After the Blizzard of 2014, most of us feel we deserve a break. And we will get one, though not without complications. The thaw begins in earnest on Friday, but the further warming and the moderate rain developing during Saturday will heighten the danger of ice jam and poor drainage flooding in parts of WNY. It’s possible as much as 1″ of rain will fall, with temps well into the 40s. Ice jams are already believed to be in place on at least 3 Buffalo area creeks, and possibly the Cattaraugus Creek as well. Following this thaw, we’ll be returning to Seasonably Cold temperatures on Wednesday.
There has been much talk of more “Cross Polar” flow redeveloping later in the month. However, in latest ensemble and model runs, there are no signs of the kind of cross polar flow we’ve been having over an extended period. In the mean, our temperatures will run Below Average much of the time after next Tuesday and especially after the 19th or 20th. We’re not looking, though, at the sorts of extreme anomalies just gone through. In addition, the lone index which looks favorable for a western ridge, the PNA, is not matched (today) by a favorable AO or NAO. The mean flow does, on the other hand, somewhat favor above average precipitation. That+seasonably cold weather MAY = above average synoptic snowfall.
This is my late Saturday afternoon post on my Facebook Pages: It may be tempting to think on a relatively milder day like this that the forecast I’ve/We’ve been giving you concerning early next week may be hype. It’s not. Conditions will still be on the mild side Sunday, so that’s the day to get things which must be done outdoors done. Rain showers will precede this powerful cold front by early Sunday evening, after a day of above average temps. In the wake of this front by the predawn hours of Monday, temps will drop suddenly and the lingering rain will turn to a quick burst of snow, with a flash freeze on road surfaces. For the AM commute Monday, roads will be slippery (but with no heavy accumulation), and strong winds will develop, with gusts of 45 mph likely…possibly 50. Lk Effect Snow will slowly develop by midday and intensify during the afternoon, possibly beginning near the metro area. Heaviest amounts will occur in Ski Country over the course of 2 days, but the metro area will not be unscathed, with some oscillation to the band–which will extend well inland. Within the band, blinding whiteouts will develop due to the strong winds which will persist at least thru Tuesday. IMPORTANT: Wind Chill temperatures will reach depths we haven’t experienced in some years running from the -20s to -30 by Monday night through Tuesday. Wind Chill of this magnitude is Dangerous, and frostbite can occur in mere minutes. Stay in touch with Meteorologists Mike Cejka tonight and tom’w night, and Bryan Shaw on Sunday Wakeup. If you must drive through this coming lake effect snow, make sure you have your fuel topped off, an emergency kit in your car (blanket, energy bars, water, etc) and your cell phone. This will be a Severe Winter Weather Event, far outweighing the bitter cold we just went through.
After the rain, the power outages from the ice storm, and the still-in-progress Tonawanda Creek flooding (at the time of this posting), the return to wintry weather will prove to be relatively benign…at least at the outset. Some limited lake snow will develop toward Tuesday morning and into Tuesday across Chautauqua County and western Cattaraugus County, with moderate to marginally heavy amounts on some hills. Thanks to a synoptic trough, snow showers will flare up over much of WNY on Tuesday, giving many parts of WNY a shot at a White Christmas, albeit a thin coating.
What is the bigger story is the return of our oft-discussed “indices” to having a role in our longer term pattern. That’s opposed to the cold weather which has resulted from a ridge over the north Pacific and an eastern trough which encouraged a polar flow from NW Canada (not Siberia). For the first time this cold weather season, the PNA will be slightly positive/cold phrase, the NAO will trend to slightly negative/cold phase, and the AO looks to trend sharply negative, as it had been earlier in the autumn. The 500mb ensemble means in the ECMWF, GFS, and Canadian GEM all support a ridge closer to the US west coast and an eastern trough–with no signs of a return to any lasting period of mild weather. We’ve already had those symptoms, but our indices were out of phase–which is quite unusual. There will be some quick ups, but undoubtedly the downs will outweigh and outnumber the ups over the next couple of weeks, minimally.
Lake Erie has bounced back to 36. That won’t last long. There are no signs of any major synoptic snowstorm in the next 6-7 days, but ski resorts will be able to make new snow and get some occasional help from nature.
Even as I type this post on Monday, lingering though weakening lake effect snow continues well south, and a little well north of the metro area. After this dissipates, the weak clipper we talked about last week will still bring us a minor snowfall later Monday night into Tuesday AM which will prove barely noticeable in places socked by Sunday evening’s LES blast. In the wake of this system, more significant LES will return later Tuesday night into Wed AM. Most models favor enough of a westerly flow to keep the bulk of this LES below the Buffalo Stowns, a trailing short wave might still be able to produce enough backing of the boundary lyr winds to get this stuff close to the Buffalo Stowns…this will bear careful watching, as accumulations in this band will likely be fairly heavy. And after this dies out Wed night, that’s the last we’ll see of LES for at least 5 days, if not longer.
