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000
CXUS55 KBOI 011940 CCA
CLMBOI

CLIMATE REPORT...CORRECTED TO ADD NARRATIVE
NATIONAL WEATHER SERVICE BOISE ID
1240 AM MST MON JAN 01 2024

...HIGHLIGHTS...

WITH AN AVERAGE TEMPERATURE OF 36.3 DEGREES, DECEMBER 2023 WAS AMONG
THE WARMEST 8% OF DECEMBERS AT THE BOISE AIRPORT AND AMONG THE
WARMEST 13% OF DECEMBERS AT ALL OFFICIAL BOISE OBSERVATION SITES.

THE MONTH`S LOW OF 21 DEGREES ON BOTH THE 24TH AND 25TH WAS THE 3RD
HIGHEST DECEMBER MINIMUM AT THE AIRPORT AND THE 4TH HIGHEST AT ALL
BOISE SITES.

THE HIGH OF 61 ON THE 5TH, A RECORD FOR THAT DATE, WAS THE 4TH
HIGHEST DECEMBER MAXIMUM AT THE AIRPORT AND THE 6TH HIGHEST AT ALL
BOISE SITES.

THE CURRENT "STRONG" EL NINO, WHICH HAD ITS BEGINNINGS LAST JUNE,
WAS LIKELY A CONTRIBUTING FACTOR.

AT THE BOISE AIRPORT, ABOVE-NORMAL DECEMBER MONTHLY AVERAGE
TEMPERATURES WERE OBSERVED DURING 47% OF EL NINOS, 25% OF WHICH ARE
CLASSIFIED AS "STRONG" (AVERAGE SEA-SURFACE TEMPERATURES IN THE
EQUATORIAL PACIFIC AT LEAST 1.5 DEGREES CELSIUS ABOVE NORMAL).

PRECIPITATION AT THE AIRPORT WAS .03 INCH BELOW NORMAL.

AT THE AIRPORT (SINCE 1940), ABOVE-NORMAL DECEMBER PRECIPITATION
OCCURRED DURING 47% OF EL NINOS, 23% OF WHICH WERE "STRONG".

SNOWFALL TOTALED 3.8 INCHES. NORMAL IS 5.5 INCHES. THE GREATEST
DEPTH WAS 2 INCHES ON THE MORNINGS OF THE 1ST AND 2ND. AN INCH
ACCUMULATED BY MIDDAY ON THE 26TH BEFORE MOSTLY MELTING.

TEMPERATURE INVERSIONS PLAGUED THE VALLEY DURING ALMOST HALF THE
DAYS OF THE MONTH. THE WORST EPISODE PERSISTED FROM THE 16TH THROUGH
THE 22ND.

FOG WAS OBSERVED ON 15 DAYS, AND DENSE FOG (VISIBILITY LESS THAN OR
EQUAL TO 1/4 MILE) OCCURRED ON 8 OF THOSE DAYS.

FOG AND LOW STRATUS LIMITED DAYTIME HIGHS. AT BOISE THERE WAS
USUALLY SOME AFTERNOON CLEARING, ALLOWING TEMPERATURES TO RISE ABOVE
NORMAL. BUT WITH A HIGH OF ONLY 30, THE 17TH WAS THE ONLY DAY WHEN
THE AIRPORT TEMPERATURE FAILED TO RISE ABOVE FREEZING.

...SYNOPSIS...

WEATHER SYSTEMS SWEEPING IN FROM THE PACIFIC BROUGHT NEARLY AN INCH
OF PRECIPITATION IN THE FORM OF RAIN AND SNOW FROM THE 1ST THROUGH
THE NIGHT OF THE 3RD.

A HIGH PRESSURE RIDGE BUILT OVER THE REGION ON THE 4TH AND SHIFTED
EAST OVER THE CONTINENTAL DIVIDE BY THE 5TH, PUTTING BOISE UNDER
SOUTHWEST FLOW ALOFT. THAT PATTERN, PLUS MOSTLY SUNNY SKIES,
RESULTED IN THE HIGH OF 61 ON THE 5TH.

