diff --git a/.travis.yml b/.travis.yml
index cc6fc9c87..3c31cd283 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,6 +19,7 @@ install:
   - pip install pytest-ordering
   - pip install coveralls
   - pip install matplotlib
+  - pip install scipy
   - pip install beautifulsoup4
 
 script:
diff --git a/appveyor.yml b/appveyor.yml
index 9b8ae4c85..c7350e1f6 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -39,6 +39,7 @@ install:
   - python -m pip install pytest-ordering
   - python -m pip install coveralls
   - python -m pip install matplotlib
+  - python -m pip install scipy
   - python -m pip install beautifulsoup4
 
 build: false
diff --git a/gwhat/common/utils.py b/gwhat/common/utils.py
index 87d021a28..f67655475 100644
--- a/gwhat/common/utils.py
+++ b/gwhat/common/utils.py
@@ -10,6 +10,7 @@
 # ---- Imports: standard libraries
 
 import csv
+import os
 
 
 # ---- Imports: third party
@@ -39,3 +40,13 @@ def save_content_to_csv(fname, fcontent, mode='w', delimiter=','):
     with open(fname, mode) as csvfile:
         writer = csv.writer(csvfile, delimiter=delimiter, lineterminator='\n')
         writer.writerows(fcontent)
+
+
+def delete_file(filename):
+    """Try to delete a file on the disk and return the error if any."""
+    try:
+        os.remove(filename)
+        return None
+    except OSError as e:
+        print("Error: %s - %s." % (e.filename, e.strerror))
+        return e.strerror
diff --git a/gwhat/hydrograph4.py b/gwhat/hydrograph4.py
index 1553bba0d..663e61ae3 100644
--- a/gwhat/hydrograph4.py
+++ b/gwhat/hydrograph4.py
@@ -45,8 +45,7 @@
 import gwhat.common.database as db
 from gwhat.colors2 import ColorsReader
 
-mpl.use('Qt4Agg')
-mpl.rcParams['backend.qt4'] = 'PySide'
+mpl.use('Qt5Agg')
 mpl.rc('font', **{'family': 'sans-serif', 'sans-serif': ['Arial']})
 
 
diff --git a/gwhat/meteo/gapfill_weather_algorithm2.py b/gwhat/meteo/gapfill_weather_algorithm2.py
index 7b5520efe..38af2dbaf 100644
--- a/gwhat/meteo/gapfill_weather_algorithm2.py
+++ b/gwhat/meteo/gapfill_weather_algorithm2.py
@@ -145,7 +145,7 @@ def load_data(self):
         if not os.path.exists(binfile):
             return self.reload_data()
 
-        # ---- Scan input folder for changes ----------------------------------
+        # ---- Scan input folder for changes
 
         # If one of the csv data file contained within the input data directory
         # has changed since last time the binary file was created, the
@@ -156,12 +156,18 @@ def load_data(self):
         fnames = A['fnames']
 
         bmtime = os.path.getmtime(binfile)
+        count = 0
         for f in os.listdir(self.inputDir):
             if f.endswith('.csv'):
+                count += 1
                 fmtime = os.path.getmtime(os.path.join(self.inputDir, f))
                 if f not in fnames or fmtime > bmtime:
                     return self.reload_data()
 
+        # Force a reload of the data if some input files were deleted.
+        if len(fnames) != count:
+            return self.reload_data()
+
         # ---- Load data from binary ------------------------------------------
 
         print('\nLoading data from binary file :\n')
@@ -183,11 +189,10 @@ def reload_data(self):
 
         n = len(paths)
         print('\n%d valid weather data files found in Input folder.' % n)
-        print('Loading data from csv files :\n')
-
+        print('Loading data from csv files...')
         self.WEATHER.load_and_format_data(paths)
         self.WEATHER.save_to_binary(self.inputDir)
-
+        print('Data loaded sucessfully.')
         self.WEATHER.generate_summary(self.outputDir)
         self.TARGET.index = -1
 
@@ -1434,7 +1439,6 @@ def load_and_format_data(self, paths):
 
             # Check if data are continuous over time. If not, the serie will be
             # made continuous and the gaps will be filled with nan values.
-            print(reader[0][1])
 
             time_start = xldate_from_date_tuple((STADAT[0, 0].astype('int'),
                                                  STADAT[0, 1].astype('int'),
@@ -1446,9 +1450,6 @@ def load_and_format_data(self, paths):
                                                STADAT[-1, 2].astype('int')),
                                               0)
 
