textproduct: Louisville

KEY MESSAGES

* Light rain ending this morning. Drier weather this afternoon and evening, with above normal temperatures peaking in the 50s by this afternoon.

* Active pattern brings waves of rainfall Friday through Sunday and then again Tuesday. * Well above normal temperatures through at least Monday.

SHORT TERM /THROUGH TONIGHT/

Issued at 321 AM EST Thu Dec 26 2024

Light rain and drizzle are across the region this morning as a weak inverted sfc trof sits overhead. Aloft, a 300mb shortwave axis is pushing east of us, with upper ridging following for later today. Expect light precip activity to diminish through this morning as this sfc trof washes out. Drier weather is expected for late morning and through the afternoon and evening, with any additional precip activity for today focusing on areas to our west later. It's possible we could see a few isolated patches of light rain or sprinkles linger in our far western counties into the early afternoon, though chances remain below 25%.

Increased cloud cover will linger for most today, but could see some breaks in the clouds this afternoon, especially in our east. With southeasterly flow continuing to provide a WAA regime, temps for this afternoon will peak in the 50s region-wide. South-central Kentucky counties will be close to 60, and may reach it if they get any decent breaks in the cloud cover later today. These temps will place us about 10-15 degrees above climate normals.

Dry weather continues for most of the night, though it will remain very mild thanks to strengthening WAA ahead of a sfc low pressure system. A deep upper shortwave over Texas will pivot towards the Ozarks tonight and take on a negative tilt, which will promote increasing southerly low-level jetting and moisture transport for the Deep South and Tennessee Valley, with the Wabash River Valley and lower Ohio Valley being on the far northern extent tonight. This will keep temps in the 40s tonight.

There remains good model agreement on nighttime storms approaching the area early Friday morning from the west-southwest, but fortunately the timing will not be favorable for sfc-based instability. General consensus here is that we will most likely see a fading line of embedded thunderstorms arrive sometime Friday morning. Due to this, we'll return PoPs back in the forecast by 09z Friday morning, with an eastward progression up to 12z. However, better overall chances will be from 12z and beyond, which is in the Long Term Discussion below.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 321 AM EST Thu Dec 26 2024

Friday through Sunday Night...

Friday through Sunday continues to look quite active with at least a few noteworthy waves of rainfall. A series of shortwave disturbances aloft are forecast to swing northeast from the southern Plains/Ozarks across the Ohio Valley. Wave 1 arrives Friday morning, characterized by strong low to mid-level wind fields, robust deep- layer ascent, and potent moisture advection. Expect breezy conditions and a band of moderate rain translating eastward across central KY and southern IN during the daylight hours. Forecast instability is nil, so the thunder chances are low despite strong forcing. Rainfall totals of 0.30-0.70 inches will be possible from 12Z Fri to 00Z Sat, with the higher totals in that range across south-central KY. Temperatures are forecast to be well above normal, with highs in the mid/upper 50s.

Will maintain chance to likely PoPs Friday night, though QPF is much lower with the arrival of a dry slot of the wave lifting northeast over the MS Valley. Deep southerly flow will keep conditions very mild for late December, with lows in the low to mid 50s.

A somewhat deeper wave organizing over the southern Plains on Saturday is forecast to swing northeast across the Ohio Valley through Sunday. The dynamics late Saturday into early Sunday look pretty healthy, with sfc cyclogenesis favored near the Lower OH Valley beneath the right entrance region of an intensifying upper level jet streak over the Great Lakes. With somewhat anomalous (NAEFS PW standardized anomaly > 1) moisture still in place, swaths of moderate to heavy rainfall will be possible. There is at least a slight chance for thunderstorms, and the convective nature could locally boost rainfall totals. However, the degree of destabilization (if any) is the big question mark given less than ideal diurnal timing and potential for deep convection across the South. An additional 1-2 inches of rainfall will be possible over the weekend in central KY, with locally higher amounts not out of the question. Highs in the upper 50s to mid 60s will be common over the weekend, with lows mostly in the 50s.

Monday through New Year's Day...

We'll see a brief lull in the action in the wake of the departing weekend storm system, with upper level flow transitioning to a more zonal pattern. Monday looks dry and mild, with highs in the mid 50s to near 60 degrees. However, yet another Pacific wave is forecast to strengthen in the lee of the Rockies and bring additional rain chances by Monday night or early Tuesday. A switch to a colder pattern then looks likely to kick off the new year. Much colder air could flood the region by the latter half of next week.

AVIATION /06Z TAFS THROUGH 12Z FRIDAY/

Issued at 118 AM EST Thu Dec 26 2024

Scattered light rain will continue for a few more hours this morning as a weak boundary sits across the area, though VFR conditions are expected. Not expecting this boundary to move anywhere fast. Continued to use PROB30 for the potential for the precip shield to impact SDF and BWG, but impacts will be minimal given unrestricted vis and VFR cigs. As the boundary washes out later this morning, look for any precip to dissipate and winds to veer to more of a SE direction.

LMK WATCHES/WARNINGS/ADVISORIES

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