Session Variables Get Lost On Browser Close

I'm creating a site. Below is my authentication tag and session tag in web.config

<authentication mode="Forms">
<forms protection="All" loginUrl="Pages/Log In/Login.aspx" name=".ASPXFORMSAUTH" cookieless="UseCookies" requireSSL="false"
defaultUrl="Pages/Common/Default.aspx" enableCrossAppRedirects="false" slidingExpiration="true" timeout="30"path="/">
</forms>
</authentication>
<sessionState mode="InProc" timeout="30" cookieless="false" cookieName=".ASPSession"/>
And I have a custom Membership Providor....
<membership defaultProvider="SqlMemberShipProvider" userIsOnlineTimeWindow="15" hashAlgorithmType="">
<providers>
<clear/>
<add
name="SqlMemberShipProvider"
type="RoalManagement.SqlMemberShipProvider"
connectionStringName="SqlServices"
enablePasswordRetrieval="true"
enablePasswordReset="true"
requiresQuestionAndAnswer="true"
writeExceptionsToEventLog="true"
applicationName="OnlineOnTheWeb"
minRequiredPasswordLength="6"
passwordStrengthRegularExpression="^.*(?=.{6,50})(?=.*[a-z])(?=.*[A-Z])(?=.*[dW]).*$"
maxInvalidPasswordAttempts="3"
requiresUniqueEmail="true"
/>
</providers>
</membership>

Now in login page after firsttime login i set some session data... like
protected void Login_LoggedIn(object sender, EventArgs e)
{
//.....
Session["EMPLOYEELOGGEDIN"] = "Y";
//.....
}

Now say i close the browser... and next time when i open the site it takes me directly to the default page [Login_LoggedIn is not called accordingly]... because i'm already logged in for 30 mins acc. to configuration. but as my session id gets changed i can't access Session["EMPLOYEELOGGEDIN"] from any page in this time. It always returns null. But how do i get back the previous session for that person?