SPC MD 1834


MD 1834 Image

Mesoscale Discussion 1834
NWS Storm Prediction Center Norman OK
0652 AM CST Sat Dec 05 2020

Areas affected...Northern CT to southwest ME

Concerning...Heavy snow 

Valid 051252Z - 051645Z

SUMMARY...Moderate rain will transition to heavy snow with rates
likely reaching 1-2 in/hr through midday.

DISCUSSION...12Z surface analysis places a cyclone just off the DE
coast which is expected to undergo pronounced deepening on its
approach towards Cape Cod through this afternoon. As this occurs,
850-mb winds will strengthen on the backside of the cyclone as well
as gradually back from northeast to north and increase low-level
cold advection. This will be coupled with further cooling from
intense upward vertical motion and likely yield a rapid changeover
to heavy snow. This process should occur first in the central
MA/Worcester vicinity just to the west of the pronounced bright band
evident on KBOX radar, and then rapidly increase in areal coverage
(mainly to the northeast) through midday. Deep, nearly isothermal
thermodynamic profiles beneath the dendritic growth zone that is
between 600-500 mb should yield large aggregates capable of
producing 1-2 in/hr snow rates, that could locally reach 2-3 in/hr
towards early afternoon. These rates are broadly supported by 09Z
SREF and 00Z HREF guidance.

..Grams.. 12/05/2020

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


LAT...LON   42227312 43027253 44017125 44367055 44427023 44227006
            43867030 43117103 42507146 42057186 41727277 41907326

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