Administrators NorthGeorgiaWX Posted May 22 Administrators Share Posted May 22 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0753 AM CDT Wed May 22 2024 Valid 221300Z - 231200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL TEXAS TO CENTRAL ARKANSAS... ...SUMMARY... Within a long swath of severe-thunderstorm potential from central Texas to the Lower Great Lakes, the greatest concentration of severe weather (mainly large hail and damaging wind) should be across parts of central Texas to central Arkansas. A few tornadoes are also possible. ...Synopsis... An active mid/upper-level pattern persists southeast through southwest of a longstanding cyclone over southern SK and paths of southern MB. That circulation will continue to meander erratically near its present location through the period. Meanwhile, a train of shortwaves will cross the northwestern and central CONUS and Great Lakes regions. A strong shortwave trough -- with embedded 500-mb low now over ON near the MN border -- should become stacked with its deep surface cyclone this morning and drift erratically over ON northwest of Lake Superior today. The stacked low then should eject toward James Bay tonight. The associated cold front -- analyzed at 11Z from northern Lower MI to southern IL, northwestern AR, southern OK, and northwest TX to the Permian Basin -- should move by 00Z to near a line from CLE-EVV-ARG-DUA-SJT-CNM. The cold front should cross the lower Great Lakes and much of NY through the end of the period, while decelerating across parts of the lower/middle Ohio Valley. The western part of the front should become more diffuse and retreat northward overnight across the southern Plains. This will occur as low-level mass response (including warm advection) intensifies, ahead of a mid/upper cyclone moving eastward across the northwestern CONUS toward the western WY/eastern ID region. A dryline -- initially drawn over the Big Bend region south of the front -- should mix eastward to northern Coahuila and a frontal intersection over west-central TX by mid/late afternoon. ...Southern Plains to Arklatex region... A broken swath of elevated thunderstorms is ongoing over parts of central OK to southeastern KS. Isolated large hail is the main concern, and should be for a few more hours. Some of this activity may aggregate into a broader belt or cluster of convection and shift eastward to southeastward through the day, toward the front. Additional thunderstorms should develop from midday through this afternoon along/ahead of the front and mid/late afternoon near the dryline, with the near-frontal activity having the longest and strongest organizational potential. A few supercells are expected early in the convective cycle, and any supercell that stays relatively discrete well into maturity will pose a risk of large to giant hail. Storm-scale/boundary processes also may locally boost tornado potential. Activity should grow upscale into the evening -- perhaps merging with remnants of earlier activity moving southeastward from OK toward the surface front. As this occurs, the main threat will transition to damaging and severe gusts. The "enhanced" area represents the overlap of greatest hail and wind probabilities with this transitional regime. The warm sector southeast of the front, and east of the dryline, will remain very moist -- characterized by upper 60s to mid 70s F surface dew points. Underlying steep midlevel lapse rates, and with strong surface heating anticipated, the result should be a corridor of 3000-4000 J/kg MLCAPE. Given the strong heating and high ambient theta-e, convective temperature may be attained even in the free warm sector (away from the front and dryline), and despite the prevalent EML. Though forecast soundings show weaknesses in the flow around 2-3 km, both low-level and deep-layer shear (effective- shear magnitudes 55-65 kt) and lengthy hodographs will be present, supporting potential for locally destructive hail. Severe downdrafts also are possible, both from individual supercells and from convection resulting from aggregated cold pools. The overall threat should decrease with this activity as it shifts eastward- southeastward toward south/east TX and over LA tonight. However, additional development atop the outflow may occur tonight farther north near the Red River, helping to maintain some severe threat (mainly in the form of hail and isolated severe gusts). ...Mid-South to Ohio Valley and lower Great Lakes... Widely scattered to scattered thunderstorms, some in clusters, are expected along this corridor from mid afternoon through the evening. Damaging gusts will be the main concern, with isolated large hail also possible. A marginal tornado threat also may develop, particularly over portions of central/eastern OH to northwestern PA and perhaps southwestern upstate NY, where low-level and deep shear will be most favorable. Once some ongoing clouds/precip over the Ohio Valley move away and break up, surface heating should destabilize the boundary layer, in concert with dewpoints commonly in the 60s F. This should yield a prefrontal corridor of MLCAPE ranging from near 3000 J/kg over parts of the Mid-South (where deep-layer lapse rates will be steepest) to around 1500 J/kg over the area adjoining the lower Great Lakes. 35-45-kt effective-shear magnitudes will support a mix of multicell and supercell modes, with upscale growth/clustering tending to limit duration of supercells. ..Edwards/Goss.. 05/22/2024 Read more View the full article Quote Link to comment Share on other sites More sharing options...
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