The Disarray Is Discouraging, to This MeteorologistFebruary 14th, 2014 at 9:44 pm by Don Paul 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.