ChescoWx

As we talked about earlier the forecasts have changed significantly for Friday - per the latest AFD The updated forecast now has highs on Friday in the mid to upper 30s for the I- 95 corridor and west with mid to upper 20s in the Poconos. Areas south and east of the I-95 corridor have highs in the low to mid 40s. Wintry precipitation is now the result for much of the area for at least part of the timeframe from daybreak Friday into Saturday. Mixed precipitation may make it as far south as parts of Delmarva. Warm air looks to gradually filter in through this event which would cause a changeover to rain. Right now, the best potential for this to be a mainly rain event looks to be in parts of Delmarva and southern New Jersey. There is a large amount of uncertainty with the forecast for Friday into Saturday and trends will need to be monitored. Uncertainty remains through the weekend but there are indications that the forecast stays unsettled.

From Meteorologist Bobby Martrich on these huge changes to Friday "Last 4 runs of the GFS are comical... and it's not alone with this idea of a colder day Friday - just after Christmas. Much colder in fact, so instead of 50s you cut 25° off the high temps and get frozen precip, not rain. This goes back to the prior video discussions where I talked about models struggling in seasonal transition and being overzealous about the supposed "torch" pattern. If you're on the colder side of that thermal gradient, it's a much different outcome. This is the result of models completely whiffing on the extent of blocking in the Northern Atlantic and Atlantic Canada and a much stronger Quebec high providing the cold air damming. While we need to see this apparent trend to continue to alter the forecast, the Friday forecast could look much different if it does."

How's that high in the 50's you bet on for Christmas Day looking? LOL!!

The latest European for Friday.....a wee bit different from prior model runs.

Below normal temperatures look to continue through at least Christmas with some models now hinting at significantly colder weather than currently forecast for Friday. We do have a chance of some light snow, sleet and freezing rain arriving tomorrow morning. While amounts will be light the timing near rush hour could be a potential problem. We should dry out by tomorrow afternoon. Christmas Eve Day looks sunny. Plenty of uncertainty regarding both temperatures and precipitation by Christmas Day and Boxing Day.

Below normal temperatures look to continue through at least Christmas with some models now hinting at significantly colder weather than currently forecast for Friday. We do have a chance of some light snow, sleet and freezing rain arriving tomorrow morning. While amounts will be light the timing near rush hour could be a potential problem. We should dry out by tomorrow afternoon. Christmas Eve Day looks sunny. Plenty of uncertainty regarding both temperatures and precipitation by Christmas Day and Boxing Day.

I suspect that high near 57 on Friday will be coming down significantly later today...

06z GFS

This may be the largest temperature swing over 1 run I have ever seen on a model. The other models have similar cold trends.

Below are my obs from Thorndale in December 1998 and from the Coatesville 2W NWS observer. Not too much snow but just enough for the White Christmas

Happy first day of Winter to those that celebrate! We are at about our high temperatures for today with a cold front passing through this morning. Today’s temperatures will drop to freezing by evening. Below normal temperatures tomorrow with near normal high temperatures through Christmas Day. The warmest day of Christmas week looks to be on Boxing Day with temperatures well into the 40's and maybe even 50 in some valley locations. We turn chilly again on Saturday. It looks increasingly likely that snow will arrive by Tuesday morning's rush hour. We should see less than an inch of snow before any change to rain for most of the area with more up toward the Lehigh Valley. Additional rain shower chances for both Christmas and Friday.

Happy first day of Winter to those that celebrate! We are at about our high temperatures for today with a cold front passing through this morning. Today’s temperatures will drop to freezing by evening. Below normal temperatures tomorrow with near normal high temperatures through Christmas Day. The warmest day of Christmas week looks to be on Boxing Day with temperatures well into the 40's and maybe even 50 in some valley locations. We turn chilly again on Saturday. It looks increasingly likely that snow will arrive by Tuesday morning's rush hour. We should see less than an inch of snow before any change to rain for most of the area with more up toward the Lehigh Valley. Additional rain shower chances for both Christmas and Friday.

A return to chillier weather today with highs in the mid-40's. We stay below normal through Monday with maybe some wet snow arriving toward Tuesday morning. This should turn to rain pretty quickly from SW To NE across the area. Temperatures look to be near normal for Christmas Eve Day before we rise to about 4 degrees above normal for Christmas Day. Boxing Day looks to be the warmest day of the week before we cool down as we move toward the New Year's holiday.

A return to chillier weather today with highs in the mid-40's. We stay below normal through Monday with maybe some wet snow arriving toward Tuesday morning. This should turn to rain pretty quickly from SW To NE across the area. Temperatures look to be near normal for Christmas Eve Day before we rise to about 4 degrees above normal for Christmas Day. Boxing Day looks to be the warmest day of the week before we cool down as we move toward the New Year's holiday.

