Weather It Is (The Tension Builds)

Good Evening:

Last week we spoke about the things we know, the things we know are not known, and the things that we don't know we don't know.

There are still plenty of things we don't know we don't know, but the things we know (or don't know) are becoming better known.

For instance, we see that our next storm -- to arrive immediately after the relatively weak (but still) wet) storm affecting us now will bring cold temperatures aloft, but nothing too chilly at lower levels. This means periods of rain mixed with graupel/hail.  This storm will be arriving from our west, as higher heights (NAO) build over Greenland - meaning that initially the ridge trough couplet (west to east, respectively) will be located at first too far to the west -- so the lower levels in the next storm will be moderated by the warm sea.

In contrast, we now have indications that the storm that should follow Shabbat or early next week will arrive from the north (as Siberian air makes its way southward).  Our current forecasts show a 60/40 in split in favor of extremely cold temperatures aloft.  This means that the forecasts are clustering around either a cold, snowy "solution" to the equations that describe our future weather or a warmer solution, with a lean toward the colder forecasts. However, there is less certainty about lower level temperatures. Still, many ensemble members show temperatures below freezing at least at some point during the storm.

So, we know that we can be more positive about the possibility of our first snow (in the Jerusalem area) early next week, but there are still a lot of unknowns (just how directly the storm arrives from the north) and even unknowns we don't know -- besides model errors, how many people want snow or don't want snow, which can sometimes tip the balance.

Barry Lynn