textproduct: Wilmington

WHAT HAS CHANGED

Tornado watch issued for eastern/southeastern Indiana, western and southwestern Ohio, and portions of northern Kentucky.

KEY MESSAGES

1) A strong storm system will move through the region today bringing the potential for multiple rounds of severe weather, flooding, and gusty winds.

2) Wind gusts up to 30-50 mph expected early Friday morning into the evening. The highest gusts will occur over portions of Western Central / Central Ohio with isolated gusts potentially reaching 55 mph.

3) Warmer and wetter conditions expected Sunday into Monday, potentially transitioning to a rain-snow mix in the early morning hours on Monday. Much colder arrives air Monday and Tuesday.

DISCUSSION

KEY MESSAGE 1) A strong storm system will move through the region today bringing the potential for multiple rounds of severe weather, flooding, and gusty winds.

Morning severe threat (updated 630am): Tornado watch: Given ongoing thunderstorms across southern Illinois and strengthening low-level shear through the morning hours, a tornado watch has been issued for the western half of the local area until noon. Additional expansions eastward are possible with time. While the watch is out right now, the main threat for the local watch area (especially eastern/southeastern Indiana) arrives around 9-10 am and continues eastward until noon. Some thunderstorms are possible before this time frame, but are not expected to pose a tornado threat.

Previous discussion...A disorganized line of thunderstorms will be moving through Indiana around daybreak with additional thunderstorms developing ahead of it between 4-7am. The line of thunderstorms approaching from the west will have the potential to reorganize during the morning hours, with damaging winds the main threat. However, quick spin up tornadoes will be possible due to favorably curved hodographs and steepening low level lapse rates. The situation becomes complicated due to the new thunderstorms, potentially elevated, developing ahead of the line. This would disrupt attempts at organized line segments. Nevertheless, these new storms will be capable of producing large hail as well as damaging winds. The radar is likely going to be quite complex and crowded throughout the morning given the above situation.

Afternoon severe threat: Heading into the afternoon, daytime heating will generate new thunderstorms ahead of and along the cold front. Any storms that develop ahead of the front would have the best chance of seeing some organization if uninterrupted by other storms. All hazards are possible with these storms, and these would likely pose the best chance of seeing a more concentrated tornado threat. At this time, locations along and south of the I-71 corridor stand the best chance of seeing this type of development. While a bit lower of a threat, the severe potential will not be completely eliminated until the cold front passes. This occurs throughout the late afternoon and early evening.

Wind threat (updated 12:15 am): Confidence has increased that two periods of non-thunderstorm related wind gusts may reach advisory level thresholds. The first will come throughout the morning hours as thunderstorms move through the area. A strong LLJ with 40 to 50 knots of wind between one and two thousand feet will mix down outside of thunderstorms. These winds may not last long as the sweep across the area, and may be sudden in nature following any thunderstorms that move through. The second period of strong wind gusts will occur during the afternoon where diurnal mixing ahead of the front will effectively mix 35 to 45 mph wind gusts. This threat will end as the cold front moves through, however, wind gusts will still remain elevated (25-30 mph) and out of the northwest behind the front.

Heavy Rain/flood threat: Given the potential for multiple rounds of thunderstorms, the heavy rain threat remains, however, the lack in confidence in one particular area continues to be too low for a flood watch. Back-building thunderstorms and west to east aligned segments stand the best chance of producing locally heavy rainfall which may lead to flooding. HREF does highlight a few localized area of 2-3" so this will have to be monitored closely, along with the area wide severe threat.

KEY MESSAGE 2) Wind gusts up to 30-50 mph expected early Friday morning into the evening. The highest gusts will occur over portions of Western Central / Central Ohio with isolated gusts potentially reaching 55 mph.

Guidance continues to bring a compact low pressure through the Great Lakes on Friday. At this time, enough confidence exists to advertise advisory levels winds for the majority of the area, primarily north of the Ohio River. Probs for wind gusts greater than 45 mph are between 30 to 70 percent from south to north. Gusts over 55 mph are around 20 percent for west-central Ohio. Have continued to highlight this in the HWO.

KEY MESSAGE 3) Warmer and wetter conditions expected Sunday into Monday, potentially transitioning to a rain-snow mix in the early morning hours on Monday. Much colder arrives air Monday and Tuesday.

ANother strong low pressure moves through the Great Lakes region Sunday into Monday. Primary threats at this time look to be another period of gusty winds associated with the low pressure. Otherwise, some mixed precipitation will be possible, but confidence is too low to project snowfall amounts this far out. Some snow showers or flurries are going to linger into Monday. Perhaps the biggest shock to the system will be the resurgence of cold temperatures Monday and Tuesday. Temperatures are below normal with feels-like temperatures in the teens on Monday and Wednesday morning. The coldest conditions are expected Tuesday morning with feels-like temperatures in the single digits.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Thunderstorms are only now beginning to form with moist southwesterly flow. MVFR CIGs have occurred off an on early this morning and that will continue throughout the afternoon as multiple rounds of thunderstorms occur.

The strong low pressure provides periods of gusty winds throughout the TAF period, including outside the thunderstorm activity. Southwest winds gusts increase to 25 to 30kts during the late morning and then peak out between 35 and 40 kts later in the afternoon with a cold frontal passage. Higher wind gusts are possible inside and outside of thunderstorm activity. As confidence increases with these gusts, some adjustments may be necessary this morning.

After the morning convective activity - additional thunderstorms are expected to develop with continued chances for locally strong wind gusts. The front is expected to pass thru KDAY around 20/21Z and thru KILN/KCVG/KLUK around 21Z/22Z and thru KCMH by 23Z. Winds will shift to the northwest and a brief period of 40 kt wind gusts will be possible during this time frame of the frontal passage outside of storms. Thunderstorm chances end with the FROPA but some lingering showers and northwest wind gusts of 25 to 30 kts continue into early evening before decreasing overnight. Expect widespread MVFR ceilings to continue through the night.

OUTLOOK...MVFR ceilings possible into Thursday. Wind gusts above 40 kts possible Friday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Wind Advisory until 7 PM EDT this evening for OHZ026-034-035- 042>046-051>056-060>065-070>074-077>082-088. KY...Wind Advisory until 7 PM EDT this evening for KYZ089>100. IN...Wind Advisory until 7 PM EDT this evening for INZ050-058-059-066- 073>075-080.