BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA DAILY DISCUSSION AND CLIMATE SUMMARY WEDNESDAY, APRIL 11, 2018   ALL TIMES ARE IN EASTERN STANDARD TIME AN INCREASING CLOUD DAY BEGINS WITH COMPLETE  UNDERCAST CONDITIONS...  We observed complete undercast fog conditions limiting visibility to 3/4 of a mile. Above the fog the sky was clear without any clouds. The fog dissipated midday  and visibility increased to 70 miles by 10:00 A.M.  With the visibility increase we also observed a dramatic drop in relative humidity from 97% at 7:00 A.M. down to  54% by 1:00 P.M.  Temperatures continue to be below seasonable today with  an overnight low of 29F, which is 7 degrees below the  daily normal of 36F. Yesterday max of 39F was 14 degrees below the daily normal of 53F. Temperatures although still below seasonable have increased today with a high  of 48F by 1:00 P.M., which is 6 degrees below the daily normal of 54F. Wind continued to be light and variable today, slightly picking up in the afternoon.  We observed an increase in cloud cover from clear skies  at 7:00 A.M. to broken skies by 1:00 P.M. This was due  to a midday drop in pressure.   Today's Observations: 7 A.M. Weather: Sky clear, complete undercast fog conditions  present in all directions  Temperature: 32F; Dew Point: 31F; Wind: Calm Sea-level pressure: 30.19 ins. Hg, rising, then more slowly     Visibility: 3/4 mile  6-hr Max temp: 32F 6-hr Min temp: 29F 24-hr precip: Trace 24-hr snowfall: Trace  Snow depth: 0 ins. BHO SA 1155 CLR 3/4F 224/32/31/0000/019/ SKC NEW SNW  PST 24 HRS TRACE COMPLETE UNDERCAST CDN BLO SMT ALQDS  WND CALM/ 51006 10032 20029  10 A.M. Weather: Scattered cumulus  Temperature: 41F; Dew Point: 28F; Wind: WSW at 3 kts, Wind: Light and variable, direction estimated   Sea-level pressure: 30.18 ins. Hg, rising then falling Visibility: 70 miles 3-hr precip: 0.00 ins.   3-hr snowfall: 0.0 ins.  BHO SA 1455 15 SCT 70 220/41/28/E2403/018/ WND L/V/  8/100 50004 1 P.M. Weather: Broken stratocumulus  Temperature: 43F; Dew Point: 28F; Wind: SE at 6 kts, Wind: Light   Sea-level pressure: 30.10 ins. Hg, falling, then more slowly Visibility: 70 miles 6-hr Max temp: 48F 6-hr Min temp: 32F 6-hr precip: 0.00 ins. 6-hr snowfall: 0.0 ins.  Snow depth: 0 ins. BHO SA 1755 E60 BKN 70 193/43/28/1406/010/ WND LGT/  8/400 56027 10048 20032 SUMMARY FOR TUESDAY, APRIL 10, 2018 TEMPERATURE (DEGREES F) MAX.....45   NORMAL.....53 MIN.....24   NORMAL.....36 MEAN....35   NORMAL.....45 DEPARTURE FROM 30-YEAR NORMAL..........................-10 TOTAL DEPARTURE FOR THE MONTH..........................-53 [-5.5 DEGREES/DAY] HEATING DEGREE DAYS (SEASON JUL TO JUN) TOTAL HEATING UNITS FOR YESTERDAY.............30   DEPARTURE.........+10 TOTAL HEATING UNITS FOR THE MONTH............275   DEPARTURE.........+53 TOTAL HEATING UNITS FOR THE SEASON..........5333   DEPARTURE........-373 TOTAL HEATING UNITS LAST SEASON TO DATE.....5108   DIFFERENCE.......+225 PEAK GUST AND AVERAGE WIND SPEED (MPH)  PEAK WIND GUST FOR YESTERDAY...................14 SSW AT 8:07 A.M.                      AERO........................13 SSW AT 8:08 A.M.                    ASOS........................14 SW  AT 8:07 A.M.                    DAVIS.......................12 M   AT 8:06 A.M ** RMY N/A FASTEST MILE FOR YESTERDAY......................8 SSW AT 8:27 A.M. MAXIMUM 2-MINUTE ASOS AVERAGE..................10 S   AT 8:36 A.M.   MAXIMUM 2-MINUTE DAVIS AVERAGE..................9 M   AT 8:08 A.M.** AVERAGE WIND SPEED AND DIRECTION..............3.0 SSE                    ASOS.......................2.8                    DAVIS......................2.8 M** ** Davis direction malfunctioning  PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M....0.00  DEPARTURE......-0.18                          ASOS..............0.00 TOTAL PRECIPITATION FOR THE MONTH..........1.13  DEPARTURE......-0.57                          ASOS..............0.97   TOTAL PRECIPITATION FOR THE YEAR..........19.93  DEPARTURE......+4.41                          ASOS.............21.06 SNOWFALL (INCHES) THROUGH THIS MORNING (EST) TOTAL SNOWFALL 24 HRS ENDING 7 A.M..........0.0  DEPARTURE........-0.1 TOTAL SNOWFALL FOR THE MONTH................2.6  DEPARTURE........+1.0 TOTAL SNOWFALL FOR THE SEASON..............92.8  DEPARTURE.......+31.4 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 4/01 58/33/46/+5/..../0.0/.../..   45 SSW AERO 43 SSW RMY N/A   4/02 38/30/34/-7/..../1.6/.../..   20 SSW AERO 15 SSW RMY 17 4/03 48/30/39/-3/..../0.0/.../..   28 SSE AERO 25 SSE RMY 25 4/04 54/36/45/+3/..../0.0/.../..   56 WNW AERO 56 WNW RMY 54 4/05 40/27/34/-9/0.00/0.0/.../..   53 WNW AERO 53 WNW RMY 52  4/06 41/25/33/-10/0.25/1.0/.../..  37 S   AERO 36 S   RMY 38 4/07 46/32/35/-4/0.00/0.0/.../..   32 WNW AERO 35 WNW RMY 34 4/08 41/29/35/-9/0.00/0.0/.../..   35 WNW*AERO 31 WNW RMY 34 4/09 45/24/35/-9/0.00/0.0/.../..   28 WNW*AERO 25 WNW RMY 29 4/10 39/31/35/-10/T/T/.../..       14 SSW AERO 13 SSW RMY N/A 4/11 Low temp since midnight is 29F; normal low is now 36F *Estimated DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated):     RECORDS FOR APRIL 11 HIGH 85 IN 2017 LOW 19 IN 1909 PRECIP 1.72 IN. IN 2003 SNOWFALL 9.5 IN. IN 1958 PEAK GUST 65 MPH NW IN 1963 RECORDS FOR APRIL 12 HIGH 82 IN 1945 LOW 17 IN 1926 PRECIP 1.51 IN. IN 1993 SNOWFALL 12.0 IN. IN 1894 PEAK GUST 65e MPH W IN 1978 TODAY'S REPORT PREPARED BY: K.A. Geagan