ChescoWx

AM low this morning 16.7 2nd coldest reading this season behind only 12/19 at 15.6. Of note today marks on average our coldest day here in Western Chester County with an average temp of 24.0 - it's all uphill from here!

They actually moved it back to PHL I think back in 2016??

The WXSIM still shows 1" to 2" of snow here at around 685 ft but it's battle regarding precip type when heavy it's snow and rain when lighter. Looks like a typical March event with precip type being heavily elevation dependent. I could see spots under 400 ft with nada / 2" over 600 ft /up to 3"+ over 700 ft in the philly burbs and NW NJ

https://www.inquirer.com/weather/snow-weather-philadelphia-winter-phl-measure-20200121.html

ruh roh! WXSIM trend is not our friend....with 18z down to 1" to 2"..... Saturday: Dense overcast. A mix of snow, sleet, freezing rain, and rain likely in the morning, then a mix of rain, snow, and sleet likely in the afternoon. High 35. Wind chill around 25. Wind east around 10 mph, gusting to 15 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly around an inch. Snow or ice (on ground) accumulation 1 to 2 inches. Above-ground freezing rain accumulation up to 0.1 inches. Saturday night: Cloudy in the evening, becoming dense overcast after midnight. A mix of rain and snow likely in the evening, then a slight chance of a mix of snow and rain after midnight. Low 31. Wind chill as low as 24. Wind north around 9 mph, gusting to 15 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. No snow accumulation expected.

took a deeper looks at the WXSIM forecast output when it thinks it is snowing....has winds ENE and temps nearing but just below 0c at 850mb....it will change with 18z!

Steve already down to only 6" to 10" trend is not our friend......

truncates NAM and all GFS once past NAM run window....

WXSIM with 12z GFS and NAM now down to "only" 6" to 10" of wet snow (keep in mind as someone questioned me on the last one - it's accuracy at this range is suspect at best - it simply takes a blend of the gfs and nam and makes a forecast based on local factors (elevation etc.) - verification will of course not be this... Friday night: Mostly cloudy in the evening, becoming mostly cloudy to cloudy after midnight. A slight chance of a mix of sleet, rain, and snow after midnight. Low 31. Wind east-northeast near calm in the evening, becoming 4 mph after midnight. Chance of precipitation less than 20 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. No snow or ice (on ground) accumulation expected. Saturday: Dense overcast. A mix of snow and rain likely. Breezy. High 35. Wind chill ranging from 22 to 27. Wind east-northeast around 12 mph, gusting to 21 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly between 1 and 2 inches. Snow accumulation 6 to 10 inches. Saturday night: Cloudy in the evening, becoming dense overcast after midnight. Patchy light fog. A mix of rain and snow likely in the evening, then a chance of a mix of snow and rain after midnight. Low 31. Wind chill ranging from 23 to 29. Wind east-northeast around 7 mph, gusting to 17 mph, in the evening, becoming west-northwest after midnight. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. Little or no snow accumulation expected.

Let's do this again - latest WXSIM for NW Chester County PA with 12z NAM and 6z GFS for next weekend- this could be a great example of an elevation driven event inland of the I95 corridor - not cold but just cold enough especially with a bit of elevation for a wet snow event....this will change a bit but I do believe this is something to keep an eye on as the week moves on Saturday: Dense overcast. A mix of snow and rain likely in the morning, then snow likely in the afternoon. High 34. Wind east around 10 mph, gusting to 17 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly around 2 inches. Snow accumulation 12 to 16 inches. Saturday night: Cloudy. A mix of snow and rain likely in the evening, then a chance of a mix of snow and rain after midnight. Low 30. Wind chill as low as 23. Wind north around 9 mph. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. Snow accumulation about an inch.

JB riding the snowiest model - the Canadian for next weekend's potential event....call me stunned!

And yet this recently completed decade was the snowiest on record for Chester County PA.....weather like many things runs in cycles and of course the climate is always and will always be changing

The sleet and now ZR looks to be winding down - total snow and sleet accumulation 2.0". Plus a nice glaze (see pix) with the ZR. Current temp 31.4

Road in poor shape here in NW Chester County Pa with sleet we may get our snow total up to 2" with this event Continues to sleet with a few flakes mixed in with heavier precip temp up to 27.4

