Sunrise 6:34 AM   Sunset 8:20 PM Moonrise 12:00 AM   Moonset 8:31 AM

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FXUS63 KJKL 290145 AFDJKL

AREA FORECAST DISCUSSION National Weather Service Jackson KY 945 PM EDT Sun Apr 28 2024

KEY MESSAGES

- Unseasonable warmth and dry weather prevails through Monday afternoon.

- Showers arrive Monday night through Tuesday, with a chance for thunder.

- More showers and storms are expected late this week.

UPDATE
Issued at 945 PM EDT SUN APR 28 2024

Only minor update this evening was to lower minimum temperatures a few degrees to the lower 50s in the typically colder valleys and raise temperatures into the mid 60s on the thermal belt ridges. Sky cover was reduced as well as satellite imagery depicts mainly clear skies prevailing. Patchy fog will be possible late in the typically favored river valley locales.

UPDATE Issued at 647 PM EDT SUN APR 28 2024

Weak radar returns that were present earlier near Lake Cumberland have diminished over the past hour or two. Some high base cumulus and mid level clouds were present across the region with the greater concentration over the western third of the area and west into central KY. Accordingly, minor adjustments have been made to the forecast with mainly just the inclusion of the latest obs and trends for the T/Td/Sky grids with this update. These minor adjustments have been sent to the NDFD and web servers.

SHORT TERM
(This evening through Monday night)
Issued at 400 PM EDT SUN APR 28 2024

19Z sfc analysis shows eastern Kentucky still between two strong weather systems - a deep low over the Plains and somewhat weaker high pressure area off to the southeast. This is maintaining a flow of southerly air into the region - generally at 10 mph with some gusts pushing 20 mph. Under mostly sunny skies, temperatures soared from somewhat cool morning lows. Currently, readings are fairly uniform in the lower 80s while dewpoints are generally in the mid and upper 50s, for most places. There are a few sprinkles in the far southwest parts of the CWA but those will be drying up towards evening.

The models, and their individual ensemble suites, remain in fairly good agreement aloft through the short term portion of the forecast. They all depict Kentucky on the northwest fringe of a large Southeast ridge through Monday afternoon while troughing approaches from the west. This brings more impulses and perturbations to the southwest mid-level flow over this part of the state Monday night into Tuesday morning. At this point, though, the models start to separate with the GFS cluster quicker in moving a shortwave through eastern Tennessee compared to the NAM and ECMWF ensembles. Even so, the model spread is small enough to use the NBM as the starting point for the short term grids along with the incorporation of the CAMs details for PoPs and timing later Monday into Tuesday morning.

Sensible weather features warm and mostly dry daylight hours into Monday evening as southerly winds continue to pump warm and increasingly moist air into this part of the state ahead of an approaching cold front. Skies will stay mostly clear tonight allowing for one last night of good radiational cooling. As a result, a decent ridge to valley temperature split has been added to the temperature grids along with a touch of valley fog. The front pushes its band of showers and thunderstorms into eastern Kentucky towards evening. The best rain chances with this move through the bulk of the area after midnight with a solid quarter to an inch or so of rain expected as it passes - heaviest west and driest in the far east. Temperatures with the rain chances Monday night will be fairly uniform and mild.

The main adjustments to the NBM starting point were centered around adding in terrain details to the hourly temperatures and lows tonight. As for PoPs: the NBM values were adjusted to include some CAMs details Monday evening through Tuesday morning.

LONG TERM
(Tuesday through Sunday)
Issued at 410 PM EDT SUN APR 28 2024

The period is expected to begin with a shortwave trough moving across the Lower Valley into the Southeast Conus, upper ridging north from the Gulf of Mexico to MO, and a broad trough near the US/Canadian border from the Northern Rockies west to the Pacific Northwest and within it an upper level low centered over northern MT and another upper low nearing the Pacific Northwest. At the surface, as the period begins, an area of low pressure is expected to be centered over Ontario near the northern end of Lake Superior with a cold front extending south of the western to Central Great Lakes to near the Lower OH Valley that is expected to be slowing down and stalling with the western end becoming a warm front from the mid MS Valley area northwest to a sfc low pressure system over the Dakotas. Sfc high pressure should also be anchored off the southeast U.S. coast at at that time. Locally, moisture is expected to be transported into the OH Valley on return flow ahead of the passing shortwave with 0Z LREF mean PW forecast in the 1 to 1.3 inch range across the CWA

Tuesday to Wednesday, the shortwave trough is expected to cross over eastern KY during the Tuesday to Tuesday evening timeframe with height rises/shortwave ridging building east into the MS Valley and then into the eastern U.S. including the OH Valley behind it.
Further to the west, the first upper level low near the U.S./ Canadian border initially centered over MT should meander east and northeast while the one nearing the Pacific Northwest as the period begins becomes an open wave and works across portions of the western Conus with the axis of the trough extending from MT to the Southwest Conus by Wednesday evening. Meanwhile, at the surface, the boundary that should be slowing down or stalling near or north of the OH River should lift back north as a warm front downstream of low pressure tracking from the Plains into Ontario. The trailing front from that low should also tend to slow down or stall north of the OH River late Tue night into Wed. Moisture and lift from the passing shortwave should lead to showers across eastern KY form Tuesday into Tuesday evening. Instability will be limited, but isolated to scattered storm are possible, especially during peak heating on Tuesday.

Wednesday night to Friday night, the upper low near the US/Canadian border should meander further north or east through the period with a rather large spread in the position and strength of the upper low by late Friday night somewhere from Manitoba to Ontario. There is also uncertainty in timing of individual waves moving from the western Conus across the Plains and into the eastern Conus during this time. Despite the differences there is a general consensus of a shortwave trough moving from the MS Valley and across the OH Valley late Thu night through Friday night with an associated cold front moving into and perhaps across eastern KY by late Friday night or early on Saturday.

Saturday to Sunday, timing differences between individual shortwaves lead to differences in tining of the passage of a cold front and departure of deeper moisture. A lull in shower chances would occur between this system and the next system approaching late in the period if not beyond the end of the period. At this point stuck with the NBM pops, though some recent guidance, including the 12Z operational GFS and 12Z operational ECMWF suggests less shower activity by late Saturday and into Sunday than currently forecast.

Clouds and convection will lead to high temperatures on Tuesday returning to near normal, briefly, before warming to above normal Wednesday to Saturday. At this time, the warmest day should be Thursday when some of the deeper valleys, especially in the Big Sandy region could reach 90 or near 90, with overall departures that day near 15 degrees above normal.

AVIATION
(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 705 PM EDT SUN APR 28 2024

Surface and upper level ridging will shift east through the period and allow a disturbance to approach from the west. Overall, no significant changes will be needed for the 0Z TAFs. High based cumulus and some mid clouds lingered at issuance time in the west though these should diminish overnight. Additional high based cumulus and or mid level clouds should return during the last 12 hours of the period. Dry weather should prevail through at least 21Z before convection possibly encroaches on western and northwestern locations late in the period, which could affect KSME and KSYM. LLWS from the south at up to 40 KT was more prevalent in the NBM guidance versus CONSSHORT was maintained for continuity and could affect the western half to two thirds of the area was maintained for a few hours between 03Z and 13Z including all the TAF sites with the exception of KSJS. South winds at 10KT or less, with some light and variable winds in valleys will prevail through around 12Z, before winds become south to southwest at 7 to 12KT areawide once daytime mixing commences.

JKL WATCHES/WARNINGS/ADVISORIES
NONE.

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