Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 AM EST Sat Dec 09 2023
 
Day 3
Valid 12Z Mon Dec 11 2023 - 12Z Tue Dec 12 2023 

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS 
OF MAINE...

The event described in more detail in the day 2 discussion will be 
ongoing Monday morning across portions of ME. More uncertainty 
exists with the forecast by this time...both with regards to ptype 
and additional QPF magnitudes. The model consensus favors mainly 
rain over eastern ME Monday, but a transition to snow is certainly 
possible over northern ME. The GFS is most aggressive with the mid 
level energy and surface low...and thus drops an impressive 4-7" 
of rain over ME for a 48 hour total. On the other hand the ECMWF 
and UKMET are more in the 2-4" range, with the official WPC 
forecast also 2-4". The PQPF 75th percentile 3-4" and the 90th 
percentile is more in the 3-5" range. Thus it becomes apparent 
that the 00z GFS is an outlier and lower probability outcome. We 
can not completely rule it out, and a solution like the GFS would 
likely pose a more significant flood risk over ME, but for the 
moment it appears like a lower probability outcome. The more 
probable rainfall of 2-4" would still pose a flood threat, but 
likely more at the Marginal risk level. Snow melt is a factor to 
consider and keep an eye on, although the more substantial SWE is 
located over northern ME...and at the moment not expecting the 50+ 
dewpoint air to make it that far north. So while snow melt may 
play some factor in the flood risk over ME, at the moment not 
expecting it to have a significant contribution to any flash flood 
risk.

Chenard
 
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt