ChescoWx

12z GFS still delivers the Christmas Miracle....if you choose to believe!

The current NWS Forecast has a High Temperature of 18 degrees and a Low of 9 degrees above zero for Christmas Eve Day. If the high is only 18 degrees that would be the coldest high temperature ever recorded on Christmas Eve day since records began for Chester County in 1894. The coldest high temp on Christmas Eve day was the 19 degree high back in 1906. Christmas Day warms up to a forecast high of 21 following a Christmas morning low of 11 degrees. If that Forecast holds the combined Christmas Eve and Day Holiday would be the 4th coldest holiday on record. With Christmas Eve the 4th coldest and Christmas Day the 3rd coldest on record. The combined top 15 combined cold holidays are in the table below. Merry Christmas to all stay warm!!

That "well respected met" JB has had his eye on this....

Another near normal late December day for the area today with temps touching 40 degrees this PM. Today is the calm before the storm that will arrive tomorrow AM. Clouds increase tonight with our temps actually rising after midnight. Some very brief sleet or freezing drizzle is possible just after rush hour tomorrow. This will quickly change to heavy rain which will last into Friday. A strong arctic cold front will sweep across Chester County during about the 10am hour on Friday. Any left over precipitation will change to snow or flurries for an hour or 2. Some models still hint at a small accumulation...more likely as we head west in the county. Either way rapidly falling temperatures on Friday afternoon with readings falling through the teens. Some models have temperatures as low as 12 degrees by 7pm. Many areas will see air temps in the single digits by Christmas Eve morning. High temperatures on Christmas Eve will not escape the teens. Wind chills will be well below zero all day. Christmas. A top 4 Coldest Christmas Eve and Christmas Day is likely. The record high for today is 62 degrees from 1971. Our record low is 1 below zero from 1942. The daily rain record is 1.56" from 1902. The daily snow mark is 2.0" from 1959.

12z GFS and NAM both showing some minor anafront snows on Friday....usually does not work out from my experience

It looks like a big fail for my analog snow forecast for December...but the below normal temps look likely....

Nothing on the 6z Euro

If you want to see what a festivus miracle can look like - the always reliable 84 hour NAM delivers a plowable snow for the western burbs of Philly on Friday!! Lock it in!!

Dry and seasonable weather will continue for Christmas Week before a stormy Thursday into Friday for Chester County PA. The storm continues to look like mainly rain after a brief start as snow or sleet. A powerful cold front will sweep across the county from west to east during the late morning hours on Friday. Most models are now showing some minor <1"of snow accumulations before the snow ends on Friday PM. A top 10 coldest Christmas holiday remains probable for the weekend.

Today was our 1st day this season that the high temperature failed to rise above freezing. The last time we failed to pass the freezing mark for a high temperature was on March 28th. That was also the latest sub freezing day in Chester County history with records back to 1894.

To put a fine point on Charlie's (Chubbs) post above. Below is a simple chart showing average actual (non-adjusted) temperature trends comparing PHL Airport (Green) vs. Phoenixville (Blue) / Glenmoore (Orange) and Coatesville Chesco (Red) from 1940 through today. The calculated trend lines very clearly show the PHL Airport trend is rapidly rising while the others show much more stable trends with slight rises at both Phoenixville and Coatesville but cooling trends shown by the Glenmoore NWS COOP observer. In fact with just 12 days remaining in 2022 both Glenmoore and Coatesville will finish between 0.5 and 1.0 degrees colder than 2021. Of course the PHL Airport is on pace to finish at greater than 1 degree warmer than 2021.

Again for the millionth time - my data is pure and not adjusted raw data. It clearly does not show what your post adjusted multiple site combined data above shows. As it shows in my data shared earlier in this thread there is a clear up and down and up and down pattern to all sites - it is not that complicated!!

Based on the current forecast it appears likely this will be a top 10 coldest Christmas Eve and Christmas Day in Chester County PA history with data back to 1894. If the current forecast verifies it would be the 9th coldest Christmas Eve and the 6th Coldest Christmas Day. See the Top 20 coldest for each day below.

