FOUS11 KWBC 060807
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
307 AM EST Wed Nov 6 2024

Valid 12Z Wed Nov 06 2024 - 12Z Sat Nov 09 2024


...Central/Southern Rockies and Adjacent High Plains...
Days 1-3...

Upper low at the base of a larger western CONUS trough lies over
southeastern UT this morning, and will continue sinking southward
today into AZ. It will slowly detach from the northern stream and
cut off as it wobbles southward then eastward into southern NM by
early Friday. Then, feeling the push of the subtropical jet, it
will lift northeastward across the northern TX Panhandle and far
western OK Panhandle to the CO/KS border by early Saturday. The
slow movement of the upper low combined with a fairly steady
stretch of moisture as well as upslope enhancement will lead to
significant snow accumulations in parts of the NM mountains and
across the CO line along the Sangre de Cristo range. Impacts may be
major to extreme in some locations.

For D1, frontal boundary over southeastern CO on the edge of the
height falls will see modest to locally heavy snow continue this
morning in an area of surface convergence and beneath bouts of PVA.
Through the day, as the upper low tucks farther southwest of CO,
heights should rise and the snow should lessen. Nevertheless,
snowfall rates of >1"/hr should yield an additional several inches
near/south of DEN and eastward over the High Plains. There, WPC
probabilities for at least 8 inches of snow after 12Z are moderate
(40-70%). Farther south over NM, closer to the stream of moisture
and vort maxes rotating around the upper low center, snow will
increase in intensity over much of the NM terrain where snowfall
just on D1 will likely exceed 8 inches (probabilities >70%) in the
terrain (e.g., Sangre de Cristos/Raton Mesa/Jemez Mnts).

By D2, slow movement of the upper low will allow for continued
snowfall to its east via persistent IVT values near/above the 90th
percentile. This could result in 1-2ft of snow over the NM terrain
(WPC probabilities for at least 12 inches are >70% over much of
northeastern NM) along with areas of blowing/drifting snow eastward
into the western OK Panhandle. Snow will continue over northern NM
into southern CO along the Sangre de Cristos and onto the High
Plains as the upper low sloshes toward the TX/OK Panhandles.
Moisture source will add in then largely switch to the western
Gulf, wrapping around the upper low and capitalizing on upslope
from the northeast through the column. Snow will finally start to
taper off by the end of the period (early Saturday).

All told, 3-day WPC probabilities for at least 24 inches of snow
are >50% above 6000-7000ft over the Sangre de Cristos and Raton
Mesa, with a large footprint of at least 6 inches over much of
eastern CO southward into central NM.


The probability of significant ice across the CONUS is less than
10 percent.


Fracasso



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