After Saturday’s crisp and comfortable conditions, warming will resume on Sunday and continue to build for a good part of the week of the 16th. An upper level ridge will strengthen in the east until later in the week. Around the periphery of this ridge, several short waves will cross the Great Lakes and bring several rounds of Showers & Tshowers. The humidity will begin to build noticeably on Monday and hold into at least midweek. There is relatively good agreement in the ensemble means that some degree of troughing will redevelop near the Great Lakes later in the week, allowing more comfortable conditions to return. At this point, this cooling doesn’t appear to be likely to bring below average temperatures for any extended period. More seasonable temperatures will prevail in the mean. It can’t be determined if this weaker troughing might continue a parade of occasional short waves or not. After the early ridging during the week of the 16th, the rest of the means either favor a zonal flow or a slight WNW flow with the weaker troughing, with no visible rebuilding of the eastern ridge.
On the matter of El Nino, there continues to be some disagreement between the more conservative forecast offered by CPC on the amplitude of the event, compared to the NASA link we’d posted earlier, and some other projections. At the current time, the positive sea temp anomalies have some similarities to those observed in June 1997. However, there has also been Kelvin wave activity which has produced some of this warming. Owing to the ENSO ensemble members I’ve seen, there are only a couple of the many members which bring amplitude beyond 1.5 degrees positive anomaly. That is, most members project a Moderate El Nino. The correlation between a Moderate amplitude and WNY winter positive temperature anomalies is much less so than in the case of a Strong el nino. The hopelessly tired cliche “time will tell” applies here. We’ll have to continue to monitor the ENSO ensemble over the next several weeks to see if the trend changes.
As we’re now into the warm weather season, the surface features on the weather map tend to be flatter and weaker, as do many of the mid-level features aloft. In other words, timing weaker more subtle systems makes for some challenging forecasting. That doesn’t mean ALL systems are weak and poorly defined. In fact, as I type this post conditions look favorable for a rather major Severe Weather Outbreak on Tuesday the 3rd over portions of Iowa, Minnesota, Nebraska, NE Kansas and west central Illinois. But in the mean, defining troughs and ridges in the 500 mb flow, properly placing them, and properly determining their strength/amplitude becomes tougher. That’s because the mean tends to produce more of a zonal look. That’s in contrast to the blocky, high amplitude pattern we had so often until recently.
And remember, this mean is often the smoothed mean of many ensemble members in the global models which have a lot of spread between one another. The mean can be a best choice by default. But it is not necessarily the most reliable choice.
There will be a cooldown with reduced humidity returning toward Wednesday morning. Almost immediately afterward, there is already low confidence as to when any showers associated with an area of low pressure going by to our south might arrive in parts of WNY, with 2 operational models bringing those showers back in by mid or late Wednesday afternoon. Odds do favor much of the rain with that system staying farther south. The GFS is blindingly fast with onset and exit times, and viewed with suspicion on that speed. After lovely and dry days on Friday and Saturday, during Sunday another area of low pressure will be approaching, probably bringing some convection in by later in the day, with a few more rounds into Monday AM. There are no signs of prolonged heat and humidity, nor are there signs of prolonged cool weather. So, at this point, much of this next weekend looks pleasant. But unlike the last 2 weekends, the finish to the weekend is in doubt.
There are no changes to the ENSO forecast this week. The so-called key Nino Region 3.4 has a +.6 degree positive SST anomaly. Generally, an el nino is not considered as such unless there are 3 consecutive months of el nino conditions. A couple of weeks doesn’t cut it, partially due to the rising and ebbing warming/cooling caused by Kelvin waves traversing the Pacific. I’m still seeing only a handful of ENSO models projecting a truly strong el nino. Many, including the mean of the CFSv2, lean toward a moderate el nino.
At mid-latitudes, we are still in something of a “blocky” pattern. A warmer ridge of high pressure will briefly peak aloft on Tue-Wed, followed by a large upper level low forming well to our NE by later in the week. That almost-cutoff low will usher in a return to below average temps for Thursday-Friday. However, it will gradually relax its grip during Saturday, allowing milder temperatures and dry air to move in for Sunday and Memorial Day. The overall 500 mb flow in the ensemble means favors above average temps much of the time next week, with an uncertainty concerning precipitation potential.
Even this week, as we draw closer to the long advertised rounds of scattered convection which arrive late Tuesday into Wednesday, precipitation potential has uncertainty. The amount of precipitable water in the lower atmosphere will be high, but the triggers for organization don’t look impressive. There may be a couple of isolated downpours. In addition, a couple of models suggest a convective complex could come riding down on a NW flow into NW PA toward Wednesday AM, which would pose a risk of heavier rainfall close to Chautauqua County, and stronger winds. Our in-house models don’t see this potential as of this posting (Monday evening). Even during our Tue-Wed moderating sfc flow, local Lake Erie shoreline/waterfront temps will remain below average–so this isn’t much of a warmup. After a Thur-Fri with high temps in just the low 60s, and a few leftover light showers possible, Saturday should bring high temps in the upper 60s inland with only a small chance of a couple of deep interior light showers. Sunday and Memorial Day look spending, with Monday being the warmest of the 3 days.
Odds for El Nino will continue to increase by early summer, and will approach 80% by autumn in CPC’s newest perusal of ENSO models from around the globe. As I’ve already mentioned in the previous thread, a summertime el nino has little if any effect on our regional weather. And, as most of you know, its impact on our cold weather months seems to be keyed to the amplitude/strength of el nino. Some researchers are suggesting evidence is growing for a strong el nino. Model ensemble members are more of a mixed bag on strength. In my judgment, uncertainty on strength remains fairly high.
A wavy cold front will be in WNY by Wednesday and may provide a pathway for a few waves of low pressure. Depending on the precise path these waves follow, locally heavy to excessive rain could reach parts of WNY by late Thursday into Friday AM. Preceding that, we’re likely to have several rounds of Showers & Tstorms, with abundant rainfree time. There are no current signs of an organized severe weather outbreak in our region. But just this Monday evening something of an unexpectedly ferocious, small outbreak developed in NE Ohio. With abundant water vapor in the air (precipitable water) and occasional small impulses of vorticity crossing our region, isolated strong to severe storms cannot be ruled out. The muggiest day of this stretch will probably be Tuesday, when interior high temps could reach or exceed 80. Unlike last week’s 82, this time the dewpoint will be higher, making things feel stickier.
Again, the exact placement of this cold front will be critical to total rainfall potential, as well as temperatures. Wednesday may be a few degrees cooler, but the warm, humid airmass may stay in place east & SE of the metro area, on the warmer side of the front. After the heavier rainfall pulls off to the east and the front passes farther to the east, temperatures will be much cooler (as forecast since last week) for several days. Soaking rain MAY still be with us Friday AM, but should be diminishing from W to E. Friday’s high temps will be in the mid-upper 50s. Saturday will be a little unsettled and cool with a few sunny breaks and a few showers. High temps will again be well below average…mid-upper 50s. Sunday looks brighter and drier, with a high near 60. There is good agreement in extended range guidance that temperatures will be heading back to above average by Wednesday or so next week, as upper level ridging rebuilds and gives us at least several warmer days.
The warmup we advertised all last week for later this week is still on the way, along with some Scattered convection at times. So, the “big picture” hasn’t changed much. As for details, the approach of a warm front midweek will probably set off some weak convection by late Wednesday, picking up at times Wednesday night into portions of Thursday. The proximity of this front and some elevated instability (bubbly air aloft out ahead of the warm front) will probably fuel a few of these tshowers. In fact, by Thursday afternoon and evening, our surface airmass will take on an “Almost Muggy” feel, with daytime highs in the 70s and overnight lows from the upper 50s to near 60–accompanied by higher dewpoints. The timing for actual warm frontal passage is still in question on this (Monday) evening. Once we get into the warm sector and that boundary has passed to the N & E of us, activity will slacken. As we move into Saturday, a wave or 2 will move up along a cool front and bring us a few rounds of showers & possible tshowers Friday night into portions of Saturday. There are signs much of this moisture will pull off to the east Saturday evening. On Sunday, the Canadian GEM is an outlier with a short wave bringing a return of showers for part of the day. But both the GFS and ECMWF seem to keep us mainly dry and seasonably mild Sunday. Monday becomes more of a question mark. The ECMWF rebuilds a strong ridge in the east, which blocks the approach of a cold front and its convection until Wednesday PM-Thursday, while the GFS brings some convection back to WNY as early as Tuesday or even later Monday night. Right now I’m leaning toward the ECMWF and its ensemble mean, but confidence remains shaky at best (both periods in the CPC outlook are of Below Average confidence — 2 out of 5), so I know I’m not alone in eyeing this model and ensemble disarray warily.
The ensemble means do bring some troughing back closer to the east central or eastern US between the 14th & the 16th, which would drop temps back below average for a few days. The ECMWF mean flattens the flow later in the period, while the GFS takes longer to show a zonal flow. Again, the zonal depiction late in the period may possibly be tied to the smoothing of the wide spread between ensemble members, rather than a realistic representation of a zonal flow. That idea doesn’t necessarily mean the troughing will persist. The ensemble member spread could also hide some modest return to western troughing and eastern ridging…too early to tell.
and that often leads to an unpromising pattern, depending upon what part of a block you find yourself under. In this case, there are signs of a near cutoff low getting closer to us by April 29-early May, and those signs are strongest in the ECMWF mean. If we were to get stuck in the “sweet spot”, a cutoff ridge, that would be a good thing. At this early juncture, that appears less likely than being near a cutoff low moving from the central US to near the Great Lakes. Cutoff systems are those which are cutoff from the higher speed westerlies which keep weather systems moving along. Late April-mid spring is the time when cutoff systems become more climatologically favored. The synoptic weather traffic jams can sometimes impact many parts of the mid-latitudes and northern latitudes.
When we’re stuck under a cutoff low, a lengthier dreary and cool pattern can result, with some showers from time to time. The GFS is also showing signs of this blocky pattern, with the Canadian less so inclined. This is the first time this spring I’ve seen the ECMWF ensembles so strong on a cutoff, so this will need to be watched carefully. For now, I’m not taking this a good sign for the extended range.
In the meantime, cooler weather will arrive Tuesday with mostly AM showers, and then another round of lighter showers Tuesday night which could be mixed with a few wet snowflakes toward Wednesday AM at the highest elevations. Wednesday will be chilly, with some sun returning by afternoon, and Thursday will be dry and sunnier with seasonable temps. Friday will be milder but wetter with some rounds of showers, followed by a damp, cool Saturday with falling temps in the afternoon–though not much accumulating rainfall. Sunday looks chilly (upper 40s) with limited sun and mostly dry conditions, though a few light showers or mixed showers can’t be ruled out. There should be some moderation early next week before the approach of any cutoff low later in the week.
This week will again present us with ups and downs, and a fairly typical early spring lack of consistency. After a Very Wet Monday evening, drier conditions will set in for the midweek with below average temperatures giving way to above average on Thursday, slipping a few degrees on Friday, and coming back above average during the weekend. One feature this spring which has not yet plagued us it the “cutoff low” in a blocking pattern. These tend to become more common in climatology as we move a little closer to mid-spring, but there are no signs yet of such a development in the next 14-16 days. So, there’s THAT–at least. Of course, in a block, you could also get under the ‘sweet spot’, the blocking ridge. THAT would be a good deal. No signs of that either.
Ensemble means (I’m relying on them more than operational models) continue to show those ups and downs into next week. By April 17-19, a flatter zonal flow shows up in the means. However, some of that flatter, low amplitude flow shows up because of the huge spread between ensemble members farther out in time. That is, the members and models cannot see short waves, their amplitudes and their paths so far in advance. When the spread between ensemble members is very large at the 500mb height level, the mean tends to be flatter. It’s a statistical compromise which has little to do with actual predictions for amplitude and teleconnections. What’s been happening so far this spring is a tendency to return to ups and downs the closer we get to the ensemble means prediction of a flat, zonal flow…as soon as the members and the models are able to “see” the short waves and the wavelengths between ridges and troughs. We’re certainly out of the extremes of winter, but for the umpteenth blog thread in a row (or so it seems), I still see no sign of a lasting pattern shift to a western trough/eastern ridge.
There are smaller uncertainties about this weekend and the timing for showers either Sunday night or Monday or, if the GFS 18z run were to be believed, showers during Sunday. There will be a transition back to Below Average temps for several days next week. Showers will again cross the region by Thursday night, exiting by early Friday. The weekend is not a lock for Sunday staying dry, but temps both days should be above average…unless 18z GFS (with the GFS’ inherent fast bias) wins out on Sunday and gets those showers and a trailing cold front in here and beats the slower ECMWF.
