Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 240957
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
557 AM EDT SUN JUL 24 2016
Decaying MCS will work across the area early in the TAF period. The
complex will continue to encounter very dry air as it works across
Lower Michigan, keeping prevailing ceilings at VFR and thunderstorms
at bay through 13Z. Conditions will then detiorate between 13Z and
15Z as another complex of storms currently over Lake Michigan drops
through Southeast Michigan. Additional moisture arriving from the
south will help sustain this complex, allowing thunderstorms to
potentially impact the terminals. Subsidence and mid-level warming
will then provide more stable conditions during the late afternoon
and first part of the evening, allowing for a break in activity and
rising ceilings. Additional showers and thunderstorms are then
possible later this evening and overnight in advance of a cold
front. MVFR restrictions may follow the front in BR until drier air
works in behind the front for Monday.
For DTW...Decaying MCS will have little impact on operations this
morning as prevailing ceilings are expected to remain above 5000
feet. Ceilings look to drop to around 4000 feet after 13Z as
additional moisture begins to arrive from the south. Complex of
storms over Lake Michigan looks to impact DTW between 15Z and 19Z
per latest linear extrapolation from radar and hi-res model data.
Ceilings should then come back up above 5000 feet around 19Z and
remain there until the cold front approaches during the late evening.
//DTW Threshold Probabilities...
* Medium for thunderstorms between 15-19Z.
* Medium for ceilings at or below 5kft.
Issued at 249 AM EDT Sun Jul 24 2016
MCS over far southwest Lower MI and northern IN should continue to
weaken early this morning as it out runs its forcing and the best
instability. The north edge of the stratiform rain may make it into
areas from Owosso to Adrian between 08z and 11z. Will monitor the
MCS evolution right to press time to see if likely or high pops will
be warranted in the south half of the forecast area.
The other area to note was over WI. Thunderstorms were developing on
the nose of the low level jet with some very good moisture
advection. There is also a shortwave over WI that is helping to
initiate the convection. This low level jet and that moisture
transport weakens as it moves over Lower MI this morning as the
shortwave passes over the region. It should be enough to keep likely
pops from I-69 on north and chance pops to the south from 12z to
18z. Severe chances with this activity seems very low with ML CAPEs
below 1000 J/kg and a weak wind field.
Once all of that passes to the east, expect some stabilization as
mid levels warm until the actual cold front moves into Lower
Michigan during Sunday night. The combination of all that convection
will keep plenty of clouds over the forecast area. Also it will be
a struggle to get the dew point front to move back north too quickly.
All of that will keep temps in the upper 80s today and dew points
around 70 which will produce heat indices below heat advisory
Tonight the cold front pass through Lower Michigan. We will get into
the right rear entrance of the 100 kt jet. Winds increase through
the column as the base of the 500 mb trof approaches and 0-6km bulk
shear tries to get up to 35 kts. Model soundings indicate ML and 850
mb CAPEs in excess of 2000 J/kg in advance of the front. Still looks
like storms will be from lifting around 900 mbs and will have a
little bit of a cap to overcome. Will not go any higher than 50
percent chance tonight for any location. And with those given
parameters the marginal risk looks about right.
Cold front will pass to the south of Lower MI by 12z Monday and will
not have any pops past that time. Drier air advects over the
forecast area with subsidence behind the today and tonight`s systems
to bring mostly sunny skies for all areas by the afternoon. With
850 temperatures still in the high teens approaching 20 C, will make
one more run to around 90 or lower 90s.
Mostly clear skies will continue for Monday night and Tuesday. Not
much cooling to the column so will stick close to the MOS guidance
for temps. The dry and warm air continues into Wednesday. By
Thursday, 500 mb troughing develops over the southern Great Lakes
and that only slowly slides through the region on Friday and
Saturday. Expect a strong diurnal component to the thundestorms with
the lack of a strong shortwave or frontal features from Thursday
Southerly winds will increase today as low pressure tracks through
Ontario. The highest speeds will occur over Lake Huron, where a
modest breeze of 15 to 20 knots is expected during the afternoon and
evening. Lighter speeds are expected over Lake St. Clair and Western
Lake Erie. A cold front will drop through the area late tonight and
early Monday morning, flipping winds to the west Monday and then
finally northwest by Monday evening. In addition to the increase in
winds, unstable conditions ahead of the cold front will bring the
chance for showers and thunderstorms. The first round of showers and
thunderstorms is expected to occur early today, with severe weather
not expected. Additional thunderstorms are then possible late today
and tonight, with a small threat for severe weather.
A round of early day showers and thunderstorms may bring around 0.25
inches of rain to the area, particularly for locations that
experience thunderstorms. Additional showers and thunderstorms will
then be possible during the later part of the day and overnight.
These will have the potential to produce locally heavy rainfall in
excess of one-inch. Dry weather is expected Monday and Tuesday.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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