In the Department of Meteorology and Atmospheric Science at Penn State.

This is weather world.

Good evening and welcome to Weather World.

On this Monday, December the 8th, I'm Marisa Ferger coming to you on a bit of a chilly day, which is ironic because class of 2023 graduate Jacob Hair is with us straight from Tallahassee, Florida.

Welcome.

Thank you very much.

I'm happy to be here on Weather World.

I wish I could have brought some of that Florida warmth to PA, but it doesn't look like it.

All right, well, Jacob is going to tell us a little bit about how cold it's going to get, but first tell us a little bit what you're doing right now.

Yeah.

Right now I'm in my PhD research and I'm studying bomb cyclones, which are the wintertime nor'easters.

So it's ironic that I go to Florida for winter time, but I'm taking it.

All right.

Well, we're going to hear your forecast in just a couple of minutes.

Also tonight Christian Spillane will be here with the extended forecast taking us through the upcoming weekend and into early next week.

But first, here's Filippo Formica with tonight's hashtag headlines.

I'm Filippo Formica and this is Hashtag Headlines, our weekly look at what's been trending in weather and climate news.

Let's get started tonight with hashtag frigid digits.

Old man winter burst through the doors across Pennsylvania Friday morning, with lows dropping into the single digits and low teens.

A cold front moved through Thursday, pulling in air straight from the Arctic Circle with clear skies and calm winds.

Overnight, radiative cooling took over, letting heat escape and sending temperatures crashing.

Several cities challenged daily record lows, including Allentown, Scranton, Williamsport and Erie.

Bradford, Dubois, Johnstown, and Mount Pocono all set.

New daily low temperature records.

The lowest official temperature in the state was eight below zero in Bradford.

This cold stretch continues this week with a chance for a reinforcing shot of Canadian air this weekend.

Hashtag Melissa wins what may be the highest hurricane wind gusts ever accurately measured has been confirmed by scientists.

A NOAA hurricane Hunter aircraft deployed dropsonde leading up to Hurricane Melissa's Jamaica landfall.

Drop zones are parachuting probes that gather information deep within storms.

After a thorough quality check by the National Center for Atmospheric Research, one of them recorded an astounding gust of 252mph, and the reading held up beyond the record books.

That is really important.

The only instruments that can safely sample a category 4 or 5 hurricane's lowest levels.

The portion of the storm that truly affects people and structures are drops ons.

Additionally, forecasters use such near-surface data to improve storm surge alarms and storm intensity advisories.

Researchers claim that the comprehensive data provided communities with vital lead time and enhanced forecast messages.

It serves as a reminder that improved science can have a quantifiable impact, even during the most hazardous storms on Earth.

Hashtag Tempest Extremes A few months ago, we talked about Google DeepMind, but did you know that Penn State has played a role in this AI tropical cyclone model?

Our department's doctor, Colin Tzatziki, alongside Penn State meteorology students, have developed a hurricane tracking toolkit that has been integrated into Google DeepMind.

This toolkit, called Tempest Extremes, has been a primary factor into why the DeepMind model has been earning the praise of meteorologists across the country.

The DeepMind model was the most accurate forecast model this past Atlantic and East Pacific hurricane seasons, with less than 150 miles of track error from five days away.

For reference, the American GFS model had close to 300 miles from the same five day forecast period.

AI is being used across the industry to improve forecast accuracy and the momentous strides of the Google DeepMind model wouldn't have been possible without Penn State meteorology and atmospheric science.

And those are this week's hashtag headlines.

Your Pennsylvania short range forecast is up next.

Well, it is certainly great to be back here on Weather World and at FSU.

I teach all the time, and I always tell my students, take five minutes a day, look at the satellites and radar, and you'll be able to get a lot of meteorological knowledge.

So today what we see is we have a storm system right now into the southeast portions of the United States.

And right now we have a low pressure system that is developing there.

So to the south of the Mason-Dixon line, we have some snow that's getting into the Mid-Atlantic, into West Virginia and Virginia.

That's going to be great for the ski resorts.

But to the to the north of this, we have a high pressure system in place.

And this is going to be providing for clearing skies tonight.

And that's going to drop our temperatures to the single digits.

In fact, if you look closely before the sun comes down, you can see that there's even some snow on the ground.

That's not clouds, that is actually snow.

So this river that we see here of storm tracks that's coming across the north, uh, of the United States, we actually have an atmospheric river that is coming into the West Coast.

Now, this is a category 4 or 5 atmospheric river.

And in fact, the National Hurricane Hunters, they actually fly into these systems to gain data for research.

And in fact, right now we could see a few feet of rain into the Cascades, which is incredible.

But otherwise, once these low pressure systems move into the upper Midwest, they can start to develop.

And we call these Clipper systems.

And right now we have one of those Clipper systems that is moving through Bismarck.

And that's going to impact the Great Lakes region.

This here this is going to be clipper system number two that will impact us on Wednesday.

If we go into the upper atmosphere, we'll see that.

We can see this ridge pattern across the west.

We have this trough across the East coast.

And this right in between is your area where these low pressure systems tend to track.

So there's a nice pipeline that would go from the West Coast and right into the East Coast.

And that's where we have our clipper systems to the south here.

That's where that low pressure system went off to shore.

And in fact, that's giving them beneficial rainfall into Florida, where they have an exceptional drought.

You can actually see this ridge trough pattern into the temperature departures from average into the west.

We have temperatures that are well above average, 10 to 15 degrees above average for most people.

And then here into the east, that's where that trough is locked into place.

