Mesoscale Discussion 0067
NWS Storm Prediction Center Norman OK
0747 PM CST Tue Jan 17 2017
Areas affected...Eastern Washington...North-central/Northeast Oregon
Valid 180147Z - 180745Z
SUMMARY...Mixed precipitation will overspread the area this evening.
Snow and sleet will be possible across the northern portion of the
area initially, while freezing rain is expected to become
established further south, with rates around 0.05 inches per hour
DISCUSSION...At 0130Z, a large precipitation shield is beginning to
spread east of the Cascades into portions of eastern Washington and
northern Oregon. With very cold temperatures in the 15-25F range
currently in place, an initial precipitation type of snow or sleet
is possible, especially across the northern portion of the MCD area
where a less substantial warm nose is in place. However, continued
warm advection above an increasingly shallow subfreezing layer will
eventually result in a changeover to freezing rain across the bulk
of the MCD area, such as what has already occurred around Yakima.
Freezing rain rates of up to 0.05 inches per hour will be possible,
with ice accretion likely to be rather efficient given the
antecedent cold airmass that is in place.
LAT...LON 46352065 46942056 47432023 47961965 48051878 47981806
47601732 46621765 45961815 45811827 45541872 45421907
45421940 45401994 45602037 46352065