The folks there are working without pay, or knowledge when they'll be paid. The Washington Post reports that this coded message is actually one of two forecasts the Weather Service issued. Here's that forecast without the plea for pay:
"While National Weather Service employees are not sure when they will get paid, they say they will continue to work through the shutdown to keep all of us safe," reported WTKR-TV, which has a good explainer on why these government employees are being asked to work without pay. It isn't clear whether this desperate plea can change that.