ChescoWx

GFS did move north a bit from it's 6z run...but still south of some of the other models.

From one of my favorite professionals Bobby Martrich at EPAWA on the upcoming milder but not torch pattern before cold returns. "A lot of talk recently about a Christmas week "torch" and yes, there have and will be changes to the late next week period to just past Christmas that will take us out of the tank where we've been for much of December, and moderate the pattern. The culprit is a nearly 5 sigma high pressure/ridge over the Bering Sea, which was poorly modeled last week, and responded to a combination of a Scandinavian blocking pattern and the EAMT that retracted the Pacific jet too far... allowing this ridge to pop over the Bering Sea. If you watched the WW video last Sunday when I had @ShaneMartrich on, he talked about his research and lack of data in the polar regions. This may be one of those cases why the models and ensembles had a knee-jerk reaction this week. Kind of their version of an "oh crap" moment. By doing so, it turns the EPO positive, so the cross-polar flow is temporarily shut off. But for transparency, this is far from a "torch" pattern for us. Milder than now, yes... but aside from a synoptically-driven spike ahead of a cutter near the 18th, temperatures return closer to average instead of 15-20° below like they have been. This will be temporary, and may last more than a week, then colder returns late month and January."

I think anyone expecting a Christmas "torch" will be unhappy. While it will of course get warmer - heck this is one of the coldest first half's of December since the 1890s. I don't see this like the 1989 pattern. I suspect Christmas week while a lot warmer than now...will be not too far above normal readings for Christmas IMHO.

Little lake effect streamer with a little whitening here in NW Chester County

We are seeing some lake effect streamers making into as far southeast as Chester County this morning and don't be surprised if we see a couple more snow showers during the day. We have already reached our high temperature for the day at about 130 this morning. Today’s temperatures will remain below freezing in most spots with wind gusts as high as 35 mph. Our top 10 coldest start to December looks like it will continue for at least the next week, and we may see a couple of snow chances over the next few days. The first one overnight Friday night looks very light while the next potential event toward Sunday morning could bring some locations their “largest” snow event this season. Of course, that would not be hard to do as our largest "event" has only been 0.5" Behind whatever happens on Sunday another very cold air mass moves in on Sunday night and lasts through Tuesday with temperatures from Sunday through Tuesday remaining in the mid to upper 20's for highs with lows in the teens.

We are seeing some lake effect streamers making into as far southeast as Chester County this morning and don't be surprised if we see a couple more snow showers during the day. We have already reached our high temperature for the day at about 130 this morning. Today’s temperatures will remain below freezing in most spots with wind gusts as high as 35 mph. Our top 10 coldest start to December looks like it will continue for at least the next week, and we may see a couple of snow chances over the next few days. The first one overnight Friday night looks very light while the next potential event toward Sunday morning could bring some locations their “largest” snow event this season. Of course, that would not be hard to do as our largest "event" has only been 0.5" Behind whatever happens on Sunday another very cold air mass moves in on Sunday night and lasts through Tuesday with temperatures from Sunday through Tuesday remaining in the mid to upper 20's for highs with lows in the teens.

How cold has this year's first 10 days of December been in Chester County PA? Glad you asked - This is the 10th coldest start to December since records began way back in 1893. Of note 5 of the top 11 cold starts to December have all occurred since 2000.

How cold has this year's first 10 days of December been in Chester County PA? Glad you asked - This is the 10th coldest start to December since records began way back in 1893. Of note 5 of the top 11 cold starts to December have all occurred since 2000.

The 850mb freezing line is sinking south - now just north of Chester County and through Northern Berks county. If precip sticks around past 5pm we might see a few flakes as far south as Chesco.

Latest control and European ensemble runs for the potential Sunday winter event.

We have seen below normal temperatures every day with the exception of one day since Thanksgiving Day. This pattern looks to continue for at least the next week. We warm enough today that except for areas in Northern Berks and Lehigh counties we should see mainly rain showers. We turn colder tomorrow and will see some light snow chances both Friday night and again during the day on Sunday.

We have seen below normal temperatures every day with the exception of one day since Thanksgiving Day. This pattern looks to continue for at least the next week. We warm enough today that except for areas in Northern Berks and Lehigh counties we should see mainly rain showers. We turn colder tomorrow and will see some light snow chances both Friday night and again during the day on Sunday.

This morning, we saw many valley locations across the area down into the single digits for low. The lowest was the 6.1 at Warwick. This was the coldest morning since late last January when many spots saw below zero temps both the 21st and 22nd of January. We continue to keep well below normal temperatures for the remainder of the week. We do warm up to closer to normal tomorrow which should allow any start of snow or freezing rain to switch to plain rain from SE to NW across the area by late morning. A couple more chances of snow look possible both on Friday night and again on Sunday morning. More frigid temperatures follow any snow potential on Sunday with the coldest day so far this year by next Monday.

This morning, we saw many valley locations across the area down into the single digits for low. The lowest was the 6.1 at Warwick. This was the coldest morning since late last January when many spots saw below zero temps both the 21st and 22nd of January. We continue to keep well below normal temperatures for the remainder of the week. We do warm up to closer to normal tomorrow which should allow any start of snow or freezing rain to switch to plain rain from SE to NW across the area by late morning. A couple more chances of snow look possible both on Friday night and again on Sunday morning. More frigid temperatures follow any snow potential on Sunday with the coldest day so far this year by next Monday.

You can tell things have slowed down with my business as we near the holidays....plenty of time for some updated analysis! Below are the Top 10 snowstorms since January 1, 2020 here in East Nantmeal Township. We have had 5 storms greater than 6 inches but only 2 storms that have exceeded 10" or more.

You can tell things have slowed down with my business as we near the holidays....plenty of time for some updated analysis! Below are the Top 10 snowstorms since January 1, 2020 here in East Nantmeal Township. We have had 5 storms greater than 6 inches but only 2 storms that have exceeded 10" or more.

Euro not so enthused

Below is the latest GFS model which paints an almost ideal view of what a classic White Christmas would look like. Below is the total snow between this weekend and Christmas Eve morning at 7am. That model has a morning temperature of 18 degrees with between 10" to 14" of model snow we will never have to shovel.

At East Nantmeal today will be our 2nd below freezing day of the season and this morning was our 16th sub-freezing low. Below are the average number of each type of day at all of the Chester County Area Climate Locations. You may notice lower elevation spots in general experience more freezing lows while the relatively higher spots see more afternoon highs with below freezing temperatures.

At East Nantmeal today will be our 2nd below freezing day of the season and this morning was our 16th sub-freezing low. Below are the average number of each type of day at all of the Chester County Area Climate Locations. You may notice lower elevation spots in general experience more freezing lows while the relatively higher spots see more afternoon highs with below freezing temperatures.

Yep 2020-21 - 52.2" here in NW Chester County

The "trusty" ICON model highlight our next 2 winter "events" the first on Wednesday and the next on Friday night....

Following the arctic front passage temps have continued to slowly drop since sunrise across the area. Temperatures do not look to rise much today and remain in the upper 20's. Tonight will be the coldest night so far this season with lows not far from 10 degrees above zero. Some local station record lows will be broken including East Nantmeal record low was 17.7 back in 2010. We warm to near normal on Wednesday (this may be the last normal high temperature through Christmas) We should also see some snow arrive that will change pretty quickly to rain. We fall back below normal for the rest of the work week with additional snow chances arriving on Friday night into Saturday morning.