BLUE HILL METEOROLOGICAL OBSERVATORY MILTON, MASSACHUSETTS 02186 ELEVATION 635 FEET, 10 MILES SSW OF BOSTON, MA   DAILY DISCUSSION AND CLIMATE SUMMARY WEDNESDAY, JANUARY 24, 2007 ALL TIMES ARE IN EASTERN STANDARD TIME   TEMPERATURES RISING TO NEAR 40 DEGREES EARLY AFTERNOON THE DAY COULD AVERAGE UP TO 5 DEGREES ON MILD SIDE OF NORMAL BUT A STRONG BLAST OF ARCTIC AIR MASS WILL SEND TEMPERATURES ON A SHARP DOWNWARD SLIDE OVER THE NEXT COUPLE OF DAYS   After an early morning low temperature of 22 degrees here at the summit above a temperature inversion the brought 12 degrees to Norwood Airport, 3 miles to our southwest, temperature have risen right through the 30's by early afternoon.    Cumulus and moderate cumulus are forming and increasing early this afternoon ahead of the third Arctic airmass invasion of this month, all occurring since the 16th.    At the end of 23 days our temperature average for January has dropped to the middle 30's after being near 40 degrees just one week ago. Over the past week six out of seven days have averaged colder than normal.  This month which was once more than 10 degrees on the warm side of average will soon have a monthly average temp- erature within a few degrees of normal despite still running 8 degrees on the warm side through the 23rd as very cold air arrives over the next couple of days.     Today's observations:   7 A.M.   Weather: Clear, few cirrus distant south Temperature: 23F, Dew point: 16F, Wind: WSW at 13 kts Sea-level pressure: 29.91 inches Hg, rising Visibility: 20 miles, hazy 6-hourly min. temp. 22 deg. 24-hourly precip and snowfall: trace  BHO SA 1155 CLR 20 128/23/16/2413/991/ CI DSNT SSE-SSW INVSN PRSNT HAZY/ 8/001 4/001 53011 10024 20022     10 A.M.    Weather: Clear, few cirrus distant S-SW  Temperature: 30F, Dew point: 19F, Wind: WSW at 08 kts Sea-level pressure: 29.93 inches Hg, rising     Visibility: 20 miles, hazy   BHO SA 1455 CLR 20 135/30/19/2408/993/ FEW CI DSNT S-SW THN K LYR ALG HRZN SW-NW-NE HAZY ALQDS/ 8/001 51007     1 P.M.    Weather: Scattered cumulus/stratocumulus/ moderate cumulus Temperature: 38F, Dew point: 20F, Wind: WSWW at 13 kts Sea-level pressure: 29.88 inches Hg, falling    Visibility: 40 miles  6-hourly max. temp. 38 deg. BHO SA 1755 38 SCT 40 118/38/20/2413/988/ CU/SC/MDT CU WND 22V28/ 8/200 58017 10038 20023   WEATHER SUMMARY FOR TUESDAY, JANUARY 23    TEMPERATURE (DEGREES F) MAX.....30    NORMAL.....33 MIN.....18    NORMAL.....18   MEAN....24    NORMAL.....25   DEPARTURE FROM 30-YEAR NORMAL.........-1 TOTAL DEPARTURE FOR THE MONTH.......+187 (+7.9 DEGREES/DAY)   HEATING DEGREE DAYS TOTAL HEATING UNITS FOR YESTERDAY..........41   DEPARTURE.......+1 TOTAL HEATING UNITS FOR THE MONTH.........710   DEPARTURE.....-184 TOTAL HEATING UNITS FOR THE SEASON.......2583   DEPARTURE.....-640 TOTAL HEATING UNITS LAST SEASON TO DATE..2846   DIFFERENCE....-263   PEAK GUST AND AVERAGE WIND SPEED (MPH) PEAK WIND GUST FOR YESTERDAY............23  NW  AT 11:40 A.M.                     AEROVANE.............23  NW  AT 11:40 A.M. *                     ASOS.................21  NW  AT 11:40 A.M.                     