ACUS11 KWNS 232309
SWOMCD
SPC MCD 232309=20
CAZ000-ORZ000-240515-

Mesoscale Discussion 0184
NWS Storm Prediction Center Norman OK
0509 PM CST Thu Feb 23 2023

Areas affected...portions of northwestern California

Concerning...Heavy snow=20

Valid 232309Z - 240515Z

SUMMARY...Heavy snow should continue to gradually become more
widespread across portions of northwestern California, with up to 1
inch/hr snowfall rates possible as low as 1000 ft in elevation this
evening.

DISCUSSION...A stacked surface-500 mb low resides just offshore of
the Pacific northwest, promoting a deep westerly fetch of moisture
which is contributing to a near saturated troposphere (per 21Z RAP
forecast soundings). The stacked low should continue to gradually
migrate south through the night, with at least one embedded
mid-level impulse expected to precede the arrival of the low. Some
of the latest deterministic guidance shows this impulse
overspreading northern CA over the next few hours, which should
increase deep-layer ascent over the region. 23Z mesoanalysis hints
at some 700 mb warm-air advection already taking place along the
northern CA shoreline, with a couple of surface observations
currently showing heavy snow near the CA/OR border, hinting at the
potential arrival of the mid-level impulse.=20

While surface temperatures are currently above freezing across
several low-terrain areas, continued cooling this evening will
support sub-freezing vertical profiles and associated accumulating
snowfall potential in lower-terrain areas. Surface-500 mb lapse
rates should remain at or above 8 C/km, that combined with the
relatively rich moisture, may also foster 100+ J/kg MUCAPE. Stronger
deep-layer mechanical lift, and ascent driven by potential
convective processes, should encourage periods of heavy snow through
the evening hours. 1 inch/hr snowfall rates are most likely in the higher-terrain areas, at least initially. However, some of the
heavier snowfall rates may occur over lower-terrain areas, perhaps
as low as 1000 ft in elevation, with dangerous travel conditions
possible into tonight.

..Squitieri.. 02/23/2023

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_0smXJC8ZST2nGFy_n7Cekj7ZRTbfQATetRXFsPE_wsE_l5t-CiF_tWRS5wUjtY8SqVujVjYP= kun984HNJA77NWamyk$ for graphic product...

ATTN...WFO...MFR...STO...EKA...

LAT...LON 41752446 42082420 42132383 41722323 40202275 39812292
39582325 39552361 39502391 41752446=20


=3D =3D =3D
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