And you have temperatures that are about 15 to 20 degrees below average.

And that's going to sustain into tonight for most of Pennsylvania.

Here's the surface maps to give us a little bit of an idea of what we can see.

So here's the high pressure system that is dominating over the East Coast with the low pressure that's to the south.

And again that's providing that nice moisture into the southeast.

This snow is going to remain to the south of the Mason-Dixon line.

The first clipper system comes through the Great Lakes region and into the northeast.

Erie is going to see some flakes, but otherwise the state will remain mostly dry.

It's the second clipper system that's going to be coming into the East Coast.

That is going to give us a little bit of a wintry mess into Pennsylvania on Wednesday, with some snow into the northwest, and then some rain into the lower elevations.

The her model actually does a good job at depicting this.

And we can see this here where tonight, first you're going to have some clearing skies, which is going to allow for those temperatures to drop rapidly.

But the first clipper system comes through into the northwest with some snow.

And then the second clipper comes through.

And then that's giving us some good snow amounts into northwest PA and along the mountain chain.

So tonight this is going to be a great night to get hot chocolate ready.

It's going to have temperatures that are going to be near record lows.

The clouds are going to start to clear out as that high pressure system is in place.

Temperatures are going to be mostly into the single digits tomorrow.

It's going to be chilly with below average temperatures, but temperatures will be on the rebound as we have that cold air tonight.

Temperatures will be mostly into the 30s and 20s with some snow into the northwest.

And for Wednesday, this is where we have a wintry Wednesday.

With the second low pressure system coming through, it's going to have some spotty showers into the southeast, but to the north, that's where we can have some snow upwards of 3 to 5in.

That's it for the forecast.

We'll be back with more.

Cold conditions.

Continue as we go throughout this extended forecast period.

Heading out into the beginning of the third week of December now, and we'll continue to see below normal temperatures throughout much of the region as a trough that's been centered over the eastern United States for much of early December will remain in place, at least throughout our extended forecast period here.

This is the current water vapor satellite imagery.

You can see the big dip in the jet stream over the eastern United States, more of a ridge of high pressure as you go out across the West Coast.

This will continue to be the theme as we start the extended forecast period during the day on Thursday.

Here's one depiction.

This is the GFS model that we're looking at here.

The American model.

You can see this big dip in the jet stream.

A system at this point has moved off to the northeast of us, and we're stuck in this northwesterly flow.

So I think we'll start the period off with a cool northwesterly flow, the breezy pattern that is typical for the winter with some lake effect snowfall, will dry out a bit by Friday before I think by the time we get towards Saturday, a weak system potentially approaches as this trough rotates around again, and then I think a larger system has the potential to develop by the time we get towards the later part of the weekend.

The GFS model shows another dip in the trough and a piece of energy with that that tries to come up the coast.

By the time we get towards the end of this coming weekend on around Sunday to Monday, although it's quite uncertain still exactly how these different pieces will move around, I think that's the potential for maybe a bit more of a robust system over the next seven days or so.

This model shows that moving off to the northeast by Monday, we can also take a look at the European model and the precipitation tracker and see what story it shows.

Here we see the cold conditions locked in here below freezing and the pink contours as we go throughout the end of the week.

Some lake effect snowfall.

European model has a weak system with some frozen precipitation.

As we go throughout Friday and into early Saturday as it scoots off the coast, and then by Sunday.

The European model doesn't show that system that the GFS has.

It shows a piece of energy moving by and not really forming until it's way off into the North Atlantic here, and eventually moving up to the north and east.

So a lot of uncertainty still with how that system will develop, maybe some light precipitation as we go throughout the day on late Friday and early Saturday.

That could be a bit of snowfall accumulation across the Mid-Atlantic region, but overall an elevated chance for some frozen precipitation as we go into this coming weekend.

And eventually by the end of the weekend, a stronger storm is possible, although a lot of uncertainty with that.

Exactly what will happen with the track, so we'll keep you updated as details become more clear.

Overall, though, continuing to be cloudy and gusty as we end the week with more lake effect accumulation possible and up to 10 to 20 degrees below average as we head into the middle of December with this persistent cold pattern just continuing across the region, that does it for the extended forecast.

We'll be back in a moment with more.

Well, a pair of Clipper systems are going to be impacting Pennsylvania.

The first one for tonight.

Uh, first off we're going to get you need to get the hot chocolate ready is what I'm going to say here, where you have temperatures that are going to be into the single digits.

And even getting to below zero here into Bradford and approaching near record lows.

But tomorrow, this is where we're going to have the first of those clipper systems where we have some snow into the northwest, but otherwise it's going to be remaining mostly dry with some cloudy to partly cloudy skies.

Temperatures are going to be about 5 to 10 degrees below average, but it will certainly be much warmer than it is tonight.

And then lastly on Wednesday, this is where we have the second clipper system that is coming through.

And here we can have some more sizable snowfall totals, especially into the northwest.

About 3 to 5in locally could be a little bit higher once you get to the east.

We just have a coating to two inches south of I-80.

That's where we can get a wintry mix to just rain, but otherwise we will certainly have that wintry Wednesday here for the Clipper system.

And that's just the main dominant pattern that we've been seeing over the past few days.

Yeah, it's very active pattern, very cold.

So welcoming you back from Tallahassee.

I hope you can handle it.

I know I'm going to have to really bundle up, especially tonight, and get the hot chocolate ready.

That's right.

Well, thank you so much for taking the time to be here.

Tomorrow night.

We're going to