DAVIS................23  NW  AT 10:55 A.M.  FASTEST MILE FOR YESTERDAY..............15  NW AT 12:34 P.M.   MAXIMUM 2-MINUTE ASOS AVERAGE...........16  NW AT 11:40 A.M. MAXIMUM 2-MINUTE DAVIS AVERAGE..........17  NW AT 11:40 A.M. AVERAGE WIND SPEED AND DIRECTION......  9.3 WNW                     ASOS...............10.2                          DAVIS.............  9.7 WNW [300 deg]  * last of several occurrences...   PRECIPITATION (INCHES) THROUGH THIS MORNING (EST) TOTAL PRECIPITATION 24 HRS ENDING 7 A.M...trace  DEPARTURE......-0.15                          ASOS..............0.00 TOTAL PRECIPITATION FOR THE MONTH..........2.87  DEPARTURE......-0.71                           ASOS..............2.80    TOTAL PRECIPITATION FOR THE YEAR...........2.87  DEPARTURE......-0.71                           ASOS..............2.80   SNOWFALL (INCHES) THROUGH THIS MORNING (EST) TOTAL SNOWFALL 24 HRS ENDING 7 A.M.........trace  DEPARTURE.....-0.5 TOTAL SNOWFALL FOR THE MONTH................0.1   DEPARTURE....-10.2 TOTAL SNOWFALL FOR THE SEASON...............3.8   DEPARTURE....-20.1   PRELIMINARY CLIMATE SUMMARY FOR JANUARY 2007......CALENDAR DAY DATA DATA REPORTED: DATE: MAX/MIN/MEAN/DEP/PRECIP/SNOWFALL/SUN(MIN.)/SUN(%)/ PEAK GUST/AERO GUST   AERO: Aerovane recording wind system when significant TSTM: Thunderstorm day ....: Data not yet available   1/1  53/30/42/+15/0.98/0/000/00     38 SE 1/2  43/31/37/+10/0.03/0/505/92     44 W    Aero 47 MPH W   1/3  49/30/40/+13/0/0/435/79        40 S   1/4  53/40/47/+20/0/0/198/36        31 SSW 1/5  61/46/54/+27/0.04/0/000/00     44 S    Aero 44 MPH S 1/6  66/48/57/+31/0.03/0/161/29     48 SSW  Aero 47 MPH SSW 1/7  50/38/44/+18/0/0/505/91        43 W    Aero 44 MPH W 1/8  52/36/44/+18/0.69/0/000/00     45 W    Aero 45 MPH W 1/9  41/29/35/+9/0/0/518/93         40 W    Aero 39 MPH W 1/10 34/22/28/+2/0/0/525/94         48 W 1/11 33/17/25/-1/0/0/336/60         36 S    Aero 38 MPH S 1/12 48/32/40/+14/0/0/168/30        38 SSW  Aero 39 MPH SSW 1/13 48/36/42/+16/0.06/000/00       30 S     1/14 38/31/35/+9/0.16/0/000/00      21 NE 1/15 40/31/36/+10/0.58/0/000/00     25 NNE 1/16 38/15/27/+1/0.05/0/000/00      40 W    Aero 42 MPH W 1/17 18/6/12/-14/0.00/0/563/99      38 WNW  Aero 43 MPH WNW 1/18 36/10/23/-3/0.13/0.1/171/30    33 SSE 1/19 38/30/34/+9/0.06/T/269/47      40 W    Aero 41 MPH W 1/20 30/12/21/-4/T/T/402/70         51 W    Aero 55 MPH WNW 1/21 24/9/17/-8/0/0/449/78          33 W 1/22 24/18/21/-4/0.05/1.0/000/00    16 WNW 1/23 30/18/24/-1/0.01/0.2/.../..    23 NW   1/24 morning low temp. 22 deg; normal now 18 deg.   DAILY EXTREMES Temperature and precipitation records back to 1885, and wind records back to 1940 (e = estimated):   RECORDS FOR JANUARY 24 HIGH 60F IN 1967 LOW -12F IN 1907 PRECIP 2.04 INS. IN 1998 SNOWFALL 11.3 INS. IN 1935 PEAK GUST 82 MPH S IN 1996   RECORDS FOR JANUARY 25 HIGH 55F IN 1990 LOW -10F IN 1935 PRECIP 2.24 INS. IN 1979 SNOWFALL 12.5 INS. IN 1941 PEAK GUST 81 MPH WNW IN 1972   TODAY'S REPORT By: Robert Skilling