Saturday, April 18, 2020

BLUE HILL METEOROLOGICAL OBSERVATORY
MILTON, MASSACHUSETTS
ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA

DAILY DISCUSSION AND CLIMATE SUMMARY
SATURDAY, APRIL 18, 2020
ALL TIMES ARE IN EASTERN STANDARD TIME

LIGHT SNOWFALL IN MID-APRIL ATOP GREAT
BLUE HILL….

We measured 4.3 inches of snowfall, with the
majority of it falling before 7 A.M. this
morning. This broke the daily record of 3.7
inches, set back in 1965. Light snow changed
over to light rain by noontime, ending by
2 P.M. Liquid precipitation amounted to an
event total of 0.74 inches. Visibility went
from 1/16th mile this morning to 20 miles,
due to a decrease in fog. Wind was north-
easterly with a maximum speed of 25 mph.

Our high temperature so far today is 35F,
which is 22 degrees below our daily normal high
temperature of 57F. The low since midnight is 31F,
which is 8 degrees below the daily normal low of 39F.

The snow today was the fourth highest snowfall
on record so late in the season.

BHO Highest Late Season Snowfalls, inches (1885-2020)

1) 7.8 on 9-10 May 1977
2) 11.0 on 28-29 April 1987
3) 8.0 on 28 April 1916
4) 4.3 on 18 April 2020
5) 3.7 on 18 April 1965

Today’s Observations:

7 A.M.
Weather: Light snow
Temperature: 32F; Dew Point: 32F; Relative Humidity: 100%
Wind: ENE at 12 kts
Sea-level pressure: 29.81 ins. Hg: falling, then more slowly
Visibility: 1/2 mile, fog
6-hr Max temp: 35F
6-hr Min temp: 31F
24-hr Precip:   0.63 ins.
24-hr Snowfall: 4.2 ins.
BHO SA 1155 X W3 1/2S-F 094/32/32/0712/981/ S-CTD NEW SNOW
PST 24 HRS 4.2 INS/ 8//// 4/004 70063 56020 10035 20031

10 A.M.
Weather: Light snow
Temperature: 33F; Dew Point: 33F; Relative Humidity: 100%
Wind: NE at 9G16 kts
Sea-level pressure: 29.78 ins. Hg: falling
Visibility: 1/16th mile, fog
3-hr Precip:   0.10 ins.
3-hr Snowfall: 0.1 ins.
BHO SA 1455 X W2 1/16S-F 085/33/33/0409G16/978/ S-CTD NEW
SNOW PST 3 HRS 0.1 INS/ 8//// 6010/ 58009

1 P.M.
Weather: Overcast stratus, light rain
Temperature: 35F; Dew Point: 35F; Relative Humidity: 100%
Wind: NNE at 11G19 kts
Sea-level pressure: 29.74 ins. Hg: falling slowly
Visibility: 15 miles
6-hr Max temp: 35F
6-hr Min temp: 32F
6-hr Precip:   0.11 ins
6-hr Snowfall: 0.1 ins
BHO SA 1755 E20 OVC 15R- 074/35/35/0311G19/974/ R-CTD NEW SNOW
PST 6 HRS 0.1 INS/ 8/6// 4/004 6011/ 56011 10035 20032

SUMMARY FOR FRIDAY, APRIL 17, 2020

TEMPERATURE (DEGREES F)
MAX…..49   NORMAL…..56
MIN…..29   NORMAL…..38
MEAN….39   NORMAL…..47

DEPARTURE FROM 30-YEAR NORMAL……………….-8
TOTAL DEPARTURE FOR THE MONTH……………….+1 [-0.1 DEGREES/DAY]

HEATING DEGREE DAYS (SEASON JUL TO JUN)
TOTAL HEATING UNITS FOR YESTERDAY……………26  DEPARTURE…….+8
TOTAL HEATING UNITS FOR THE MONTH…………..353  DEPARTURE…….-1
TOTAL HEATING UNITS FOR THE SEASON…………5226  DEPARTURE……-612
TOTAL HEATING UNITS LAST SEASON TO DATE…….5728  DEPARTURE……-502

PEAK GUST AND AVERAGE WIND SPEED (MPH)
PEAK WIND GUST FOR YESTERDAY………………..41 W   AT 11:24 A.M.
AERO…………………….39 W   AT 11:02 A.M
ASOS…………………….39 W   AT 11:42 A.M.
DAVIS……………………43 W   AT 11:42 A.M. RMY 41
FASTEST MILE FOR YESTERDAY………………….27 W   AT  8:39 A.M.
MAXIMUM 2-MINUTE ASOS AVERAGE……………….24 W   AT  8:39 A.M.
MAXIMUM 2-MINUTE DAVIS AVERAGE………………25 W   AT  8:39 A.M.
AVERAGE WIND SPEED AND DIRECTION…………….13.9 W
ASOS…………………….13.7
DAVIS……………………14.2 W [263 deg.]

