diff --git a/wxdata/include/scwx/wsr88d/rpg/cell_trend_data_packet.hpp b/wxdata/include/scwx/wsr88d/rpg/cell_trend_data_packet.hpp
new file mode 100644
index 00000000..071cb045
--- /dev/null
+++ b/wxdata/include/scwx/wsr88d/rpg/cell_trend_data_packet.hpp
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <scwx/wsr88d/rpg/packet.hpp>
+
+#include <cstdint>
+#include <memory>
+
+namespace scwx
+{
+namespace wsr88d
+{
+namespace rpg
+{
+
+class CellTrendDataPacketImpl;
+
+class CellTrendDataPacket : public Packet
+{
+public:
+   explicit CellTrendDataPacket();
+   ~CellTrendDataPacket();
+
+   CellTrendDataPacket(const CellTrendDataPacket&) = delete;
+   CellTrendDataPacket& operator=(const CellTrendDataPacket&) = delete;
+
+   CellTrendDataPacket(CellTrendDataPacket&&) noexcept;
+   CellTrendDataPacket& operator=(CellTrendDataPacket&&) noexcept;
+
+   uint16_t    packet_code() const;
+   uint16_t    length_of_block() const;
+   std::string cell_id() const;
+   int16_t     i_position() const;
+   int16_t     j_position() const;
+   uint16_t    number_of_trends() const;
+   uint16_t    trend_code(uint16_t t) const;
+   uint8_t     number_of_volumes(uint16_t t) const;
+   uint8_t     latest_volume_pointer(uint16_t t) const;
+   uint16_t    trend_data(uint16_t t, uint8_t v) const;
+
+   size_t data_size() const override;
+
+   bool Parse(std::istream& is) override;
+
+   static std::shared_ptr<CellTrendDataPacket> Create(std::istream& is);
+
+private:
+   std::unique_ptr<CellTrendDataPacketImpl> p;
+};
+
+} // namespace rpg
+} // namespace wsr88d
+} // namespace scwx
diff --git a/wxdata/source/scwx/wsr88d/rpg/cell_trend_data_packet.cpp b/wxdata/source/scwx/wsr88d/rpg/cell_trend_data_packet.cpp
new file mode 100644
index 00000000..e3c5ad19
--- /dev/null
+++ b/wxdata/source/scwx/wsr88d/rpg/cell_trend_data_packet.cpp
@@ -0,0 +1,221 @@
+#include <scwx/wsr88d/rpg/cell_trend_data_packet.hpp>
+
+#include <istream>
+#include <string>
+
+#include <boost/log/trivial.hpp>
+
+namespace scwx
+{
+namespace wsr88d
+{
+namespace rpg
+{
+
+static const std::string logPrefix_ =
+   "[scwx::wsr88d::rpg::cell_trend_data_packet] ";
+
+struct CellTrendData
+{
+   uint16_t              trendCode_;
+   uint8_t               numberOfVolumes_;
+   uint8_t               latestVolumePointer_;
+   std::vector<uint16_t> trendData_;
+
+   CellTrendData() :
+       trendCode_ {0},
+       numberOfVolumes_ {0},
+       latestVolumePointer_ {0},
+       trendData_ {}
+   {
+   }
+};
+
+class CellTrendDataPacketImpl
+{
+public:
+   explicit CellTrendDataPacketImpl() :
+       packetCode_ {0},
+       lengthOfBlock_ {0},
+       cellId_ {0},
+       iPosition_ {0},
+       jPosition_ {0},
+       trendData_ {}
+   {
+   }
+   ~CellTrendDataPacketImpl() = default;
+
+   uint16_t    packetCode_;
+   uint16_t    lengthOfBlock_;
+   std::string cellId_;
+   int16_t     iPosition_;
+   int16_t     jPosition_;
+
+   std::vector<CellTrendData> trendData_;
+};
+
+CellTrendDataPacket::CellTrendDataPacket() :
+    p(std::make_unique<CellTrendDataPacketImpl>())
+{
+}
