Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
255 PM EDT Sat Apr 13 2024

Valid 00Z Sun Apr 14 2024 - 00Z Wed Apr 17 2024


...California...
Day 1...

Deep upper low off the northern CA Coast will slowly pivot
east through tonight as it weakens. Sufficient moisture and height
falls along a progressing cold front allows heavy snow to swing
through the central and southern Sierra Nevada this evening. Heavy
rates of 1-2"/hr can be expected in this brief burst of snow above
snow levels around 5000ft with Day 1 PWPF for >6" 50-80% over this
terrain.

A shortwave rounding the low lifts up the Sierra tonight,
promoting surface cyclogenesis over the Great Basin and shifting
the heavy snow focus back north over the Shasta/Siskiyou east
through the Warner Mtns in the far northeast corner of CA into
Sunday with snow levels remaining around 5000ft. A few rounds of
snowbands containing 1-2"/hr snow rates are expected into early
Sunday. Day 2 PWPF for >6"is 40-80% over this terrain.


...Great Basin to the Colorado Rockies...
Day 2-3...

Upper low will continue an eastward progression through the Great
Basin on Sunday into Monday with large scale ascent focused into
Utah Sunday night into Monday. PWPF increases to 60-80% for >6" of
snowfall across the southern and central UT mountains with some
minor probabilities for upwards of 12" with PWPF indices between
40-60% for >8" and only 10-20% for >12". The progressive nature of
the disturbance will cap potential in-of the above area with snow
levels generally around 7000'.

Upper low will continue to migrate eastward into CO by D3 with
increasing ascent focused into the central Rockies. Snow levels
will be hovering around 8000' MSL, so the higher accumulations will
be confined to the terrain over northern CO northwest of the
Divide. Widespread 50-70% PWPF's of >6" over the aforementioned
area with max of 90% located into the Medicine Bow peaks over
9500'. Higher PWPF's are indicated for >12" snow amounts compared
to UT thanks to greater upslope component from lee cyclogenesis
over the CO Front Range. This will generate the heaviest period of
snow Monday night through the end of the period.

For days 1-3, the probability of significant icing is less than 10
percent.


Snell/Kleebauer