diff --git a/.gitmodules b/.gitmodules
index bb3e3a50a..1325b4228 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -20,7 +20,7 @@
 [submodule "ncar-physics"]
         path          = src/physics/ncar_ccpp
 	url           = https://github.com/ESCOMP/atmospheric_physics
-	fxtag         = 26f4f553da47fc4b347f0ee80ea1041dd0da7988
+	fxtag         = d2e6f343356f02229bcc66427d300e578e09c64f
         fxrequired    = AlwaysRequired
         fxDONOTUSEurl = https://github.com/ESCOMP/atmospheric_physics
 [submodule "rrtmgp-data"]
diff --git a/cime_config/testdefs/testlist_cam.xml b/cime_config/testdefs/testlist_cam.xml
index 5b1f8c55d..4681270a8 100644
--- a/cime_config/testdefs/testlist_cam.xml
+++ b/cime_config/testdefs/testlist_cam.xml
@@ -88,6 +88,15 @@
       <option name="comment">Test for Holtslag-Boville boundary layer scheme and vertical diffusion</option>
     </options>
   </test>
+  <test compset="FPHYStest" grid="ne3pg3_ne3pg3_mg37" name="SMS_Ln2" testmods="cam/outfrq_uw_vdiff_derecho">
+    <machines>
+      <machine name="derecho" compiler="gnu" category="aux_sima"/>
+    </machines>
+    <options>
+      <option name="wallclock">00:10:00</option>
+      <option name="comment">Test for Bretherton-Park (UW) boundary layer scheme and vertical diffusion</option>
+    </options>
+  </test>
   <test compset="FPHYStest" grid="ne3pg3_ne3pg3_mg37" name="SMS_Ln2" testmods="cam/outfrq_gw_cam4_derecho">
     <machines>
       <machine name="derecho" compiler="gnu" category="aux_sima"/>
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq_hb_vdiff_derecho/user_nl_cam b/cime_config/testdefs/testmods_dirs/cam/outfrq_hb_vdiff_derecho/user_nl_cam
index 82e619371..6831304d1 100644
--- a/cime_config/testdefs/testmods_dirs/cam/outfrq_hb_vdiff_derecho/user_nl_cam
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq_hb_vdiff_derecho/user_nl_cam
@@ -1,6 +1,6 @@
 ! these are FHIST_C4 snapshots
-ncdata = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhistc4_vertical_diffusion_hb_snapshot_derecho_gnu_before_c20250717.nc'
-ncdata_check = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhistc4_vertical_diffusion_hb_snapshot_derecho_gnu_after_c20250717.nc'
+ncdata = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhistc4_vertical_diffusion_hb_snapshot_derecho_gnu_before_c20260609.nc'
+ncdata_check = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhistc4_vertical_diffusion_hb_snapshot_derecho_gnu_after_c20260609.nc'
 
