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KEY MESSAGES

* Gradient wind gusts increase late this afternoon and evening as a strong low pressure system approaches the Great Lakes. Non- thunderstorm wind gusts of 30-40 mph expected later today and into tonight. A few gusts over 40 mph are possible.

* An approaching cold front is expected to bring a line of strong to severe thunderstorms into the area later tonight. Greatest severe threat is north of the Ohio River, but we could see strong to severe storms as far south as the WK/BG Pkwys overnight. Damaging winds are the main hazard possible, but can't rule out a tornado or hail risk either. Nighttime tornadoes are notably more dangerous.

* A Flood Watch is in effect from 9 PM EDT tonight to 9 AM EDT tomorrow, mainly along and north of I-64.

* The cold front stalls across the region, leading to additional potential for scattered strong to severe storms, excessive rainfall, and isolated flash flooding across south-central KY on Thursday.

* A reprieve from rainfall comes Friday and Saturday before the next round of widespread rain returns starting late Saturday night.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 329 PM EDT Wed Jun 17 2026

Things are currently warm, gusty, and dry across the CWA however expecting more active weather as we go into the evening and overnight. The first concern to address is the gusty wind potential this afternoon into the early evening as the low level jet core is starting to overspread the area. Seeing some 40 knot observations upstream of us, however we are also seeing cloud cover from the MCS over IL/IN starting to overspread our northern counties. This should provide some low level stability as we get into the late afternoon and early evening. Still like the messaging of widespread 30 to 40 mph, with a few localized gusts of 40+ MPH possible, especially along and west of I-65. Will continue the Special Weather Statement to handle that messaging.

The next issue is the upstream MCS that has been threatening to impact our northern tier or two of counties. It continues to leak southward toward a Jasper, IN to Madison, IN line and could bring a round of training heavy rainfall in those areas before it pushes east. Most likely timing would be entering our northern tier as early as 5 or 6 PM EDT. This feature hasn't been severe warned upstream, and for now, it only looks like brief heavy rainfall would be the main threat. A quick 1 to 2 inches could fall from this, and prime the area for Flooding potential later tonight when the next round of showers and storms moves through.

Aside from those two early concerns, the main focus for the forecast continues to be tonight into tomorrow. Strong surface cyclogenesis is expected to occur from the upper Midwest into the Great Lakes region this evening as the exit region of a strong mid to upper level jet overspreads the area. A low level jet more characteristic of a late winter or early spring system will respond over our area beneath the favorable mid to upper level jet dynamics. It should peak around 45-55 knots later tonight across the northern third of the CWA, and it will aid in both enhancing the overall shear profile significantly, and will add moisture transport for training showers and storms. Decided to lift a Flood Watch (Flash Flooding) for the northern third of the CWA due to the threat for training heavy rainfall. HREF mean 24 QPF totals aren't overly impressive in the watch area and generally range from .75 to 1.5" for most areas. However, the PMM/LPMM data suggests localized pockets of 3-5+ amounts could develop where the storms train. Given the residence time of the intense low level jet, 1/3/6 hour FFG values still diminished in some areas(Floyd/Harrison for example) from recent heavy rainfall, and the fact this is a nighttime event was enough to go with the Flood Watch for the area.

We've become modestly unstable this afternoon and 17/12z HREF probabilities suggest around 1000-1500 J/KG of instability should be around tonight ahead of the next line of storms set to move into the area from the NW. Some surface stability will likely set up after sunset as has consistently been suggested by hi-res forecast soundings, however with ML CAPE values still in the modest to moderate range, and the added forcing do think robust and rotating updrafts are sustainable into our area overnight. SPC has moved the damaging wind probs and 2-5% tornado probs farther south to account for the upstream MCS impact on where storms set up later tonight. Given the overall shear profile, including 0-1km SRH values of at least 250-300 m2/s2 and potential for embedded supercells or mesovortex formation the threat for a few tornadoes, and perhaps a stronger tornado, seems warranted across our northern CWA. It has been noted that the overall 0-3 km shear vector should line up more parallel to the line of storm orientation, so this could limit mesovortex damaging wind/tornado potential from that mechanism, but embedded supercell storm mode is still in play. Won't rule out mesovortices either as the shear magnitude is so strong that it doesn't need to be perpendicular to the line for RIJ intrusion. The best overlap of shear and instability does drop off with southward extent across our area, and by the time the storms get into northern and central KY, we will be deeper into the night where a bit more low level stability can help mitigate a bigger severe concern.