-            print(time_start, time_end, len(STADAT[:, 0]))
-            print(time_end - time_start + 1)
-
             if (time_end - time_start + 1) != len(STADAT[:, 0]):
                 print('\n%s is not continuous, correcting...' % reader[0][1])
                 STADAT = self.make_timeserie_continuous(STADAT)
diff --git a/gwhat/meteo/gapfill_weather_gui.py b/gwhat/meteo/gapfill_weather_gui.py
index 2b837cc4e..c1df64f76 100644
--- a/gwhat/meteo/gapfill_weather_gui.py
+++ b/gwhat/meteo/gapfill_weather_gui.py
@@ -29,6 +29,7 @@
 
 # ---- Third party imports
 
+from PyQt5.QtCore import pyqtSlot as QSlot
 from PyQt5.QtCore import pyqtSignal as QSignal
 from PyQt5.QtCore import Qt, QThread, QDate, QRect
 from PyQt5.QtGui import QBrush, QColor, QFont, QPainter, QCursor, QTextDocument
@@ -54,6 +55,7 @@
 from gwhat.meteo.merge_weather_data import WXDataMergerWidget
 from gwhat.common import IconDB, StyleDB, QToolButtonSmall
 import gwhat.common.widgets as myqt
+from gwhat.common.utils import delete_file
 
 
 class GapFillWeatherGUI(QWidget):
@@ -82,7 +84,7 @@ def __init__(self, parent=None):
     def __initUI__(self):
         self.setWindowIcon(IconDB().master)
 
-        # ---- TOOLBAR ----
+        # ---- Toolbar at the bottom
 
         self.btn_fill = QPushButton('Fill Station')
         self.btn_fill.setIcon(IconDB().fill_data)
@@ -113,13 +115,12 @@ def __initUI__(self):
 
         widget_toolbar.setLayout(grid_toolbar)
 
-        # ----------------------------------------------------- LEFT PANEL ----
+        # ---- Target Station groupbox
 
-        # ---- Target Station ----
-
-        target_station_label = QLabel(
-                '<b>Fill data for weather station :</b>')
         self.target_station = QComboBox()
+        self.target_station.currentIndexChanged.connect(
+                self.target_station_changed)
+
         self.target_station_info = QTextEdit()
         self.target_station_info.setReadOnly(True)
         self.target_station_info.setMaximumHeight(110)
@@ -127,26 +128,38 @@ def __initUI__(self):
         self.btn_refresh_staList = QToolButtonSmall(IconDB().refresh)
         self.btn_refresh_staList.setToolTip(
             'Force the reloading of the weather data files')
-        self.btn_refresh_staList.clicked.connect(self.load_data_dir_content)
+        self.btn_refresh_staList.clicked.connect(self.btn_refresh_isclicked)
 
         btn_merge_data = QToolButtonSmall(IconDB().merge_data)
         btn_merge_data.setToolTip(
                 'Tool for merging two ore more datasets together.')
         btn_merge_data.clicked.connect(self.wxdata_merger.show)
 
+        self.btn_delete_data = QToolButtonSmall(IconDB().clear)
+        self.btn_delete_data.setEnabled(False)
+        self.btn_delete_data.setToolTip(
+                'Remove the currently selected dataset and delete the input '
+                'datafile. However, raw datafiles will be kept.')
+        self.btn_delete_data.clicked.connect(self.delete_current_dataset)
+
+        widgets = [self.target_station, self.btn_refresh_staList,
+                   btn_merge_data, self.btn_delete_data]
+
         # Generate the layout for the target station group widget.
 
         self.tarSta_widg = QWidget()
         tarSta_grid = QGridLayout(self.tarSta_widg)
 
         row = 0
-        tarSta_grid.addWidget(target_station_label, row, 0, 1, 3)
-        row = 1
-        tarSta_grid.addWidget(self.target_station, row, 0)
-        tarSta_grid.addWidget(self.btn_refresh_staList, row, 1)
-        tarSta_grid.addWidget(btn_merge_data, row, 2)
-        row = 2
-        tarSta_grid.addWidget(self.target_station_info, row, 0, 1, 3)
+        tarSta_grid.addWidget(QLabel('<b>Fill data for weather station :</b>'),
+                              row, 0, 1, len(widgets))
+        row += 1
+        tarSta_grid.addWidget(self.target_station, 1, 0)
+        for col, widget in enumerate(widgets):
+            tarSta_grid.addWidget(widget, row, col)
+        row += 1
+        tarSta_grid.addWidget(self.target_station_info,
+                              row, 0, 1, len(widgets))
 
         tarSta_grid.setSpacing(5)
         tarSta_grid.setColumnStretch(0, 500)
@@ -314,7 +327,7 @@ def advanced_settings(self):
         self.stack_widget.addItem(MLRM_widg, 'Regression Model :')
         self.stack_widget.addItem(advanced_widg, 'Advanced Settings :')
 
