Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 280703
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
303 AM EDT SUN AUG 28 2016
A corridor of fast low to mid level west-southwest flow has resided
across Lower Mi during the overnight period. Moist isentropic ascent
along the nose of the low level jet, tied to the entrance region of
an upper jet max within the base of the upper trough now rotating
across wrn Lake Superior, resulted in the development of a cluster
of thunderstorms over central Lower Mi overnight. This localized
forcing will continue on a northeast track across Saginaw Bay during
the pre dawn hours.
The upper trough will continue on an eastward track across Lake
Superior/nrn Ontario today. The entrance region of the upper jet
will linger over srn Mi throughout the day and will force a narrow
region of mid level frontogenesis. This frontal forcing, now
extending from srn Lake Mi into cntl Lake Huron, will gradually
slide south across the forecast area during the course of the day.
Mid level dry air and subsidence will follow in its wake. This
forcing will generally provide a slight chance of morning convection
across the northern half of the forecast area. The chances being
limited substantially be weak available instability. Daytime
destabilization will provide a little better chance for some
afternoon convection as the forcing slides south of a KPHN to KOWZ
line this afternoon. Meanwhile, daytime heating will erode morning
fog and low clouds and will support afternoon highs into the 80s.
The deepening daytime mixed layer and low-mid level dry air
advection will result in a slight drop in sfc dewpoints across the
Saginaw Valley early this afternoon, spreading south into Metro
Detroit during the evening.
Mid level confluent flow and building heights following the
departure of the mid level wave to the east of Lake Superior tonight
will force sfc high pressure to expand into the area from the west.
North-northeast low level flow across Lake Huron into Se Mi will
occur in advance of this high. The latest NAM, HRRR, and ARW all
suggest marine stratus will have a difficult time eroding today.
This moisture will then advect across Se Mi tonight with the onshore
flow. Fog and/or low stratus will result and will likely persist
through the Mon morning rush hour. Once the low level moisture mixes
out lat Mon morning, a warm and dry afternoon can be expected on as
the sfc high continues to influence the region.
Model trends have been a little slower bringing a sfc cold front
into the area from the north next week. The latest model suite do
not bring the sfc cold front across Se Mi until Tues night. The
front will be driven south by a mid level wave forecast to track
from nrn Manitoba into nrn Quebec. Limited forcing and instability
along the front as it tracks across the area will support very low
chances for convection. The passage of the front will however mark a
substantial airmass change. Long wave trough amplification across
ern Canada during the latter half of the week will drive much cooler
air into the Great Lakes (850mb temps forecast to drop into the
single digits by Thursday). Thus cool temps (highs in the 70s and
lows in the 50s) can be expected the latter half of the work week.
Westerly winds today will be predominantly in the 5 to 15 knot range,
except across northern lake huron will sustained winds look to be
closer to 20 knots. Winds will shift to the north tonight as high
pressure continues to build in, allowing for light and variable
winds on monday. Modest southwest winds expected on Tuesday
ahead of a weak cold front tracking through.
Issued at 1158 PM EDT Sat AUG 27 2016
Warm and humid air will remain over SE Michigan for the rest of
tonight through mid morning as a weak surface trough moves through
the region. Light wind within these features, combined with wet
ground from earlier widespread rainfall, will support IFR
restriction. Uncertainty has been with the distribution between fog
and stratus during this time which the most recent observations
support as stratus. Light surface wind could still allow intervals
of lower visibility where breaks occur in the clouds and prior to or
within the surface trough. There could also be a heavier shower MBS
to FNT while the trough can support activity. Expect IFR stratus
improving to MVFR during the morning post trough as the wind field
will be slightly stronger and with increased daytime heating.
Westerly flow leading weak high pressure into the region will bring
improvement to VFR early to mid afternoon into Sunday evening.
For DTW... IFR stratus developed well south into NE Indiana and NW
Ohio and now shows some persistence prior to sunrise. Light wind and
humid conditions will also contribute and help produce some fog at
times when breaks in the clouds occur. IFR transitioning MVFR and
then VFR during the morning into mid afternoon.
//DTW Threshold Probabilities...
* High for ceiling 5000 feet or less tonight through mid afternoon.
* Low for ceiling/visibility below 200 ft or 1/2 sm tonight.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online