textproduct: Wilmington

WHAT HAS CHANGED

Isolated storms possible this afternoon and evening. Another chance for showers and storms later tonight.

KEY MESSAGES

1) A line of strong to severe storms will move into the region tonight, bringing the potential for gusty to isolated damaging winds. The complex of storms will slowly be weakening with eastward progression late into the night, with the greatest severe threat near/west of I-71.

2) A drier and somewhat cooler airmass will move in behind the cold front for Friday afternoon and into Saturday. A secondary cold front will bring additional showers and thunderstorms on Sunday along with cooler temperatures for early next week.

DISCUSSION

KEY MESSAGE 1) Over the course of the past several hours, we have seen a surge of high theta-e to the N/NE overspreading a larger portion of the OH Vly, including the ILN FA. This is helping further destabilize the environment, despite the rapid approach of sunset. Although the BL/near sfc layer will stabilize/cool somewhat past sunset, a strongly-unstable environment, characterized by MLCAPE >2500 J/kg, will still be entrenched across parts of the ILN FA, particularly near/W of the I-71 corridor.

The thermodynamic environment, along with the approach of better LL/deep-layer shear and forcing, lends itself to some concern for the maintenance of the storm complex currently upstream in IL further into the local area than previously expected. This concern is greatest for parts of EC IN and WC OH where the better overlap of LL shear and strong instby will evolve as we approach midnight, helping maintain some degree of organization with the bowing line. There is an increasing signal, including within some of the recent WoFS guidance, for the potential for strong/severe storms to impact NW/W third of the ILN FA around midnight, with damaging winds being the primary threat as the bowing line progresses E/SE through 2 AM. This will especially be of concern from about Wayne Co IN to Hardin Co OH and points further to the NW, including much of WC OH.

There is the expectation for the line to gradually weaken with SE extent due to a less favorable environment near/SE of I-71. This weakening will be most pronounced by/after 2 AM as the complex becomes increasingly outflow-dominant. This being said, the DCAPE environment will still be plenty supportive of downward transfer of winds from aloft to the sfc. This, combined with quite a bit of momentum of the complex, means that the potential for gusty winds will likely extend well beyond even the maintenance of thunder itself. It is likely that, at some point within the weakening organization, that a pronounced outflow will still bring with it gusty winds even in the absence of thunder. This very well could reach locales SE of the I-71 corridor near/after 2 AM.

Brief torrential rainfall rates is also expected with the arrival of the line, particularly in EC IN and WC OH. However, with the steady forward progression of the MCS, prolonged heavy rain and flooding are not expected to be a primary threat.

KEY MESSAGE 2) A cold front associated with a low in Canada pushes east through the region on Friday morning. Drier and slightly cooler air moves into the Ohio Valley behind the front. High pressure progresses across the area on Saturday bringing dry conditions and near average temperatures.

Shower and storm chances increase once again on Sunday when another cold front associated with a low far to the north in Canada moves through. There could be a window for severe weather as some models are depicting instability overlapping with increasing shear ahead of the front during the day on Sunday. The best potential for storms appears to be in the southeast where frontal passage occurs later in the day.

Cooler and drier air arrives for the start of next week behind the front.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

A band of SCT VFR Cu along the leading edge of a surge of higher moisture continues to work its way NE, initiating a few spotty SHRA in the process. This would only be of concern for KDAY/KCMH/KLCK through the first hour or so of the TAF period before the focus will shift quickly to the incoming line of storms expected to be near KDAY by about 05z.

There is the expectation for a mature, but steadily weakening, line of storms to progress to the SE near/through the local terminals between about 05z-09z. While there is some uncertainty regarding maintenance of TS with eastward extent, confidence is high enough that included a TEMPO TS at KDAY. Better confidence in coverage and timing of this decaying complex allowed for TEMPO SHRA to be added elsewhere at KCVG/KLUK/KILN/KCMH/KDAY for a 2-3 hour period each. The main item of concern with the arrival of this line will be abrupt/drastic changes in wind speed, direction, and visibility. However, these will be added to the fcst as confidence increases in the likely impacts at each site.

The TSRA/SHRA will push off to the SE quickly by/after 09z, with dry conditions thereafter.

There will likely be some SW LLWS on the order of about 40kts coincident with the bowing line of TSRA/SHRA, but this will relax with the passage of the convection. SW sfc winds around 8-10kts will go out of the WNW following the FROPA by 09z, with MVFR CIGs expected to briefly overspread the sites during the several hours around daybreak. These MVFR CIGs will lift/scatter quickly as drier air rushes in between 15z-18z in the post-frontal environment.

OUTLOOK... Thunderstorms possible again on Sunday.

ILN WATCHES/WARNINGS/ADVISORIES

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