textproduct: Wilmington

WHAT HAS CHANGED

Added potential for locally heavy rainfall during the early part of the week.

KEY MESSAGES

1) Two rounds of showers and thunderstorms today into this evening with the second round possibly having some strong to severe storms.

2) Showers and some thunderstorms will move across the region Monday afternoon into Tuesday night with the potential of locally heavy rainfall.

3) Very warm temperatures will develop in the latter part of next week with some places possibly reaching 90.

DISCUSSION

KEY MESSAGE 1) Short wave over the western Great Lakes will continue to progress east southeast through the early afternoon. Showers and storms that are occurring out ahead of this will push into northern counties this morning, mainly affecting areas from west central Ohio into central Ohio. Main concern is cluster of storms in northern Illinois. All guidance indicates that this will weaken by the time it gets this far east, but it is that time of year when early morning convection can sometimes maintain itself and progress much further than any guidance suggests.

Instability will increase in the wake of this impulse with HREF probability of surface CAPE > 2000 J/kg being 50 percent or higher from the I-70 corridor northwards during peak heating. Instability will drop off towards and especially after 00Z. There will be a zone of 0-6km bulk shear > 30 kt translating from west central Ohio into central Ohio around the time of maximum instability. This provides a window for strong to severe storms in an broad west-east band across the northern part of the forecast area. Damaging wind still looks to be the primary threat. Isolated hail or even a tornado cannot be ruled out in parts of central Ohio.

Weakening convection may continue into the late evening south of I-70, but the potential for stronger storms will diminish quite a bit. And areas near and south of the Ohio River may not see any storms at all.

KEY MESSAGE 2) A high amplitude mid level ridge will quickly develop on Sunday from the Ohio Valley into the Great Lakes. Within a weakness in the ridge there will be a shear axis that pushes into the region. A weak front will sag into the forecast area and stall. This will be the focus for diurnal showers and thunderstorms. Bulk shear will be very weak.

A short wave moving from the mid Mississippi Valley into the Great Lakes on Monday will push the ridge eastward. This short wave will only make slow eastward progress on Tuesday. The front that was across the area on Sunday will weaken and any remnants will lift north by Monday. However, a very moist atmosphere will spread into the region. Ensemble mean precipitable water is forecast to become at least 1.8 inches with a 30 percent chance of 2 inches or greater. This airmass will move into western counties on Monday afternoon and then be area wide on Tuesday.

Showers and some embedded storms will develop and spread in from the southwest in association with the approach of mid level forcing Monday afternoon. Activity will diminish but not completely dissipate on Monday night. There will be another increase in coverage as well as intensity on Tuesday which will then taper off Tuesday night as the short wave finally moves east. With the very moist airmass as well as warm cloud depth increasing to around 4 km, rain processes could be very efficient leading to locally heavy rainfall.

KEY MESSAGE 3) Broad mid level ridge will expand from the southern Plains up the Ohio Valley and into New England for the latter part of the week. The humid airmass that moves in Monday and Tuesday will remain, but temperatures will rise and get very warm. Forecast is probably a couple of degrees too warm from Thursday onwards given bias in the NBM, but nonetheless, there could be some locations that do reach 90 with apparent temperature in the mid to upper 90s.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

A VFR deck is across the region to start the period. Showers and some thunderstorms tracking across northern Illinois and Indiana will move east southeast. These should weaken by the time they reach KCMH/KLCK. There is a chance that they could affect KDAY as well but more likely will stay north of there. This will all move east of the area by 18Z with some scattering of the clouds. Additional thunderstorms will develop north of the terminals after 21Z and could affect KDAY to KCMH/KLCK and even possibly get as far south as KILN. A VFR deck will develop late in the period. South southwest winds will increase early with some gusts at or above 20 kt. Winds will start to decrease towards 00Z and become lighter late.

OUTLOOK...Thunderstorms are possible, mainly during the afternoon and evening, each day from Sunday through Wednesday. MVFR ceilings and visibilities possible Monday night into Tuesday night.

ILN WATCHES/WARNINGS/ADVISORIES

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