PRECIPITATION (INCHES) THROUGH THIS MORNING (EST)
TOTAL PRECIPITATION 24 HRS ENDING 7 A.M….0.63  DEPARTURE……+0.49
ASOS…………..0.62
TOTAL PRECIPITATION FOR THE MONTH……….5.55  DEPARTURE……+2.26
ASOS…………..5.72
TOTAL PRECIPITATION FOR THE YEAR……….14.88  DEPARTURE……-2.41
ASOS………….15.45

SNOWFALL (INCHES) THROUGH THIS MORNING (EST)
TOTAL SNOWFALL 24 HRS ENDING 7 A.M……….4.2  DEPARTURE…….+4.1
TOTAL SNOWFALL FOR THE MONTH…………….4.2  DEPARTURE…….+1.8
TOTAL SNOWFALL FOR THE SEASON…………..31.8  DEPARTURE……-30.3

PRELIMINARY CLIMATE SUMMARY FOR APRIL CALENDAR DAY DATA
DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOW/SUN(MIN.)/SUN(%)/PEAK GUST/AERO/RMY GUST
AERO: Aerovane wind recording system gust
RMY:  R.M. Young wind gust recording system
TSTM: Thunderstorm day (thunder heard some time during day)
….: Data not yet available, records not finalized
M:    Missing data

04/01  42/28/35/-6/0.00/0.0/…/..         28 NE  AERO 28 NE  RMY 30
04/02  46/35/41/0/…/0.0/…/..           39 NW  AER0 40 NW  RMY 41
04/03  42/38/40/-2/…./0.0/…/..         48 NE  AERO 53 NE  RMY 49
04/04  46/36/41/-1/…./0.0/…/..         38 NE  AERO 38 NE  RMY N/A
04/05  55/36/46/+3/T/0.0/…/..            22 S   AERO 21 S   RMY 21
04/06  61/40/51/+8/0.00/0.0/…/..         29 NW  AERO 30 NW  RMY 29
04/07  63/42/53/+10/0.00/0.0/…/..        29 W   AERO 30 W   RMY 28
04/08  50/41/46/+2/…./…/…/..         23 S   AERO 22 S   RMY 22
04/09  47/37/42/-2/…./…/…/..         58 W   AERO 58 W   RMY 56
04/10  47/35/41/-4/0.02/T/…/..           48 W   AERO 50 W   RMY 53
04/11  51/33/42/-3/0.00/0.0/…/..         38 WNW AERO 39 WNW RMY 40
04/12  60/33/47/+2/0.00/0.0/…/..         38 S   AERO 40 S   RMY N/A
04/13  59/50/55/+9/1.42/0.0/…/..         79 S   AERO 83 S   RMY 78
04/14  57/41/49/+3/0.00/0.0/…/..         41 W   AERO 40 W   RMY N/A
04/15  52/36/44/-3/0.02/0.0/…/..         37 W   AERO 36 W   RMY 37
04/16  47/32/40/-7/T/T/…/..              33 WNW AERO 33 WNW RMY 32
04/17  49/29/39/-8/…./4.3/…/..         41 W   AERO 39 W   RMY 41

04/18 The low since midnight is 31F, daily normal minimum is 39F

DAILY RECORDS FOR APRIL 2020

4/18/2020
NEW RECORD SNOWFALL OF 4.3 INS, REPLACING
SNOWFALL OF 3.7 IN. IN 1965

DAILY EXTREMES
Temperature and precipitation records back to 1885, and
wind records back to 1940 (e = estimated):

RECORDS FOR APRIL 17
HIGH 93 IN 2002
LOW 21 IN 1908
PRECIP 1.68 IN 1954
SNOWFALL 1.0 IN. IN 1899
PEAK GUST 63 MPH ESE IN 2011

RECORDS FOR APRIL 18
HIGH 92 IN 1976
LOW 23 1887
PRECIP 1.48 IN 1954
SNOWFALL 4.3 INS. IN 2020
PEAK GUST 59 MPH S IN 1982

TODAY’S REPORT PREPARED BY: Benjamin Turner