textproduct: Wilmington

WHAT HAS CHANGED

No major changes.

KEY MESSAGES

1) A period of showers and thunderstorms late this afternoon into the evening with isolated severe thunderstorms possible.

2) Cold front late this evening into tonight will bring cool and dry conditions through Tuesday with patchy frost possible Sunday night, then a freeze possible Monday and Tuesday nights.

DISCUSSION

KEY MESSAGE 1) Surface low pressure will lift from the Upper Midwest into eastern Ontario today and tonight. Ahead of the low, an unseasonably warm and humid air mass will persist in the middle Ohio Valley. High resolution models currently point toward showers and storms developing along a pre-frontal trough late this afternoon into the early evening hours. While lapse rates are steep in the lower atmosphere, warmer temperatures above 600mb lead to modest Surface- based instability of around or less than 1000J. In addition, the latest runs show a bit less effective bulk shear -- around 30-35 knots -- with the highest values north of the Ohio River. Hodographs are generally straight through the mid-levels. Based on this latest information, the primary threat with this afternoon's storms appears to remain straight-line winds.

The cold front itself is likely to follow the convection with winds shifting westerly after 8PM or so. Cold air advection will drop temperatures into the 40s by morning.

KEY MESSAGE 2) Much cooler air will be in place from Sunday through Tuesday night. Initially, it's likely winds will keep frost very patchy Sunday night. However, a reinforcing cold front on Monday will allow for low temperatures to dip to near or just below freezing Monday and Tuesday nights. The highest chance of frost will likely be Tuesday night as surface high pressure shifts across the Lower Great Lakes. Warmer conditions on the back side of the high will arrive Wednesday and continue through the end of the forecast period.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Main aviation impact for this TAF cycle will be a period of showers and storms late this afternoon into the early evening. Will likely need to add stronger wind gust potential once confidence on timing improves. A strong cold front will shift winds to the west late this evening, with a few hour period of MVFR ceilings possible just behind the front. However, by 06Z or so, lower clouds are expected to start decreasing as dry air mixes into the Ohio Valley.

OUTLOOK...No significant aviation impacts are expected.

ILN WATCHES/WARNINGS/ADVISORIES

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