Over 0.50" of rain has already fallen here in East Nantmeal with as much as another 0.50" possible for some areas. We have already reached out high for the day of 56.6 just before 6am. Temperatures have fallen over 6 degrees since then and will continue to fall into the 30's by 4pm and freezing by 6pm. Lows tonight will fall to near 20 degrees and highs tomorrow only in the mid-30's. Temperatures will be near normal in the low 40's pm Sunday before falling back to below normal levels through Christmas Eve day. There is a chance of some snow by Tuesday morning that could be mixed with rain further south across the area.

Over 0.50" of rain has already fallen here in East Nantmeal with as much as another 0.50" possible for some areas. We have already reached our high for the day of 56.6 just before 6am. Temperatures have fallen over 6 degrees since then and will continue to fall into the 30's by 4pm and freezing by 6pm. Lows tonight will fall to near 20 degrees and highs tomorrow only in the mid-30's. Temperatures will be near normal in the low 40's pm Sunday before falling back to below normal levels through Christmas Eve day. There is a chance of some snow by Tuesday morning that could be mixed with rain further south across the area.

Today will be our mildest day since the day before Thanksgiving with highs in the mid to upper 40's. Rain heavy at times arrives after midnight and continues into tomorrow morning. Combined with the melting snow and ice we could see some local flooding. Temperatures will rise into the low 50's toward morning before a strong cold front passes through with maybe a thunderstorm and then temperatures crash tomorrow during the day reaching near freezing by 5pm. There is a wind advisory in effect tonight into tomorrow so watch for some power outtages in the usual spots across the county. We then look to see temperatures bouncing below normal on Saturday, Monday and near normal Sunday, Tuesday and Christmas Eve. Our next chance of some snow or rain looks possible by Tuesday.

Today will be our mildest day since the day before Thanksgiving with highs in the mid to upper 40's. Rain heavy at times arrives after midnight and continues into tomorrow morning. Combined with the melting snow and ice we could see some local flooding. Temperatures will rise into the low 50's toward morning before a strong cold front passes through with maybe a thunderstorm and then temperatures crash tomorrow during the day reaching near freezing by 5pm. There is a wind advisory in effect tonight into tomorrow so watch for some power outtages in the usual spots across the county. We then look to see temperatures bouncing below normal on Saturday, Monday and near normal Sunday, Tuesday and Christmas Eve. Our next chance of some snow or rain looks possible by Tuesday.

Poor Timmy where is that 50 plus degrees you were preaching about for Christmas Day earlier this week? LOL

Today will be near to slightly above normal with highs in the middle 40's. We warm a bit more tomorrow into the upper 40's and then the low 50's by Friday. Rain arrives by Thursday night and would expect to see some areas of fog as the snow melt ramps up tomorrow night. We could see 3/4 to an inch of rain. We then turn colder again for the weekend and into the start of Christmas week.

Today will be near to slightly above normal with highs in the middle 40's. We warm a bit more tomorrow into the upper 40's and then the low 50's by Friday. Rain arrives by Thursday night and would expect to see some areas of fog as the snow melt ramps up tomorrow night. We could see 3/4 to an inch of rain. We then turn colder again for the weekend and into the start of Christmas week.

How cold has the first half of December been....well here in Chester County PA with 132 years of climate data this December is the 11th coldest start to the final month of the year. Below are the 20 coldest first halfs of December. While we will moderate a bit to near or slightly above normal for the remainder of this month we will still end December with below normal temperatures and finish the 2025 calendar year with 7 of the 12 months averaging below normal temperatures.

How cold has the first half of December been....well here in Chester County PA with 132 years of climate data this December is the 11th coldest start to the final month of the year. Below are the 20 coldest first halfs of December. While we will moderate a bit to near or slightly above normal for the remainder of this month we will still end December with below normal temperatures and finish the 2025 calendar year with 7 of the 12 months averaging below normal temperatures.

True! I did not really catch that but indeed!!

With this week's snow event across Chester County PA we are now up to 9.9" of snow so far this season. Through the end of December our typical average snow total is 7.1". So, what could this mean for our snow totals by the time the final flake falls possibly as late as April? Well to date this is the 36th snowiest December with records back to 1893. Below is all 36 years along with where we ended up for seasonal snow that winter. Of note 25 of the 35 years or 71% of the time we ended up with above average seasonal snowfall. Average seasonal snowfall ranges between 32" to 36" across the county. The overall average snowfall across these 35 years was 48.4" of snow. The greatest seasonal snow was the 95.0" that fell in 1898-1899 and the least was the 17.1" in 1912-1913. For Team Snow you should feel fairly good that we end up with above average snowfall this season.