Look at this flow to get the data from the global context variable.
[{"id":"f57d7589dd5a9b5c","type":"inject","z":"be03f9025a1f137a","name":"","props":[],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":235,"y":75,"wires":[["fcb8501ba4e0c02b"]]},{"id":"fcb8501ba4e0c02b","type":"function","z":"be03f9025a1f137a","name":"function 1","func":"msg.sun = global.get('homeassistant').homeAssistant.states[\"sun.sun\"];\nmsg.sun_state = global.get('homeassistant').homeAssistant.states[\"sun.sun\"].state;\nmsg.sun_attr_next_dawn = global.get('homeassistant').homeAssistant.states[\"sun.sun\"].attributes.next_dawn;\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":375,"y":75,"wires":[["36f148efe227cbac"]]},{"id":"36f148efe227cbac","type":"debug","z":"be03f9025a1f137a","name":"debug 7","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":525,"y":75,"wires":[]}]
You can see the values yourself by opening up the Context Data menu in the upper right corner of Node Red and then click the refresh icon next to the Global headline.
You might also be able to use a dynamically set up sensor.
I have no idea if this can just be made a binary sensor by adding binary to its name, but else a normal sensor might also work in your case.
Just remember this is not a permanent sensor, so it will not be available in HA before it has been populated by NodeRed.
[{"id":"25ef1c9c74581477","type":"ha-api","z":"be03f9025a1f137a","name":"sensor","server":"541ade28.b4a62","version":1,"debugenabled":false,"protocol":"http","method":"post","path":"/api/states/{{entity_id}}","data":"","dataType":"json","responseType":"json","outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"results"}],"x":800,"y":660,"wires":[[]]},{"id":"06ac8e03a8a85876","type":"function","z":"be03f9025a1f137a","name":"make final payload","func":"msg.entity_id = `sensor.weather_alert`;\n\nmsg.payload = {\n data: {\n state: '2',\n attributes: {\n 'name': 'test_entity3',\n 'entries': [\n {'title':'WEATHER ADVISORY, Barrie'},\n {'title': 'SPECIAL WEATHER STATEMENT, Barrie'}\n ],\n friendly_name: 'Test Entity 3',\n icon: 'mdi:pulse'\n }\n }\n};\nreturn msg;\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":630,"y":660,"wires":[["25ef1c9c74581477","fee8ca78ceac8578"]]},{"id":"39963ed0628d85b4","type":"inject","z":"be03f9025a1f137a","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":450,"y":660,"wires":[["06ac8e03a8a85876"]]},{"id":"541ade28.b4a62","type":"server","name":"Home Assistant","version":5,"addon":true,"rejectUnauthorizedCerts":true,"ha_boolean":"","connectionDelay":false,"cacheJson":false,"heartbeat":false,"heartbeatInterval":"","areaSelector":"friendlyName","deviceSelector":"friendlyName","entitySelector":"friendlyName","statusSeparator":"at: ","statusYear":"hidden","statusMonth":"short","statusDay":"numeric","statusHourCycle":"h23","statusTimeFormat":"h:m","enableGlobalContextStore":true}]