textproduct: Wilmington

WHAT HAS CHANGED

The main focus is on the severe risk Wednesday into Thursday; specifically Wednesday night.

KEY MESSAGES

1) A deep low pressure system brings the chance for severe thunderstorms, isolated flooding, and gusty winds Wednesday into Thursday. The most widespread severe storm risk is Wednesday night.

2) An isolated severe storm is possible this afternoon/evening northeast of Dayton.

DISCUSSION

KEY MESSAGE 1)

A second, very deep low moves across the Great Lakes on Wednesday and Thursday bringing potentially impactful weather to the Ohio Valley. On Wednesday afternoon/early evening, the low pressure system lifts a warm front through the Ohio Valley. An axis of impressive shear (effective shear > 50 knots; 0-1 km SRH over 100 m2/s2) overlaps with instability in the vicinity of the warm front supporting a conditional risk for all modes of severe weather late in the afternoon in a fairly focused area. This area of interest is likely to be located near and north of the I-70 corridor in eastern Indiana and western Ohio around rush hour. Although CAMs to not show much convective activity along the warm front, the impressive environment will require close monitoring for any convective activity.

For Wednesday night, a widespread severe threat develops ahead of a trailing cold front south of the deep low. CAMs are depicting a line of storms ahead of the front entering areas northwest of Dayton at roughly 9pm before overspreading southeast during the overnight. The kinematic profiles remain extremely robust in terms of both shear (effective shear around 60 knots; 0-1 SRH 471 m2/s2) and wind speed (70 knots less than 1km AGL). Instability is not as impressive, but ML CAPE around 500 J/kg likely is sufficient to maintain a severe risk well into the overnight. Damaging straight line winds are the main threat due to very strong winds just off the surface. Extreme low level shear values and strung out hodographs also support a tornadic risk overnight Wednesday despite not as impressive low level thermodynamic profiles. The highest risk for severe weather is along and west of I-71 where the strongest shear and instability overlap. Storms are expected to maintain a gradual weakening trend as they move east overnight.

Isolated flash flooding cannot be ruled out with high PWATs (2+ inches) in place. High rain rates of 1-2+ inches per hour will occur in the strongest storms. The severe and flood risk will not completely end until the front pushes fully southeast of the area sometime Thursday morning.

Gusty winds can be expected on Wednesday night and on Thursday both inside and outside any storm activity. Winds aloft Wednesday night exceed 50 knots just off the surface and it will not take much to mix these winds down. Gradient winds remain elevated on Thursday behind the front.

KEY MESSAGE 2)

A low pressure system continues to move across the Great Lakes this afternoon and evening bringing the chance for showers and thunderstorms mainly northwest of I-71. A few storms could be strong to severe as they move in from the northwest. The overall trend should be toward weakening storms as they move deeper into the Ohio Valley. The weakening trend is supported by the better axis of forcing and instability remaining to the northwest despite shear increasing locally (effective shear greater than 40 knots). Straight line winds are the main threat with any storms this evening.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR ceilings work in from the northwest late this afternoon/early evening as a decaying line of showers and storms moves southeast. An isolates shower or storm cannot be ruled out for KDAY and the Cincinnati sites this afternoon and evening. Otherwise, VFR conditions are likely for the TAF period. Widespread showers and thunderstorms occur Wednesday night.

Southwesterly flow persists for the TAF period.

OUTLOOK...Thunderstorms and gusty winds are expected at times Wednesday afternoon through Thursday afternoon.

ILN WATCHES/WARNINGS/ADVISORIES

OH...None. KY...None. IN...None.