Tuesday, July 21
Statewide Humidity Surge with West-to-East Rain Progression
A split weather pattern will define Tuesday across Kentucky. Western regions will experience early-day rain followed by intense afternoon heat, while Central and Eastern Kentucky contend with more persistent showers and cloud cover that will keep temperatures slightly lower.
Confidence Assessment
Confidence is high that everyone will feel the humidity, but the timing of the rain-to-sun transition remains a major point of contention between global models, leading to high uncertainty in peak afternoon temperatures.
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Purchase Area
Expect a wet start to the day with rain likely through mid-morning. Skies will clear by the afternoon, allowing temperatures to surge into the mid-90s. Rainfall totals will stay around 0.10 inches before the sun takes over.
Northwest Pennyrile
A soggy morning will give way to a hot and humid afternoon. Rain will end by midday, with totals near 0.20 inches.
Southwest Pennyrile
Expect waves of rain through most of the day. It will feel very heavy outside with humidity levels remaining high even between showers.
Barren River
Rain will become more widespread by the afternoon hours. Totals are expected to reach nearly half an inch.
Louisville Metro
A few showers are likely during the morning drive. Clouds will break in the afternoon, sending temperatures toward 90 degrees with high humidity.
Lincoln Trail
Rain will pick up in frequency and intensity during the afternoon. Expect around 0.35 inches of rain.
Lake Cumberland
Expect several rounds of rain throughout the day. It will remain warm and very muggy with totals near 0.45 inches.
Northern Kentucky
Rain will be most consistent during the morning hours. Afternoon will remain cloudy and very humid with highs in the mid-80s.
Inner Bluegrass
Lexington can expect a windy day with gusts up to 34 mph and steady rain showers through the afternoon. Totals will reach around 0.35 inches.
Bluegrass Foothills
Rain showers will become more frequent as the day progresses. It will be a gray, humid day with around 0.40 inches of rain.
Northeast Kentucky
Expect a very wet day with over half an inch of rain likely. The steadiest rain will occur during the afternoon and evening hours.
Southeast Kentucky
Rain will persist all day in the mountains with the heaviest arrival this evening. Watch for valley fog late tonight. Totals near 0.50 inches.
Possible Outcomes
Weather forecasting involves uncertainty. Below are two scenarios representing the range of possible outcomes: the "Boom" scenario shows the worst-case/highest-impact result if conditions align unfavorably, while the "Bust" scenario shows the best-case/lowest-impact result if the forecast doesn't materialize as expected.
The 'Boom' Scenario
The ECMWF verifies completely: A robust moisture plume brings a soaking 0.50" to 0.75" of rain statewide, effectively capping temperatures in the mid-80s and providing much-needed relief to parched soils.
The 'Bust' Scenario
The GFS 'Heat Ridge' wins: Mid-level capping suppresses rainfall to mere sprinkles or 'virga' in the east, while the west and metro areas bake under clear skies with heat indices approaching 105 degrees.
Model Disagreements
When models disagree, a call must be made to determine the most likely outcome. This decision is based on a combination of factors including model performance, historical data, and the models general accounting of each climatic region of Kentucky.
The Western Dry-Slot Dispute
The GFS maintains a dry, high-pressure influence over Western KY, while the Euro suggests the shortwave trough is strong enough to trigger morning rain as far west as the Purchase region.
Why EURO Wins
With PWATs exceeding 1.7 inches, the GFS's total lack of precipitation in the west seems physically unlikely given the strength of the incoming shortwave divergence.
The Northeast Thermal Ceiling
A massive 15-degree discrepancy exists for afternoon highs in Northeast KY. GFS predicts 98F with light drizzle, while Euro predicts 83F with steady rain.
Why BLEND Wins
The GFS is likely over-mixing the boundary layer, while the Euro may be too pessimistic on cloud clearing. A middle-ground approach accounts for high humidity keeping temps in the upper 80s.
Celestial Almanac
First Quarter
Purchase Area
Northwest Pennyrile
Southwest Pennyrile
Barren River
Louisville Metro
Lincoln Trail
Lake Cumberland
Northern Kentucky
Inner Bluegrass
Bluegrass Foothills
Northeast Kentucky
Southeast Kentucky
Forecast Charts
These maps are generated by the weather agencies based on the raw data that the weather models predict. The final forecast is generated using the same raw data shown on the map. Keep in mind that the models (and therefore the maps) will generally disagree on specific parts of the forecast. Use these as guidance - not as a final prediction.
Dive Deeper Into the Models
This forecast is a synthesis of raw data from the NAM, GFS, ECMWF, and GEM models. These models provide detailed atmospheric analyses including 500mb vorticity, precipitation rates, and more. You can take a look at the raw model data by clicking the links below.