BETHLEHEM, Pa. — Every winter forecast, especially when nor’easters are involved, comes with a caveat: expect the unexpected.
And what happened over the past few days was that the storm that blitzed the Lehigh Valley shifted, and then shifted again.
On Monday night, it shifted even more, leaving even the most seasoned weather forecasters exasperated.
“This has been a tremendously difficult storm to forecast due to rapidly changing conditions/temperatures expected and the difference in timing,” the National Weather Service said in its forecast discussion.
“The same goes for the storm track. Any difference plus or minus a couple miles will have rather large implications in snow totals."
Snow maps were presented, then adjusted, then readjusted.
The final call for the Lehigh Valley?
Let's just say if you were betting on this storm you should've taken the over.
Early Tuesday, forecasters were largely calling for warning-level snow in the southern Poconos, 4 to 8 inches in the Lehigh Valley, and 1 to 4 inches in the Interstate 95 corridor.
Snowfall totals quickly exceeded expectations, topping double digits in some areas and coming close in others as the snow was winding down. (Though not before it caused plenty of trouble for local utilities, with more than 11,000 people without power).
@NWS_MountHolly germansville-Lehigh lhpa-056 6.5” snow, heavy snow falling 0620 hrs @epawawx
— josh bingham (@Carver012Josh) February 13, 2024
Model madness
“I have not slept in 20 hours and this storm is getting on my last nerve,” EPAWA meteorologist Bobby Martrich said in his Tuesday video update.
Like many others, EPAWA — known for its first and final call maps — also adjusted on the fly around 11 p.m. Monday because of a large spread in model guidance and rapidly changing conditions.
EPAWA's 2/13 and week ahead outlook, covering:
— Bobby Martrich | EPAWA (@epawawx) February 13, 2024
■ Timing the end of the snow and the storm's exit
■ Cold and breezy conditions through Wednesday
■ A couple of minor systems in the week aheadhttps://t.co/nGpN4H9Xt8
“This is a very finicky system and it is a thread-the-needle system, as we described it all week,” Martrich said.
He then took a deep breath and added, “This storm has been a handful.”
Even as snow began creeping into the region, some of the global deterministic guidance significantly backed off on QPF (or total moisture equivalent precip) on the northwest side of the storm, which, in theory, should have lowered snow totals.
The North American Mesoscale Forecast System, better known as the NAM, had the Lehigh Valley somewhere in the 8- to 11-inch range.
The ECMWF, or the European Center for Medium-Range Weather Forecasts, was stuck right around 8 or 9 inches.
The GFS, or the American Global Forecast System, was similar.
The HRRR, or NOAA’s High-Resolution Rapid Refresh, was less enthusiastic with just 6 inches.
In the end, it didn't matter what the models were saying. This storm had a mind of its own and totals largely outperformed projections.
Martrich said temperatures were a big reason.
"Models collectively were never lower than 33 degrees and we got lower than that," he said.
"It changes snow consistency and allows depth unabated with no melting or compacting. Hence more snow here and the Poconos."
Winter Weather Impacts
Aside from the usual traffic impacts — with speed limits lowered on area highways and the Pennsylvania Turnpike — schools across the area shuttered, with many announcing closures Monday night.
Around 9 a.m. Tuesday, LANtaBus canceled all service for the remainder of the day.
Additionally, all Carbon Transit trips, including CT Bus, CT Flex, and CT Shared Ride were canceled.
Forecasters said even as the storm pulled away that heavy, wet snow could have continued impacts on power lines and cause minor tree damage.
The good news? Around 10:30 a.m. a rapid departure of the system was evident, with sunshine to follow.