 ! tolerances for testing
 ncdata_check_err = .true.
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/shell_commands b/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/shell_commands
new file mode 100644
index 000000000..c409a410f
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/shell_commands
@@ -0,0 +1 @@
+ ./xmlchange CAM_CONFIG_OPTS="--dyn none --physics-suites vdiff_bretherton_park"
diff --git a/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/user_nl_cam b/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/user_nl_cam
new file mode 100644
index 000000000..cfecff331
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/cam/outfrq_uw_vdiff_derecho/user_nl_cam
@@ -0,0 +1,45 @@
+! these are FHIST_C5 snapshots
+ncdata = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhist_c5_vertical_diffusion_uw_snapshot_derecho_gnu_before_c20260309.nc'
+ncdata_check = '/glade/campaign/cesm/community/amwg/sima_baselines/cam_sima_test_snapshots/cam_ne3pg3_fhist_c5_vertical_diffusion_uw_snapshot_derecho_gnu_after_c20260309.nc'
+
+! tolerances for testing
+ncdata_check_err = .true.
+min_difference = 2e-15
+
+! cam5 vertical levels.
+pver = 30
+
+! namelist options for CAM5 UW PBL.
+am_correction = .false.
+do_iss = .true.
+eddy_lbulk_max = 40.D3
+eddy_leng_max = 40.D3
+eddy_max_bot_pressure = 100.D3
+eddy_moist_entrain_a2l = 30.D0
+eddy_wstarent = .true.
+kv_freetrop_scale = 1.D0
+kv_top_pressure = 0.D0
+kv_top_scale = 1.D0
+
+! history output
+hist_output_frequency;h1: 1*nsteps
+hist_max_frames;h1: 1
+hist_add_inst_fields;h1:WGUSTD,UW_errorPBL,UW_pblh,UW_pblhp
+hist_add_inst_fields;h1:UW_tpert,UW_qpert,UW_wpert,UW_ustar
+hist_add_inst_fields;h1:UW_tkes,UW_minpblh
+hist_add_inst_fields;h1:UW_ncvfin_o,UW_ncvfin_mg,UW_ncvfin_f
+hist_add_inst_fields;h1:UW_n2,UW_s2,UW_ri
+hist_add_inst_fields;h1:UW_sfuh,UW_sflh,UW_cldn,UW_qrl,UW_ql
+hist_add_inst_fields;h1:BPROD,SFI,SPROD
+hist_add_inst_fields;h1:UW_sfi,UW_chu,UW_chs,UW_cmu,UW_cms
+hist_add_inst_fields;h1:UW_tke,UW_wcap
+hist_add_inst_fields;h1:UW_kvh,UW_kvm,UW_turbtype
+hist_add_inst_fields;h1:UW_gh,UW_sh,UW_sm,UW_ria,UW_leng
+hist_add_inst_fields;h1:UW_kbase_o,UW_ktop_o,UW_kbase_mg,UW_ktop_mg
+hist_add_inst_fields;h1:UW_kbase_f,UW_ktop_f,UW_wet,UW_web
+hist_add_inst_fields;h1:UW_jtbu,UW_jbbu,UW_evhc,UW_jt2slv
+hist_add_inst_fields;h1:UW_n2ht,UW_n2hb,UW_lwp,UW_optdepth
+hist_add_inst_fields;h1:UW_radfrac,UW_radf,UW_wstar,UW_wstar3fact
+hist_add_inst_fields;h1:UW_ebrk,UW_wbrk,UW_lbrk
+hist_add_inst_fields;h1:UW_ricl,UW_ghcl,UW_shcl,UW_smcl,UW_wsed
+hist_precision;h1: REAL64
diff --git a/src/control/cam_comp.F90 b/src/control/cam_comp.F90
index 0930ff759..186299fc1 100644
--- a/src/control/cam_comp.F90
+++ b/src/control/cam_comp.F90
@@ -320,16 +320,6 @@ subroutine cam_timestep_init()
       is_first_timestep = is_first_step()
       nstep = get_nstep()
 
-      !----------------------------------------------------------
-      ! First phase of dynamics (at least couple from dynamics to physics)
-      ! Return time-step for physics from dynamics.
-      !----------------------------------------------------------
-      call t_barrierf('sync_stepon_timestep_init', mpicom)
-      call t_startf('stepon_timestep_init')
-      call stepon_timestep_init(dtime_phys, cam_runtime_opts, phys_state, phys_tend,   &
-           dyn_in, dyn_out)
-      call t_stopf('stepon_timestep_init')
-
       !----------------------------------------------------------
       ! TEMPORARY:  Set initial MUSICA constituent values
       !
@@ -346,6 +336,16 @@ subroutine cam_timestep_init()
               constituent_properties)
       end if
 
+      !----------------------------------------------------------
+      ! First phase of dynamics (at least couple from dynamics to physics)
+      ! Return time-step for physics from dynamics.
+      !----------------------------------------------------------
+      call t_barrierf('sync_stepon_timestep_init', mpicom)
+      call t_startf('stepon_timestep_init')
+      call stepon_timestep_init(dtime_phys, cam_runtime_opts, phys_state, phys_tend,   &
+           dyn_in, dyn_out)
+      call t_stopf('stepon_timestep_init')
+
       !
       !----------------------------------------------------------
       ! PHYS_TIMESTEP_INIT Call the Physics package
diff --git a/src/data/registry.xml b/src/data/registry.xml
index 9df2e3dbd..fd9a8aa0c 100644
--- a/src/data/registry.xml
+++ b/src/data/registry.xml
@@ -1477,6 +1477,13 @@
       <initial_value>273.15_kind_phys</initial_value>
       <ic_file_input_names>tpert pbuf_tpert</ic_file_input_names>
     </variable>
+    <variable local_name="wsedl"
+              standard_name="sedimentation_velocity_of_liquid_stratus_cloud_droplet"
+              units="m s-1" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension vertical_layer_dimension</dimensions>
+      <ic_file_input_names>pbuf_WSEDL</ic_file_input_names>
+    </variable>
 
