MGorse

Epic lake effect snow event!

This was the third tornado this year. The first one was in Bucks County at the end of March, second one was in Monmouth County in May. The new tornado ally continues.

That looks to be just about over NWS Mount Holly, so I will let you know.

That is a Weather Channel naming thing.

Just curious. Thanks.

That wording sounds like a Winter Storm or Ice Storm Warning should be issued for at least parts of that region. Maybe that is what they are implying?

You can tell them it is actually an upgrade. Look at the coding (UPG)… NJZ007-008-PAZ060>062-242200- /O.UPG.KPHI.WS.A.0005.220225T0000Z-220225T1800Z/ /O.NEW.KPHI.WW.Y.0012.220225T0000Z-220225T1800Z/ Warren-Morris-Berks-Lehigh-Northampton- Including the cities of Washington, Morristown, Reading, Allentown, Bethlehem, and Easton 338 AM EST Thu Feb 24 2022 ...WINTER WEATHER ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO 1 PM EST FRIDAY...

Zones overall match the county borders. There are some exceptions like Bucks, Montgomery and Chester counties which were split years ago to better define the more urban from the higher elevation areas. Splitting of counties/zones is a long process. Emergency Managers do no set the criteria. They review what is planned to be in place basically to provide feedback. The criteria is based in part on climatology. PennDOT is usually not involved because the criteria is not strictly for what accumulates on roads. That is very difficult to predict. Some adjustments for as least some areas to the warning/advisory criteria were made over the years. There is some wiggle room when it comes to winter storm warnings as combined impacts can be taken into account despite the individual snow and ice amounts being below warning criteria. Lastly, I had no hand in expanding the winter storm watch this afternoon.

Great observation! Dew points will be first to really drop with the frontal passage. Main cold air push is during tonight.

Yeah those are different and based on known impacts tied to a river gage level.

Yup especially with watches, warnings and advisories. Appreciate it!

Perhaps but a challenge given the recent warmth. I could see more sleet occurring over snow.

Thank you for the kind words and understanding.

The warning and advisory criteria is by zones not mountain ranges and such. The criteria is also run by each county Emergency Manager. We try to factor in many things when deciding where to issue a watch. We did not purposely leave out Lehigh County, but focused where the higher snow/sleet is forecast plus where the higher confidence was. We have to start somewhere. Look for additional forecast updates later this afternoon and again tonight. We try our best and we are certainly not perfect!

Some of these comments…oh my.

Sleet is included with snow regarding accumulations. Sleet can be messaged separately if significant but otherwise it is combined.

Interesting event. I recall at least some of the model guidance showing pronounced 700 mb or 850 mb FGEN farther northwest of I-95 and closer to the I-78 corridor, yet some were showing less snow. It is like what the model was showing at the surface was playing catch-up to the dynamics aloft. Colder air deeper farther west which placed that lift much better into the favored dendritic snow growth zone.

No I referenced New Castle County because that is farther southwest and had 3-6 inches. The 4-5 inch reports in Philadelphia County seen too low. As for that PNS, I am not sure why those old reports were added back in.

Thanks for asking.

There were several 3-6 inch reports in New Castle County, DE. Given that and some other reports in Philly, I would say 4 inches in south Philly is too low.

I feel like I am being interviewed. Lol. That statement sums it up well. Many times this is being said incorrectly because the energy is not being transferred. New coastal low develops due to incoming upper level support (results in surface pressure falls) while the inland low weakens then dissipates as the upper level support leaves it behind.

If we do not receive an updated report or final report then that is removed from the PNS. This is because it then becomes less representative. We do our best to quality control all reports but there are times when some slip through. If we catch it later then it is removed. We usually get tons of reports for snow events (overwhelming at times). Also, keep in mind that the airports that measure snow (PHL, ABE, ILG and ACY in our area) continue to measure and report every 6 hours.

I continue to post here from time to time, and yes I am still at NWS Mount Holly. The PHL measurement has not been taken in National Park, NJ in years. It is done at the airport. Airport’s are not the best places to measure snow but they do their best. As for snow ratios, we have in-house tools where we can blend different models to get the values desired. WPC also provides guidance on the ratios. Lots of internal collaboration occurs especially with big events like yesterday. We then use tools that take the forecast QPF and apply the selected ratios to give snowfall amounts. This can also account for temperatures as well. So in short, our forecast snowfall does account for ratios.

It is technically in Delaware County. We list it as in Philadelphia County though for continuity plus it represents Philadelphia.

According to his Facebook post a few hours ago, 6ABC has Philly in the 6-12 inch range (highest east into interior south NJ).