Tag Archives: Phasing

WEATHER UPDATE FOR FRIDAY

This post was revised

The mystery of why the models are showing rain instead of snow has been solved.  The models are forecasting a layer of warm air in the lowest 1500 feet of the atmosphere.

The Friday storm discussed earlier this week still remains a forecast challenge.  Let me start by saying that ALL models currently forecast rain, not snow, for our area because near surface temperatures are expected to be well above freezing.

That said, there are many model parameters that historically predict snow for us and many features that still need to watched.

Basically a low pressure system was expected to come together and phase with an upper low resulting in an intense coastal storm.   That scenario has faded, as phasing is expected to occur later, out in the Atlantic.

Here’s the current GEFS (Statistical Ensemble) mean forecast for Friday at 12 PM:

GEFS 12 PM Friday forecast  Blue Arrow points to upper low and the black arrow to the surface low.

Below is the current SREF (Short Range Ensemble) forecast, showing a somewhat similar position of the surface low, but with this forecast, I have drawn in the snow-critical temperature lines.  Notice that we are on the north side of these critical temperatures, usually meaning snow for us.

SREF 12 PM with critical snow thickness.  We are north of these critical snow temperatures, usually meaning snow for us.

I’m sure the models ‘know what they’re doing’ regarding snow forecasting, but with this complex upper-low/surface low combination, it will be interesting to see what actually happens.

What I expect is for some snow to mix in with the rain especially later in the day, but no accumulation.  Let’s see what happens.

 

Coastal Storm Saturday?

This post was revised

Much uncertainty about the intensity and timing of a coastal storm expected to develop and move up the coast, affecting our area sometime early Saturday into Sunday.  Several models have backed away from a super storm that had been forecast by the European Model (ECMWF) and Canadian (CMC) models and to some extent the GFS.

The latest model forecasts suggest that the northern stream and southern stream low pressure systems won’t phase because the northern stream disturbance will arrive too late.  However, the ECMWF still has a considerable storm forming and affecting us Saturday into Sunday.

The latest GFS moves the low pressure through faster and keeps the two storms separate. In fact the lack of phasing with the GFS keeps the southern stream coastal storm moving fast and robbing it of some punch.

It’s still way too early to know which way things will go, but the trend is towards a rainy but otherwise unremarkable Saturday.

I’ve been following this for several days and I’ll update if things change.