SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Thu Jun 05 2025 Valid 051630Z - 061200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE SOUTHERN AND CENTRAL PLAINS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHEAST... ...SUMMARY... Scattered severe thunderstorms are expected across the southern and central Plains into tonight. Several tornadoes (some possibly strong), large to very large hail, and severe gusts are possible. Severe gusts are also possible over parts of the Northeast this afternoon. ...Southern High Plains... Morning surface analysis depicts a convectively reinforced quasi-stationary surface boundary extending across north-central TX westward through the TX South Plains to southeast/east-central NM. This boundary may have a tendency of moving slowly northward as a warm front over the High Plains later this afternoon -- in response to an approaching midlevel impulse and gradually deepening lee cyclone over southeast CO. Along/immediately south of this boundary (over the TX South Plains), deep/rich boundary-layer moisture (upper 60s/lower 70s dewpoints) is in place, with impressive moisture sampled by the 12Z MAF sounding (15.8 g/kg mean mixing ratio). Persistent cloud coverage will tend to shelter this moisture from diurnally driven boundary-layer mixing through the afternoon, while heating in cloud breaks will still yield strong surface-based instability (upwards of 3000 J/kg MLCAPE). As a low-amplitude impulse and related jet streak advance east-northeastward across the central High Plains, peripheral large-scale ascent will aid in scattered thunderstorm development across east-central/southeast NM into the TX South Plains -- focused near the intersection of the northward-moving warm front and lee trough. Around 50-60 kt of effective shear and the modest large-scale ascent will favor discrete supercells, initially posing a risk of very large hail. However, a strengthening evening low-level jet atop the backed low-level flow near the boundary will support enlarging clockwise hodographs (300+ m2/s2 effective SRH). Given the deep/rich moisture and enhanced helicity, a focused corridor for tornadoes (some possibly strong) is evident over the TX South Plains -- where 10-percent tornado probabilities were added. Localized upscale growth into organized clusters is expected into western North Texas this evening, where a swath of severe wind is possible. Father south from the TX South Plains to parts of the TX Trans-Pecos vicinity, deep boundary-layer mixing amid lower/middle 60s dewpoints will contribute to moderate-strong surface-based instability, with a long (albeit straighter) hodograph away from the surface boundary. This will also support intense discrete/semi-discrete supercells, though the primary concern here will be very large hail (possibly 3+ inches). ...Central High Plains into the southern Plains... In the left-exit region of a 40-50-kt midlevel jet streak impinging on the central High Plains, thunderstorm development is expected ahead of a gradually deepening lee cyclone over southeastern CO this afternoon. Diurnal heating (within cloud breaks) of a moist air mass (lower 60s dewpoints) will yield moderate surface-based instability ahead of developing storms. Given around 50 kt of effective shear (characterized by a long/generally straight hodograph), several semi-discrete supercell clusters are expected. Large hail and severe wind gusts are expected, though the rich/sheltered boundary-layer moisture and sufficient low-level streamwise vorticity for established right-mover cells will support a couple tornadoes as well. With time, storms will spread east-southeastward into northwest OK -- where upscale growth into an MCS seems increasingly likely. This will favor an increased risk of a swath of severe wind gusts into the overnight hours. ...Northeast... Widely scattered thunderstorms are expected along/ahead of a cold front draped across the region this afternoon. Visible satellite imagery shows a moist/destabilizing air mass ahead of the front, where moderate surface-based instability is expected. The warm/moist air mass, combined with around 30 kt of effective shear, should promote a few loosely organized clusters capable of producing wind damage -- aided by the steepening boundary-layer lapse rates. ..Weinman/Smith.. 06/05/2025