     <!-- Temporary initializations for gravity wave parameterizations -->
     <variable local_name="ttend_clubb"
@@ -1577,6 +1584,23 @@
     </variable>
 
     <!-- vertical diffusion solver variables - need to be kept in the CAM registry -->
+    <variable local_name="kvm"
+              standard_name="eddy_momentum_diffusivity_at_interfaces"
+              units="m2 s-1" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension vertical_interface_dimension</dimensions>
+      <initial_value>0.0_kind_phys</initial_value>
+      <ic_file_input_names>pbuf_kvm</ic_file_input_names>
+    </variable>
+    <variable local_name="kvh"
+              standard_name="eddy_heat_diffusivity_at_interfaces"
+              units="m2 s-1" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension vertical_interface_dimension</dimensions>
+      <initial_value>0.0_kind_phys</initial_value>
+      <ic_file_input_names>pbuf_kvh</ic_file_input_names>
+    </variable>
+
     <variable local_name="tauresx"
               standard_name="eastward_reserved_stress_at_surface_on_previous_timestep"
               units="N m-2" type="real" kind="kind_phys"
@@ -1603,7 +1627,7 @@
     </variable>
     <!-- REMOVECAM: the final standard name for these quantities below are
          {east,north}ward_turbulent_orographic_form_drag_stress_at_surface.
-         however, it is shared with tautmsx; in order to distinguish between these two in CAM snapshots,
+         however, it is shared with tautms{x,y}; in order to distinguish between these two in CAM snapshots,
          an alternate standard name is currently used. When CAM snapshots are retired, only either
          Beljaars or TMS (which are mutually exclusive) provide the {east,north}ward_orographic_form_drag_stress_at_surface. -->
     <variable local_name="taubljx"
@@ -1622,6 +1646,36 @@
       <initial_value>0.0_kind_phys</initial_value>
       <ic_file_input_names>pbuf_taubljy</ic_file_input_names>
     </variable>
+    <!-- REMOVECAM: the final standard name for these quantities below are
+         {east,north}ward_turbulent_orographic_form_drag_stress_at_surface.
+         however, it is shared with taublj{x,y}; in order to distinguish between these two in CAM snapshots,
+         an alternate standard name is currently used. When CAM snapshots are retired, only either
+         Beljaars or TMS (which are mutually exclusive) provide the {east,north}ward_orographic_form_drag_stress_at_surface. -->
+    <variable local_name="tautmsx"
+              standard_name="eastward_turbulent_mountain_surface_stress_tbd"
+              units="N m-2" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension</dimensions>
+      <initial_value>0.0_kind_phys</initial_value>
+      <ic_file_input_names>pbuf_tautmsx</ic_file_input_names>
+    </variable>
+    <variable local_name="tautmsy"
+              standard_name="northward_turbulent_mountain_surface_stress_tbd"
+              units="N m-2" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension</dimensions>
+      <initial_value>0.0_kind_phys</initial_value>
+      <ic_file_input_names>pbuf_tautmsy</ic_file_input_names>
+    </variable>
+    <variable local_name="ksrftms"
+              standard_name="turbulent_orographic_form_drag_coefficent_at_surface"
+              units="kg s-1 m-2" type="real" kind="kind_phys"
+              allocatable="allocatable">
+      <dimensions>horizontal_dimension</dimensions>
+      <initial_value>0.0_kind_phys</initial_value>
+      <ic_file_input_names>pbuf_ksrftms</ic_file_input_names>
+    </variable>
+
     <variable local_name="apply_non_wv_cflx_in_free_atm_vdiff"
               standard_name="do_apply_ccpp_constituent_fluxes_excluding_water_vapor_in_vertical_diffusion"
               units="flag" type="logical">
diff --git a/src/dynamics/none/stepon.F90 b/src/dynamics/none/stepon.F90
index 153a7b4e6..b562cddec 100644
--- a/src/dynamics/none/stepon.F90
+++ b/src/dynamics/none/stepon.F90
@@ -37,6 +37,10 @@ subroutine stepon_timestep_init(dtime_out, cam_runtime_opts, phys_state,   &
       use time_manager,   only: get_step_size
       use cam_abortutils, only: endrun
 
