4 Warn Weather

Several Rounds of Convection This Week; Possible Hvy Rain Late Week, then Much Cooler

May 12th, 2014 at 10:55 pm by under 4 Warn Weather

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.


Warmer Weather Arrives, but Isn’t Ready to Dig in Its Heels

May 5th, 2014 at 9:44 pm by under 4 Warn Weather

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.


It’s That Time of the Year; A “Blocky” Pattern Will be Evolving…

April 21st, 2014 at 2:14 pm by under 4 Warn Weather

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.


The More Things Change, the More They Revert to The Same

April 7th, 2014 at 9:50 pm by under 4 Warn Weather

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.


Lengthy Period of More Seasonable Weather In Sight

March 24th, 2014 at 9:33 pm by under 4 Warn Weather

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.


More Ups and Downs To Come; Fewer Extremes but…

March 14th, 2014 at 9:39 pm by under 4 Warn Weather

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.


Adjustments on the Wednesday Snowstorm? For South of the Metro Area, Probably

March 10th, 2014 at 9:51 pm by under 4 Warn Weather

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.


No Warm Pattern Change Currently in View, but We WILL Get Some Relief

March 3rd, 2014 at 12:15 pm by under 4 Warn Weather

There are no real signs of a fundamental warm pattern change going out through at least March 18th. However, we will get somewhat warmer. We HAVE to. It is March, and the sun angle is getting higher in the sky. Climatology virtually dictates the kind of cold we have this Monday, March 3rd will become a thing of the past. With the higher sun angle, the high Arctic and polar region will no longer be able to produce the unseasonably frigid air masses which have been so common for the central and eastern parts of the nation this winter.

And what our extended range guidance does show is more frequent incursions of Pacific air mixing in with and modifying the Arctic air reaching the Great Lakes over the next couple of weeks. Again, this is not to say we’re going to be experiencing many days with above average temperatures. It means we will have more days with tolerable chill instead of frigid conditions. The “bright” side to that is a reduced risk of renewed ice jam flooding, and a prolonging of the ski season. The negative side is the likely prolonged ice season on Lake Erie (the Great Lakes are more than 90% ice covered as of March 2nd), which makes an early spring much less likely downwind of that Lake. Over the next couple of weeks, the MEAN will be below average temperatures. But from day to day, there will be more ups and downs, and more days during which spending some time outdoors won’t seem like such a shivery idea.


No Rest for the Winter Weary…at least for a While

February 24th, 2014 at 9:47 pm by under 4 Warn Weather

As we’re staring down the barrel of another very cold to occasionally Bitter cold week, it’s almost tempting for a meteorologist to cherry pick for favorable trends in the extended range. It does get tiring giving one wintry forecast after another, but I’m not going to succumb to that temptation.

Fact is, as cold as this week will be, there will be a little improvement in temperatures in the mean for next week. The 500 mb flow flattens somewhat for a few days, allowing more Pacific air to mix in with the Arctic air. That doesn’t equate to mild, but it does equate to more bearable. As I posted on the previous thread, a rapid thaw after this week would again spell probable trouble in the way of increased risk of new ice jams forming. A gradual thaw, of course, reduces that threat (not that we’re looking at anything yet you’d call a thaw). There also were signs over this past weekend that the PNA ridge was going to be building and the Great Lakes trough would be moving toward reamplification around March 9-10. As of today, that western ridge looks a bit less permanent and a little more progressive, and the eastern trough looks a bit shallower. If these ensemble mean solutions worked out, we’d be tolerably cool rather than truly cold–after this week. The operational ECMWF today wants to paint some synoptic snow into our region Sunday night-Monday night from a storm going by to our SE, while the GFS keeps that storm farther away.

This week’s snow will be sporadic and spotty, but no major storm is foreseen during the week.

Back to that extended range…there are still no signs of a fundamental pattern shift to western trough/eastern ridge with any staying power. The PNA ensemble and GFS outlook still point to a positive PNA further out in time, near the end of the extended range.


The Disarray Is Discouraging, to This Meteorologist

February 14th, 2014 at 9:44 pm by under 4 Warn Weather

The big picture…a coming warmup…seems simple enough. There will be one. But the details are fuzzy and getting fuzzier. After a mostly uneventful February weekend, the 2nd half of which will be colder, a storm system will be approaching our region by late Monday or Monday night. The deterministic GFS is much faster than ECMWF or the Canadian with this low. The ECMWF on Friday actually slowed the low down further than its already slower solution, not bringing its snow in until after dark Monday. There still is enough warm advection so that some sleet might mix in and hold down accumulations, while the Canadian and GFS keep us with all snow. The ECMWF is slow enough so that snow or a mixture turning back to snow would still be around for the Tuesday AM commute.

After that system is by us, Pacific air will dominate for some days to come. Some additional moderation will occur on Wednesday into Thursday. However, this (Friday) evening’s models and ensembles are not quite so warm as previous runs, even in the warmest model for this time frame, the GFS. With that in mind, I’m having to shave a few degrees off the Wed and Thursday highs, though temps will still be above average. If it had been just one model and/or ensemble which took the edge off the peak warming, I would have left the numbers unchanged. But because both the ECMWF and the GFS  do so, and the Canadian ensemble mean does so, I’m changing the numbers a little. The low 50s I’d put out for Thursday earlier today are now back to the mid 40s. Of course, all this could change in additional runs. But the overall trend is to make the warmup more irregular, with another Pacific cold front taking us back down a few degrees on Friday. The GFS deterministic model seems set on bringing a wet plains low up into the western Grt Lks on Saturday, while the ECMWF is less organized with this low. In any case, periods of rain with this warmup will add to the risk of ice jam and poor drainage flooding by late next week. The less reliable GFS deterministic run shows a sharp arctic front crossing our region next Sunday, bringing us quickly back into a significantly colder pattern. The ECMWF is a little slower with that cold progression.

While a colder pattern is assured for the following week, it remains unclear how much colder. The Canadian and GFS ensemble mean take us back to significantly colder than average, with a well defined western ridge/eastern trough. The ECMWF had been moving in that direction all along, but just to throw in an additional note of disarray, it flattens that ridge on the last day of the run in the ensemble. This could just be a signal of a strong Pacific short wave showing up. It’s impossible to know if that’s a trend, or a one day special. The other 2 ensemble means are now in good agreement on the western ridge through at least March 1st.