Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 201717

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
117 PM EDT Sun May 20 2018


Persistent MVFR clouds will maintain through the balance of the
afternoon. The near surface layers will slowly dry from north to
south late this afternoon into the evening hours - lifting and
breaking ceilings somewhat. The greatest thinning of clouds will be
observed at the northern terminals. North flow will veer to
northeast and hold through the night, before becoming more easterly
Monday morning. Ongoing scattered showers will continue to dissipate
as they approach the terminals this afternoon. Will maintain a
vicinity mention for the first few hours. An area of light rain is
expected to advance northeast across Southeast Michigan starting mid-
morning Monday. There will likely be a break in the rainfall during
the late afternoon.

For DTW...Ceilings will remain below 5kft through the afternoon into
the early evening. Ceilings may dip below 5kft once again toward
midday Monday into Monday afternoon.


* High for cigs aob 5000 ft today, medium this evening and again
  Monday midday.


Issued at 953 AM EDT Sun May 20 2018


As of 950 AM EDT...Continue to monitor upstream showers coming off
Lake Michigan into western lower Michigan early this morning, aided
by an embedded shortwave ejecting out of Illinois/Wisconsin and
remnant midlevel post-frontal forcing behind the cold front that
exited last night. Observed 12z KDTX sounding revealed some drying in
the midlevels, but still enough ample moisture that this shower
activity should continue to make eastward progress into southeast
Michigan, albeit mainly west of US 23/I-75. This solution is favored
by much of the hi- res guidance, including consensus blends as well,
so have reintroduced slight chance/chance PoPs into the areas
mentioned above for light shower potential late this morning and into
the first half of the afternoon.

The sounding also revealed a sharp low-level capping inversion, with
plenty of remnant boundary layer moisture trapped beneath. Coupled
with cooler air filtering in from the north, low stratus will
continue to entrench much of southeast Michigan through the remainder
of the day. Despite diurnal heating lifting the cloud deck slightly
as the day progresses, temperatures will have a hard time
responding, only warming into the 60s for inland areas and 50s along
the Lake Huron coastline. If some more persistent breaks in cloud
cover occur late this afternoon, some inland locations will have a
shot at 70 degrees.

Issued at 302 AM EDT Sun May 20 2018


An elongated region of sfc high pressure will expand from northern
Minnesota/Lake Superior this morning into northern Lower Mi this
afternoon within mid level confluent flow across the northern lakes.
There has already been a push of shallow cool air across Se Mi
within the low level north-northwest flow preceding the sfc ridge
axis. This shallow cool layer has led to a deepening low level
inversion, supporting ample low clouds and fairly widespread
drizzle. Persistent low level northerly flow this morning will
advect drier boundary layer across Se Mi, this will end the drizzle
from north to south across the area during the early morning hours.

The cluster of showers/thunderstorms across SW Wisconsin overnight
have struggled to to make much progress to the east. There will be a
push of lower mid level theta e air across srn Mi from the north
today which will hold any semblance of elevated instability well to
the south and west of the area. There will also be subtle mid level
height rises across Lower Mi through the day. These factors will
make it unlikely for ongoing convective activity across srn WI to
advance into Se MI. While low clouds will tend to diminish from
north to south across the area during the course of the day, the
shallow cool air will limit mixing depths and likely hold afternoon
highs mainly in the 60s, with much cooler readings along the Lake
Huron shoreline.

The sfc high will build into Se Mi tonight. Mid/high level clouds
will likely inhibit radiational cooling potential across the
southern half of the forecast area. The likelihood for clearing skies
across the Saginaw Valley and thumb combined with the dry airmass
will warrant min temps into the low 40s (with some upper 30s
possible across the thumb).

There is a fair amount of model divergence with respect to timing
and amplitude of short wave impulses lifting out of the upper
Midwest and traversing srn Mi Monday into Tuesday. This will affect
the strength of mid level southwest flow which in turn will
determine the degree of mid level moisture/instability advection
into Se Mi. In light of the confluent flow overhead, preference lies
with those solutions which dampen the upper energy more
significantly, thereby only supporting just low chances of
convection (mainly south of M-59). High pressure will strengthen
across the Great Lakes midweek behind an amplifying mid level trough
over eastern Canada, supporting dry conditions across Se Mi. Mid
level ridging will then expand across the Great Lakes toward the end
of the week, leading to a steady warming trend.


Light winds today as high pressure builds into the area. Light winds
will persist through at least Wednesday, as high pressure more or
less holds over Lake Huron. Chance of showers and thunderstorms
early next week will be mainly confined to Lake St. Clair and Lake


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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