-        # SUBGRIDS ASSEMBLY :
+        # ---- LEFT PANEL
 
         grid_leftPanel = QGridLayout()
         self.LEFT_widget = QFrame()
@@ -340,7 +353,7 @@ def advanced_settings(self):
 
         self.LEFT_widget.setLayout(grid_leftPanel)
 
-        # ---- Right Panel ----
+        # ---- Right Panel
 
         self.FillTextBox = QTextEdit()
         self.FillTextBox.setReadOnly(True)
@@ -382,7 +395,7 @@ def advanced_settings(self):
 #        RIGHT_widget.addTab(self.gafill_display_table,
 #                            'New Table (Work-in-Progress)')
 
-        # ---- Main grid ----
+        # ---- Main grid
 
         grid_MAIN = QGridLayout()
 
@@ -397,17 +410,16 @@ def advanced_settings(self):
 
         self.setLayout(grid_MAIN)
 
-        # ---- Progress Bar ----
+        # ---- Progress Bar
 
         self.pbar = QProgressBar()
         self.pbar.setValue(0)
         self.pbar.hide()
 
-        # ---- Events ----
+        # ---- Events
 
         # CORRELATION :
 
-        self.target_station.currentIndexChanged.connect(self.correlation_UI)
         self.distlimit.valueChanged.connect(self.correlation_table_display)
         self.altlimit.valueChanged.connect(self.correlation_table_display)
         self.date_start_widget.dateChanged.connect(
@@ -439,14 +451,32 @@ def set_workdir(self, dirname):
 
         self.wxdata_merger.set_workdir(os.path.join(dirname, 'Meteo', 'Input'))
 
-    # =========================================================================
+    def delete_current_dataset(self):
+        """
+        Delete the current dataset source file and force a reload of the input
+        daily weather datafiles.
+        """
+        current_index = self.target_station.currentIndex()
+        if current_index != -1:
+            basename = self.gapfill_worker.WEATHER.fnames[current_index]
+            dirname = self.gapfill_worker.inputDir
+            filename = os.path.join(dirname, basename)
+            delete_file(filename)
+            self.load_data_dir_content(reload=True)
+
+    def btn_refresh_isclicked(self):
+        """
+        Handles when the button to refresh the list of input daily weather
+        datafiles is clicked
+        """
+        self.load_data_dir_content(reload=True)
 
-    def load_data_dir_content(self):
-        '''
+    def load_data_dir_content(self, reload=False):
+        """
         Initiate the loading of Weater Data Files contained in the
-        */Meteo/Input* folder and display the resulting station list in the
-        *Target station* combo box widget.
-        '''
+        */Meteo/Input folder and display the resulting station list in the
+        target station combobox.
+        """
 
         # Reset UI :
 
@@ -460,10 +490,11 @@ def load_data_dir_content(self):
         self.CORRFLAG = 'off'
         # Correlation calculation won't be triggered when this is off
 
-        if self.sender() == self.btn_refresh_staList:
+        if reload:
             stanames = self.gapfill_worker.reload_data()
         else:
             stanames = self.gapfill_worker.load_data()
+
         self.target_station.addItems(stanames)
         self.target_station.setCurrentIndex(-1)
         self.sta_display_summary.setHtml(self.gapfill_worker.read_summary())
@@ -535,16 +566,20 @@ def correlation_table_display(self):  # ===================================
             self.FillTextBox.setText(table)
             self.target_station_info.setText(target_info)
 
-    def correlation_UI(self):  # ==============================================
+    @QSlot(int)
+    def target_station_changed(self, index):
+        """Handles when the target station is changed on the GUI side."""
+        self.btn_delete_data.setEnabled(index != -1)
+        if index != -1:
+            self.correlation_UI()
 
