ITHACA, N.Y. — Dig out the long johns and extra blankets. As a storm system continues to push across the weekend to close out the weekend, bitter cold will enter into the region and hang out for at least a couple of days before moderating to more seasonable temperatures later in the week.

Graphic courtesy of NWS Binghamton

Your Weekly Weather

A large and powerful storm system is sweeping across the continent from Hudson’s Bay Canada down to Texas, and if you attempted a trek outdoor this morning or afternoon, you’re aware of its icy impacts. With cold air sitting across the region prior to the system’s arrival, as the warm sector worked into the Southern Tier overnight, that warm air rode above the cold air layer. That’s because of a bit of physics – cold air is denser than warm air, so while a cold front easily shunts warm air skyward, warm air has a harder time working its way down to the ground.

What this means is that when you have below-freezing temperature air at ground level and air warm enough and moist enough to create rain aloft at cloud level, the rain falls and freezes at ground level as a sheet of ice – the classic dynamic for a not-so-fun bout of freezing rain. Dunno about you folks, but it took a little while to break apart my car’s version of a candy-coating shell this morning.

We’ve had some assistance this afternoon as warm air has finally worked its way down to surface level, though not as warm as some of the model indicated, with temperatures in the mid 30s rather than the low 40s that was predicted, with a mix of intermittent light rain and snow. That lack of warmer air could end up changing the forecast in the coming few days as the cold front stampedes across Tompkins County this evening.

Winds will turn away from the south and start gusting quite strongly out of the northwest in the next few hours as the cold front passes overhead. There’s still a fair amount of snow on the ground in many areas, and as a bitterly cold Arctic air mass enters into the region, that remnant snow cover will help to push temperatures down, as it tends to reflect incoming sunlight and insulate the ground itself, which means there’s less energy radiated from the ground into the surface air layer. Physics lesson number two for today: not only does sunlight heat up the atmosphere, when solar energy hits the surface, it heats up the ground, and the ground re-transmits that sunlight’s energy into the atmosphere as heat.

The long story short is, if it’s colder to start and there’s more remnant snow, it could very well be colder than forecast. That’s important, because we have a wind chill advisory already posted from 1 AM to 10 AM Tuesday, and wind chills are already expected to approach -20 F in some areas. Frost bites sets in within minutes with a wind chill that severe, so do dress appropriately (multiple layers, keep skin covered) if you’ll be out Monday night into Tuesday.

Turning back to the actual forecast details, expect blustery northwest winds and rapidly dropping temperatures tonight with mostly cloudy skies and a few lake effect showers to the north (if you’ll be heading to Syracuse or Watertown, the lake effect machine will be in full force with two feet of snow possible in Oswego County, so be careful). By daybreak, temperatures will be in the low teens.

Monday will be a dry but frigid day as the Arctic high builds in from the Upper Midwest. Expect some isolated show showers primarily north of Ithaca, and partly cloudy skies otherwise, along with continued gusty northwest winds. Temperatures will likely top out in the upper teens in most areas, and those winds will make it feel more like single-digits. Monday night will be bitterly cold with mostly cloudy skies and scattered lake-enhanced show showers as the winds turn more northerly, and lows 0-5°F above zero. With those gusty winds Monday night into Tuesday, the wind chill will be -10 to -20°F, so once again, stay inside if possible and dress accordingly if you have to be outdoors. New snowfall amounts will be 1-2″ in most areas, though the wind will be whipping it around, reducing visibility on the roads.

Tuesday will be even colder, but the snow showers should wind down by noon as the core of the high moves overhead and tamps down the northerly wind. Expect mostly cloudy skies with a high in the lower teens. By Tuesday night, the core of the high shifts eastward, and with light southerly flow on its rear flank, lows will be 5-10°F above, but with little additional wind chill and partly cloudy skies.

Wednesday sees considerable improvement as the southerly winds pick up thanks to a storm system passing to the north, which tightens the gradient on the high’s rear flank and builds up the southerly wind accordingly. Expect breezy south winds with highs in the mid 30s and partly cloudy skies becoming mostly cloudy later in the day as the frontal boundary of that northern storm system moves southeastward towards the Northeast. Wednesday night will be mostly cloudy but dry with lows in the mid 20s.

Thursday will likely see a few rain and snow showers during the afternoon hours as the disorganized frontal boundary crosses Upstate, but nothing significant is anticipated. It will be mostly cloudy with highs in the mid to upper 30s. Thursday night will be mostly cloudy with a few lingering snow showers before midnight. Winds will turn northwesterly, and this will result in a colder but seasonable night with lows in the upper teens.

Friday will be dry but chilly as a Canadian high asserts itself from the northwest. This doesn’t look as strong or as cold as the Arctic high that starts off the week, but temperatures will be cooler, topping out in the upper 20s with partly cloudy skies. Friday night will be partly cloudy with a few lake-enhanced snow showers possible closer to Lake Ontario, and lows will be in the upper teens.

Looking ahead into next weekend, a weak shortwave passes southeastward through the region Saturday night into Sunday, dropping 1-2″ of snow Saturday night but otherwise having little impact. Temperatures for both days will be seasonable on the balance, rising into the upper 20s for highs (a little below normal), with lows in the upper teens (a little above normal).

Graphics courtesy of the NOAA Climate Prediction Center.

Extended Outlook

Looking into the second half of the month, a deep jet stream ridge over Alaska will likely have the downstream effect of colder than normal conditions over the eastern half of the continental United States. The jet stream trough will be far enough south and west that the chances for abnormally-high precipitation will be over the Mountain West and down by the Gulf of Mexico and Southeast. It’s likely to be a cold if dry period as we head into the climatologically coldest part of the year in Tompkins County.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.