textproduct: Louisville

KEY MESSAGES

* Highs in the low 70s with lows in the 40s and isolated 30s will continue through the weekend.

* Patchy dense valley fog is expected to form again tonight and into the morning hours, slowly becoming patchier and isolated heading towards and west of I-65.

* Stubborn ridging promotes a prolonged dry period with pleasant afternoons through at least early next week.

DISCUSSION

Issued at 225 PM EDT Tue Oct 20 2026

====== Dense River Valley Fog & Warm Afternoons =====

There is a mid to upper level low swinging through southern KY and can see the swirl on water vapor imagery. This is just bringing passing high level clouds in our SE. Light northeasterly flow is keeping temperatures mild in the upper 60s to low 70s across the area. Arguably, the most exciting thing to monitor would be dew points today and for the following days. This will determine how dry and comfortable each afternoon will feel, along with the chances of fog formation each morning as well. Relative humidity values are generally bottoming out in the low and mid 30s but will recover to near 100% overnight and into tomorrow morning.

Low temperatures tonight will reach the low to mid 40s and mid to upper 30s in our deepest, decoupled river valleys. Just as this morning, dense fog will likely form in river valleys in the east, becoming more patchy dense fog in valleys west of I-65. As we saw this morning, fog will dissipate by late morning, with the latest being near 10-11 AM EDT in eastern areas. Then by Wednesday afternoon, the locked in ridge pattern overhead will lock in sunny skies and generally light N-NE flow. As long as the deep low off the east coast and troughing over the western US continues, our pattern will remain the same.

We'll have to monitor the dew points tomorrow as well as this will alter fog chances for Thursday morning. Fog may become more prevalent by then, but this will be fine tuned between now and tomorrow night.

===== Stubborn Ridging and Next Potential Rain Chance =====

As mentioned before, with troughing on either side of the central/eastern US, our daily weather won't change much. An Omega Blocking pattern seems to really take hold and last through the weekend. A weak cold front may push through Thursday morning though it is expected to remain so dry there won't be a noticeable change in weather besides a shift of winds from the N-NW briefly. PWATs generally remain under the 30th climatological percentile through Thursday but as the ridging generally begins to very slowly weaken, southerly flow will return. This will bring PWATs, temperatures and dew points slowly higher over the weekend. Not any big changes are expected from this slow moving pattern as highs go from the low to mid 70s by Sunday and Monday. Mornings remain crisp and potentially patch-ily foggy, mostly in river valleys. With incremental increases in PWATs, a potential cold front from a swinging trough in southern Canada may bring a line of broken showers Tuesday afternoon. Confidence is very low in this, but it is the largest potential change in the weather pattern with highs mid week in the upper 60s. Drought will likely worsen as a response to this pleasant, yet dry period.

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 130 PM EDT Tue Oct 20 2026

VFR conditions are expected through the rest of the afternoon through the overnight into Wednesday morning. Passing high level cirrus clouds will move over RGA in the next few hours. Winds are light and from the NE and will become calm or near calm overnight. There is low confidence of fog formation at RGA although this remains a non-zero chance early Wednesday morning. VFR conditions expected Wednesday afternoon as well.

LMK WATCHES/WARNINGS/ADVISORIES

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