+    def correlation_UI(self):
         """
         Calculate automatically the correlation coefficients when a target
         station is selected by the user in the drop-down menu or if a new
         station is selected programmatically.
         """
-
         if self.CORRFLAG == 'on' and self.target_station.currentIndex() != -1:
-
             index = self.target_station.currentIndex()
             self.gapfill_worker.set_target_station(index)
 
@@ -1529,8 +1564,7 @@ def sizeHint(self):
         app.setFont(QFont('Ubuntu', 11))
 
     w = GapFillWeatherGUI()
-    w.set_workdir("C:\\Users\\jsgosselin\\OneDrive\\WHAT"
-                  "\\WHAT\\tests\\@ new-prô'jèt!")
+    w.set_workdir("C:\\Users\\jsgosselin\\OneDrive\\GWHAT\\Projects\\Example")
     w.load_data_dir_content()
 
     lat = w.gapfill_worker.WEATHER.LAT
diff --git a/gwhat/tests/test_gapfill_weather_data.py b/gwhat/tests/test_gapfill_weather_data.py
new file mode 100644
index 000000000..11798d608
--- /dev/null
+++ b/gwhat/tests/test_gapfill_weather_data.py
@@ -0,0 +1,86 @@
+# -*- coding: utf-8 -*-
+"""
+Created on Fri Aug  4 01:50:50 2017
+@author: jsgosselin
+"""
+
+# Standard library imports
+import sys
+import os
+
+# Third party imports
+import numpy as np
+from numpy import nan
+import pytest
+from PyQt5.QtCore import Qt
+
+# Local imports
+sys.path.append(os.path.dirname(os.path.dirname(os.path.realpath(__file__))))
+from gwhat.meteo.gapfill_weather_gui import GapFillWeatherGUI
+
+
+# Qt Test Fixtures
+# --------------------------------
+
+
+working_dir = os.path.join(os.getcwd(), "@ new-prô'jèt!")
+
+
+@pytest.fixture
+def gapfill_weather_bot(qtbot):
+    gapfiller = GapFillWeatherGUI()
+    gapfiller.set_workdir(working_dir)
+    qtbot.addWidget(gapfiller)
+
+    return gapfiller, qtbot
+
+
+# Test RawDataDownloader
+# -------------------------------
+
+expected_results = ["IBERVILLE", "IBERVILLE (1)",
+                    "L'ACADIE", "L'ACADIE (1)",
+                    "MARIEVILLE", "MARIEVILLE (1)",
+                    "Station 1", "Station 1 (1)"]
+
+
+@pytest.mark.run(order=5)
+def test_refresh_data(gapfill_weather_bot, mocker):
+    gapfiller, qtbot = gapfill_weather_bot
+    gapfiller.show()
+
+    # Load the input weather datafiles and assert that the list is loaded and
+    # displayed as expected.
+    qtbot.mouseClick(gapfiller.btn_refresh_staList, Qt.LeftButton)
+
+    results = []
+    for i in range(gapfiller.target_station.count()):
+        results.append(gapfiller.target_station.itemText(i))
+
+    assert expected_results == results
+
+
+@pytest.mark.run(order=5)
+def test_delete_data(gapfill_weather_bot, mocker):
+    gapfiller, qtbot = gapfill_weather_bot
+    gapfiller.show()
+
+    # Load the input weather datafiles and select the last one in the list.
+    qtbot.mouseClick(gapfiller.btn_refresh_staList, Qt.LeftButton)
+    last_index = gapfiller.target_station.count()-1
+    gapfiller.target_station.setCurrentIndex(last_index)
+    assert gapfiller.target_station.currentText() == expected_results[-1]
+
+    # Delete the currently selected dataset.
+    qtbot.mouseClick(gapfiller.btn_delete_data, Qt.LeftButton)
+
+    results = []
+    for i in range(gapfiller.target_station.count()):
+        results.append(gapfiller.target_station.itemText(i))
+
+    assert expected_results[:-1] == results
+
+
+if __name__ == "__main__":
+    pytest.main([os.path.basename(__file__)])
+    # pytest.main()
diff --git a/runtests.py b/runtests.py
index 910631f4a..2eb69824c 100644
--- a/runtests.py
+++ b/runtests.py
@@ -9,6 +9,8 @@
 """
 
 import pytest
+import matplotlib as mpl
+mpl.use('Qt5Agg')
 
 
 def main():