diff --git a/Source/TimeIntegration/ROMSX_advance_3d.cpp b/Source/TimeIntegration/ROMSX_advance_3d.cpp
index 452ac658..55816940 100644
--- a/Source/TimeIntegration/ROMSX_advance_3d.cpp
+++ b/Source/TimeIntegration/ROMSX_advance_3d.cpp
@@ -82,6 +82,9 @@ ROMSX::advance_3d (int lev,
         Box gbx11 = mfi.growntilebox(IntVect(NGROW-1,NGROW-1,NGROW-1));
         Box gbx21 = mfi.growntilebox(IntVect(NGROW,NGROW,NGROW-1));
 
+        Box xbx = mfi.nodaltilebox(0);
+        Box ybx = mfi.nodaltilebox(1);
+
         Box gbx2D = gbx2;
         gbx2D.makeSlab(2,0);
 
@@ -144,16 +147,18 @@ ROMSX::advance_3d (int lev,
           cff=0.25*dt_lev*23.0/12.0;
         }
 
-        amrex::ParallelFor(gbx2,
+        amrex::ParallelFor(xbx,
+        [=] AMREX_GPU_DEVICE (int i, int j, int k)
+        {
+            u(i,j,k) += cff * (pm(i,j,0)+pm(i-1,j,0)) * (pn(i,j,0)+pn(i-1,j,0)) * ru(i,j,k,nrhs);
+            u(i,j,k) *= 2.0 / (Hz(i-1,j,k) + Hz(i,j,k));
+        });
+        amrex::ParallelFor(ybx,
         [=] AMREX_GPU_DEVICE (int i, int j, int k)
-            {
-                u(i,j,k) += tbxp2.contains(i-1,j,0) ? cff * (pm(i,j,0)+pm(i-1,j,0)) * (pn(i,j,0)+pn(i-1,j,0)) * ru(i,j,k,nrhs) :
-                                                      cff * (2.0 * pm(i,j,0)) * (2.0 * pn(i,j,0)) * ru(i,j,k,nrhs) ;
-                v(i,j,k) += tbxp2.contains(i,j-1,0) ? cff * (pm(i,j,0)+pm(i,j-1,0)) * (pn(i,j,0)+pn(i,j-1,0)) * rv(i,j,k,nrhs) :
-                                                      cff * (2.0 * pm(i,j,0)) * (2.0 * pn(i,j,0)) * rv(i,j,k,nrhs);
-                u(i,j,k) *= tbxp2.contains(i-1,j,0) ? 2.0 / (Hz(i-1,j,k) + Hz(i,j,k)) :  1.0 / (Hz(i,j,k));
-                v(i,j,k) *= tbxp2.contains(i,j-1,0) ? 2.0 / (Hz(i,j-1,k) + Hz(i,j,k)) : 1.0 / (Hz(i,j,k));
-            });
+        {
+            v(i,j,k) += cff * (pm(i,j,0)+pm(i,j-1,0)) * (pn(i,j,0)+pn(i,j-1,0)) * rv(i,j,k,nrhs);
+            v(i,j,k) *= 2.0 / (Hz(i,j-1,k) + Hz(i,j,k));
+        });
 
         {
         amrex::Gpu::synchronize();
@@ -168,26 +173,26 @@ ROMSX::advance_3d (int lev,
 #ifdef AMREX_USE_GPU
     Gpu::synchronize();
 #endif
-        vert_visc_3d(gbx1,1,0,u,Hz,Hzk,oHz,AK,Akv,BC,DC,FC,CF,nnew,N,dt_lev);
+        vert_visc_3d(xbx,1,0,u,Hz,Hzk,oHz,AK,Akv,BC,DC,FC,CF,nnew,N,dt_lev);
 
         // Reset to zero
         mf_DC[mfi].template setVal<RunOn::Device>(0.,gbx21);
         fab_CF.template setVal<RunOn::Device>(0.,gbx21);
 
-        vert_visc_3d(gbx1,0,1,v,Hz,Hzk,oHz,AK,Akv,BC,DC,FC,CF,nnew,N,dt_lev);
+        vert_visc_3d(ybx,0,1,v,Hz,Hzk,oHz,AK,Akv,BC,DC,FC,CF,nnew,N,dt_lev);
         }
 
         // Reset to zero
         mf_DC[mfi].template setVal<RunOn::Device>(0.,gbx21);
         fab_CF.template setVal<RunOn::Device>(0.,gbx21);
 
-        vert_mean_3d(gbx1,1,0,u,Hz,DU_avg1,DC,CF,pm,nnew,N);
+        vert_mean_3d(xbx,1,0,u,Hz,DU_avg1,DC,CF,pm,nnew,N);
 