AS THE RIDGE EXITED EAST OF THE ROCKIES, AN UPPER LEVEL TROUGH
PUSHED INLAND ON THE 7TH, PROVIDING BOISE WITH OVER A QUARTER INCH
OF RAN AND A TRACE OF SNOW. COLDER AIR FROM THE GULF OF ALASKA
FOLLOWED, RESULTING IN A HIGH OF 39 (CLOSE TO NORMAL) ON THE 9TH.

ON THE 10TH AND 11TH, A WEAK DISTURBANCE BROUGHT LIGHT RAIN AND
SNOW, ALONG WITH SLIGHTLY WARMER AIR.

THAT SYSTEM HEADED SOUTH AS A RIDGE BUILT OVER THE PACIFIC NORTHWEST
ON THE 12TH.

THE RIDGE KEPT OUR WEATHER DRY, BUT WARM AIR ALOFT CAPPING COOL
MOIST AIR IN THE VALLEY RESULTED IN THE WEEK-LONG TEMPERATURE
INVERSION WHICH STARTED ON THE 16TH.

LATE ON THE 22ND, A TROUGH FROM THE GULF OF ALASKA PROVIDED ENOUGH
COOLING ALOFT AND WIND AT THE SURFACE TO BREAK THE INVERSION.

ANOTHER RIDGE BUILT OVER THE WEST COAST ON THE 23RD AND KEPT SKIES
MOSTLY CLEAR WITH TEMPERATURES NEAR NORMAL ON THE 24TH AND 25TH.

ON THE 26TH, A WEAKENING DISTURBANCE MOVING INTO THE RIDGE FROM THE
WEST WAS DEFLECTED INTO CANADA, BUT IT CAME CLOSE ENOUGH TO GIVE
BOISE AN INCH OF SNOW ON THE 26TH.

FOR THE REST OF THE MONTH, THE RIDGE SUCCESSFULLY BLOCKED ONCOMING
SYSTEMS, ALLOWING ONLY A FEW HIGH CLOUDS TO REACH THE TREASURE
VALLEY. TEMPERATURES AVERAGED 5-10 DEGREES ABOVE NORMAL FROM THE
27TH THROUGH THE 31ST.

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

...THE BOISE ID CLIMATE SUMMARY FOR THE MONTH OF DECEMBER 2023...

CLIMATE NORMAL PERIOD 1991 TO 2020
CLIMATE RECORD PERIOD 1875 TO 2023

WEATHER         OBSERVED          NORMAL  DEPART   LAST YEAR`S
                VALUE   DATE(S)   VALUE   FROM     VALUE
                                          NORMAL
..............................................................
TEMPERATURE (F)
HIGHEST           61   12/05
LOWEST            21   12/24
                       12/25
AVG. MAXIMUM    42.3               38.8     3.5
AVG. MINIMUM    30.2               25.4     4.8
MEAN            36.3               32.1     4.2
DAYS MAX >= 90     0
DAYS MAX <= 32     2
DAYS MIN <= 32    22
DAYS MIN <= 0      0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM        5.96   1871
TOTALS          1.51               1.54   -0.03
DAYS >= .01       11
DAYS >= .10        5
DAYS >= .50        0
DAYS >= 1.00       0
GREATEST
 24 HR. TOTAL   0.46   12/02 TO 12/03

SNOWFALL (INCHES)
TOTALS           3.8
SINCE 7/1        3.9
GREATEST
 SNOW DEPTH        2   12/02
 24 HR TOTAL     2.5   12/01 TO 12/01

DEGREE DAYS
HEATING TOTAL    858               1020    -162     1102
 SINCE 7/1      1845               2231    -386
COOLING TOTAL      0                  0       0        0
 SINCE 1/1      1342               1044     298
..............................................................

WIND (MPH)
AVERAGE WIND SPEED              5.6
HIGHEST WIND SPEED/DIRECTION    24/300    DATE  12/07
HIGHEST GUST SPEED/DIRECTION    33/300    DATE  12/07

AVERAGE RH (PERCENT)     77


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

$$