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

This is weather world.

Good evening and welcome to Weather World on this Thursday, March 5th.

I'm your host, Matthew Carlson joined alongside our forecaster Ben Reppert.

And Ben, Quite a wet day across the state.

Precipitation ranging from corner to corner.

Yeah, almost like a good day to be a duck.

But with 50% of the state in drought, we do need the moisture.

That's right.

Additionally, many of you might have noticed a lot of really dense fog last night, especially in valleys that didn't experience a ton of wind.

Look forward to that or stay aware of that for future nights as well.

But we'll look into Ben's forecast here in a moment.

And more of the rain, more of the fog.

We've got it all as it continues over the next couple of days.

And let's start tonight by looking at the observed rainfall that we've seen basically since the start of this week.

If you're in a blue color, you've seen at least a half of an inch of rain.

And that's most folks, except for some communities north of route six, and also this little spot here from York and Lancaster counties, parts of southwestern Pennsylvania have actually picked up one and a half to two inches of rain.

Going back to Monday afternoon, and we're not quite done with it yet.

In fact, throughout most of the day, as Matthew mentioned, periods of rain have been here and there and even a blossoming of some steady rain again into this afternoon and this evening.

This will continue to cross Pennsylvania from west to east, and I think there will even be some rumbles of thunder embedded in here as well.

And that thunder, if you hear it tonight, I think it is going to be loud, because a lot of us are experiencing what we call an inversion right now.

Warm air above cold air.

So any rumbles of thunder, I think you will certainly notice this evening and overnight tonight.

Winds.

Not too much of a factor in terms of the speed.

I'm showing you this though, because direction means everything in terms of the temperature department.

Eastern Pennsylvania has been socked in an easterly flow, and that's coming from a location with a lot of cool maritime air right now.

Meanwhile, western Pennsylvania has been starting to get into southwesterly flow, and that southwesterly flow will be delivering warmth to western Pennsylvania over the next several days.

It will be riding up and over the cold air in eastern Pennsylvania, and that's a recipe for keeping eastern Pennsylvania socked in.

More of this.

And that is cool, damp conditions.

It's only in the 40s over most of the eastern two thirds of the state today.

Meanwhile, southwestern Pennsylvania has approached or gotten to 60 degrees, and this disparity in general is going to continue, although the warmth is going to gradually win out more and more.

In fact, Richmond, Virginia, sitting at 80 degrees this afternoon, that's just a couple hundred miles away and quite a bit of warmth now, starting to run around the southeastern corner of the United States.

More and more of this will be making a run at Pennsylvania over the next couple of days, but not everybody is going to be able to cash in on the action.

So if you're in eastern Pennsylvania and you have a desire for spring, that spring fever, you still are going to have to wait your turn.

Hopefully, by the time we get to the early to mid part of next week, the main precipitation action in the United States right now is in our neck of the woods, although another area of low pressure is starting to organize over the Deep South.

This is going to kick off a multi-day severe weather event over the central and the Southern Plains by Saturday that will get into western Pennsylvania, and we could have some strong thunderstorms of our own, especially in the West by that point.

So here's how it all shakes out on tonight's weather map.

An area of high pressure to the north is helping to turn that wind out of the east and eastern Pennsylvania.

We've had a series of weak systems rippling along a stationary front, so the latest one brings the rain tonight.

It largely clears out overnight.

Tomorrow.

Not much happening in the precipitation department.

And then by Saturday, that's when this next system will begin to approach Pennsylvania.

We'll see a lot of clouds still in eastern PA.

Western PA breaks into sun and that will help to fuel some showers and thunderstorms in the afternoon.

Out ahead of that cold front, I want to quickly take a zoom in and show you how this shakes out in a close up view tonight.

Periods of rain and some rumbles of thunder, especially focused in eastern Pennsylvania.

Still around through 1011 or midnight and then largely clears out.

We're left with low clouds, fog, some drizzle patches.

Other than that, most of the steady rain will be done come early tomorrow morning.

Friday, generally a dry day minus a few showers in southwestern Pennsylvania.

And then Saturday Western Pennsylvania breaks into some sun, but that will help to fuel some showers and thunderstorms by about dinnertime Saturday.

Some of those could actually be strong.

We could have some thunderstorms tonight.

As I mentioned in eastern Pennsylvania, along with the steady rain, that's where it will also be on the cooler side.

Lows dipping into the 30s.

Meanwhile, dense fog developing in the west.

But it will also be milder in the west.

Not much wind to scour out the fog, either.

On Friday, seasons will be sparring.

The low clouds and that easterly flow continue in eastern Pennsylvania.

Highs there only in the 40s.

Central Pennsylvania is the battleground and then west of the mountains, 60s and maybe even low 70s with some sunny breaks.

That disparity continues on Saturday, although I think everyone is at least a little bit milder.

Still not much sun in the east.

Partly sunny in the west, boosting temperatures into the 70s, but that fuels some late day thunderstorms.

Stay there.

More weather world in just a moment.

Breakfast.

Some call it the most important meal of the day, and sometimes there's nothing better than enjoying one.

Topped with the sweetness of maple sirup.

The process of getting that sirup from tree to table is a long one, and it's very dependent on the weather.

According to the USDA, Pennsylvania ranks as a top eight maple producer in the United States, producing 165,000 gallons of sirup in 2021.

And it's our climate that makes it possible.

While maples can be found as far south as Florida, maple sap, which is the base from which sirup is made, can only be extracted from trees at certain temperatures.

That's because these trees have an intricate system of water flowing through them, similar to that of a human circulatory system.