         // Reset to zero
         mf_DC[mfi].template setVal<RunOn::Device>(0.,gbx21);
         fab_CF.template setVal<RunOn::Device>(0.,gbx21);
 
-        vert_mean_3d(gbx1,0,1,v,Hz,DV_avg1,DC,CF,pn,nnew,N);
+        vert_mean_3d(ybx,0,1,v,Hz,DV_avg1,DC,CF,pn,nnew,N);
 
         update_massflux_3d(gbx2,1,0,u,ubar,Huon,Hz,on_u,DU_avg1,DU_avg2,DC,FC,CF,nnew);
 
@@ -277,6 +282,7 @@ ROMSX::advance_3d (int lev,
         //------------------------------------------------------------------------
         //
         //Should really use gbx3uneven
+        //TODO: go over these boxes and compare to other spots where we do the same thing
         Box gbx1D = gbx1;
         gbx1D.makeSlab(2,0);
 
@@ -404,7 +410,7 @@ ROMSX::advance_3d (int lev,
         fab_on_u.template setVal<RunOn::Device>(dx[1],makeSlab(tbxp2,2,0));
         fab_om_v.template setVal<RunOn::Device>(dx[0],makeSlab(tbxp2,2,0));
 
-        vert_visc_3d(gbx1,0,0,temp,Hz,Hzk,oHz,AK,Akt,BC,DC,FC,CF,nnew,N,dt_lev);
-        vert_visc_3d(gbx1,0,0,salt,Hz,Hzk,oHz,AK,Akt,BC,DC,FC,CF,nnew,N,dt_lev);
+        vert_visc_3d(bx,0,0,temp,Hz,Hzk,oHz,AK,Akt,BC,DC,FC,CF,nnew,N,dt_lev);
+        vert_visc_3d(bx,0,0,salt,Hz,Hzk,oHz,AK,Akt,BC,DC,FC,CF,nnew,N,dt_lev);
     } // MFiter
 }
diff --git a/Source/TimeIntegration/ROMSX_vert_visc_3d.cpp b/Source/TimeIntegration/ROMSX_vert_visc_3d.cpp
index 78447a7f..03329395 100644
--- a/Source/TimeIntegration/ROMSX_vert_visc_3d.cpp
+++ b/Source/TimeIntegration/ROMSX_vert_visc_3d.cpp
@@ -3,13 +3,13 @@
 using namespace amrex;
 
 //
-// prestep_uv_3d
+// vert_visc_3d
 //
 
 void
 ROMSX::vert_visc_3d (const Box& phi_bx, const int ioff, const int joff,
                      Array4<Real> phi,
-                     Array4<Real const> Hz, Array4<Real> Hzk,
+                     Array4<Real const> Hz, /*temp var */ Array4<Real> Hzk,
                      Array4<Real> oHz,
                      Array4<Real> AK, Array4<Real> Akv,
                      Array4<Real> BC, Array4<Real> DC,
@@ -25,13 +25,6 @@ ROMSX::vert_visc_3d (const Box& phi_bx, const int ioff, const int joff,
     ParallelFor(phi_bx, [=] AMREX_GPU_DEVICE (int i, int j, int k)
     {
         Hzk(i,j,k)=0.5*(Hz(i-ioff,j-joff,k)+Hz(i,j,k));
-    });
-
-    //
-    // Define oHz = (1/Hz)
-    //
-    ParallelFor(phi_bx, [=] AMREX_GPU_DEVICE (int i, int j, int k)
-    {
         oHz(i,j,k) = 1.0/ Hzk(i,j,k);
     });
 
@@ -98,16 +91,16 @@ ROMSX::vert_visc_3d (const Box& phi_bx, const int ioff, const int joff,
     ParallelFor(makeSlab(phi_bx,2,0), [=] AMREX_GPU_DEVICE (int i, int j, int )
     {
        for(int k=0; k<=N; k++) {
-       //
-       //  Backward substitution.
-       //
-       DC(i,j,N)=0.0;
-
-       if(N-k+1<=N && N>=k) //-N,1,-1 => kidx =N-k+1
-       {
-           if(N+1<k || N+2<k) amrex::Abort("-1 here");
-           DC(i,j,N-k) -= CF(i,j,N-k)*DC(i,j,N-k+1);
-       }
+           //
+           //  Backward substitution.
+           //
+           DC(i,j,N)=0.0;
+
+           if(N-k+1<=N && N>=k) //-N,1,-1 => kidx =N-k+1
+           {
+               if(N+1<k || N+2<k) amrex::Abort("-1 here");
+               DC(i,j,N-k) -= CF(i,j,N-k)*DC(i,j,N-k+1);
+           }
        }
     });