The long advertised temporary moderating trend will set up on Thursday, with rainshowers moving in on Friday. Temps will drop back a bit on Saturday, but all 3 deterministic models show a well organized low coming up the Ohio Valley on Sunday, bringing widespread rain on the currently projected path. After that storm goes by, a colder pattern (not quite as cold as what we’ve been experiencing the last few days) will return for most of Christmas week. It’s a bit out in time, but the GFS and ECWMF both show a weak clipper approaching toward Christmas Eve, and another possibly better organized one behind it by the 26th. So, we may get a thin fresh coating of new snow to cover up the crustier older snow left after the rain.
Buffalo has a 30 year 57% probability of having 1″ of snow on the ground. I’d say our odds this year in the metro area are a little higher than climatology. However, the probability of 5″ or more is 23%, and I’m not prepared to make a call on that one. Some of it will be contingent on how much old snow survives the moderation and rain.
And this week will be no exception. As of this posting (midday Monday), it appears lake effect snow will begin fitfully with some minor amounts this evening, possibly near the metro area for a time, before settling to south of the metro area. On Tuesday, what’s called an anticyclonic curvature will be found in lower level winds, which makes for more drying and sinking motion in the boundary layer at least into early afternoon. When winds back to SW later in the day, ahead of a trough/short wave, lake snow will begin to become better organized…but there still may be some disruptive shear for a short time due to the trough. After a relatively brief visit to the metro area, with some limited accumulation, the axis of the trough will pass and winds will quickly veer to the Westerly flow which sends the LES into Ski Country. Between Tuesday and Thursday, several short waves will traverse the northern Great Lakes, each producing some backing and veering. The amount of backing (which would impact the metro area & possibly NE ‘burbs) is low confidence. The MEAN dominance of the westerly flow is somewhat higher confidence but, as some of you know, that doesn’t tell the whole story. There also will be variations in moisture availability and periods of shear. That means this isn’t going to be a “steady state” singular snow band all the way from Tuesday evening through Thursday. There will be ebbs and pulses, making for extraordinarily difficult accumulation forecasts.
In the extended range, the zonal-ish flow at the 500mb level toward mid-December no longer looks so zonal. The 3 main ensemble means show a rebuilding of the ridge in the eastern Pacific, and some troughing crossing the N Central states and the Great Lakes. The ECMWF and Canadian GEM are strongest with that ridge as we get closer to Christmas. The GFS ensemble is strong with it initially next week, but weakens iT during the 21st-24th. But even the GFS shows heights which would be cold enough to support snow in advance of the holiday. Before we get to that, though, there is good agreement in the medium range of an area of low pressure bringing us some synoptic snow during this next weekend. It may be on the slushy side, and it doesn’t currently look like a blockbuster snow storm, but it doesn’t look like a 90 pound weakling, either.
The work week will see readings moderate on Wednesday into Thursday, ahead of a slow moving cold front later in the week. An area of low pressure passing across the northern Great Lakes should bring a downslope flow on Wednesday, allowing readings to rise into the low–possibly mid 50s. Rainfall in scattered showers arriving late Wednesday and Wednesday night looks minor. A cold front oozing across the region by Friday may provide a pathway for some mixed precipitation, but most guidance takes the front far enough south and east so that WNY would miss the bulk of the moisture headed up to the middle Atlantic and NE states. Friday will be Cooler, and the weekend will be Colder, but nothing extreme. Some model ensemble members bring an area of low pressure close to us by Sunday night or Monday, but the majority of guidance shows nothing all that impressive. The European deterministic/operational model at 00z Monday was showing next week to be colder in general, but the ensemble mean doesn’t look as cold as the operational model.
Not my most exciting blog entry to be sure. But on the other hand, December is not shaping up to be milder than average in its first 2 weeks.
By Tuesday evening, WNY & northern PA may be under the gun…a snow gun…of highly uncertain caliber. As I’m posting this late on a Sunday (due to expected workload on Monday), there continue to be increasing signs of measurable snow heading into our viewing area Tuesday night from a deepening storm system which has a most favored track taking it into southern VA, then southern NJ. As per usual, track uncertainty on a tighter but critical scale remains high, even if the overall broader track has come together better today. A small shift to the west in the track would bring heavy snow into parts or all of our region, and a slightly greater shift to the west would cause the snow to become a mixture. A shift to the east could leave us with minor snow or snow showers. The speed of the storm suggests the steadiest and heaviest precipitation would occur Tuesday overnight, with somewhat lighter snow showers lingering on Wednesday. On this most favored track, major east coast cities and their airports would be impacted by heavy rain and gusty winds, causing air traffic delays (though not nearly as bad as heavy snow would produce) Tuesday night and Wednesday. In the storm system’s wake, Thanksgiving Day will be Cold with the chance of limited multiple bands of lake snow again on a NNW flow. It will be a cold and breezy Turkey Trot, with a significant wind chill. The afternoon high is likely to be in the mid to upper 20s, with some sunny breaks as well to help with the chill. Some moderation in temperatures will occur next Friday into the weekend, getting back toward the upper 30s by next Sunday.
