textproduct: Wilmington

WHAT HAS CHANGED

Increased chances for showers and storms Saturday afternoon and evening.

KEY MESSAGES

1) Showers and some thunderstorms will occur into Saturday evening. There is potential for heavy rainfall into Saturday morning.

2) Hot and humid next week.

DISCUSSION

KEY MESSAGE 1) An MCV moving from central into eastern Kentucky has developed some storms ahead of it. It is not out of the question that these could build northward into Lewis and Scioto Counties over the next few hours. Cannot rule out a stronger storm in that area where there is an intersection of some instability and shear.

Another MCV in southeast Missouri will follow, moving across Kentucky tonight. And yet another weak disturbance may follow that. There will be a west southwest-east northeast oriented low level jet overnight that will maximize moisture transport. So the axis of high precipitable water that extends across the southern part of the forecast area will increase further. Warm cloud depth will also become deeper. Thus the ingredients will be in place for heavy rainfall and the potential for repeated storms. It is not clear whether that will develop into the forecast area or remain further south across Kentucky. But the flood watch seems to have the area of greatest threat covered.

There is a weak surface boundary extending from central Illinois into northern Ohio that may not move very much. Some convective-allowing models are trying to develop storms that move along this boundary. This area is along the precipitable water gradient, but should still have plenty of moisture to work with. Thus, there could be a secondary rainfall axis north of I-70. Confidence in occurrence and coverage is low.

More widespread showers are forecast to finally move off to the east on Saturday morning, although given the nebulous forcing there is uncertainty how that evolves. There will be a left over west-east boundary extending across the region with a weak low pressure system tracking along it from the afternoon into the evening. With daytime destabilization, even if it is limited, expect showers and storms to redevelop Saturday afternoon and continue into the evening. Shear is quite weak but deep moisture will still be in place. So the potential for localized heavy rainfall will persist until these storms diminish Saturday evening.

KEY MESSAGE 2) Excellent agreement within the model suite that an expansive mid level high will predominate from Monday through Thursday. There is some spread heading into Friday how quickly the high may get suppressed as a short wave drops southeast across the Great Lakes. Heat and humidity will be building on Monday. The hottest conditions are forecast for Wednesday and Thursday. Small errors in forecast temperature and dew point can add up to larger errors in the apparent temperature forecast. Even within the probabilistic space, there has been some fluctuation in probabilities of apparent temperatures exceeding 100 and 105 just between last night's runs and today's. It remains safe to say that there will be a heat wave next week. Heat advisories are almost certain. It is not out of the question that parts of the area could reach excessive heat warning threshold for one or more days, although probability of that is still relatively low (25 percent or less).

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Prevailing -ra/shra is expected for at least the next 12-18 hours, and for all terminals. While the entire period will not be raining, there's no signal for me to try and dry anyone out until tomorrow afternoon. Cigs will drop to IFR and remain low for this time frame as well, and even if the rain becomes less prevalent tomorrow morning, mvfr vsbys in lingering fog/low clouds (possibly ongoing sprinkles) probably won't begin to lift until the tail end of the forecast. Wind through the period will be light <8kt. Generally southerly turning southwest tomorrow afternoon at CVG/LUK, and more easterly elsewhere turning south at times later overnight.

Thunder will be a possibility but attm it is behaving like the non- rainy periods, i.e. no clear signal for inclusion to the forecast. Even a prob30 is a bit overdone, and there would need to be both a time frame and location in mind.

OUTLOOK...Thunderstorms are possible Saturday afternoon and evening. MVFR to IFR ceilings and visibility will likely continue into Sunday morning.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Flood Watch through Saturday morning for OHZ063-070>073-077>082-088. KY...Flood Watch through Saturday morning for KYZ089>100. IN...Flood Watch through Saturday morning for INZ066-073>075-080.