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ANNUAL CLIMATIC SUMMARY FOR GREAT FALLS
NATIONAL WEATHER SERVICE GREAT FALLS MT
700 PM MST SAT JAN 1 2000 
 
   
ANNUAL WEATHER SUMMARY FOR GREAT FALLS, 1999
 
MONTH  HIGH LOW AVG   DEP  PRECIP    DEP  SNOW  DEP   HDD   CDD
                      NOR  LIQUID         FALL         
 
JAN    52   -14 27.4  +6.2  0.33    -0.58  9.4  -0.5  1156    0
FEB    59     4 34.5  +7.1  0.36    -0.21  7.0  -1.4   846    0
MAR    73    10 37.8   4.5  0.53    -0.57 10.0  +0.4   839    0
APR    75     5 39.9  -3.7  1.43    +0.02  8.4  -1.2   746    0
MAY    86    21 49.7  -3.4  2.29    -0.23  2.8  +1.6   473    4
JUN    86    31 57.8  -3.8  1.74    -0.65  0.0  -0.2   222    9
JUL    99    36 63.6  -4.6  0.63    -0.61  0.0   0.0   115   80
AUG    97    38 68.0  +1.1  2.08    +0.54  0.0   0.0    30  131
SEP    86    27 52.5  -4.1  1.83    +0.59  0.6  -1.2   372    3
OCT    77    17 46.7  -0.8  0.67    -0.11  5.4  +1.6   561   18
NOV    76    16 43.3  +9.7  0.46    -0.20  1.7  -6.7   642    0
DEC    58    13 35.2 +11.3  0.03    -0.60  0.2  -9.7   919    0
YEAR   99   -14 46.3  +1.5 12.38    -2.83 45.5 -17.2  6921  227
                                                      -820 -161
 
THE FIRST THREE MONTHS OF THE YEAR WERE WARMER AND DRIER THEN NORMAL AS
A BROAD UPPER LEVEL RIDGE DOMINATED THE WEATHER OVER THE WESTERN UNITED
STATES.
 
