ChescoWx

The latest RRFS which will replace the NAM this year comes in with a snowier less sleety solution than it's older parent...

Looking at the 12z 3km NAM only through 7pm but it shows what I suspect will happen - a quick 6" to 9" of snow across Chester County up to the LV and a change to sleet all the way up to ABE from noon through 3pm from south to north. Then 0.5" north to 2" south of sleet which gets totals to 7" to 10" of snow/sleet by 7pm....if this went further I believe it will show a change back to all snow later like the 12km at night with maybe a couple more inches which gets us to 9" to 12" across the area from Southern Chesco up to ABE.

A cold weather advisory from the NWS goes into effect from 10pm tonight till 10am tomorrow morning. Highs today before an arctic frontal passage will get close to freezing in spots before dropping quickly by late afternoon. We should fall to the teens during the 7pm hour and near single digits by midnight tonight. Lows tonight should be near 4 degrees above zero and we recover tomorrow to no higher than 15 to 17 degrees. Wind chills near 10 below tomorrow. The well-advertised snowstorm arrives after midnight tomorrow night and could last into Monday morning. Most of Chester County will transition from heavy snow to heavy sleet during the late afternoon on Sunday. This will stop fast accumulating snow and move the area to slow accumulating sleet which does count as snow accumulation....be sure to clean off your snowboards when the snow turns to sleet. Once the storm passes on Monday we will see little melting for at least the next week - in fact, models are hinting we may not see another above freezing day till Groundhog Day in early February. Oh, and indeed I do not think we have seen our last snow event either.

A cold weather advisory from the NWS goes into effect from 10pm tonight till 10am tomorrow morning. Highs today before an arctic frontal passage will get close to freezing in spots before dropping quickly by late afternoon. We should fall to the teens during the 7pm hour and near single digits by midnight tonight. Lows tonight should be near 4 degrees above zero and we recover tomorrow to no higher than 15 to 17 degrees. Wind chills near 10 below tomorrow. The well-advertised snowstorm arrives after midnight tomorrow night and could last into Monday morning. Most of Chester County will transition from heavy snow to heavy sleet during the late afternoon on Sunday. This will stop fast accumulating snow and move the area to slow accumulating sleet which does count as snow accumulation....be sure to clean off your snowboards when the snow turns to sleet. Once the storm passes on Monday we will see little melting for at least the next week - in fact, models are hinting we may not see another above freezing day till Groundhog Day in early February. Oh, and indeed I do not think we have seen our last snow event either.

Updated and latest NWS Forecast

I am sure you know but that slop will likely be accumulating sleet which counts as snow....

I way prefer a sleetfest to ZR!!!

NAM 12km hitting the sleet hard past Allentown....

Folks will need to measure and wipe their snowboards as the sleet begins (plus run out and shovel). Sleet counts as snow albeit at about 3:1 a bit slower accumulations!

Snow first plus sleet second....change back to snow before ending?

Thanks Mike!! would have mentioned you too but was not sure you were on the forum. Take care Paul

Below is the sounding above KMQS Coatesville Airport at 7pm off the 12z Euro this appears to be the warmest hour on the model at 850mb previous 2 hours had some warmth at 700mb that looks like clearly IP to me. Does the below look like IP or ZR....I think it's close to ZR but mainly sleet - can our professional Mr. Newman weigh in? Thanks!

I remember it well! I was in KOP at the time....21 degrees with heavy ZR

Truth!

not a stupid question at all! minus 4 celcius- verbatim that would still be snow up at ABE - a little too close so I suspect sleet where it is minus 2 or higher

The latest NAM through 4pm with looking at how close the upper level temps are to freezing looks like sleet already at most spots across at least Chesco and up to close to Reading....but the damage has been done.

CAMS will be a great tool to see the mids warm. Below is the 6z NAM through 1pm

A significant winter storm begins toward midnight on Saturday night. Today should be our last relatively mild day for the rest of the month of January and into the start of February. Tomorrow we return to near normal temperatures with highs in the middle 30’s. An arctic cold front will cross the area later tomorrow afternoon temperatures will fall quickly to single digits above zero by midnight. Saturday will be very cold and breezy with highs only in the mid-teens. The snow arrives overnight and continues through at least 1pm on Sunday. By that point, most areas of Chester County could see between 6” to 8” of snow. At some point after that we should begin to see the snow mix with and change to sleet and freezing rain from SE to NW across the area This will cut into any additional potential snow accumulations. The final snow/sleet accumulation totals will depend on how fast this changeover occurs. Either way there will be plenty of snow and sleet accumulation. Unseasonably cold weather follows the storm with temperatures likely not rising above freezing for possibly at least the next 10 days.

A significant winter storm begins toward midnight on Saturday night. Today should be our last relatively mild day for the rest of the month of January and into the start of February. Tomorrow we return to near normal temperatures with highs in the middle 30’s. An arctic cold front will cross the area later tomorrow afternoon temperatures will fall quickly to single digits above zero by midnight. Saturday will be very cold and breezy with highs only in the mid-teens. The snow arrives overnight and continues through at least 1pm on Sunday. By that point, most areas of Chester County could see between 6” to 8” of snow. At some point after that we should begin to see the snow mix with and change to sleet and freezing rain from SE to NW across the area This will cut into any additional potential snow accumulations. The final snow/sleet accumulation totals will depend on how fast this changeover occurs. Either way there will be plenty of snow and sleet accumulation. Unseasonably cold weather follows the storm with temperatures likely not rising above freezing for possibly at least the next 10 days.

That is a great stat there!! thanks!!

Our best storms always have some non-snow in the mix.