Our stretch of chilly weather looks to continue for most of the remainder of 2022. In fact December looks likely to finish as our coldest December since at least 2017 and possibly the coldest since 2010! Dry weather should continue before snow arrives on Thursday morning before quickly changing to rain. A strong arctic cold front will sweep through from west to east on Friday afternoon dropping temps from the 50's at 1pm to below freezing by 8pm. High temperatures on Christmas Eve day and Christmas Day may struggle to reach the low to mid 20's. The record high for today is 62 degrees set in 1929. The record low is 1 above zero from 1951. The daily rain record is the 1.30" that fell in 1934. Our daily snow record I remember well as 15" of snow fell today back in 2009. It started at 5am and was over by 10pm. There was still 4" of snow on the ground on Christmas morning which was our next to last White Christmas - with our last such one 10 years ago in 2012 when we had 2" of snow on the ground that fell on Christmas Eve 2012.

Great info!! It looks like they reached their peak steel production in 1953. They are still in production today - even making some of the steel for the new WTC in NYC! An interesting idea - and no doubt it may have contributed a bit to the warming...but since the same pattern of cyclical warming and then cooling was seen at all of the other Chester County observation locales in West Chester, Phoenixville and Devault during that 1930's through early 1950's time frame. It provides some additional support for the observations at all the chesco spots.

Sorry Steve -I should have clarified - I am of course only looking at all of the Chester County NWS COOP sites for my local suburban Philly county, With the cyclical flow of my analysis of only Chester County PA (see below). We have a clear history at least here in Chester County PA of multiple decades of warming (1930's thru 1950's) followed by multiple decades of cooling (look at those 60's through 80's decades).... now followed by our recent decades of warming - so I am extremely confident we should see multiple decades of cooling as that is what the historical records show us. I am a big believer in the cyclical nature of climate and a huge believer in predictable normal climate change. I understand a lot of folks think warming will continue unabated but I just can't find any actual real world data to support this hypothesis. I am a fact based data guy and I just can't find any long term historical data points outside of heat island locations like PHL airport that support this. Does this make sense?

Of note today will be our 10th of 18 days that have been below normal. Looking ahead regarding temps we are well on our way to only our 3rd below normal December in the last 12 years as we look to be starting the next cooling cycle of our local climate.

Yes Virginia if the NBM were to verify we may see a change to snow before ending and we would see our 1st White Christmas in 10 years! Need a festivus miracle!! Or technically a little anafront action!!

As has been the case for this early winter season here in Chester County it appears we will see below normal temperatures for the upcoming week but then a brief but sharp warm up just in time to turn any brief snow at the start to a heavy rain on Thursday. For those who want snow we need these low pressure systems to track off the coast to our east to keep the cold air locked in. After the storm we will turn sharply colder by Friday PM with our coldest weather of the season so far on tap for Christmas weekend. Christmas eve day may struggle to escape the low to mid-20's for high temps.

Yep lock that up a White Christmas in Chester County...

Some interesting climate data analysis by month for Western Chester County PA. I wanted to see the differences in our local county climate comparing NWS coop observations taken at 340 ft above sea level (ASL) which were recorded from January 1894 through 1982 (89 years) vs. the observations that have been recorded now for the last 40 years at over 660 ft ASL. Some results that might be surprising to some. Overall very little change in our average temperatures since the 1890's +0.7%. However, somewhat cooler warm season months and warmer cold season months. The biggest differences have been in increased precipitation +9.7% and increased snowfall by 14.1%.

Quiet but seasonably chilly stretch of weather on the way through Wednesday. Then as the National Weather Service is saying this morning "Stay tuned for changes to the forecast, and our area should prepare for anything from heavy rain and gusty winds with some coastal flooding to snow and ice Thursday into Friday, with a very cold airmass likely to follow for next weekend." Lots of model disagreements but expect to gain a bit more consensus by Tuesday AM. The record high for today is 62 degrees from 2000. The record low is 1 below zero from 1910. Daily rain record is 2.99" from 2000. The daily snow record is the 7.5" that fell in 1932.

climate has of course not changed....climate cycles change and we have gone from a cold to a warmer and now I suspect we are trending into another colder cycle. We have been in a much snowier cycle during the last 2 decades....it will return again. Patience!

The EURO does not look right at all!! A bomb to lakes does not make sense....this will shift east in future runs although not saying it will be enough to bring a SECSy finish!!

as expected Euro follows - the ex-US models. Still nice to see some relative high level consensus at this range as I am sure we will see some more big swings over the next 6 days! Buckle up!!