Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 260711
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
311 AM EDT Sun Mar 26 2017

.DISCUSSION...

With the exception of the tri cities region, Se Mi has remained
largely dry during the night. This is due to the fact that the mid
level deformation has held north and west of the forecast area,
while mid level ridging has held firm across the eastern Great
Lakes. An upper low is churning over the MO/IA/IL border region
early this morning. The water vapor imagery shows a steady stream of
deep layer moisture into the wrn/cntl Ohio Valley within the warm
conveyor belt of this system.

The mid level circulation is forecast to elongate as it rotates into
far srn Lake Mi this afternoon, with the mid level trough axis
taking on a negative tilt as it lifts into srn Lower Mi. This will
result in a fairly good region of mid level height falls
overspreading Se Mi this afternoon and evening. An axis mid level
deformation is forecast to pivot from SW to NE across the forecast
area this afternoon within a region of good upper level difluent
flow. These forcing mechanisms combined with the deep moist plume
being driven into the area will support widespread showers today
into this evening. The showers will increase in coverage across the
southern sections of the forecast area late this morning before
lifting northward during the afternoon. The upper low is forecast to
transition to an open wave as it lifts across Lower Mi this evening.
There will still be decent mid level cooling (especially south of
the I-69 corridor). This will warrant isolated to scattered
thunderstorms during the latter half of the day.

As is often the case this time year, the afternoon temperature
forecast carries a high degree of uncertainty. Temperatures are
likely to vary widely across the forecast area today. The cold front
which rolled across the area Fri night/Sat morning is still located
over central IN/OH early this morning. The associated sfc low will
lift into central Michigan this evening. The sfc low is weak and
there is some concern that the front will not make it this far north
given the dense near sfc cold layer to the north. The ARW and HRRR
do at least lift the front into srn Mi, suggesting some locations
may be able to see temps into the 50s and possibly low 60s.

This upper wave will rapidly dampen as it exits northeast of the
region late tonight allowing mid level short wave ridging to
overspread the area by Monday, supporting a dry forecast. There will
be little cold air intrusion into srn Mi in the wake of this system.
While there is likely to be some residual cloud cover, diurnal
mixing with light w-sw flow will support daytime highs into the 50s
to low 60s. THere are model differences with respect to a mid level
short wave firecast to lift out of the srn plains and across the
Ohio Valley Mon night along with the amplitude of a northern stream
wave fcst to drop into the nrn Great Lakes. The GFS is much more
amplified with this northern stream wave. This causes the model to
produce a region of stronger moist isentropic ascent across Lower Mi
and even suggests some interaction with the southern stream
triggering enhanced mid level deformation right over Se Mi. This GFS
solution is thus rather bullish on precip chances Mon night into
Tues morning. The ECMWF and Canadian on the other hand are weaker
and suggest much lower precip probabilities. Given the uncertainty,
a chance of rain will suffice attm.

Expanding high pressure into the northern Great Lakes by mid week
will support a northeast component to the sfc wind across srn Mi and
thus relatively cool temperatures. The potential for another wave to
lift into the region from the srn plains will support the next
chance of rain late in the work week.

&&

.MARINE...

A weakening low pressure system will track northeastward through the
Great Lakes today and tonight bringing lighter winds to the region.
Initially easterly winds funneling between the low and high pressure
to the north will stay slightly elevated but should remain below 25
knots for the entire Huron basin. Highest winds will be located
across the northern third of the lake. Light winds will persist into
early next week as high pressure tries to build into the region.

&&

.HYDROLOGY...

Periodic rain showers will continue for yet another day across
southeast Michigan. So far the two day totals across the area are
around 1 inch with an additional quarter inch expected today. A
thunderstorm or two may lead to locally higher amount. Regardless of
todays totals, no flooding is anticipated due to the long duration
of the event and relatively low totals over the course of 3 days.

&&

.PREV DISCUSSION...
Issued at 112 AM EDT Sun Mar 26 2017

AVIATION...

Ceilings, bordering on IFR/MVFR should trend down somewhat overnight
as moist, easterly flow weakens below 10 knots. Fog has been slow to
form given gradient flow to this point, but still expect MFVR to IFR
vsbys late tonight into early Sunday morning. Low pressure lift into
area on Sunday and transition wx to showers with cigs/vsbys coming
up somewhat.

For DTW...Ceilings bordering on MVFR/IFR should become predominantly
IFR overnight into early Sunday morning as easterly flow drops to 6-
7 knots. Showers will increase in the 15z-17z time frame and persist
into evening as low pressure wobbles slowly into/across area.

//DTW THRESHOLD PROBABILITIES...

* High for cigs below 5000 feet much of the forecast.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...SC
MARINE.......DRK
HYDROLOGY....DRK
AVIATION.....DG


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at www.weather.gov/detroit.



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