Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251724

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
124 PM EDT WED MAY 25 2016


A weak surface boundary between FNT and MBS will lift slowly
northward this afternoon. High based cu has formed along this
boundary and there will be a slight chc for a shower or thunderstorm
to develop during the afternoon and evening along this but too small
chc to add to tafs.   Elsewhere this afternoon and evening,
southwesterly flow will continue to gradually advect in more
moisture leading to diurnal cu fields generally aoa 6k ft. There
remains a slight chc for a shower or thunderstorm this evening
across southeastern tafs. Tonight a mid level wave will eject out of
the Missouri Valley and move through lower Michigan. This will cause
surface winds to back slightly overnight before veering again to the
southwest Thursday. This wave will produce enough lift to overcome
weak capping allowing for scattered coverage of showers to develop.
There will also be a chance for some thunder but probability and
coverage is too low to include in tafs. Fog around 5 miles is also
likely with and shortly after shower passage.

FOR DTW...a slight chc exist this evening for a shower or
thunderstorm from heating of day and disturbance passing across
northern Ohio. scattered showers are likely to swing through
during the 06-12z time frame with a slight chance for thunder.
Ceilings should remain vfr.

//DTW Threshold Probabilities...

* Low for ceiling 5000 FT or less tonight and Thursday.

* Low for thunderstorms affecting DTW/D21 air space.


Issued at 1139 AM EDT Wed May 25 2016


Straight into a mid to late summer weather pattern for
southeastern Michigan with warm daytime temperatures and weak
shear owing from persistent upper level ridging. The forecast
item to watch for this afternoon is the potential for sct-iso
shower and thunderstorm development generally along and north of a
line from Saginaw To Port Sanilac. Not obvious but cursoryglance
through models show that a trigger could in fact be a warm frontal
feature, 850mb theta e gradient that is now lifting northward
through central sections of the cwa. KDTX 0.5 Z is showing this
feature lifting northward through the I 69 corridor and 8-10 kft
agl base altocumulus development over the northern portion of the
cwa is along this boundary. Explicit convection hi- res output
supports shower development with low thunder potential beginning
around 17-18Z and possibly persisting to as late as 21Z. A few
thoughts on character of behavior. Models are trying to keep
surface dewpoints at 60 degrees this afternoon. Latest surface
observation trends and the relative aggressive cloud development
this morning suggests there is a chance these surface dewpoints
could actually stay up because of moisture pooling along and ahead
of the 850mb theta e gradient. With this near surface moisture
content, looking at MLCAPES ranging 500-800 J/kg possible this
afternoon. Marginal instability, low 0-6km bulk shear values, and
weak environental winds does not support a severe or even strong
storm risk with the activity along and north of Saginaw to Port
Sanilac. High cloud bases with a pseudo inverted v structure or a
wet microburst could potentially support some wind gusts up to 40
mph. Shower and thunderstorm movement will be generally to the
east northeast at 20 to 25 mph.

Issued at 333 AM EDT Wed May 25 2016


Appears in the long range models that the current western conus
trough and eastern conus ridge will hold through the next week or
more. This means the current warm airmass will hold in place with
high temperatures largely in the 80s through the forecast. It also
means the northeast flow regime will persist with a series of
shortwaves ejecting out of the trough up through the Midwest keeping
chances of thunderstorms in the forecast nearly every day. It won`t
be a complete wash out this week though as best chances of
precipitation will be tied to shortwaves with an overall lack of
lower level lifting mechanisms. One other thing to watch for will be
upstream MCS`s and the potential they can hold together into lower

Currently there is a stalled cold front draped across mid Michigan
which was the focus for some showers and thunderstorms on Tuesday
and Tuesday night. A narrow ribbon of enhanced theta e was co-
located along the front providing a boost in moisture to a
relatively dry column, while weak convergence developed at the
surface at the front. A fairly strong mid level short wave has
lifted out of southern California and will pass through MN and into
Ontario this evening. A lobe of vorticity extending southeast from
the developing mid level low will sweep through southern Michigan
this evening, which will change the stalled front into a warm front
that will lift north toward the straits by early Thursday afternoon.
This will present one of the best opportunities for thunderstorms in
the forecast as the nose of a strong theta e surge lifts into the
area behind the warm front. Elevated levels of CAPE around 500-1000
J/Kg, shear increasing to around 30 knots, and favorable mid level
lapse rates and LI`s will also accompany the front. Some storms
could become strong but stability in the lower levels will keep
things more elevated which could reduce gust potential. Coverage
should increase over the western and northern part of the SE MI but
most locations will have at least a high chance of showers.

Another wave is set eject through the flow Friday morning presenting
the next good chance at widespread showers and thunderstorms across
the area. Upstream trough amplification will lead to the resident
ridge getting pulled back to the west which will pull the better
support westward as well. Will have to watch how this all evolves
moving forward as large convective systems in the plains may keep
the lower heights further south and east.

Heading into the weekend the wave train continues but timing any of
these features is difficult at best with this type of active
pattern. It is worth noting that outside of the two more dominate
waves heading into the weekend, the models are all fairly uniform in
presenting more of a diurnal component to the shower activity. Once
we get the higher dew points into the region, a summer like pattern
will ensue with diurnal heating popping a few showers in the
afternoon. With lack of any focusing mechanism coverage will be ill
defined, hence a daily chance pop lingers in the forecast.


A weak cold front will remain the focal point for marine weather in
the short term as it settles into southern Lake Huron and central
lower Michigan today and then returns northward tonight. The wind
will be light within and around the frontal zone leaving the main
impact to be showers and thunderstorms that will become more
numerous tonight. Fog will also become increasingly prevalent as the
warm and humid air pools over the colder open waters of Lake Huron.

The front will move northward into Canada Thursday and leave light
southerly wind over all marine areas that will maintain warm air
Friday into Saturday. Showers and storms remain possible but will be
less organized until possibly later Saturday and Saturday night as
low pressure develops over the upper Midwest. This system will also
help maintain warm conditions and light south wind well into the
holiday weekend.


Warm air with increasing humidity will pool along a front settling
as far south as the I-69 corridor today. High temperatures returning
to the lower and mid 80s could result in a few thunderstorms along
the front during the afternoon and evening. Showers and storms are
then expected to increase coverage overnight with the help of low
pressure over the Midwest that will pull the front northward
Thursday. Rainfall amounts are expected to vary widely depending on
thunderstorm coverage but should average 0.25 to 0.5 inch for the
Wednesday night-Thursday period with locally higher totals near 1
inch possible in thunderstorms. Warm and humid air will then remain
in place to support shower and thunderstorm potential into the
weekend with less organization until arrival of the next low
pressure system possibly by Saturday into Saturday night.


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



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