textproduct: Jackson

KEY MESSAGES

- Temperatures 10 to 20 degrees above normal are expected through early next week.

- Widespread rainfall will affect eastern Kentucky at times from Friday evening through Sunday morning.

- The rainfall will be locally heavy at times, especially from Saturday afternoon through the Sunday morning.

UPDATE

Issued at 650 AM EST THU DEC 26 2024

A few light radar returns continue to cross western and northwestern portions of the area. KLEX and KFGX have recently reported rain or drizzle from this activity. No changes were made to pops and associated isolated shower and sprinkle chances for the western and northwestern areas this morning. Otherwise, minor adjustments were made to hourly grids based on recent observations of temperatures and dewpoints. This generally led to no significant changes. Highs this afternoon should climb to about 10 degrees above normal or to similar levels as what was observed on Christmas Day.

LONG TERM

(Friday night through Wednesday) Issued at 522 AM EST THU DEC 26 2024

The period starts off on a wet note Friday evening. A warm front will have traversed northward through the state during the day, with a strong influx of southerly flow and moisture into the region ahead of an approaching cold front. These boundaries will be the result of a strong surface low pressure system located across the Midwest as of 0Z Saturday, combined with a strong upper level shortwave. This shortwave will also promote large-scale troughing across much of the Conus, resulting in strong SW flow into the Ohio Valley aloft as well. All this to say that precipitation will likely be imminent. With the WAA, there shouldn't be any worry about freezing precipitation (lows will remain in the low 50s), but rather just light to moderate rainfall.

Heading into the first part of the day Saturday, the track of the low pressure system, and the shortwave aloft, will change course, becoming almost completely northward bound. The low pressure system will reach Lake Superior by 0Z Sunday according to the latest ECMWF. Because of this movement, it will stall the progression of the cold front parked just to our west, and will leave much of Kentucky in a strong S to SW flow pattern, continuing the warm air and moisture advection into the region.

By Saturday afternoon, sites turn to another system to our southwest across the Southern Plains. This second shortwave will develop in the overall longwave troughing pattern, accompanied by a deepening surface low. As the system quickly begins to move ENE, Kentucky will find itself with another increase in the SW flow, promoting an influx in precipitation coverage once more. Models are coming into better agreement about the track of the low, which should bring it nearly directly across or skirting just north of the the Commonwealth by Saturday night and Sunday morning. Another cold front will stretch southward from this surface low, sweeping across eastern Kentucky briefly as the system quickly exits to the northeast during the first half of the day Sunday. Given the position of the low almost directly overhead, and temperatures climbing into the upper 50s and low 60s, the NBM did hint at some slight thunder potential Saturday night and Sunday. The latest GFS soundings show steep lapse rates, and a completely saturated increase sounding, but nearly no CAPE. So while it can't be ruled out, confidence isn't super high, so didn't go more than lowest end chances (under 20%). Meanwhile the larger concern, perhaps, is the continued agreement in WPC's Marginal Risk Outlook for excessive rain from 12Z Saturday through 12Z Sunday. With the increased energy and strong SW flow, rain could be moderate to heavy at times from Saturday evening through Sunday morning, and will be falling on top of already saturated soils. This is reflected in the saturated soundings and the forecasted QPF - ranging from about 1.5 inches in the northeast CWA to just under 2.25 inches in the far SW CWA (Saturday 18Z through Monday 6Z). Continued to message this heavy rain potential in the HWO.

There is still some uncertainty as to how long precip might hold on behind the departing system, and this really has to do with the placement of the associated shortwave aloft. The GFS pulls the shortwave farther north faster, with rising heights across the state and the advection of drier air, allowing precip to end by 6Z Monday. Meanwhile, the ECMWF holds onto the shortwave across the region a little while longer, resulting in lower heights and the potential for some continued scattered precip into Sunday night, before finally exiting Monday morning. Given the uncertainty, stuck with the NBM solution, which seems to be a bit more in line with the ECMWF, exiting by Monday at 12Z.

Once this system finally does exit, a brief area of high pressure will begin to build in from the west, giving us our (potentially) one dry day of the period on Monday. The interesting thing on Monday is the temperatures. Despite being right behind a cold front and departing low, the upper levels will be coming out of the longwave troughing pattern, and heights will actually be becoming more zonal across the region, preventing deep cold air advection into the region. This will couple will winds becoming more southerly during the afternoon as the high is already beginning to depart to the east ahead of the next approaching system. All this to say that temperatures on Monday will still be quite warm, with highs in the mid and upper 50s, to around 60 degrees in a few locations.

Unfortunately, by 18Z Monday, yet another large surface low pressure system will be developing across the Southern Plains, and is expected to move eastward along this zonal flow, headed straight towards Kentucky. Models were in very poor agreement about this system yesterday, so it's promising to see them come into much better agreement as of this last run - at least for part of the time. Both the GFS and ECMWF show the low traversing just north of Kentucky Monday night and into Tuesday. However, then the GFS pushes the system farther north much quicker (this seems to be an ongoing trend to be farther north and faster than the ECMWF), while the ECMWF lingers, with the low just to our northeast by 0Z Wednesday. While they both agree that precip from this system should start Monday night/Tuesday morning, the exit time is drastically different - therefore stuck with the NBM given the low confidence in the pops. Again, it seems to be favoring the ECMWF solution a bit more, keeping isolated to chance pops in place well into the day Wednesday (and even into Wednesday night - something that neither model shows).

This will also be the system that finally results in an airmass change. As this system reaches Kentucky, the shortwave will have strengthened into a closed low, creating more large-scale troughing across much of the conus again. As the system exits, strong NW flow will begin to advect in on the backside of the upper level trough. While highs on Tuesday will be in the mid 50s once more, highs on Wednesday, behind the exiting system, will only be in the low 40s. Wednesday night will be the first time we could see below freezing temperatures in quite some time.

AVIATION

(For the 12Z TAFS through 12Z Friday morning) ISSUED AT 650 AM EST THU DEC 26 2024

A few sprinkles or isolated showers are possible early near KSME and KLOZ over to KSYM and perhaps as far east as KJKL with these falling from mid level clouds. Overall, VFR and light winds were observed at issuance time and are forecast through the period as an upper level ridge over the southeast to eastern seaboard leads to a general increase in mid level clouds by the last 18 hours of the period and any substantial weather north and west of the area.

JKL WATCHES/WARNINGS/ADVISORIES

NONE.