+CellTrendDataPacket::~CellTrendDataPacket() = default;
+
+CellTrendDataPacket::CellTrendDataPacket(CellTrendDataPacket&&) noexcept =
+   default;
+CellTrendDataPacket&
+CellTrendDataPacket::operator=(CellTrendDataPacket&&) noexcept = default;
+
+uint16_t CellTrendDataPacket::packet_code() const
+{
+   return p->packetCode_;
+}
+
+uint16_t CellTrendDataPacket::length_of_block() const
+{
+   return p->lengthOfBlock_;
+}
+
+std::string CellTrendDataPacket::cell_id() const
+{
+   return p->cellId_;
+}
+
+int16_t CellTrendDataPacket::i_position() const
+{
+   return p->iPosition_;
+}
+
+int16_t CellTrendDataPacket::j_position() const
+{
+   return p->iPosition_;
+}
+
+uint16_t CellTrendDataPacket::number_of_trends() const
+{
+   return static_cast<uint16_t>(p->trendData_.size());
+}
+
+uint16_t CellTrendDataPacket::trend_code(uint16_t t) const
+{
+   return p->trendData_[t].trendCode_;
+}
+
+uint8_t CellTrendDataPacket::number_of_volumes(uint16_t t) const
+{
+   return p->trendData_[t].numberOfVolumes_;
+}
+
+uint8_t CellTrendDataPacket::latest_volume_pointer(uint16_t t) const
+{
+   return p->trendData_[t].latestVolumePointer_;
+}
+
+uint16_t CellTrendDataPacket::trend_data(uint16_t t, uint8_t v) const
+{
+   return p->trendData_[t].trendData_[v];
+}
+
+size_t CellTrendDataPacket::data_size() const
+{
+   return p->lengthOfBlock_ + 4u;
+}
+
+bool CellTrendDataPacket::Parse(std::istream& is)
+{
+   bool blockValid = true;
+
+   std::streampos isBegin = is.tellg();
+
+   is.read(reinterpret_cast<char*>(&p->packetCode_), 2);
+   is.read(reinterpret_cast<char*>(&p->lengthOfBlock_), 2);
+
+   p->packetCode_    = ntohs(p->packetCode_);
+   p->lengthOfBlock_ = ntohs(p->lengthOfBlock_);
+
+   if (is.eof())
+   {
+      BOOST_LOG_TRIVIAL(debug) << logPrefix_ << "Reached end of file";
+      blockValid = false;
+   }
+   else
+   {
+      if (p->packetCode_ != 21)
+      {
+         BOOST_LOG_TRIVIAL(warning)
+            << logPrefix_ << "Invalid packet code: " << p->packetCode_;
+         blockValid = false;
+      }
+      else if (p->lengthOfBlock_ < 12 || p->lengthOfBlock_ > 198)
+      {
+         BOOST_LOG_TRIVIAL(warning)
+            << logPrefix_ << "Invalid length of block: " << p->packetCode_;
+         blockValid = false;
+      }
+   }
+
+   p->cellId_.resize(2);
+
+   is.read(p->cellId_.data(), 2);
+   is.read(reinterpret_cast<char*>(&p->iPosition_), 2);
+   is.read(reinterpret_cast<char*>(&p->jPosition_), 2);
+
+   p->iPosition_ = ntohs(p->iPosition_);
+   p->jPosition_ = ntohs(p->jPosition_);
+
+   if (blockValid)
+   {
+      size_t trendSize = p->lengthOfBlock_ - 6;
+      size_t bytesRead = 0;
+
+      while (bytesRead < trendSize)
+      {
+         CellTrendData trendData;
+
+         is.read(reinterpret_cast<char*>(&trendData.trendCode_), 2);
+         is.read(reinterpret_cast<char*>(&trendData.numberOfVolumes_), 1);
+         is.read(reinterpret_cast<char*>(&trendData.latestVolumePointer_), 1);
+
+         trendData.trendCode_ = ntohs(trendData.trendCode_);
+
+         size_t trendDataSize =
+            static_cast<size_t>(trendData.numberOfVolumes_) * 2u;
