National Weather Service United States Department of Commerce

Forecast commentary -

Temperatures are holding steady near 30 degrees this morning as the state remains socked in with
lake effect clouds within northwest flow regime. Passing shortwave is providing just enough lift to
generate flurries over the area as well as some modest banding extending into Tuscola, Lapeer, and
parts of Oakland/macomb counties from Saginaw Bay. Introduced chc pops given that a couple tenths of
accumulation will be possible within this corridor.

Main forecast issue is very low confidence cloud trends today. Given satellite trends and existing
synoptic support over the area for the next several hours, confidence is high enough to raise cloud
cover substantially through the early morning. As the mid-level wave exits east in the 12-15z
period, suspect downsloping will begin to take more of a toll over the Saginaw valley and Thumb
areas. Building high pressure from the west will contribute to backing boundary layer flow working
southeastward from Lake Superior during the late morning, perhaps sufficiently interrupting the
Superior-Michigan connection enough to allow for additional mid-day cloud erosion. Developing
westerly flow over Lake Michigan will likely force clouds back into western and northern portions of
the area during the afternoon. Westerly flow will trend wswly as low amplitude approaches within nw
flow aloft. Even so, expect the bulk of clouds will pull back toward Lake Michigan tonight as dry
advection forces stable 0-1Km theta-e lapse rates over all but the far east quarter of the lake.
This potential for evening clearing and surface high pressure centered south of the area may allow
for some early radiational cooling. However, temps will quickly level off or slowly rise for the
remainder of the night as the sw gradient ramps up ahead of the incoming surface trough. Antecedent
dry column will make any snow hard to come by on Thursday morning. The exception may be the Saginaw
valley area where forcing will be a bit stronger and some modest lake enhancement to low-level
moisture field will be possible. In any case, there is no expectation for accumulation.

Background height rises will contribute to moderating temperatures Thursday and especially on Friday
as NWP continue to indicate a deep low tracking north of Lake Superior. Temps will approach or
eclipse 50 degrees as the strengthening gradient forces sustained winds of 15 to 20 kts Friday aftn
into Friday night. With no gulf moisture feed, there is a decent chance that the attendant cold
front and attendant low level jet pass through precipitation-free on Friday night.

. . posted at 300 AM EST Wed Nov 22 2017