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Created: 6:00 AM EST, November 11, 2015
The main impacts of this storm are still expected to be driven by strong winds. We'll see showers and perhaps a thin line of thunderstorms move through late this evening. With strong winds in the lower levels and good mixing, it won't take much to pull down strong winds.
However, once the convective window has passed, surface winds will increase substantially Thursday morning as colder air wraps into the system. Soundings/BUFKIT wind profiles suggest the inversion mixes out prior to sunrise, and we mix into the 50-60 knot layer.
GFS sounding for GRR valid at 00Z, 06Z, and 12Z Thursday:
Wind gusts over 50 mph seem possible across the southern half of the CWA, and we issued a High Wind Watch Thursday into Friday morning for this potential. The northern CWA will likely need a Wind Advisory during this time as well. Wind gusts will remain in the 30-40 knot range most of Friday before gradually subsiding late in the day. We opted to use the GFS as a starting point over the NAM with wind gusts. The NAM seems to be initializing too cool in the boundary layer and doesn't have realistic mixing heights. GFS BUFKIT overview shows mixing well into the 50 kt layer, whereas the NAM does not:
The extended period of strong winds will generate large waves on Lake Michigan. Likely 50-60 knot gusts over the lake and lakeshore will build waves into the 10 to 18 foot range Thursday and Friday. The combination of higher Lake Michigan water levels and very large waves is expected to cause beach and dune erosion and may also result in lakeshore flooding.
A thin line of thunderstorms may push through just ahead of the occluded front late this evening. This will be yet another good example of a high shear, low CAPE environment. Very strong wind fields in the low to mid levels support a marginal risk for damaging winds, including a 90+ knot southwesterly mid-level jet streak just off to our south and a 60 knot low-level jet ahead of the system:
A secondary shot of cold air will push through on Friday and will result in mixed rain and snow showers with temperatures holding in the low to mid 40s. Snow showers should be ending Friday evening as inversion heights fall below 5,000 feet. Accumulation is not expected. Fair weather follows for the weekend.