Sunday, October 2, 2016

Tropical in the East, Late Fall in Utah

This morning, it's worth taking a step back and looking at the "Supernational" view of the GFS 50-mb height, precipitation, and cloud forecast for today through Friday morning.

Let's begin in the east where the big story is Hurricane Matthew, which is currently a major hurricane (category 4) with sustained winds to 140 mph.  In the loop above, the 500-mb low associated with Matthew moves into the picture on Monday when it is expected to be affecting Jamaica and Haiti. Beyond wind and storm surge, the National Hurricane Center is calling for total rainfall accumulations of 15 to 25 inches in Haiti, with local accumulations of up to 40 inches.

Matthew is a slow moving storm presently, but is expected to accelerate as it moves northward.  Most models and ensemble members call for it to move northward near or east of the US East Coast.  It is worth paying close attention to forecasts over the next few days if you live along the eastern seaboard or are planning to travel there.

Moving back west, tonight marks an abrupt change and we can expect the work week to bring the coldest stretch of weather we have seen in a long time to northern Utah as a series of troughs moves through the state.  Forecast 700-mb (10,000 ft) temperatures for 6 AM tomorrow morning through 6 PM Thursday are between about -7ºC and -3ºC, closer to the averages for late October and early November, so consider this a practice run for the late fall.

And yes Virginia, there will be periods of snow in the mountains.  Looking at the latest model runs, there don't appear to be any huge storms on tap and it is likely that by the end of the lake we will see a Purgatory-like snowpack.  Not enough snow to ski and too much to hike.  Of course, I saw video of many people skiing after the last storm, so perhaps my standards are too high and there's always the hope that we come in on the high side (or above) projections.  This is a pattern with a wide range of possibilities, so perhaps northern Utah skiers should pay attention to forecasts too.

Personally, I think it's too early for these sorts of storms.  Better to hold off until later in the month or early November and then open the spigot.  Early snow frequently turns into weak snow when the inevitable fall ridge returns.


  1. The superstitious among us often worry that early-mid fall stormy patterns preclude late fall-early winter stormy patterns; that somehow the precipitation and low pressure systems use up all the good stuff and leave us with severe clear in November. Anything to that besides paranoia and fantasy?

    1. It's fantasy.

      There's very little correlation between October precipitation and November-April precipitation. We have covered this previously here: