It's likely because you've enabled $logAlerts = true; // true=log alerts false=don't log alerts
in nws-alerts-config.php and the current copy of ./alertlog/NWSalertLog20230323.txt contains <?php
$daily_log = NULL;
?>
which is not an array, but NULL and Curly's code doesn't handle that in PHP over 5.6.
Change nws-alerts-config.php to $logAlerts = false; // true=log alerts false=don't log alerts
and the warnings should disappear.
I see logs with data on the 21st and 22nd, with a lot of Hydrologic Alerts, but the 23rd has no alerts.
The default for the template set was to NOT use alert logging, so I'd not adapted the Curly script to handle the $daily_log = NULL; issue.. turning it off is your best course for now.