Have you heard rumors of possible snow this weekend? Even without being at work today, I know regular folks must be hearing things because hits to this blog just about doubled since yesterday, to the highest level since the end of January’s snow & flooding almost a month ago. That’s with no interesting weather occurring right now! Here’s the scoop…
1. Over the past 5 days, computer model simulations of the weather patterns (moisture, temps, weather systems etc…) have been showing some variation or another of a cool or cold spell coming somewhere this Friday or beyond. We get several runs from each different model each day, and each goes out to at least 15 days. You can imagine the amount of information we have available nowadays! Our job in the past 15 years has morphed from one of forecasting to one of forecast model babysitting! Which one is correct or which two are most likely seeing something the others aren’t? You get the idea.
2. Some models at varying times have shown a historic late season cold spell and decent chance for snow to sea level, while at times others have not.
3. They ALL agree on AT LEAST cooler than average weather with snow down into the higher hills again Saturday through sometime next week.
4. They do NOT agree that snow will be showing up in the lowlands.
5. As of right now (10:45pm Monday), the best guess is marginal hilltop snow showers Saturday night and/or Sunday and no snow in the lowest elevations, and no blast of arctic air either.
6. The main issue right now is models are all over the place on details except for #3 above.
WEATHER GEEK DISCUSSION FOLLOWS:
Main issue this evening is models appearing to have no clue what is going to occur beyond Friday (other than the general trend of colder). I have a feeling this is why local meteorologists are playing it quite safe with snow talk tonight. One could hardly reconcile the excitement and wishcasting going on in weather forums/blogs and Facebook sites around the region right now with what is seen on TV and official forecasts.
The 12z/18z GFS and 12z ECMWF were all pretty reasonable with a decent chance for lowland snow beginning Saturday evening once 850mb temps dropped to -7 or so. But they were also very dry, or at least just flurry-ish. I’m not working (just today), but if I was doing the 7 Day forecast, I would have gone maybe 40 both Sunday and Monday and lows 25-28. Just a few flurries on Sunday’s forecast too based on these runs. If one of those earlier and colder models was correct, maybe only mid-upper 30s for a high Monday?
But now the 00z GFS comes in and produces far more of a splitting system Saturday, and then a return to more westerly flow Sunday and beyond. The 00z GFS barely gives the hills a chance for snow…game over on that one. However, the GFS has been really bad lately, so let’s throw that one out. Note the huge variability in the 00z GFS ensemble chart after Sunday morning (just before the “27th”):
The new 00z ECMWF is in now in…slightly different, but quite a bit warmer. It has a first wave coming through Saturday as all the model do, but warmer with thicknesses barely supporting hilltop snow too in strong onshore flow. Then a 2nd wave comes down from the north late Sunday with a better chance for snow to lower elevations; although still marginal. The ECMWF now has only -7 or -8 at 850mb as it bottoms out Monday morning as it too shows colder air digging farther south offshore with a very slight “splitty” look to that trough:
If you take both 00z runs at face value:
1. We don’t have any arctic air on the way (although only a few runs/models have shown that the last few days anyway)
2. Snow to the lowest elevations could be very spotty Sunday if at all.
I don’t think one can read too much into any one model run or any one time period of runs, but it’s fair to say there is a lot of uncertainty to this weekend’s forecast. It is possible we get out of this with very little interesting weather, or this evening’s run are just having issues with shortwaves. Brian MacMillan’s 7 Day forecast sure looks good now…
Chief Meteorologist Mark Nelsen