The low level jet will steadily let go of our region between 09 and 15z tomorrow, with convective intensity and coverage diminishing across our central CWA. There will likely be a few hours of lull from mid to late morning to early afternoon before showers and storms redevelop on the existing outflow boundary and/or differential heating boundary. In addition, a surface cold front trailing from the eastern Canada surface low will also start to slide into the area. As a result, numerous to widespread showers and storms should then resume progressing W to E ahead of the boundaries, while the overall progress of the line shifts slowly southeastward tomorrow afternoon and evening. Overall shear profiles will be weaker tomorrow, and more unidirectional, so expect storm mode would primarily be multicell clusters or perhaps a few supercells. Primary hazard should be damaging winds along with an isolated flash flooding potential for any areas that see repeated training. May have to consider a separate Flood Watch for southern KY tomorrow, but confidence isn't high enough just yet, and didn't want to add any confusion for tonight's threat farther north.

Things should quiet down later Thursday evening as the front progresses through the area, and surface high pressure begins to build in behind the front. Overnight lows Thursday night should fall into the 60 to 65 degree range for most.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 329 PM EDT Wed Jun 17 2026

Friday - Saturday...

The cold front associated with Wednesday's low pressure system departs to the southeast by Friday morning, setting up a brief stretch of warm and dry weather to end the workweek and start the weekend. Surface high pressure fills in behind the cold front, and calm northwesterly flow will keep temperatures just below average for this time of year. Highs on Friday will get into the low 80s, with mid 80s currently forecast for Saturday. Dew points will only be in the upper 50s/low 60s both days, so conditions will be quite comfortable as a result.

Saturday Night - Monday Night...

The calmer stretch of weather won't last for long as our next round for rainfall begins Saturday night. A shortwave ejects from the eastern Rockies on Saturday, with a rapidly developing surface low following with it towards the Mississippi and Ohio River Valleys. Once it arrives in the region Saturday night, LREF is showing that the MSLP from this system is anomalous for this time of year (~10th percentile climatologically). Numerous showers and scattered thunderstorms are currently forecast, though the intensity of these storms is still uncertain. Wind shear appears to be decent but also semi-uniderectional, with instability only being modest at this point in time. As a result, confidence is low on the extent of stronger storms for this event. Though there will be limited time for moisture to move over the area, PW values ahead of the low will quickly soar to the 1.6-1.8" range, persisting until the low departs. LREF guidance is painting a broad area of ~1.5" of storm total rainfall from this event, so we'll continue to monitor this in case a flooding threat becomes more apparent.

Tuesday - Midweek...

The surface low will depart off to the east Monday evening, with high pressure again filling in behind it. Guidance has numerous shortwaves moving over the area, but with high pressure and drier air in place, chances for showers to develop will be low (<15%). Temperatures will again be slightly below average, with highs in the low 80s forecast.

AVIATION /00Z TAFS THROUGH 06Z FRIDAY/

Issued at 807 PM EDT Wed Jun 17 2026

Gusty southwesterly winds will prevail for the next few hours. Sustained winds will be elevated through the overnight period. A line of showers and storms will drop south through the overnight hours, mostly after midnight. Some storms will be strong to severe bringing a chance for severe weather hazards and heavy rainfall. This line of showers and storms will weaken as it moves south. VIS will likely drop to 1-2SM at times. South of I64, CIGs are expected to be high-end MVFR in the morning and into the early afternoon and showers and storms continue.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Flood Watch through Thursday morning for KYZ025-029>043-049. IN...Flood Watch through Thursday morning for INZ076>079-083-084- 089>092.