+      use physics_types,  only: is_first_timestep
+      use phys_comp,      only: ncdata_check
+      use cam_initfiles,  only: unset_path_str
+
       ! Dummy arguments
       real(r8),              intent(out)   :: dtime_out  ! Time-step (s)
       type(runtime_options), intent(in)    :: cam_runtime_opts
@@ -54,6 +58,15 @@ subroutine stepon_timestep_init(dtime_out, cam_runtime_opts, phys_state,   &
          if (dtime_out <= 0)  call endrun('stepon_timestep_init: bad dtime')
       end if
 
+      if (trim(ncdata_check) /= trim(unset_path_str)) then
+         !Because when running with snapshots (using the null dycore)
+         !for snapshot validation,
+         !the snapshots are always from the second timestep onwards,
+         !override here the value of is_first_timestep to .false. as it is
+         !never truly the first timestep for the physics
+         is_first_timestep = .false.
+      end if
+
    end subroutine stepon_timestep_init
 
    !===========================================================================
diff --git a/src/physics/ncar_ccpp b/src/physics/ncar_ccpp
index 26f4f553d..d2e6f3433 160000
--- a/src/physics/ncar_ccpp
+++ b/src/physics/ncar_ccpp
@@ -1 +1 @@
-Subproject commit 26f4f553da47fc4b347f0ee80ea1041dd0da7988
+Subproject commit d2e6f343356f02229bcc66427d300e578e09c64f
diff --git a/src/physics/utils/physics_data.F90 b/src/physics/utils/physics_data.F90
index 155afc18d..67eb78919 100644
--- a/src/physics/utils/physics_data.F90
+++ b/src/physics/utils/physics_data.F90
@@ -589,6 +589,16 @@ subroutine read_constituent_dimensioned_field_2d(const_props, file, std_name, ba
          var_found = .false.
          call cam_pio_find_var(file, [file_var_name], found_name, vardesc, var_found)
 
+         ! Some constituents whose names are not specified in the registry
+         ! will have cnst_ prepended to them (e.g., cnst_dst_a1); also try reading
+         ! from file by removing this prefix:
+         if (.not. var_found) then
+            if (constituent_name(1:5) == 'cnst_') then
+               file_var_name = trim(base_var_names(base_idx)) // '_' // trim(constituent_name(6:))
+               call cam_pio_find_var(file, [file_var_name], found_name, vardesc, var_found)
+            end if
+         end if
+
          if (var_found) then
             ! Read the variable
             if (masterproc) then
diff --git a/test/existing-test-failures.txt b/test/existing-test-failures.txt
index 1b9153871..06a8c5afd 100644
--- a/test/existing-test-failures.txt
+++ b/test/existing-test-failures.txt
@@ -2,7 +2,7 @@ SMS_Ln9.ne3pg3_ne3pg3_mg37.FKESSLER.derecho_intel.cam-outfrq_se_cslam_multitape
   - known NLFAIL due to cime validation error on multiple history tapes (#430)
 
 SMS_Ln9.ne3pg3_ne3pg3_mg37.FADIAB.derecho_gnu.cam-outfrq_se_cslam
-  - known FAIL on shr_reprosum_calc call from src/dynamics/se/dycore/global_norms_mod.F90
+  - known FAIL on shr_reprosum_calc call due to commented out cnst_init_default (constituent default value initialization) in src/dynamics/se/dyn_comp.F90 (#509)
 
 SMS_Ln2.ne3pg3_ne3pg3_mg37.FPHYStest.derecho_gnu.cam-outfrq_zm_derecho (Overall: DIFF) details:
   - known failure due to ZM science update after merging atmos_phys #392