Climatological Report (Monthly)
Issued by NWS Boise, ID

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CXUS55 KBOI 020037
CLMBOI

CLIMATE REPORT...CORRECTED TO ADD NARRATIVE
NATIONAL WEATHER SERVICE BOISE ID
1141 AM MST SUN JAN 1 2017

...................................

...THE BOISE ID CLIMATE SUMMARY FOR THE MONTH OF DECEMBER 2016...

DECEMBER 2016 WAS THE 5TH COLDEST AT THE AIRPORT, WHERE RECORDS GO
BACK TO 1940. ONLY 1983 THROUGH 1985 AND 1990 HAD COLDER DECEMBERS.
FOR THE GREATER BOISE AREA, GOING BACK TO 1864, IT RANKS NUMBER 7.

DURING THE FIRST 15 DAYS OF DECEMBER, HALF THE DAYS HAD ABOVE NORMAL
TEMPERATURES. THERE WAS ONE COLD SPELL FROM 5TH THROUGH THE 9TH,
WHEN A BRIEF INVASION OF ARCTIC AIR RESULTED IN LOWS IN THE TEENS
AND HIGHS BELOW FREEZING. THIS PREVIEWED WHAT WAS TO COME DURING THE
LAST HALF OF THE MONTH.

STARTING ON THE 10TH, WESTERLY FLOW ALOFT BROUGHT MILDER PACIFIC
AIR, WITH HIGHS IN THE MID 30S TO LOWER 40S.

ON THE MORNING OF THE 14TH, A TEMPERATURE INVERSION HAD DEVELOPED,
WITH LOWS IN THE MID 20S IN THE VALLEY. MOIST AIR FLOWING OVER THE
TOP OF THE INVERSION DROPPED AROUND 2 INCHES OF SNOW ON THE VALLEY
BY THE MORNING OF THE 15TH.

BY THE 16TH, NORTHERLY FLOW OVER WESTERN CANADA SENT COLDER AIR INTO
THE INTERMOUNTAIN REGION, INSURING THAT THE SNOW IN THE BOISE AREA
WOULD NOT MELT. SNOW COVER HINDERED DAYTIME WARMING AND ENHANCED
OVERNIGHT COOLING, RESULTING IN TEMPERATURES 20 DEGREES BELOW NORMAL
ON THE 17TH AND 21 DEGREES BELOW NORMAL ON THE 18TH.

BY THE 19TH, THE PATTERN HAD SHIFTED TO WESTERLY FLOW ALOFT, BUT IT
BROUGHT ONLY SLIGHT DAYTIME WARMING TO THE VALLEY FROM THE 20TH
THROUGH THE 23RD. SIGNIFICANT WARMING WAS PREVENTED BY PERSISTENTLY
COLD NIGHTS.

ON THE 23RD AND 24TH, A STRONG AND VERY MOIST PACIFIC WEATHER SYSTEM
DUMPED 3 INCHES OF SNOW AT THE AIRPORT ON THE 23RD, AND 4.7 INCHES
ON THE 24TH. THIS SET NEW SNOWFALL RECORDS FOR BOTH DAYS. THE SNOW
DEPTH OF 9 INCHES AT THE AIRPORT ON THE 25TH WAS THE MOST SNOW ON
THE GROUND EVER RECORDED ON CHRISTMAS DAY.

THE SNOWFALLS 1.9 INCHES ON BOTH THE 14TH AND THE 16TH ALSO SET NEW
DAILY RECORDS.

FOLLOWING THIS STORM, WESTERLY FLOW ALOFT PERSISTED. WITHOUT SNOW
COVER, THIS PATTERN USUALLY BRINGS MILD TEMPERATURES, AS IT DID
EARLIER IN THE MONTH. BUT THE DEEP SNOW DURING THE LAST HALF OF THE
MONTH MAINTAINED ARCTIC-LIKE CONDITIONS.

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1875 TO 2016

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE
                                          NORMAL
.............................................................
TEMPERATURE (F)
HIGHEST            45   12/04
                        12/03
LOWEST              0   12/18
AVG. MAXIMUM     30.7              37.5    -6.8
AVG. MINIMUM     15.9              24.0    -8.1
MEAN             23.3              30.7    -7.4
DAYS MAX >= 90      0
DAYS MAX <= 32     19
DAYS MIN <= 32     30
DAYS MIN <= 0       1

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         5.96   1871
TOTALS           1.99              1.55    0.44
DAYS >= .01        13
DAYS >= .10         8
DAYS >= .50         0
DAYS >= 1.00        0
GREATEST
 24 HR. TOTAL    0.63   12/09 TO 12/10

SNOWFALL (INCHES)
TOTALS           14.0
SINCE 7/1        14.0
GREATEST
 SNOW DEPTH         9  12/25
 24 HR TOTAL      5.8  12/23 TO 12/24

DEGREE_DAYS
HEATING TOTAL    1284              1061     223     1023
 SINCE 7/1       2189              2315    -126
COOLING TOTAL       0                 0       0        0
 SINCE 1/1       1001               942      59
..............................................................

WIND (MPH)
AVERAGE WIND SPEED              5.9
RESULTANT WIND SPEED/DIRECTION   1/176
HIGHEST WIND SPEED/DIRECTION    24/300    DATE  12/16
HIGHEST GUST SPEED/DIRECTION    33/180    DATE  12/22

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM

AVERAGE RH (PERCENT)     79


-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.

$$



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