Administrators NorthGeorgiaWX Posted December 8, 2023 Administrators Share Posted December 8, 2023 SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0654 AM CST Fri Dec 08 2023 Valid 081300Z - 091200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE ARKLATEX REGION TO THE OZARKS... ...SUMMARY... Isolated large hail is possible this evening and tonight from parts of the Arklatex region to the Ozarks. ...Synopsis... An eastward-moving, amplifying, mid/upper-level trough is expected to shift into the central CONUS during the period, spreading an extensive field of height falls and strengthening flow aloft across much of the Plains States and Mississippi Valley. Within the associated cyclonic flow, two main shortwave troughs will exert the most influence on large-scale lift and low-level mass response: 1. A northern-stream perturbation, apparent in moisture-channel imagery over the northern High Plains, forecast to move eastward and evolve to a closed 500-mb cyclone over MN by 12Z tomorrow. 2. An elongated, initially negatively tilted trough from the southern ID/northern NV region southeastward toward the Four Corners. The southeastern part will break eastward/northeastward across the south-central Rockies today, reaching the MKC area around 06Z, then accelerating northeastward into confluent flow fringing the northern-stream shortwave trough. Meanwhile, the remainder should dig southeastward, consolidate and amplify, reaching northern NM and southern CO by 12Z. At the surface, 11Z analysis showed a low over extreme northwestern MN, with occluded/cold front arching across south-central IA and south-central KS to a weak low over northwestern OK, then over portions of the central/southern TX Panhandle and northeastern NM. By 00Z, the main low should eject to northwestern ON, while the southern one ripples northeastward along the trailing cold front to southeastern KS. The front should extend from there southwestward across south-central OK to northwest TX and east-central/ southeastern NM. By 12Z, the southern low should continue moving northeastward along the front to the MKE vicinity, with front trailing over east-central IL, southeastern MO, to near a line from LIT-TXK-ACT-FST. An early-stage dryline was drawn from west-central OK south-southwestward to near BPG, then southward into northern Coahuila. The dryline should shift eastward and become better- defined through the day, and by 00Z, extend from a frontal intersection over northeastern OK across north-central TX to the DRT area. Overnight, the front will overtake a then-quasistationary dryline from north-south across OK. ....Ozarks to Arklatex... Widely scattered to scattered thunderstorms are possible tonight from western MO southward into parts of eastern OK/western AR, becoming more isolated toward the Arklatex region. A few cells may organize enough to produce severe hail, particularly where more discrete convection is at least temporarily possible from the Ozarks southward. Strong gusts also may penetrate to the surface from more linear, frontal convection over MO, but boundary-layer instability in that regime currently appears too limited to warrant an organized severe threat. Thunderstorms may develop over western parts of the outlook area (eastern OK and perhaps northeast TX) between 00-03Z, then move eastward to northeastward into portions of AR and the Arklatex region, offering occasional hail near severe limits. In general, deep shear will increase with time area wide, while still being stronger with northward extent. Meanwhile, moisture and buoyancy should increase southward. The environment over southern parts of the outlook area -- around the Red River and Arklatex east of the front and dryline -- will become increasingly moist throughout the period, with 60s F surface dewpoints becoming common into parts of eastern OK and western AR. This will support technically surface- based effective-inflow parcels in forecast soundings overnight. However, a nocturnally cooled (temperatures also in the 60s), somewhat diabatically stabilized near-surface layer should be present. Frontal convection may be messy in mode, and lift sufficient to force surface-based storms in the warm sector appears nebulous at best. As such, a seemingly favorable parameter space (e.g., MLCAPE around 1000-1500 J/kg collocated with 300-400 J/kg effective SRH under the LLJ, and 250-300 J/kg of 1/2-km SRH), may not be fully realized. For now, the tornado potential (dependent on sustained, surface-based storm) is not zero, but still looks too conditional and low-end to introduce an unconditional area for that hazard. The bulk of convection should be at least slightly elevated, with similar MUCAPE values and around 40-45 kt effective-shear magnitudes. ..Edwards/Gleason.. 12/08/2023 Read more View the full article Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.