When you look at this thing, it's essentially a straw.

And what's being set up then is during the growing season, kind of a a water gradient whereby the trees are trying to maintain about 100% moisture or water inside the stems and inside the cells, and then outside as the atmosphere becomes anything less than 100% humidity wise, that sets up that gradient and the trees really can't stop.

There's mechanisms, occasional mechanisms they've developed in lineages, but they really can't stop the passive flow of moisture through that gradient.

It's because of this cycle.

That early spring is when peak sap flow occurs as temperatures rise above freezing during the day, sap inside of the tree begins to thaw and move through the trunk, also known as the stem.

At night, when temperatures dip below freezing, water is drawn back into the tree from the roots, which keeps the system flowing.

And so that is what sets up that pressure differential, that drives kind of that movement in the stem as this embolisms form, right.

These little oxygen bubbles in the stem as things are waking up, going to sleep, waking up, going to sleep kind of thing, and respiring in the process.

At night, the moisture will move from the root system into the stem, and then during the day, as the stem warms up, it starts to move the moisture around the stems and sometimes back to the root or out to some of the tissues or to the developing branches.

Just depends on what time of the season.

It's about a 6 to 8 week process here.

And it's not just the changes in temperature this time of year that get the sap flowing.

There's also another atmospheric phenomenon that plays a major role because these trees are functioning off of this complicated movement of water that's driven by atmospheric conditions and day length and so on.

Uh, one of the things they tend to do is gush a little bit more ahead of an incoming front.

You get this kind of pressure differential, barometric change, whatever it is that's in the atmosphere that birds recognize, the trees are recognizing it, too, and responding to it.

And so you'll get oftentimes some of your best sap flows ahead of changing weather conditions.

Other tree species in the northeast U.S.

also go through similar cycling, but their sugar content differs from that of maples, so production of their sirup isn't nearly as high.

You'll find that people in Pennsylvania and New York and other places are starting to make walnut sirup.

So we have walnuts, we have birches, and people are playing around with sycamores and beeches as well at this point.

So a number of different species that have been discovered to have this kind of cycling going on, as well as an agreeable flavor and some sugar content that are being investigated, that cycling allows for prime SAP collection.

In the late winter and early spring, the sap flow ends as the maples begin to bud, and temperatures are no longer dipping below freezing on a nightly basis, which is why the season typically lasts 6 to 8 weeks here in Pennsylvania.

However, in years with an early thaw like in March of 2012, the season may end much more abruptly.

These spy holes just dried up, and the trees never produced any more sap for the rest of the season.

It was just too warm, and it just conditioned those trees to say, I'm about ready to break buds, so it's time to transition.

And so it's interesting how they will respond to those kinds of erratic temperatures, especially if they're really abnormal.

Those shortened seasons can have a big economic impact on maple producers in the near term.

It's this kind of stochastic stuff that we've got going on where one year will be great for SAP flow, and we have perfect conditions like we've traditionally experienced.

And then the next year, uh, you know, we get temperatures all over the place, right?

Uh, that kind of thing, if you're a serious commercial producer, is not just disruptive, but it's hard to count on the income to make those investments right over time, because it does add up.

The investments are in the form of equipment, spiles and buckets or tubing for when you tap, and evaporators, which are machines used to turn the sap into sirup.

These can cost anywhere from a few thousand dollars for hobbyists to up to a half million dollars for working farms.

The equipment and the technology, if you start to invest in it, can add up very quickly.

And so as a result, these, uh, irregular seasonal conditions that we're having in the near term make it unpredictable and rather risky for a lot of people to get in this in a serious way.

As temperatures continue to rise over time, experts worry that there may be a long term impact on maple production here in Pennsylvania, but for us, we're right at that zone where, you know, we're going to be changing gardening zones really quickly within the next 50 to 100 years.

And what that means is these sugar maples are just going to migrate along that gradient.

And so in many parts of the southern areas of the state that are at lower elevations, it probably won't have enough sugar maple in the long term or enough of a season to make it worthwhile.

So the next time you sit down to enjoy a breakfast complete with maple sweetness, remember how much the weather and climate played a role in getting it on your plate.

For Weather World, I'm Marisa Ferger.

Unfortunately, I don't think anybody saw any sun pillars today.

We've been socked in with gloom and tonight if you don't see some gloom, you might actually hear some boom, some rain and rumbles of thunder continuing to move through eastern Pennsylvania.

It will taper off late, central and west.

We're just giving way to some dense fog developing, and there will be some patchy drizzle as well heading into the day on Friday, it's not going to be nearly as wet.

In fact, most areas will escape dry.

Just a few spotty showers in southwestern Pennsylvania.

Low clouds will be stubborn again in the east.

Temperatures held in the 40s once again, maybe getting to 50.

In the central mountains west of the mountains, southwesterly flow and some sunny breaks will boost temperatures into the 60s, maybe even some low 70s.

The same disparity is true on Saturday, but I think everyone at least comes up a few degrees mid to upper 70s in the west, where some sunshine will also create some late day thunderstorms.

Some of those could be strong central and east, generally cloudier, also cooler.

Matthew.

It will be resembling May in western Pennsylvania by the weekend.

More like March in the east.

I know you'll get to actually benefit from some of that warmth.

That's right.

Going to Pittsburgh for Penn State spring break.

Looking forward to some warmer temperatures as well as not all doom and gloom, this precipitation is good as a significant part of the state still in drought conditions, but come back tomorrow for the Friday forecast frenzy from all of us here at the show.

Have a great night.