SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Fri Sep 13 2019 Valid 131300Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM SOUTHEAST LOWER MI INTO NORTHERN OH... ...SUMMARY... A few severe thunderstorms with damaging winds are expected from southeast Lower Michigan into northern Ohio this afternoon. ...Southeast Lower MI into IN/OH this afternoon/evening... A midlevel low over northern MN is evolving into an open wave while moving northeastward towards James Bay, as embedded speed maxima rotate around the southeastern periphery of the low. At the surface, a cold front will progress eastward across IN/Lower MI during the day, and the warm sector will spread northeastward into southeast Lower MI ahead of the front. A corridor of surface heating is expected from IN/OH into southeast Lower MI, to the southeast of the thicker clouds associated with ongoing (pre-frontal) convection from northeast IL to central Lower MI. Midlevel lapse rates will remain rather modest (less than 7 C/km) within the warm sector today. Still, surface temperatures warming to near 80 F in southeast Lower MI and well into the 80s across IN/OH, in combination with 68-70 F boundary-layer dewpoints, will result in MLCAPE of 1000-1500 J/kg. Storms are expected to form by early afternoon from northeast IN into southeast Lower MI, and then continue eastward across northern OH into this evening. Diurnal destabilization will coincide with an increase in midlevel flow/vertical shear, which will support both organized storm clusters/supercells along the cold front with a primary threat for damaging winds. A low-end tornado threat is expected from southeast Lower MI into northern OH where low-level shear/hodograph curvature will be greater near the surface warm front this afternoon/evening. The severe threat will diminish to the south in conjunction with weakening vertical shear. ...Western NC into SC this afternoon... Strong surface heating and lingering low-level moisture along and southwest of a reinforcing frontal surge could provide some focus for thunderstorm development this afternoon. Thermodynamic profiles will favor some potential for isolated damaging downbursts given DCAPE values near 1000 J/kg. ...Southeast FL coast today... Convection with gusty winds will be possible along the southeast FL coast, where northeasterly low-level winds will increase to about 30 kt around the northwest periphery of a tropical disturbance near the southeast Bahamas. Moist profiles, however, should limit the potential stronger/damaging outflow winds. ..Thompson/Gleason.. 09/13/2019
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