...Guidance/Predictability Assessment...
Model guidance generally remains in good agreement with the
aforementioned large scale pattern evolution, however differences
in the details persist. The most notable question deals with the
degree of interaction between the southern stream and northern
stream energy over the Plains, and the overall depth/strength of
the resultant phased trough. More/earlier interaction and a
stronger trough would likely result in stronger downstream ridging
and thus an overall storm track farther north. Latest guidance from
this morning and afternoon do continue to show this farther north
scenario compared to just a day ago. Confidence in this northward
shift has increased slightly today, given the 12z guidance coming
in close to prior 00z guidance. But there is still plenty of time
for things to shift again (whether further north or back south).
But we may be starting to see some better consolidation in the
forecast and less run to run swings. Despite this, the exact
details of these features is far from settled upon and will
continue to change for any one given location. Either way, it
should be stressed that in just about every outcome we get a
widespread and major winter storm with many areas getting
significant impacts regardless of these exact details. These
details are, however, important for exactly where the maximum snow
and ice totals occur. The current WPC QPF and mass fields are
slightly north of continuity, and consistent with the latest
trends, and as a result, brings more major East Coast cities (NYC
and Boston) into play.