The first 3 days and nights of this work week we’ll still be stuck with harsh cold and true arctic air. But that all changes beginning Thursday. The northern/polar branch of the jetstream will be changing to a much lower amplitude flow, losing its connection with arctic air and bringing mainly Pacific air across the lower 48. This does not equate to mid-spring warmth in the mean, but it does mean there will be no true arctic blasts in the foreseeable future. During this time, the northern branch will be active, sending frequent short waves with their warm fronts and trailing cold fronts across the northern tier of the US. That will probably bring more frequent rounds of precipitation, and more frequent ups and downs with our temperatures. However, the downs will not be AS down. The cold fronts will bring cooler air masses rather than harsh cold. The warm fronts, of course, will bring periods of above average temperatures as well. In the mean, we’re looking at a more seasonable pattern. It’s not “June Is Busting Out All Over”, but it will have to do until the real thing comes along.
We’ll have to monitor area streams and creeks on Friday with the potential for moderate rainfall accompanying seasonably mild temperatures. There continue to be some ice jams in place.
We’re still in neutral ENSO conditions and should be for some months to come, with a slightly greater than 50% probability of el nino developing toward or during the summer. In my view, it’s not possible to know the amplitude of this possible el nino this far in advance. I’ve previously written its development would have little impact around here during the summer. The probability of neutral ENSO conditions shrinks into the 40-45% range by mid/late summer, and la nina drops to under 10%. Currently, there are early signs of a developing el nino with SSTs and near sfc Pacific tropical temps beginning to rebound, with cool anomalies at those latitudes restricted to the far eastern Pacific.
STILL Cooler/Colder than average in the mean. During the week of March 17th, we’ll start on a cold note, with some moderation on Tue-Wed ahead of a storm system crossing the northern Great Lakes. However, the lows and highs this week appear to be of a lesser amplitude. It won’t be as warm on the warmer days, and it won’t be as cold on the colder days…a little bit of a smoother ride. The Great Lakes storm will be vigorous as we move toward Wednesday night, but its cold front won’t be tapping much Gulf moisture and the low will be too far north to present us with that much rain or snow. Behind, some Pacific-moderated colder air will take us back to the 30s on Thursday-Friday. Another system could bring us some mixed precip or rain by later Saturday, with cooler air returning by Sunday or Monday the following week. After that, week 2 looks smoother with a more zonal characteristic to the flow…but not quite pure zonal. There will still be very broad, weak troughing in the northern branch of the jet. In such a fast flow, it’s virtually impossible to pick out short waves in that flow, so the mean looks smoother. With the broad troughing, the mean anomaly still points pretty clearly to below average temperatures. Whatever western ridge exists will probably be out well west of N America, so no cross polar flow will be possible in such a regime.
So I have to go back to my tired phrase: “more tolerable.” There is no sign of a western trough which would teleconnect with an eastern ridge, and no sign of a prolonged warming period. Again, though, there is no sign of a cross polar flow with the kind of cold we had on Thursday and will have Sunday-Monday. Unforeseen short waves in week 2 could change that, though there is no way to know that at the time of this posting.
This Monday evening, our in-house Rapid Precision and Vividcast models are both nudging what will be an intense low pressure storm system closer to us on Wednesday. What this may mean is less snow south of the metro area (more mixed precipitation may hold actual snow accumulations down quite a bit), but a stripe of genuinely Heavy Snow farther north, on the Niagara Frontier. As we’ve been telling you, the storm impact will be enhanced by strengthening NE to N winds producing lots of blowing and drifting north, and bringing Lake Ontario enhancement into the picture. The good news in these 2 models is that not much snow will yet be on the ground for the start of the AM commute on Wednesday. In fact, rain is depicted closer to PA. However, jumping with both feet into a model shift like this is risky business, and needs to be blended in with other models to avoid the flip-flop syndrome.
So I’m dropping amounts back to the south, but my dropback is less than these 2 in-house models show. The Heavy Snow for the Niagara Frontier looks at least as intense as it did in earlier runs. The RPM brings totals close to a foot, with Vividcast going several inches higher. This time around in the man-machine mix, man will have the heavier hand in projecting amounts.
Travel will deteriorate more rapidly by late Wed AM into the early evening, and the afternoon commute looks tough. Temps will still take the plunge in the afternoon, and head into the single digits by Thursday AM, with a high of just 10-14. That rapid recovery to the upper 30s is still on for Friday; Seasonably Chilly conditions for Saturday and Colder conditions for Sun-Mon.