ChescoWx

Thanks for all the messages and emails for a WXSIM forecast for next week! Here is the early view (take with the proverbial grain of salt this far out) WXSIM sees a 1" to 3" snow event next Saturday afternoon into the evening for NW Chester County PA

In my opinion this is by far the best Snowstorm threat so far this season. Now whether it is more white than wet....who knows but a big storm signal is there - as is common with most of the major East Coast events....interesting week ahead!

It's coming Mike....but remember it is just spitting out what the GFS and NAM are selling.....it is NOT a model.....just a tool. It will swing with every model change which we know this year is major from run to run

2.25" of rain so far here in East Nantmeal Township - this is the highest daily rainfall since way back on August 13, 2018 when 4.17" fell. It is also the 1st time with 2" or greater precipitation in a day since August 31, 2018. However, we did not set a daily precip record for the day that was set on the last day of the 1909 blizzard that left the county blanketed under 29.0" of snow with 2.54" of w.e. on this day the 25th in 1909.

Since we are in a bit of a weather lull outside of a nice rainstorm. I got to thinking about great rock bands that have recorded songs about the weather or in the title. Of course I immediately go to the all-time greatest rock band in history The Beatles for what was probably the 1st great rock song that was influenced by non over the counter drug prescriptions and the weather...very appropriate for our upcoming system - Rain. See link below for a black and white version of this great track from the Fab Four from back in August of 1966.....probably my favorite Ringo Starr drum track (as an amateur drummer a very tough track to play) Post your favorite weather inspired tracks if so inclined - thanks! https://www.youtube.com/watch?v=cK5G8fPmWeA

WXSIM with 6z data has up to 2" of rain maybe a couple ice pellets at the start at around 4am Saturday AM.....I do see a snow flurry on Tuesday around midnight....keep the faith!

Snow began in East Nantmeal Township PA at 5:45pm on the 22nd with 4" of snow accumulating by midnight. An additional 22" of snow fell on the 23rd. The 26.0" of snow made this the 8th largest storm in Chester County PA history (largest being the 45.3" blizzard ending on Feb 14, 1899) and the 15th storm to exceed the 20" mark. This was the 3rd twenty inch plus storm in the county in the 6 years between 2010-2016.

Agreed!!

K If that model was to verify I would bet snow would fall 100 miles NW of that surface low - N and W of philly would snow....but that is in la la land time frame

WXSIM with 6z data warmed about 1 degree from last forecast - still shows a mix of rain and S+ during heaviest precip but with the slightly warmer temps only a slushy 1/4 inch of snow - maybe we are back to a foot with the 12z GFS and NAM data! Since there is no real snow in the forecast we track WXSIM snow!! See you on the anticline this weekend! Friday night: Mostly cloudy to cloudy in the evening, becoming dense overcast after midnight. A mix of rain, sleet, and snow likely after midnight. Low 32. Wind chill ranging from 23 to 40. Wind east-southeast around 6 mph in the evening, becoming 13 mph, gusting to 20 mph, after midnight. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around half an inch. Snow or ice (on ground) accumulation about a quarter inch. Saturday: Dense overcast in the morning, becoming mostly cloudy to cloudy in the afternoon. A mix of rain and snow likely in the morning, then rain likely in the afternoon. High 40. Wind east-southeast around 15 mph, gusting to 21 mph, in the morning, becoming 6 mph in the afternoon. Chance of precipitation 80 percent. No snow accumulation expected.

LOL! That made me laugh!! Can you imagine if JB had access to this output? If so he would have no doubt sited it this week....he can always find the snowiest model or outcome!! The WXSIM programmer mainly designed it for forecasting temps....which like last weekend actually outperformed the NWS point and click for my area. The WXSIM steadfastly stuck with temps below freezing while the NWS said 37....Like any program it is only as good as the data it is ingesting....in this case the GFS for longer term and the NAM blended in for shorter term forecasts. Plus like any model when multiple days out it will not be as accurate. When it comes to snow forecasts it will often bounce around especially as it tries to account for my areas relative higher elevation mainly for storms like this upcoming weekend which have the feel of a March storm (which often has big differences over short distances based on just 200 ft of elevation gain etc.) it tries to nail the BL issues and will make a totally different forecast if the BL goes up a degree (like the latest 6z run this AM see below - where it is back to a mix with little accumulation) It should get more consistent as we get within 24 hours. I have had the tool for over 10 years and it is a fun tool for the weather hobbyist and really the only one that let's you make a true in your backyard forecast. But like any tool it is just one I would use if making a forecast....all of our go to forecasts should today and always remain the great team at the NWS in Mount Holly (we are fortunate to have the best office in the USA in my humble opinion!!) Paul

WXSIM with 18z data continues to see a real battle of precip types based almost entirely on relative elevation on Saturday. When the precip is heavy it see S+ as it lightens it's just rain. Temps never fall below freezing at the surface hanging between 32.7-33.7 with 850's just below 0c during the time of heaviest precipitation. WXSIM is back up to around 10" of very wet snow. Really feels like a March type snowstorm. In some ways reminiscent (of course not the amounts) of the March 1958 elevation driven event where just 6 miles up the road at my elevation Morgantown PA recorded 50" between the 19th-21st with 44" falling on the 20th alone with temps just above freezing for most of the event. The 6 days leading up to the event saw temps in the mid to upper 40's and the day after the snow ended went right back up toward the 50's and within 5 days all 50" was gone.

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