ITHACA, N.Y. — Okay, let’s just rip the meteorological bandaid off quickly. A deep, pronounced cold pattern will be setting in this week, with reinforcing waves of colder air as air from Siberia literally gets shunted across the North Pole and plunges into the eastern third of the United States, with some models showing snow as far south as the Central Appalachians within 7-10 days. Sorry folks.
One could look at the upcoming cold spell as a continuation of the cold weather encountered in April. According to the Northeast Regional Climate Center, the Cornell Game Farm Road weather station in Dryden recorded an average temperature of 40.6 °F, 4.1 °F below normal and the 12th coldest April in 122 years of record-keeping. The story was the same throughout much of the Northeast and Mid-Atlantic. Out of 30 first-tier climate site in the NRCC’s purview, only one recorded an April temperature average on the plus side of normal (Allentown, Pennsylvania, with a +0.6 °F).
The weaker-than-normal jet stream was easily locked into high-amplitude meanders reinforced by strong storm systems, resulting in cold air plunging from the subarctic into the Midwest and Northeast, while a dome of unusually hot air sat over the Desert Southwest, reinforcing a ridge over the western third of the continental United States.
On the precipitation side, however, there wasn’t as much to write home about. Game Farm Road received 3.13″ of liquid and liquid-equivalent (4.5″ of melted snow, vs. the usual 3.4″ for April), and half of that total fell in last five days of the month. That’s a notch below the April average of 3.25″. The deep trough in the jet stream generally meant that storm systems traveling along the course of the jet stream passed to the south of Upstate New York, leaving much of the region with below normal precipitation and pummeling the Central Appalachians. The jet stream started to curve upward again over the Eastern Atlantic, and with the storms following along its path, this resulted in above normal precipitation in much of Eastern New England.
Onto May. At least the weekend was warm, thanks to an area of low pressure passing over Ontario and Quebec. While this created some rain late Saturday, it also resulted in some fairly mild temperatures as it drew in air from the south – the airport broke 75 °F Sunday, the warmest it’s been since October 2nd 2019. But, as relayed at the start, this was only a short reprieve in a cold pattern, one that will only get more intense and abnormal in the coming days.
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The first wave of cold air will come in the backside of that Canadian low’s counterclockwise circulation. As it continues to move east, a cold front is sweeping across the Southern Tier this evening, and behind it winds will turn to the northwest and become quite brisk – case in point, as I write this, Albany’s near 70 °F, Syracuse is about 60 °F, and Buffalo’s in the low 50s. A lack of moisture and instability in our region means this will be a dry front, with very little in the way of precipitation. Expect partly cloudy skies, and temperatures that will steadily drop off tonight with that northwest wind, down to the low 40s.
Monday will be brisk. The northwest wind over the lake and more unstable conditions as the low dips southward over New England will create mostly cloudy skies and a few lake-enhanced lake showers, with the probability of rain increasing closer to Lake Ontario. Highs will be in the low 50s. The loss of daytime heating and the movement of the low further east and away from us will allow skies to clear up Monday evening and night, with mostly clear skies and a low in the low 30s.
Tuesday will be a fairly quiet day, with an area of Canadian high pressure over to our northwest keeping a light northerly wind in place and temperatures on the cool side. Plan for partly cloudy skies and highs in the low 50s. Tuesday night will be quiet, with the winds slackening as the core of the high pressure passes just to our north. It will be mostly clear with lows in the mid 30s.
Wednesday should be by most accounts a pleasant day. Now on the rear flank of the high’s clockwise flow, winds will be light of the south, allowing temperatures to top out in the upper 50s. Some mild atmospheric instability channeled in from a strengthening low passing to the south may set off a few showers Wednesday evening, but they will not be widespread or substantial. Wednesday night will be mostly cloudy and dry as only a few widely isolated rain or even snow showers remain by late evening, and lows will be in the mid 30s.
Thursday will see an increasing influence from that low, now over the Atlantic and strengthening. As it does, winds out of the northwest will steadily strengthen. This will likely generate some lake-enhanced instability clouds and perhaps a few rain showers, but otherwise expect partly cloudy skies and highs in the upper 50s. Thursday night will see the winds slacken as the low moves east, and the showers will wind down leaving partly cloudy skies and lows in the mid to upper 30s.
Friday’s where the next cold wave comes in. A secondary low will spin up in the wake of that coastal low, over interior New England. This will draw in colder air – and it just so happens that an unusually intense cold pool will be over Central and Eastern Canada. This is Siberian air that passed over the North Pole and some of the coldest in all of the Northern Hemisphere. Cross-polar flow is rare, especially in May, and is typically associated with subzero cold snaps in mid-winter. But with a weak polar vortex, it will basically slide off the pole and into Canada – and soon, into the eastern United States.
As we start to tap into that air Friday, it will be partly cloudy with a chance for some rain showers due to that developing New England low, and highs will be in the low 50s. Friday night, as the air turns colder, expect mostly cloudy skies and chance for rain or snow showers with a low in the low 30s.
Saturday….gosh, folks, you never want to see the National Weather Service use the word “unprecedented” in a forecast discussion. But that’s exactly what this is. Temperatures will be in the mid 40s in Ithaca, and some models show temperatures not even breaking 40 °F in parts of the Southern Tier Saturday – these values are 20-30 °F below normal and potentially record cold. With Lake Ontario warmer than this air, lake effect rain showers and mostly cloudy skies will be persistent. These rain and perhaps some snow showers would continue into Saturday night as the New England low parks itself over Atlantic Canada, and lows would be in the upper 20s to around 30 °F.
Sunday shows some reprieve as the low pulls away, which will allow some modest recovery of temperatures into the low 50s with partly sunny skies.
Now comes for the part of the forecast that is part of the reason why tonight’s is so late. Sometimes you just see model runs that make you say aloud “please tell me these models are wrong”. It’s looking less and less likely they’re wrong.
The setup would be that another coastal low developing, another storm out of the Deep South that would intensify, while the Canadian low is still spinning away. These would work in tandem to funnel some of that coldest air in all the Northern Hemisphere, well into the Eastern United States. There are medium-range model runs showing the cold pool passing as far south as Washington D.C., with accumulating snow in Virginia and Kentucky early next week, and freezing temperatures down to Atlanta! We’re talking extreme cold for May that lingers for days. Record-shattering stuff that becomes the subject of case studies and local lore.
Ever wonder when we start issuing frost/freeze products? This map shows the median date of the last spring freeze. The majority of our area’s growing season will begin on 5/11, but it has already started across portions of the Finger Lakes and the Wyoming Valley. #NYwx #PAwx pic.twitter.com/gbBSDah9GC
— NWS Binghamton (@NWSBinghamton) May 4, 2020
This would be absolutely devastating for agricultural interests if it pans out. Our growing season is only just starting and our cold April delayed it, which may actually save our tails locally. But for much of the eastern U.S. where the growing season has already started, this will destroy plants (and farms) on a wide scale. I am frankly in awe of these latest model runs for all the worst reasons.
If there’s any hope, it’s that models may change considerably in the next several days as initial conditions are updated and the latest data is run through the supercomputers. Right now, the collective approach from local forecast offices seems to be a “wait and see” approach, and if it still looks bad in a few days, start sounding the alarms. Keep your fingers crossed this does not turn out as bad as it looks right now.
On the bright side — grasping at straws, I know — precipitation will be around normal to perhaps on the dry side for the period, because the jet stream trough bottoming out over the Deep South will keep most storms far to our south and bring them poleward well to our east.