ChescoWx

GFS ensemble catching on to snow chances next week...

Some really interesting statistics for Chester County PA that really makes you question some of the historical temperature trending data we see. Incredibly the NCEI data set for Chester County PA. Of note from 1895 through 1970 (77 years) the reported average Chester County PA temperatures for 73 of those 77 (95%) years is now reported as lower than any available reporting site in the county in those years. So are we to assume all stations in Chester County were faulty and or needed post hoc adjustment for 95% of the reporting observations through 1970??

Some really interesting statistics for Chester County that really makes you question some of the historical temperature trending data we see. Incredibly the NCEI data set for Chester County PA. Of note from 1895 through 1970 (77 years) the reported average Chester County temperatures for 73 of those 77 (95%) years is now reported as lower than any available reporting site in the county in those years. So are we to assume all stations in Chester County were faulty for 95% of the reporting observations through 1970??

Some really interesting statistics for Chester County that really makes you question some of the historical temperature trending data we see. Incredibly the NCEI data set for Chester County PA. Of note from 1895 through 1970 (77 years) the reported average Chester County temperatures for 73 of those 77 (95%) years is now reported as lower than any available reporting site in the county in those years. So are we to assume all stations in Chester County were faulty for 95% of the reporting observations through 1970??

Sunny skies should be the rule through Thursday. Chillier today with temps remaining in the 30's but warming trend starts tomorrow topping out well into the 50's by Saturday. Shower chances increase on Sunday night and much colder air appears likely with even some wintry weather chances next week. Records for today: High 66 (2008) / Low 6 below (1895) / Precipitation 3.00" (1896) / Snow 12.3" (2010)

Sunny skies should be the rule through Thursday. Chillier today with temps remaining in the 30's but warming trend starts tomorrow topping out well into the 50's by Saturday. Shower chances increase on Sunday night and much colder air appears likely with even some wintry weather chances next week. Records for today: High 66 (2008) / Low 6 below (1895) / Precipitation 3.00" (1896) / Snow 12.3" (2010)

In comparing the NCEI average post observation temperature adjustments applied to the actual recorded averages recorded by the NWS Chester County Coop data show the average temperature data was adjusted downward every single year from 1895 through 2004 or for 110 consecutive years. The greatest adjustments were reductions in average temperatures of 2.76 degrees in 1945 / 2.69 degrees in 1943 /2.62 degrees in 1942 / 2.58 degrees in 1951. Conversely. In the 18 years since 2005 every year has been adjusted upwards with the exception of 2019 with the greatest adjustments upward to temperatures being applied to 2018 +1.87 degrees and 2005 with a +0.66 degree adjustment. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/time-series/PA-029/tavg/ytd/12/1895-2023

In comparing the NCEI average post observation temperature adjustments applied to the actual recorded averages recorded by the NWS Chester County Coop data show the average temperature data was adjusted downward every single year from 1895 through 2004 or for 110 consecutive years. The greatest adjustments were reductions in average temperatures of 2.76 degrees in 1945 / 2.69 degrees in 1943 /2.62 degrees in 1942 / 2.58 degrees in 1951. Conversely. In the 18 years since 2005 every year has been adjusted upwards with the exception of 2019 with the greatest adjustments upward to temperatures being applied to 2018 +1.87 degrees and 2005 with a +0.66 degree adjustment. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/time-series/PA-029/tavg/ytd/12/1895-2023

Since 2000 using the 1991-2020 average temperature for December through February which is 32.8 degrees here in Chester County - we have seen 10 winters that have averaged below normal temps.... but none have been below normal since the DFJ of 2015 - winters with below normal DJF have been 2000/2001/2003/2004/2005/2009/2010/2011/2014/2015

Since 2000 using the 1991-2020 average temperature for December through February which is 32.8 degrees here in Chester County - we have seen 10 winters that have averaged below normal temps.... but none have been below normal since the DFJ of 2015 - winters with below normal DJF have been 2000/2001/2003/2004/2005/2009/2010/2011/2014/2015

Most spots were in the 20's to start the day with the lowest I could find in both Warwick Township and down in Kennett Square at 22 degrees. Tomorrow and Wednesday look to be close to normal temps while the rest of the week should see above normal temps rising into the 50's toward the weekend. Next week should see a return to a stretch of below normal temps. Records for today: High 66 (1991) / Low 11 below (1918) / Precipitation 1.90" (1907) / Snow 12.0" (1907)

Our beautiful stretch of February weather looks to continue for most of the next week with average to above temps and sunshine much of the upcoming week. The rumored pattern change to colder....if it occurs is still at least 10 or more days away. Records for today: High 63 (1991) / Low 1 below (1898) / Precipitation 1.35" (1920) / Snow 9.1" (1995)

Go Phillies!!!!!

