MONTHLY WEATHER DATA AND OBS - WESTMONT 1.1W PA DECEMBER 2011 OBSERVER NATE MULLINS Special Observations: F=fog, T=thunder, H=hail, S=sleet, G=glaze, DW=damaging winds Observation time for this station is midnight (Eastern US). Temperature, °F Precipitation, In. Liquid Solid 7am 24-hour At Rain Snow/ Snow Date Max Min Obs Equiv Ice Depth Special Obs. 1 41 27 27 2 41 24 30 3 45 23 33 4 56 31 37 5 60 36 50 .05 6 53 40 40 .26 F 7 41 27 27 1.06 2.0 F,S 8 28 22 25 .03 0.2 2 9 37 21 33 T T 2 10 33 20 20 T T 1 11 35 13 25 1 12 40 17 27 1 13 42 20 34 1 14 43 32 39 T 15 57 38 43 .07 16 43 29 29 T T 17 29 26 26 .18 3.0 T S 18 30 23 23 .10 1.5 4 19 44 22 42 T 3 20 42 39 40 .30 T F 21 56 40 46 .62 F 22 48 42 43 .34 F 23 43 29 29 .21 T S 24 33 26 27 .01 0.1 T S 25 42 26 35 T T S 26 37 29 31 T T 27 39 30 32 .78 T F,S,G 28 32 19 19 .09 0.7 1 29 37 19 32 .02 0.2 1 30 47 32 41 1 31 41 37 38 .13 F AVG/SUM 41.8 27.7 33.0 4.25 7.7 0.6 (avg) EXT 60 13 50/19 1.06 3.0 4 Date 5 11 5/28 7 17 18 *=Also occurred on earlier dates Miscellaneous Stats Mean Monthly Temperature: 34.7°F (+4.4°F) Year precipitation to date: 65.21" (+17.52" - final total for 2011) Monthly precipitation departure: +0.92" (normal December 3.33") Season snowfall to date: 19.4" Number of days with: Fog 7 Sleet 6 Glaze 1 DETAILED OBSERVATION NOTES SUNNY, WARMING TREND 1: Clearing skies overnight and cold with heavy frost. Sunny, seasonably cool, light W winds. 2: Another chilly night with heavy frost. Partly cloudy, breezy, brisk W winds, still cool. 3: Seasonably chilly with another clear frosty morning and a mostly sunny pleasant afternoon. 4: Partly sunny, quite mild high 56 F, light SW winds, unusually nice day for December. 5: Becoming cloudy overnight with steady temps. Partly to mostly cloudy and very mild high 60 with light S winds. Light rain late this evening, still 50 @ midnight. RAIN THEN SNOW - COLDER 6: Mild overnight with fog & drizzle. Periods of rain, mostly this morning, cloudy, mild, then temperatures falling during the evening with more rain showers developing late. 7: A steady soaking rain commencing shortly before daybreak and continuing through the morning before mixing with snow/sleet around noon. Rain/snow mix continued through 3pm before finally changing to all snow and sticking to the ground. 2.0" fell by 7pm - less snow than predicted though the day's overall precip (1.06") was higher than predicted. Only flurries after 7 pm. 8: Mostly cloudy with very light snow or flurries this morning. Gradual PM clearing - clear and cold after sunset. First sub-freezing max of the season (28 F). 9: Partly cloudy & chilly overnight. Mostly sunny, seasonably cold day. Becoming mostly cloudy this evening with a few snow flurries late. 10: A few flurries overnight with the day's high of 33 set at midnight - temps during the day remained in the upper 20s despite mostly sunny skies again. Clear, chilly evening. 11: Cold overnight low 13 F, clear/sunny all day with light variable winds, high of 35. 12: Another cold clear night (17) and a sunny near calm day, high of 40. 13: Another sunny and seasonably cold December day. Skies became cloudy late this evening. 14: Mostly cloudy with light variable winds, temps fairly steady in the upper 30s. 15: Cloudy & mild high 57 F with occasional light rain showers, strong SW to W winds. 16: Cloudy and cooler but with calmer winds. A few late evening snow flurries. SOME SNOW, THEN WARMER - RAINY 17: Periods of light snow and flurries, occasionally mixed with light ice pellets (sleet), after 8am. A total of 3.0" of snow/ice and .18" melted precip. 18: Light snow and flurries overnight another 1.0" by 7am. Another half-inch fell thru mid-day before some partial clearing when the sun melted about an inch of the snow back. Still cold. 19: Milder and very windy today with mostly cloudy skies - most of the past 2 day's snow melted. Some light drizzle at times but it seemed to evaporate on contact. 20: Periods of light rain and drizzle developed overnight and became a steady but light rain through mid-afternoon .30" fell. Temps steady around 40 all day. Some fog this evening. 21: A mild changeable 1st "official" day of winter. Rain showers of varying intensity on and off through the day with a few brief peaks of sun .62" fell. Gusty W winds began after 5:30pm. 22: Cloudy all day with temperatures still on the mild side in the mid 40s. Steady light rain developed by mid-evening and became heavier towards midnight with dense fog developing. 23: Occasional rain continued overnight with fog also. Light NW breezes with slowly falling temps all day and intermittent light showers of snow and very fine ice pellets. 24: A few flurries and ice pellets overnight and this morning, then some partial clearing in the afternoon, the high struggled to 33. 25: A clear frosty morning but no snow for Christmas here for the 5th of the past 8 years. A sunny AM and a partly cloudy mild PM with mostly high clouds, becoming cloudy and windy this evening with spits of snow and small ice pellets but no measurable accumulation of snow/ice. 26: A few flurries overnight. Variably cloudy skies, breezy with seasonable temps in the 30s. RAIN/MIX 27: Rain began this morning around 9am. There was a very thin layer of glaze on some surfaces before temps slowly rose through the 30s. Rain was steady and heavy at times before mixing with sleet and snow around 1:30pm. Precip turned back to rain and temps got warmer - direct opposite of the forecast for falling temps and several inches of snow. Became very windy in the evening with West winds gusting 30-40 mph and light snow showers, still no accumulation. 28: Flurries and light snow showers overnight and through the mid-afternoon 0.7" snow fell. This was again very light compared to what was forecast. Quite cold/blustery, very windy. 29: Cold overnight but slight warming as clouds moved in again. A period of very fine light snow late this AM (0.2"), mostly cloudy, more spits of light snow and flurries this evening. 30: Overcast overnight and this morning with mild temps and breezy conditions. Mostly cloudy, a few PM peaks of sun. 31: A few showers overnight and early this morning, ended by 8:30am, .13" fell. Occasionally gusty winds from the west, still mild. Very light PM drizzle/fog, no more measurable precip. MONTHLY SUMMARY December was a typical 2011 weather month - above normal temperatures and precipitation. There was a lack of any significant snow, and the few small snows that did fall did not remain on the ground for long. There was more snow from the Oct 29 storm (11.0") than in November and December combined (8.4"). There was also a notable lack of any Arctic air, with only 4 sub-freezing highs and also only 4 lows below 20. The first week was the mildest, with temperatures in the 40s and 50s, reaching a balmy 60 on the 5th. Above normal lows and highs continued virtually all month. December was the 8th of the past 9 months and the 9th of 12 in 2011 with above average temps. Precipitation fell frequently - almost all as rain. The most substantial system was a cold front that passed through on the 7th, when rain turned to snow. 2" of snow fell with well over an inch of melted precipitation. From the 15th on, at least a trace of precip fell on all but one day. The month's heaviest snow of 4.5" - mostly a lake-effect event - fell on the 17th and 18th. The next stormy period - again, almost all rain - occurred from the 20th-23rd with nearly 1.5" of rainfall. The month's and year's final significant weather event was a cold rain on the 27th that occasionally mixed with sleet, freezing rain and snow. All of the final 5 months of 2011 had above normal precipitation, and 2011 was one of the wettest years on record with 65.21".