+         trendData.trendData_.resize(trendData.numberOfVolumes_);
+
+         is.read(reinterpret_cast<char*>(trendData.trendData_.data()),
+                 trendDataSize);
+
+         SwapVector(trendData.trendData_);
+
+         p->trendData_.push_back(std::move(trendData));
+
+         bytesRead += 4 + trendDataSize;
+      }
+   }
+
+   std::streampos isEnd = is.tellg();
+
+   if (!ValidateMessage(is, isEnd - isBegin))
+   {
+      blockValid = false;
+   }
+
+   return blockValid;
+}
+
+std::shared_ptr<CellTrendDataPacket>
+CellTrendDataPacket::Create(std::istream& is)
+{
+   std::shared_ptr<CellTrendDataPacket> packet =
+      std::make_shared<CellTrendDataPacket>();
+
+   if (!packet->Parse(is))
+   {
+      packet.reset();
+   }
+
+   return packet;
+}
+
+} // namespace rpg
+} // namespace wsr88d
+} // namespace scwx
diff --git a/wxdata/source/scwx/wsr88d/rpg/packet_factory.cpp b/wxdata/source/scwx/wsr88d/rpg/packet_factory.cpp
index 074888c6..cdaa0e17 100644
--- a/wxdata/source/scwx/wsr88d/rpg/packet_factory.cpp
+++ b/wxdata/source/scwx/wsr88d/rpg/packet_factory.cpp
@@ -1,5 +1,6 @@
 #include <scwx/wsr88d/rpg/packet_factory.hpp>
 
+#include <scwx/wsr88d/rpg/cell_trend_data_packet.hpp>
 #include <scwx/wsr88d/rpg/digital_precipitation_data_array_packet.hpp>
 #include <scwx/wsr88d/rpg/digital_radial_data_array_packet.hpp>
 #include <scwx/wsr88d/rpg/generic_data_packet.hpp>
@@ -59,6 +60,7 @@ static const std::unordered_map<uint16_t, CreateMessageFunction> create_ {
    {18, PrecipitationRateDataArrayPacket::Create},
    {19, HdaHailSymbolPacket::Create},
    {20, PointFeatureSymbolPacket::Create},
+   {21, CellTrendDataPacket::Create},
    {23, ScitForecastDataPacket::Create},
    {24, ScitForecastDataPacket::Create},
    {25, StiCircleSymbolPacket::Create},
diff --git a/wxdata/wxdata.cmake b/wxdata/wxdata.cmake
index aa1d2521..95263135 100644
--- a/wxdata/wxdata.cmake
+++ b/wxdata/wxdata.cmake
@@ -47,6 +47,7 @@ set(SRC_WSR88D_RDA source/scwx/wsr88d/rda/clutter_filter_map.cpp
                    source/scwx/wsr88d/rda/rda_status_data.cpp
                    source/scwx/wsr88d/rda/volume_coverage_pattern_data.cpp)
 set(HDR_WSR88D_RPG include/scwx/wsr88d/rpg/ccb_header.hpp
+                   include/scwx/wsr88d/rpg/cell_trend_data_packet.hpp
                    include/scwx/wsr88d/rpg/digital_precipitation_data_array_packet.hpp
                    include/scwx/wsr88d/rpg/digital_radial_data_array_packet.hpp
                    include/scwx/wsr88d/rpg/generic_data_packet.hpp
@@ -76,6 +77,7 @@ set(HDR_WSR88D_RPG include/scwx/wsr88d/rpg/ccb_header.hpp
                    include/scwx/wsr88d/rpg/wind_barb_data_packet.hpp
                    include/scwx/wsr88d/rpg/wmo_header.hpp)
 set(SRC_WSR88D_RPG source/scwx/wsr88d/rpg/ccb_header.cpp
+                   source/scwx/wsr88d/rpg/cell_trend_data_packet.cpp
                    source/scwx/wsr88d/rpg/digital_precipitation_data_array_packet.cpp
                    source/scwx/wsr88d/rpg/digital_radial_data_array_packet.cpp
                    source/scwx/wsr88d/rpg/generic_data_packet.cpp