With our 1.8" of snow/sleet so far this is our "biggest" event of our winter season so far. Depending if we stay sleet with the next band maybe we can pass the 2" snow/sleet mark with this one. Of note we have now had 3.6" of snow so far here in January only 1.4" below normal 5.0" through today. Seasonal snowfall is at 5.6" exactly 50% of our normal of 11.2" through today. Yet I received a message from a twitter follower today asking me why we are so low in snow this January against normal....I replied and told him we are one major snow event from being above normal for the season....stay tuned! Currently here in East Nantmeal the sleet is getting heavier and as the IP gets heavier some more flakes are mixing in - temp continues to slowly rise up 1 degree in last hour and up to 26.5

Hey Mike great question and not trolling for sure....keep in mind the WXSIM is only as good as the models being used - in this case it is a simple mix of the NAM and GFS....all models have been mighty poor this season especially days in advance. The WXSIM relies on the quality of these models if it's garbage in it's garbage out. What is is good for is nailing very local specifics to my backyard. Temps, start time of precip etc. as the models get better within 24 hours so does WXSIM. Does that make sense? Paul

East Nantmeal Township Chester County PA Sleet mix began at 230pm lighter now still some mangled flakes Snow/Sleet so far 1.8" at 3pm obs Temp 25.0 DP 20.0

Latest WXSIM with 6z - looks like WXSIM is winning for now the great battle vs NWS temp wise....NWS has now moved my P&C to 32 degree high - WXSIM still colder. Today: Dense overcast. A slight chance of a mix of snow and sleet in the morning, then sleet likely in the afternoon. High 27. Wind south near calm in the morning, becoming 6 mph in the afternoon. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly between a quarter and half an inch. Snow or ice (on ground) accumulation about half an inch. Tonight: Dense overcast in the evening, becoming cloudy after midnight, with scattered light frost possible. A mix of snow and sleet likely in the evening, then a slight chance of freezing rain after midnight. Low 25, but temperatures rising after midnight. Wind chill ranging from 16 to 24. Wind south-southwest around 9 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly around half an inch. Snow or ice (on ground) accumulation 2 to 3 inches. Little if any freezing rain accumulation.

WXSIM with 18z GFS/NAM backing off on the snow but hitting sleet harder - thus reducing snow/sleet totals by about an inch - total now 2" to 3" at most - however as I mentioned early this AM I am not surprised NWS brought the WWA down into Western Chester County with their 4pm update - the fascinating (to me) big battle tomorrow will be on temps - the NWS P&C has me at 37 while WXSIM only 26.....very rare to see that large spread between WXSIM and NWS...who will win the great battle of NW Chesco weather??? stay tuned!! Saturday: Cloudy in the morning, becoming dense overcast in the afternoon. A slight chance of snow in the morning, then a mix of sleet and snow likely in the afternoon. High 26. Wind south near calm in the morning, becoming 7 mph in the afternoon. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around half an inch. Snow or ice (on ground) accumulation 1 to 2 inches. Saturday night: Dense overcast in the evening, becoming mostly cloudy to cloudy after midnight, with scattered light frost possible. A mix of sleet, snow, and freezing rain likely in the evening, then a slight chance of a mix of freezing rain and sleet after midnight. Low 24, but temperatures rising after midnight. Wind chill ranging from 15 to 21. Wind south-southwest around 9 mph. Chance of precipitation 80 percent. Precipitation (liquid equivalent) mostly around half an inch. Snow or ice (on ground) accumulation about an inch. Little if any freezing rain accumulation.

Just looked closer at the 18z GFS....that may be the strangest snow map I have ever seen for a non-Miller B event - verification chances.....I would not bet a lot on that

I suspect that will not be happening.....

WXSIM with 12z data again ticked a bit colder and a little more snow/sleet accumulation with a bit earlier start time - total snow sleet 3.5" to 4.5" Here is the rundown: 10am snow arrives temp (22.2) 1pm Moderate IP (23.6) 4pm Heavy IP (23.4) 7pm Heavy Snow (23.6) Snow ends around 8pm

Keep in mind sleet counts as snow - it just accumulates relatively slow with a rule of thumb rate of w.e. to sleet of only 5:1 vs snow which is 10:1

My current thoughts (crude as it may be) on the upcoming event

Latest WXSIM with 6z NAM/GFS data has trended colder for NW Chester County I'm a bit surprised my zone forecast does not include a WWA. It could be the NWS cannot split the zone north vs. south. My point and click has a high of 37 for me tomorrow in East Nantmeal... I will take the way under - I will be surprised if we get near or above freezing. Total snow and sleet accumulation around 2" to 3". Here is the rundown of precipitation types temperatures and timing 12 noon Light snow (temp) (25.3) 1pm Moderate sleet (24.7) 4pm Heavy sleet (23.6) 7pm Heavy snow (23.6) 8pm snow ending (23.9)