FEBRUARY TURNED OUT TO BE A WARM...DRY AND WINDY MONTH. WIT A MEAN WIND
SPEED OF 17.2 MPH...IT WAS THE WINDIEST FEBRUARY SINCE 1976 AND THE
WINDIEST MONTH SINCE JANUARY 1992.
MARCH WAS DRIER AND WARMER THAN USUAL. ALTHOUGH THE MONTH ENDED WITH A
RECORD 24 HOUR PRECIPITATION TOTAL ON THE 31ST OF 0.44 INCHES...AND A
RECORD 24 HOUR SNOWFALL TOTAL OF 8.1 INCHES...GREAT FALLS WAS ABOUT ONE-
HALF INCH OF PRECIPITATION BELOW NORMAL. WITH A FAIRLY PERSISTENT HIGH
PRESSURE RIDGE OVER MONTANA DURING THE MONTH...TEMPERATURES WERE ALMOST
5 DEGREES ABOVE NORMAL.
DURING APRIL...THERE WERE 8.4 INCHES OF SNOW...WHICH WAS 1.2 INCHES
BELOW NORMAL. FOR THE 1998-1999 SEASON...GREAT FALLS RECEIVED 48.8
INCHES. A LARGE COLD UPPER LEVEL LOW PRESSURE SYSTEM PERSISTED OVER THE
WESTERN U.S. FOR MOST OF THE MONTH...RESULTING IN THE COOLER THAN NORMAL
TEMPERATURES. 
IN MAY...COOL AND DRY CONDITIONS PREVAILED IN THE GREAT FALLS AREA.
TEMPERATURES AVERAGED 3.4 DEGREES BELOW NORMAL. LACK OF PRECIPITATION
MADE MAY 1999 THE 7TH DRIEST MAY IN HISTORY...BUT A MOIST MEMORIAL DAY
WEEKEND PUSHED THE MONTHLY TOTAL UP TO JUST SHY OF ONE-QUARTER OF AN
INCH BELOW NORMAL. 
COOL AND DRY CONDITIONS WERE PREVALENT IN THE GREAT FALLS AREA DURING
THE MONTH OF JUNE. TEMPERATURES WERE 3.8 DEGREES BELOW NORMAL FOR THE
MONTH. TWO RECORD LOWS WERE SET DURING JUNE. ON THE 10TH...THE LOW WAS
31 DEGREES...BREAKING THE OLD RECORD OF 37 SET BACK IN 1995 AND ON THE
26TH...THE LOW WAS 36...CLIPPING THE OLD RECORD OF 37 SET BACK IN 1951.
PRECIPITATION WAS TWO THIRDS OF AN INCH BELOW NORMAL. 
COOL...DRY CONDITIONS WERE OBSERVED IN THE GREAT FALLS AREA DURING JULY.
SEVERAL RECORD LOWS WERE ESTABLISHED AS A SERIES OF COLD CANADIAN AIR
MASSES MOVED INTO MONTANA. THIS RESULTED IN JULY 1999 AS THE FOURTH
COLDEST JULY ON RECORD. ONLY 51 PERCENT OF THE NORMAL PRECIPITATION FOR
JULY WAS RECORDED...LEAVING THE YEAR TO DATE TOTAL WATER EQUIVALENT AT
28 PERCENT OF NORMAL. 
OVERALL...AUGUST TURNED OUT TO BE A NEAR NORMAL MONTH IN TERMS OF
PRECIPITATION AND TEMPERATURES. THE AVERAGE TEMPERATURE WAS ONLY ABOUT 1
DEGREE ABOVE NORMAL...WHILE PRECIPITATION WAS ABOUT ONE-HALF INCH ABOVE
NORMAL. A COUPLE OF RECORDS WERE SET DURING THE MONTH. ON AUGUST 1ST...A
RECORD LOW OF 38 DEGREES WAS SET...WHILE A NEW RECORD HIGH OF 97 DEGREES
WAS TIED ON AUGUST 30TH. 
FOR SEPTEMBER...DURING THE FIRST FEW DAYS...A LARGE UPPER LEVEL LOW
PRESSURE SYSTEM ENTERED MONTANA FROM THE WEST AS A COLD CANADIAN AIRMASS
SETTLED EAST OF THE DIVIDE. COPIOUS MOISTURE ASSOCIATED WITH THESE
FEATURES RESULTED IN 1.22 INCHES OF RAINFALL ON THE 2ND AND 3RD. COOL
AIR PREVAILED DURING THE MONTH...GIVING GREAT FALLS AN AVERAGE MONTHLY
TEMPERATURE OF 4.1 DEGREES BELOW NORMAL. MUCH NEEDED PRECIPITATION DID
FALL. GREAT FALLS RECEIVED 48 PERCENT ABOVE THE NORMAL PRECIPITATION FOR
THE MONTH...YET THE YEAR TO DATE TOTAL WAS STILL 1.70 INCHES BELOW
NORMAL. 
OCTOBER WAS GENERALLY COOLER AND DRIER THAN NORMAL. A COLD AIRMASS
AFFECTED THE AREA ON THE 2ND AND 3RD...RESULTING IN A RECORD LOW
TEMPERATURE ON THE 3RD. THE LOW OF 17 DEGREES BROKE THE PREVIOUS RECORD
OF 24 SET IN 1957. WITH THIS SYSTEM...2.1 INCHES OF SNOW FELL. A COLD
FRONT MOVING THROUGH ON THE 26 AND 27TH PRODUCED 49 HUNDREDTHS /0.49/ OF
AN INCH OF MOISTURE ALONG WITH 3.3 INCHES OF SNOW FALL. 
A FAIRLY PERSISTENT UPPER LEVEL RIDGE OF HIGH PRESSURE DOMINATED THE
WEATHER PATTERN OVER MONTANA FOR MUCH OF NOVEMBER. THIS RESULTED IN
TEMPERATURES WELL ABOVE NORMAL FOR THE MONTH...ALONG WITH BELOW NORMAL
PRECIPITATION AMOUNTS. IN FACT...THE AVERAGE TEMPERATURE WAS ALMOST 10
DEGREES WARMER THAN NORMAL. FIVE RECORD HIGH TEMPERATURES WERE RECORDED
DURING THE MONTH...76 ON THE 7TH...69 ON THE 5TH...74 ON THE 12TH...71
ON THE 14TH...AND 63 ON THE 30TH. IN ADDITION...THE RECORD HIGH OF 76 ON
THE 7TH TIED THE ALL TIME RECORD HIGH TEMPERATURE FOR THE MONTH OF
NOVEMBER...PREVIOUSLY RECORDED IN 1975. MEASURABLE PRECIPITATION WAS
ONLY REPORTED ON THREE DAYS...THE 18TH...25TH...AND 26TH. WIND-WISE...A
NOTABLE RECORD WAS SET THIS MONTH. A MEAN DAILY WIND SPEED OF ZERO MPH
ON THE 27TH SET A RECORD AS TE CALMEST DAY SINCE WIND RECORDS BEGAN IN
1942. THE OLD RECORD WAS 0.6 MPH SET THREE YEARS EARLIER.

THE UPPER LEVEL RIDGE OF HIGH PRESSURE CONTINUED TO DOMINATE THE WEATHER
FOR MUCH OF DECEMBER. THIS ALLOWED FOR VERY MILD TEMPERATURES TO
CONTINUE OVER CENTRAL MONTANA...ALONG WITH VERY DRY AND WINDY
CONDITIONS. GREAT FALLS HAD THE 3RD DRIEST DECEMBER ON RECORD...ALONG
WITH THE 9TH AVERAGE WARMEST ON RECORD. ONE RECORD HIGH TEMPERATURE WAS
SET ON THE 28TH...WITH A HIGH TEMPERATURE OF 58 DEGREES. A PEAK WIND OF
67 MPH ON TE 16TH SET A NEW RECORD FOR THE DATE. THIS WAS THE STRONGEST
WIND RECORDED IN DECEMBER SINCE 1980. ALSO...THIS WAS THE STRONGEST WIND
SPEED AT GREAT FALLS SINCE 70 MPH WAS SEEN IN OCTOBER 1991. 
 




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