diff --git a/apps/src/components/fields/skill.tsx b/apps/src/components/fields/skill.tsx
index 99eee296b..5d423a198 100644
--- a/apps/src/components/fields/skill.tsx
+++ b/apps/src/components/fields/skill.tsx
@@ -8,16 +8,27 @@ import { __ } from '@/context/locale-provider';
 import TooltipWidget from '@/components/ui/tooltip-widget';
 import React from 'react';
 
+import { useClimateVariable } from '@/hooks/use-climate-variable';
+import { ForecastDisplays } from '@/types/climate-variable-interface';
+
 export interface S2DForecastDisplaySkillFieldCheckboxProps {
 	tooltip?: React.ReactNode;
 }
 
+/**
+ * @see {@link selectLowSkillVisibility} — "skill" is an S2D-specific concept
+ */
 export const MaskLowSkillField = (
 	props: S2DForecastDisplaySkillFieldCheckboxProps,
 ) => {
+	const { climateVariable } = useClimateVariable();
+
 	const dispatch = useAppDispatch();
 
 	const checked = useAppSelector(selectLowSkillVisibility());
+	const forecastDisplay = climateVariable?.getForecastDisplay();
+	const isForecast = forecastDisplay === ForecastDisplays.FORECAST;
+
 	const onCheckedChange = (checked: boolean) => {
 		dispatch(setLowSkillVisibility({visible: checked}));
 	};
@@ -29,6 +40,7 @@ export const MaskLowSkillField = (
 	const fieldProps = {
 		checked,
 		onCheckedChange,
+		disabled: !isForecast,
 		...propsRest,
 	};
 
@@ -36,12 +48,12 @@ export const MaskLowSkillField = (
 		<div className="flex items-center space-x-2">
 			<Checkbox
 				id='mask-low-skill-checkbox'
-				className="text-brand-red"
+				className="text-brand-red disabled:data-[state=checked]:bg-neutral-grey-medium disabled:data-[state=checked]:border-neutral-grey-medium"
 				{...fieldProps}
 			/>
 			<label
 				htmlFor='mask-low-skill-checkbox'
-				className="text-sm font-medium leading-none cursor-pointer"
+				className="text-sm font-medium leading-none cursor-pointer peer-disabled:opacity-50 peer-disabled:cursor-default"
 			>
 				{__('Mask Low Skill')}
 			</label>
diff --git a/apps/src/components/map-layers/low-skill-layer.tsx b/apps/src/components/map-layers/low-skill-layer.tsx
index 5fe60ec87..37a0798ca 100644
--- a/apps/src/components/map-layers/low-skill-layer.tsx
+++ b/apps/src/components/map-layers/low-skill-layer.tsx
@@ -6,6 +6,7 @@ import { useS2D } from '@/hooks/use-s2d';
 import { useAppSelector } from '@/app/hooks';
 import { selectLowSkillVisibility } from '@/features/map/map-slice';
 import { buildSkillLayerName, buildSkillLayerTime } from '@/lib/s2d';
+import { ForecastDisplays } from '@/types/climate-variable-interface';
 import L from 'leaflet';
 
 interface LowSkillLayerProps {
@@ -14,13 +15,17 @@ interface LowSkillLayerProps {
 
 /**
  * Leaflet layer for the "low skill".
+ *
+ * @see {@link selectLowSkillVisibility} — "skill" is an S2D-specific concept
  */
 const LowSkillLayer = ({
 	pane,
 }: LowSkillLayerProps): React.ReactElement | null => {
 	const { climateVariable } = useClimateVariable();
+	const forecastDisplay = climateVariable?.getForecastDisplay();
+	const isForecast = forecastDisplay === ForecastDisplays.FORECAST;
 	const { releaseDate } = useS2D();
-	const isLowSkillMasked = !useAppSelector(selectLowSkillVisibility());
+	const isLowSkillVisible = useAppSelector(selectLowSkillVisibility());
 	const {
 		opacity: { mapData },
 	} = useAppSelector((state) => state.map);
@@ -33,6 +38,9 @@ const LowSkillLayer = ({
 		timeValue = buildSkillLayerTime(climateVariable, releaseDate);
 	}
 
+	const hasLayerData = layerName && timeValue;
+	const shouldHideLayer = !isForecast || !isLowSkillVisible;
+
 	// Update the opacity on the *existing* layer if it exists. We do it like
 	// that because we don't want a change in opacity to recreate the layer.
 	// Instead, we want to update the existing layer (else it creates flashing
@@ -49,7 +57,7 @@ const LowSkillLayer = ({
 	// attributes change.
 	return useMemo(
 		() => {
-			if (isLowSkillMasked || !layerName || !timeValue) {
+			if (shouldHideLayer || !hasLayerData) {
 				return null;
 			}
 
@@ -78,7 +86,12 @@ const LowSkillLayer = ({
 		// above takes care of that). But we still use it as an initial value.
 		//
 		// eslint-disable-next-line react-hooks/exhaustive-deps
-		[pane, isLowSkillMasked, layerName, timeValue]
+		[
+			layerName,
+			pane,
+			shouldHideLayer,
+			timeValue,
+		]
 	);
 };
 
diff --git a/apps/src/features/map/map-slice.ts b/apps/src/features/map/map-slice.ts
index 81ee9c5ad..ecdd63368 100644
--- a/apps/src/features/map/map-slice.ts
+++ b/apps/src/features/map/map-slice.ts
@@ -201,7 +201,9 @@ export const {
 } = mapSlice.actions;
 
 /**
- * Selector that returns the visibility of the "low skill" layer.
+ * Selector that returns the visibility of the low-skill vector mask overlay.
+ *
+ * @see {@link MapState.isLowSkillVisible}
  */
 export const selectLowSkillVisibility =
 	() => (state: RootState) =>
diff --git a/apps/src/lib/s2d.ts b/apps/src/lib/s2d.ts
index ed9fc1be0..9c7ecbd20 100644
--- a/apps/src/lib/s2d.ts
+++ b/apps/src/lib/s2d.ts
@@ -152,6 +152,10 @@ export function formatPeriodRange(periodRange: PeriodRange): [string, string] {
 /**
  * Create and return the GeoServer layer name for the Skill layer.
  *
+ * "Skill" in meteorology refers to forecast accuracy relative to a baseline
+ * (e.g., climatology). The skill layer is a vector mask overlay showing
+ * diagonal lines over regions where forecast confidence is low.
+ *
  * The name is `CDC:s2d-skill-<VAR>-<F>-<REF-PERIOD>`
  *
  * Where:
diff --git a/apps/src/types/types.ts b/apps/src/types/types.ts
index ea3447eb1..9f69dc390 100644
--- a/apps/src/types/types.ts
+++ b/apps/src/types/types.ts
@@ -216,8 +216,14 @@ export interface MapState {
 	 */
 	messageDisplayStates: {[key: string]: boolean};
 	/**
-	 * True if the "low skill" layer is visible (i.e. true if "mask low skill"
-	 * is checked)
+	 * Whether low-skill areas are masked on the map.
+	 *
+	 * "Mask" is the verb — to visually cover low-confidence forecast areas
+	 * with diagonal lines. When `true`, those areas are masked.
+	 *
+	 * Only meaningful for S2D variables when Forecast Display = "Forecast".
+	 *
+	 * Controlled by `MaskLowSkillField` in `components/fields/skill.tsx`.
 	 */
 	isLowSkillVisible: boolean;
 	/**