Scientific Forecaster Discussion
fxus63 kdtx 191059
Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
659 am EDT Wed Sep 19 2018
MVFR stratus with patches of MVFR/IFR fog will slowly erode this
morning, leading to partly/mostly cloudy mid/upper level clouds by
this afternoon. Some thickening of clouds possible tonight, after
06z generally as convection gradually spreads toward the area along
warm front lifting back north into area. Will forgo mention of shras
of tsras for this forecast, but not out of the question very late in
the forecast kfnt/kmbs and perhaps kptk. Light northeast flow will
persist and veer to east/southeast late as warm front lifts into the
For dtw...MVFR cigs will erode by 16z-18z with patchy fog
dissipating early than that. VFR thereafter, aside from perhaps
patchy 5-6sm br again late tonight. Light northeast flow 5-6kts
today with a trend to east-southeast this evening/tonight.
Dtw threshold probabilities...
* high for ceiling 5000 ft or less into early this afternoon.
issued at 354 am EDT Wed Sep 19 2018
High based showers resulting from a subtle shortwave and upper jet
support that moved through overnight have moved east of the area.
Surface analysis shows the weak cold front that moved through
yesterday has stalled out south of state. This has allowed slightly
cooler air to move over Michigan under northerly flow. Mid level
height rises will creep northward over Michigan pushing the upper jet
to the north this afternoon as the large area of high pressure moves
across the lower Mississippi Valley. This will help keep conditions
mostly dry across much of the area during the afternoon. The one
exception will be across northern portions of the County Warning Area where an
elevated front may kick up some activity with help from moisture off
the lake, though the limiting factor will be the presence of a cap
through much of the day. Increased cloud cover with the cooler
airmass will keep high temperatures today mostly in the 70s with
locations across the northern thumb in the mid to upper 60s.
Pacific wave entering the intermountain west today will help
strengthen a developing low pressure system across the Central
Plains. This will draw the stalled front northward into Lower/Middle
Michigan. Flow aloft will also begin turning southwesterly with a
strengthening low level jet, which will set up a transport of higher
moisture into Michigan over this front. As shortwave energy moves
through the flow and fgen begins increasing, precipitation will
begin increasing later tonight into tomorrow morning moving from west
to east along the front. Front placement looks to be across mid
Michigan which will lead to likely pops across the northern portions
of the County Warning Area and decreasing to chances across the south. There will be
thunderstorms with some severe potential during the overnight period
into tomorrow morning with enough bulk shear, increased mid level
lapse rates and stronger low level jet winds.
As the surface low lifts into northern Michigan tomorrow evening it will
draw the warm front further north placing Southeast Michigan in the
warm sector. Precipitation chances will decrease slightly as the
warm front moves into northern Michigan, but believe there could
still be some scattered thunderstorm activity during the day within
the strong warm air advection. Increased instability and bulk shear
will keep a maintain potential for a severe thunderstorm threat with
any storms that develop. Surge of warm air will also bring high
temperatures tomorrow back into the upper 70s and 80s.
Upper level trough will deepen the surface low as it tracks through
the western Great Lakes and through northeastern Ontario. Gradient
flow will be increasing Thursday night into Friday with this potent
low pressure along with a cold front getting pushed through Michigan
Friday. There will be potential for a line of storms to be riding
this front as it drives through Michigan and exits by late
afternoon. Main threat with this line will be damaging winds, though
already breezing conditions expected to occur during the day with
winds gusts up to 40 mph possible.
High pressure will be building in behind the front along with much
cooler and drier conditions for the weekend. Dry weather looks to
continue into early next week with weak ridge translating over the
region with an expansive surface high. Below normal temperatures in
mostly in the 60s on Saturday will gradually increase each day into
Monday. Another trough and developing surface low across the plains
is forecast to send a warm front north into Michigan late Monday
into Tuesday. This may bring the next shot at precipitation for
Michigan, though there is still some uncertainty with how this
system plays out next week.
A stalled frontal system over the Ohio Valley will promote light
easterly flow today into tonight as high pressure to its north
builds eastward across Ontario. These favorable conditions will
begin to worsen late tonight into Thursday as the front moves north
and shower and thunderstorm activity increases. An increasing wind
component will also occur as low pressure organizes over the Central
Plains and strengthens over the northern Great Lakes. Much warmer
air surging north across lower Michigan and Lake Huron will increase
stability and limit wind gusts to some extent. However, gusts to 30
knots look possible in southwest flow late Thursday into Thursday
night from parts of Saginaw Bay on it Central Lake Huron.
Once the low crosses the northern Great Lakes and continues into
Ontario early Friday morning, an associated cold front will push
southeast through the central Great Lakes. The front will bring
veering winds to the northwest with considerably colder air
reversing the thermal profile to an unstable configuration. The
strength of the low could support a wind field capable of gusts to
near gale force over the open waters of Lake Huron Friday into
Friday night. Will forgo a gale watch at this time and allow for a
more larger suite of hires model runs to hone in on the forecast
strength and position of the low pressure system as it passes north
of Lake Huron on Friday. Once this system passes, high pressure will
then bring more tranquil conditions during the weekend.
Shower and thunderstorm chances will increase gradually late today
into this evening. However, widespread activity is expected to hold
off until overnight into Thursday morning as a warm front lifts
north into the region in response to developing low pressure to the
west. The warmer and more humid air moving into the area with this
front will supply enough moisture for rainfall totals averaging 0.25
to 0.50 inches from tonight through Thursday morning. Totals at the
higher end of the range are more likely across the Tri Cities and
northern thumb where localized rainfall around 1 inch will also be
possible. While widely scattered showers or thunderstorms may occur
into Thursday afternoon and evening, the most significant activity
should shift north of the region with the warm front. The potential
for flooding is minimal with this activity, limited to ponding of
water on roads and minor flooding of poor drainage areas.
Lake St Clair...none.
Michigan waters of Lake Erie...none.