textproduct: Wilmington

WHAT HAS CHANGED

Increased concern for the potential of locally heavy rainfall on Wednesday.

KEY MESSAGES

1) Showers and some thunderstorms will start to spread into the area this afternoon with additional precipitation overnight into Wednesday. Locally heavy rainfall will be possible Wednesday.

2) Highs near normal through the week. Lows moving from above normal to slightly below normal.

DISCUSSION

KEY MESSAGE 1) Warm front near the Tennessee-Kentucky border to start the period will slowly move north today, not quite reaching the forecast area. But it will move into the area tonight and then stall, mostly likely somewhere in the vicinity of I-70 by daybreak Wednesday. An approaching short wave will help push the front south, but not until Wednesday afternoon.

Low level moisture will move northwards today and showers will develop in overrunning. Expect pretty good coverage across northern Kentucky, but as this band of precipitation gets further north, and therefore further from the lift, it will diminish.

Some spotty activity is possible in the evening, but showers will really blossom during the overnight hours as a low level jet strengthens and pushes into the area. This jet will be making a turn with winds starting out from the south southwest and eventually becoming westerly by 12Z Wednesday. This change in orientation will decrease convergence somewhat, but it will still be sufficient for a new band of showers and possibly some elevated storms to develop across the middle of the forecast area.

Precipitable water will be increasing to 1.6-1.8 inches and warm cloud depth will be approaching 4 km. So efficient warm rain processes may be in play which could lead to some locally heavy rainfall late tonight into midday Wednesday. In addition, with showers and storms continually being favored in a west-east zone, there is the potential for multiple rounds of rain in any one location. With soils being fairly wet across much of the area, there is some concern for flooding. The HREF shows the area of greater precipitation from east central Indiana into central Ohio. The REFS is not as focused suggesting that there is greater spread in its members, although the 00Z RRFS has a similar look to the HREF.

Heading into Wednesday afternoon, showers and storms become more progressive as there is a southeastward push thanks to the approaching short wave. Both precipitable water and warm cloud depth decrease a bit, so perhaps a somewhat lessened heavy rain threat. All of this activity should be southeast of the forecast area by 00Z Thursday.

KEY MESSAGE 2) Weak mid level ridging will evolve into northwest flow for the latter part of the week as a long wave trough becomes established across eastern Canada and the northeast US. Short wave that initiates this transition on Wednesday/Wednesday night will push a cold front through the area. The primary change in air mass will be that it is drier. So diurnal ranges will increase.

Highs will be within 3 degrees of normal into the weekend. But the mild lows in the lower 60s that will continue for the next couple of nights will then drop into the lower to mid 50s for the latter part of the week into the weekend.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Extensive cirrus shield across the region to start. Moisture will stream northwards today which will bring in some lower clouds and showers after 17Z. There will be a lull towards 00Z with conditions returning to VFR. But additional showers will develop late in the period and ceilings will fall to IFR.

OUTLOOK...MVFR to IFR ceilings and visibilities are likely and thunderstorms are possible Wednesday.

ILN WATCHES/WARNINGS/ADVISORIES

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