SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1158 PM CDT Sat Jul 10 2021 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL NEW MEXICO INTO SOUTHEAST ARIZONA...AND FROM NORTHERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY... ...SUMMARY... Strong to severe thunderstorms may impact a corridor from the southern Rockies into the lower Mississippi Valley, and over parts of the Ohio Valley and Northeast. ...Synopsis... A broad upper trough is forecast to remain centered over the mid MS Valley vicinity, as multiple smaller-scale vorticity maxima move through the mean trough position. An upper ridge will remain over the Southwest, with one or more vorticity maxima potentially moving southwestward into the southern Rockies and lower deserts to the east/southeast of the ridge. A surface low is forecast to move into portions of the OH Valley/lower Great Lakes, as a warm front moves northward through the Mid Atlantic and a trailing cold front sags southward across portions of the southern Plains and mid MS Valley. ...NM into AZ... Storms will develop this afternoon across the higher terrain of central and western NM and into southeast AZ, mainly after 21Z and coincident with strong heating. SBCAPE in excess of 1000-1500 J/kg and 30-40 kt deep-layer shear will support a threat of localized downbursts and hail with the initial storms. Potential will again exist for outflow-driven clusters to move into the lower elevations, with a few damaging gusts expected. Hail over 1.00" diameter is also possible given the sufficient deep-layer shear, supporting cellular storm mode. Earlier in the day, storms will also be possible over eastern NM near the stalling front, but the position of this boundary may be dictated by outflow. Mixed-mode storms will be possible at this time, perhaps with strong wind gusts or marginal hail. ..Parts of TX eastward into the lower MS Valley... Scattered thunderstorms will likely be ongoing along the front early in the day as it pushes south into northern TX, LA and MS. Areas of strong wind gusts can be expected. As heating occurs ahead of the front and the very moist air mass destabilizes further, an uptick in storm intensity and/or organization is possible, with damaging wind and marginal hail expected. MUCAPE will exceed 2000 J/kg, with dewpoints in the 70-75 F range. A few strong storms may linger overnight near the stalling front, from eastern TX into MS, with heavy rain threat. ...Ohio Valley into the Northeast... A warm front will lift north across PA and OH, with height rises aloft. Winds at 850 mb will increase to around 25 kt out of the south, resulting in 200+ effective SRH along the warm front after 18Z. Upper 60s F dewpoints and heating will contribute to 1000-1500 J/kg MUCAPE. Storms are expected to form after 18Z over OH, possibly associated with a embedded midlevel wave moving across the OH Valley. While rain and elevated storms are expected early north of the warm front, surface based storms may form over parts of PA after 20Z. SRH south of the warm front will be much less than north of it, but a supercell cannot be ruled out with storms that can interact with the boundary. Otherwise, a few damaging wind gusts will be possible with storms that develop over OH and travel into PA late. ..Jewell/Wendt.. 07/11/2021 Read more LIVE: spc.noaa.gov
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