage of deep convective development. Along these lines, various convection-allowing models have shown semi-dramatic sub-regional spatial shifts between 00Z and 12Z of preferred severe corridors later today, while various HRRR runs have also exhibited considerable run-to-run variability (supercells vs. essentially no development) this morning. Scattered showers and some thunderstorms along with multi-layer cloud cover remain prevalent across the region at midday, related to east/northeastward-transitioning southern-stream forcing for ascent embedded with a strong (100+ kt at 250 mb) subtropical jet stream. In the wake of this scattered precipitation/thicker clouds, cloud breaks and some additional low-level moist influx should allow for relatively rapid destabilization especially across north-central/east-central Texas to the near/east of a dryline and along/south of an east/southeastward-extending front. But given some hindered heating through early afternoon and the early timing of the aforementioned southern-stream impulse, the likelihood and extent of deep convective development later today remains questionable, particularly given that areas such as north-central Texas may be influenced by subsidence aloft during peak heating. Accordingly, the overall scenario seemingly remains largely conditional, with the notion that any sustained surface-rooted development could evolve into supercells capable of very large hail and some tornado risk in the presence of steep mid-level lapse rates, moderate buoyancy, and favorable hodographs for large diameter (potentially significant 2+ inch) hail. Further outlook refinements/adjustments can be expected with the 20Z update. ...Lower Mississippi Valley to Southeast States... A weak impulse or two (and/or MCV) should semi-focus thunderstorm clusters across the region today, such as is occurring across southern Mississippi at midday. While buoyancy will not be overly strong, 40+ kt effective shear could support some bowing segments and possibly even a transient supercell or two. Damaging winds and possibly some hail should be the primary concerns. ...Portions of Texas Panhandle/western Oklahoma into Kansas... At least some severe-weather potential should exist later this afternoon through early evening with anticipated low-topped storm development across the region. Very limited moisture will exist within/north of a narrowing warm sector, but steep lapse rates and moderately strong wind profiles could support some strong to severe storms across the Texas Panhandle/northwest Oklahoma northeastward into southern Kansas. ..Guyer/Marsh.. 03/18/2018 Read more

http://www.spc.noaa.gov/products/outlook/day1otlk_1630.html

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