KEY MESSAGE 2...
There remains a high amount of uncertainty with the development
and track of a coastal low Sunday into Monday. However, there
has been a clear trend to the NW the last 24-36h in the low
track with ECAIFS, AIGFS, the GEFS, and to a lesser extent the
GEPS. The operational GFS and GDPS (Canadian) the last 2 to 3
runs have a low track that has been close enough to see some
snowfall across the region, but not a major event. Bottom line,
there has been a lot of jumping around of the guidance and this is
likely due to complex interaction between multiple streams/upper
lows embedded within a longwave trough across the western half of
the country. This could still be the case another 24h or so before
we see better consistency amongst all of the guidance.
Given the uncertainty, the forecast has continued to follow the
NBM. NBM probabilities for 6 inches or more are generally less
than 15 percent, highest across LI. Even advisory level snows
get no higher than 20 percent. That being said, the guidance
being all over the place has kept these numbers low. The system
though is very much worth watching because of its potential with
incredible deepening of the low Sunday afternoon and night.
Pressure falls around 24 mb in 12h in the 00Z GFS and GDPS. The
potential for high winds and heavy precipitation is a concern
should a more western track become the consensus.
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