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Mesoscale Discussion 2259
NWS Storm Prediction Center Norman OK
0215 AM CST Wed Dec 11 2024

Areas affected...Southern Maine

Concerning...Freezing rain 

Valid 110815Z - 111215Z

SUMMARY...Light to moderate freezing rain appears likely through 12
UTC across parts of southern Maine.

DISCUSSION...Recent surface observations from southern ME have
reported a wintry mix of light freezing rain and snow over the past
hour as light precipitation migrates over the region. The 00 UTC GYX
sounding sampled sub-freezing surface temperatures in the upper 20s
with a 2 C warm nose at around 850 mb. This warm nose is expected to
intensify through 12 UTC, amid strengthening low to mid-level warm
air advection, within the warm conveyor belt of an intensifying
cyclone. This should promote a change over from a wintry mix to
predominantly liquid hydrometeors over the next couple of hours. 

Latest surface analyses/observations show the surface warm front
remains well displaced to the south, so the shallow sub-freezing
layer should remain in place through sunrise. Light precipitation
should continue as isentropic ascent increases, but precipitation
rates will increase closer to 10-12 UTC as a broader plume of
stratiform rain (associated with deeper large-scale ascent and
closer to the surface warm front) migrates from New England
northeast into southern ME. It remains unclear how surface
temperatures will respond as this precipitation approaches, given
the coincident arrival of the surface warm front. However, latest
high-res guidance suggests the sub-freezing layer will persist long
enough to realize moderate freezing rain rates between 10-12 UTC,
especially within deeper valleys.

..Moore.. 12/11/2024

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...CAR...GYX...

LAT...LON   43927097 44437066 44847012 45106936 45156876 45096831
            44936819 44696829 44626860 44386910 43996980 43727015
            43517051 43487072 43547087 43647093 43927097