Our beautiful stretch of February weather looks to continue for most of the next week with average to above temps and sunshine much of the upcoming week. The rumored pattern change to colder....if it occurs is still at least 10 or more days away. Records for today: High 63 (1991) / Low 1 below (1898) / Precipitation 1.35" (1920) / Snow 9.1" (1995)

Things have been slower on the work front so finally had a chance to download and consolidate all 23 available Chester County climate data sites (see below table for detail). All stations have been weighted equally for all years they were reporting data . I then compared the all average temperature by decade data to the NCEI NOAA Chester County PA average temperatures reported by decade. As expected the greatest downward post observation adjustments to the data were during the warmest raw data reported decades of the 1930's and 1940's with a gradual reduction in cooling that started in the 1950's finally resulting in what are now warming adjustments during the most recent 2 decades.

Things have been slower on the work front so finally had a chance to download and consolidate all 23 available Chester County climate data sites (see below table for detail). All stations have been weighted equally for all years they were reporting data . I then compared the all average temperature by decade data to the NCEI NOAA Chester County PA average temperatures reported by decade. As expected the greatest downward post observation adjustments to the data were during the warmest raw data reported decades of the 1930's and 1940's with a gradual reduction in cooling that started in the 1950's finally resulting in what are now warming adjustments during the most recent 2 decades.

Back to back snowstorms "only" 2 weeks away.... as that well respected MET says....delayed but not denied!!

Happy Groundhog Day to those that celebrate! No shadow this year so spring is around the corner....or maybe not! Some light rain overnight with County totals including East Nantmeal 0.13" / Atglen 0.11" / Chester Springs 0.14" / Glenmoore 0.14" / Devault 0.11" / West Chester 0.12" / London Grove 0.11" and Kennett Square 0.09", Looks like some great winter weather on tap for much of the upcoming week with sunny skies and seasonably chilly but not cold temps. A nice break after all the drearies! Records for today: High 60 (1967) / Low 6 below (1918) / Precipitation 1.69" (1897) / Snow 8.5" (1897)

Happy Groundhog Day to those that celebrate! No shadow this year so spring is around the corner....or maybe not! Some light rain overnight with County totals including East Nantmeal 0.13" / Atglen 0.11" / Chester Springs 0.14" / Glenmoore 0.14" / Devault 0.11" / West Chester 0.12" / London Grove 0.11" and Kennett Square 0.09", Looks like some great winter weather on tap for much of the upcoming week with sunny skies and seasonably chilly but not cold temps. A nice break after all the drearies! Records for today: High 60 (1967) / Low 6 below (1918) / Precipitation 1.69" (1897) / Snow 8.5" (1897)

Below is the area climate summary for Chester County for the Month of January. Warwick Township was the chilliest and West Chester Airport the warmest. Both East Nantmeal and West Chester finished with their 34th warmest January with 131 and 132 years of data respectively. Devault finished with their 27th warmest January with 123 years of record. West Chester finished with their 3rd wettest January and East Nantmeal and Devault both finished with it's 4th such first month of the year.

Below is the area climate summary for Chester County for the Month of January. Warwick Township was the chilliest and West Chester Airport the warmest. Both East Nantmeal and West Chester finished with their 34th warmest January with 131 and 132 years of data respectively. Devault finished with their 27th warmest January with 123 years of record. West Chester finished with their 3rd wettest January and East Nantmeal and Devault both finished with it's 4th such first month of the year.

We will end our cloudy January today. I will post the East Nantmeal Twp. and combined All Chester County climate data tomorrow. However, we will end the month with a much colder January then last year with most stations across the county averaging 6 to 8 degrees colder than 2023 (of course last year was the warmest Jan on record!). We will finish January about 1" below average snowfall for the month... but it will be our 3rd snowiest January in the last 10 years and 4th wettest on record. Dry weather for much of the next week with tomorrow being our warmest day with temps well into the 40's. Records for today: High 65 (1916) / Low minus 4.8 (2019) / Precipitation 1.25" (1914) / Snow 4.3" (2021)

We will end our cloudy January today. I will post the East Nantmeal Twp. and combined All Chester County climate data tomorrow. However, we will end the month with a much colder January then last year with most stations across the county averaging 6 to 8 degrees colder than 2023 (of course last year was the warmest Jan on record!). We will finish January about 1" below average snowfall for the month... but it will be our 3rd snowiest January in the last 10 years and 4th wettest on record. Dry weather for much of the next week with tomorrow being our warmest day with temps well into the 40's. Records for today: High 65 (1916) / Low minus 4.8 (2019) / Precipitation 1.25" (1914) / Snow 4.3" (2021)

Light snow here in East Nantmeal and 33.3 degrees

It is interesting watching the moisture moving westbound from the ocean...as this move inland this will become the scattered snow showers and flurries later for some...