Here’s the portion for more familiar weather enthusiasts: The 12z GFS and its ensemble mean have come into better agreement with the Canadian GEM and the ECMWF. All 3 operational models keep the heaviest snow just east of the 8 western counties, as do the ensemble means. However, when you examine the individual ensemble members, there is still enough spread so that mixed precip can’t be ruled out, as well as heavy snow–nor can lighter snow be ruled out with some of the eastern members. All in all, however, the probabilities for significant snow have increased, if not exactly heavy, and the probabilities of a “miss” have decreased. Our 15z RPM shows all snow, with moderate to heavy amounts, the heaviest E & S of Buffalo. Just E/SE of Allegany & McKean Co, a mixture shows up. Greater precision is just not possible right now.
Here is the just released Winter Outlook from the National Weather Service’s Climate Prediction Center. It is NOT a high confidence outlook, to be sure. But I agree with the uncertainties the Center has detailed:
This is a time of year in which normal climatology brings us lots of ups and downs in weather. We’ve recently had a few Novembers in which temperatures averaged a fair amount above average. This November often been Windier and occasionally Stormier than in those recent years.
This week of November 18th starts out seasonably cold and shifts over to seasonably mild temperatures before another transition to wintry temperatures occurs this weekend. This weekend: “Aye, there’s the rub.” Lots of uncertainty abounds, with large difference between the models, and their ensemble means. Sunday night, there were signs in the European model of a storm system which would have headed toward eastern New England and which might have given us a chance at some widespread snow. The Euro’s subsequent run took that storm farther north and east, with something of a cold blast moving in by Saturday night and Sunday. The GFS never showed that first Euro storm being close enough to us to give us widespread snow, nor did the Canadian. However, there is good agreement the coldest airmass of the season will be on its way this weekend with gusty winds and snow showers, along with some lake effect snow potential on a NW flow, which would focus the heavier LES on the hills again, well south. The GFS is considerably faster, bringing that arctic airmass in Saturday afternoon. I won’t dismiss that speed, since last week’s late week GFS wasn’t bad on the speed of Sunday night’s cold front. As of this Monday evening (bottom line) there are no good signs of a widespread heavier synoptic snowfall in WNY this weekend–though I’m not ruling out such signs recurring in future runs. But there’ll be no questioning the wintry atmosphere, with temps probably staying in the mid-upper 20s on a cold, windy Sunday, with a little moderation early next week. The GFS is chillier for Thanksgiving Day than the Euro, which has kept us consistently seasonable for that day. I won’t touch precipitation this far out.
For the bigger picture, the Climate Prediction Ctr (for newcomers…we just call it CPC) expresses high confidence for below average temperatures in the 6-10 day outlook, and average confidence for the 8-14 day outlook. That major 6-10 day cold anomaly may imply much below average temperatures for that whole stretch. However, I’m still expecting some ups within those downs. Here’s why. The indices don’t match up with a western ridge/eastern trough all that well. While I would expect the 2nd half, or even the last 2/3 of the weekend to be much colder than average, the pattern remains too progressive for a stable wrn ridge/ern trough to take up residence for too long a time. Plus, the positive heights which are showing up so frequently over the far SE also may be related to the lack of a persistently -NAO/-AO, and help to flatten the trough in the Grt Lks and NE. There continue to be no signs of a fundamental change in the PNA to cold/+ phase, so a western ridge which could force a cross polar flow simply won’t be there in the next 2 weeks. This doesn’t mean I’m expecting big Ups with any major above average temp periods…just not steady arctic air.
The MJO remains “incoherent”, weakly active, and is not expected to have a measurable impact on global weather in the next 2 weeks, at least not at our latitude. The ENSO forecast remains unchanged…neutral through next spring.
Temperatures will be heading back to near normal, then well above normal as we get into the weekend and next Monday. The initial warming will be tempered by gusty winds, adding a wind chill to the air. These winds will relax on Friday, and Saturday a more southerly flow will boost readings into the 50s. We’ll be even warmer on Sunday, with a gusty SSW wind. However, a deepening area of low pressure to our west will inject moisture into our region. The storm system will bring a strong, moist southerly flow to WNY on Monday. Both the ECMWF and GFS deterministic/operational models are in good agreement now this storm system will be deep as it passes to our north. It will bring more widespread showers into our region on a warm & windy Monday, and I’m seeing signs we may also experience some Sct Tshowers or even TStorms as a strong cold front approaches Monday night.
With this new agreement between the models, it now appears temperatures will drop rather sharply by Tuesday into Wednesday, ahead of some moderation later next week. Post frontal winds may be an issue, possibly reach Advisory criteria (or even stronger–too early to tell).
The ensemble means suggest some weak troughing either over the north central states or the Great Lakes right around Thanksgiving. As per usual, at that time range short waves and their respective amplitudes can’t be seen. The mean may end up being the smoothed mean of a higher amplitude flow. The Canadian mean has that hinted-at troughing moving back toward N & S Dakota, while the ECMWF has the trough axis at the Great Lakes. If the timing doesn’t change (and the odds on it not changing are fairly slim), Thanksgiving Day would be more likely to be cool than warm.