textproduct: Louisville

KEY MESSAGES

* Areas of frost are expected Friday night, with freezing conditions possible (20-30% chance) over southern Indiana. A more widespread freeze is forecast Saturday night.

DISCUSSION

Issued at 309 AM EST Thu Nov 5 2026

*** PATCHY FOG EARLY THURSDAY MORNING ***

At 245am Thursday morning, clouds are gradually pushing east of the I-65 corridor as drier air attempts to work its way into the region behind a weak cold front. This has allowed patchy fog to develop in rural, low-lying areas where light winds have permitted temperatures to sink like a rock - into the mid 40s in spots. I lowered temperatures and added some patchy fog to the forecast through 8am to account for this, but it should quickly dissipate thereafter as surface heating eradicates PBL saturation. Also helping disperse any residual morning fog will be increasing winds which mixing techniques via Bufkit forecast soundings suggest may gust up to 20 mph late morning into the afternoon across northern Kentucky and especially southern Indiana. Temperatures this afternoon will climb into the low to mid 60s, which, though cooler than we've become used to recently, is near normal for early November in the Bluegrass state.

*** FROST AND FREEZE THIS WEEKEND ***

Cloud cover will increase again from the north tonight into tomorrow morning as a cold core low dives southeast towards the area. Consequently, highs will run a few degrees cooler tomorrow, particularly across areas near and north of the I-64 corridor where the Rapid Refresh Ensemble Forecast System (REFS) mean brings 850mb temperatures to < -2 degC. In addition, the RAP shows 0-1km RH > 90%, light QPF, and a 0% probability of cloud ice tomorrow morning into the early afternoon - implying we may see some patchy drizzle, if not true rain showers over the Bluegrass where weak diurnal instability will develop by early afternoon. Highs in the upper 50s to low 60s will give way to Saturday morning lows in the 30s - coolest over southern Indiana where clouds should depart by midnight, allowing patchy frost to form.

Cool advection will continue through the day on Saturday, confining highs to the 50s despite partly to mostly sunny skies. Then, with enough clearing, Saturday night lows will take a sharp dive, particularly with high pressure settling over the area to promote light-calm winds. The result will be area-wide frost and in some locations, a freeze. NBM probabilities for sub 32 degF lows are highest (60-90%) along two corridors: one over southern Indiana west of the Louisville Metro, and another across the Bluegrass. It is this second area where a hard freeze may also be achieved, primarily in low-lying rural areas; NBM probabilities for such (< 28 degF) temperatures are 30-50%. While the horticulture growing season is over, such freezing temperatures promote prussic acid formation in certain plants - suggesting possible livestock impacts in the absence of protective action. As a result, we will likely need frost/freeze headlines to highlight this potential beginning tomorrow night and again on Saturday and/or Sunday nights.

Dry and mild weather is expected going into next work week, with afternoon highs in the 60s following crisp mornings in the 30s.

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/

Issued at 1200 PM EST Thu Nov 5 2026

VFR conditions are ongoing this afternoon across the region. A weak cold front is expected to arrive tomorrow, though precip chances remain below 20%. Biggest impact with this frontal passage will be lowering cigs, which are forecast to drop to MVFR for all terminals during this forecast period. Expect lowering cigs first at HNB by 09z tomorrow morning, followed by SDF, then LEX/BWG and then finally at RGA by 16z. For the extended SDF forecast, should see VFR return by tomorrow afternoon beyond 18z. Otherwise, sfc winds will switch around from a SW flow today to a NW flow behind the front tomorrow.

LMK WATCHES/WARNINGS/ADVISORIES

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