Climatological Report (Monthly)
Issued by NWS Boise, ID

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CXUS55 KBOI 011729
CLMBOI

CLIMATE REPORT
NATIONAL WEATHER SERVICE BOISE ID
1124 AM MDT MON MAY 1 2017

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

...THE BOISE ID CLIMATE SUMMARY FOR THE MONTH OF APRIL 2017...

APRIL WAS CHARACTERIZED BY CHANGEABLE WEATHER TYPICAL OF SPRING.
MILD PERIODS WERE INTERRUPTED BY DAYS WITH BELOW NORMAL
TEMPERATURES. THE ONLY RECORD WAS THE UNSEASONABLY WARM LOW OF 52 ON
THE 6TH, WHICH BROKE THE OLD RECORD OF 51 SET IN 1898.

THE UNSETTLED WEATHER WAS THE RESULT OF A STEADY PROGRESSION OF
UPPER LEVEL RIDGES AND TROUGHS ACROSS THE INTERMOUNTAIN REGION.

UNSEASONABLY COLD SEA SURFACE TEMPERATURES AND COLD AIR ALOFT
RESIDED OFF THE NORTHWEST COAST FOR THE ENTIRE MONTH, CONTRIBUTING
TO SEVERAL COOL SPELLS AND FROSTY MORNINGS IN BOISE.

IT WAS THE 16TH WETTEST APRIL SINCE 1878, AND THE 9TH WETTEST APRIL
SINCE 1940, WHEN RECORDKEEPING BEGAN AT THE BOISE AIRPORT.

THE .51 INCH ON THE 8TH ECLIPSED THE OLD RECORD FOR THE DATE OF .40
INCH SET IN 1881. THIS EVENT WAS CAUSED BY AN INCREASINGLY MOIST AND
UNSTABLE SOUTHWEST FLOW AHEAD OF AN UPPER LEVEL OFFSHORE TROUGH. THE
SCENARIO WAS AIDED BY A RELATIVELY WEAK DISTURBANCE MOVING THROUGH
THE FLOW AHEAD OF THE MAIN TROUGH.

A TENTH OF AN INCH OF SNOW FELL ON THE 8TH, BUT THERE WAS NO
ACCUMULATION.

IT WAS A BREEZY MONTH. NEARLY HALF THE DAYS HAD GUSTS WHICH REACHED
OR EXCEEDED 30 MPH.

THE MAIN EVENT WAS THE 53 MPH GUST FROM THE SOUTHWEST ON THE MORNING
OF THE 7TH. CONVECTIVE SHOWERS WERE FORMING IN MOIST AND UNSTABLE
AIR AHEAD OF A STRONG COLD FRONT. SOUTHWEST WINDS EXCEEDED 40 MPH AS
LOW AS 5000 FEET ABOVE THE SURFACE, AND A DOWNDRAFT FROM A SHOWER
APPROACHING THE AIRPORT ADDED TO THIS WIND AS IT DESCENDED TO GROUND
LEVEL.


CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1875 TO 2017

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE
                                          NORMAL
.............................................................
TEMPERATURE (F)
HIGHEST            72   04/12
                        04/05
LOWEST             28   04/04
AVG. MAXIMUM     59.5              62.3    -2.8
AVG. MINIMUM     39.3              39.3     0.0
MEAN             49.4              50.8    -1.4
DAYS MAX >= 90      0
DAYS MAX <= 32      0
DAYS MIN <= 32      4
DAYS MIN <= 0       0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         4.73   1869
TOTALS           2.01              1.23    0.78
DAYS >= .01        13
DAYS >= .10         6
DAYS >= .50         1
DAYS >= 1.00        0
GREATEST
 24 HR. TOTAL    0.51   04/18 TO 04/18

SNOWFALL (INCHES)
TOTALS            0.1R
SINCE 7/1        39.1
GREATEST
 SNOW DEPTH         T   04/08
 24 HR TOTAL      0.1   04/08 TO 04/08

DEGREE_DAYS
HEATING TOTAL     460               429      31      254
 SINCE 7/1       5239              5224      15
COOLING TOTAL       0                 3      -3        5
 SINCE 1/1          0                 3      -3
..............................................................

WIND (MPH)
AVERAGE WIND SPEED              9.5
RESULTANT WIND SPEED/DIRECTION   1/225
HIGHEST WIND SPEED/DIRECTION    38/220    DATE  04/07
HIGHEST GUST SPEED/DIRECTION    53/230    DATE  04/07

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM

AVERAGE RH (PERCENT)     57


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

$$


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