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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
124 PM EDT Sat Jul 4 2015


A scattered coverage of late day diurnal cumulus will fade with the loss
of daytime heating this evening. There remains a lower probability
for a shower or thunderstorm to impact mbs through this evening as a
weak frontal boundary enters the region. Otherwise clear skies and
light winds through Sunday. This environment may support a brief
period of shallow fog development during the early morning hours.

//Dtw threshold probabilities...

* none.


Previous discussion...issued 315 am EDT Sat Jul 4 2015

Short and tonight

Upper level trough axis passing through the central Great Lakes this
morning will be replaced with upper level ridge building in for
tonight. The main question mark is whether sufficient warming of the
middle levels will occur to prevent any shower/thunderstorm activity
from going up this afternoon...mainly just across far
north...closer to 500 mb cold pool of -15 to -16 c over Georgian
Bay. The surface trough did have activity over the western Great
Lakes yesterday evening...and with 00z regional Gem/NAM both
indicating activity over Tri-Cities region/near Saginaw
Bay...seems prudent to carry chance probability of precipitation. However...both models
showing moisture pooling and surface dew points increasing to upper
60s...which seems a bit excessive...and prefer just a slight
chance mention as sbcapes will probably peak out around 1000 j/kg
with weak low level cap in place. Further modification of the
airmass today under a good deal of 850 mb temperatures
advertised to rise between 13 to 14 c....which should be good
enough for highs around 80 degrees. Favorable radiating conditions
once again tonight...likely allowing most locations to dip into
the middle/upper 50s.

Long term...Sunday through Friday

Large scale subsidence will persist through the day Sunday as a middle
level ridge influences lower Michigan. This will sustain a strong capping
inversion...thus inhibiting any convective development. Ample mixing
depths under full insolation will support afternoon highs into the
middle 80s. Amplification of a middle level trough axis over the Dakotas
Sun night and Monday...associated with a northern stream wave over
Canada... will force the middle level ridge into the eastern Great Lakes by
Monday. The 00z model suite also suggests the approach of this upper
trough will hold deeper moisture and instability associated with a
weak upper wave lifting up from the Tennessee to Ohio valleys well southeast of the
forecast area...thereby supporting another dry day over Southeast Michigan. There
will be an increase in the S-SW gradient over lower Michigan Monday ahead of
a cold front being driven into the western Great Lakes. 850mb temperatures
will rise into the upper teens in response. With full insolation...
this will boost daytime highs into the upper 80s/near 90. The
increased gradient will also support relatively mild nighttime mins
sun and Monday nights in comparison to the last several days.

Large scale dynamics will be fairly strong across the frontal
boundary moving through the upper Midwest/western Great Lakes Monday/Monday
night due to strong baroclinicity for July. Strong prefrontal
southerly flow will aid in transporting ample deep layer moisture
/pwats possibly up to 2 in/ into WI and Upper Michigan ahead of this cold
front. The 00z model suite suggest the upper jet axis and better middle
level height falls will lift north of the Great Lakes late Monday night
into Tuesday...which should cause the forward speed of the
associated surface front to slow. In terms of the 00z model
suite...the GFS is almost 12 hours faster than the
European model (ecmwf)/Canadian/NAM solutions in bringing the surface front and deep
layer moist axis across Southeast Michigan. The GFS looks to have some convective
feedback issues. This and in light of recent trends...the slower
solutions are preferred at this time...all of which indicate the better
chances for convection will be on Tuesday. Coverage of showers and
thunderstorms will be somewhat dependent upon the degree of
destabilization on Tuesday as the large scale forcing is expected to
weaken as the front pushes east. The later frontal passage offered by the
European model (ecmwf) and Canadian suggest there will be some daytime
destabilization ahead of the front...supporting high chance to
likely probability of precipitation Tuesday. A cooler and drier Post frontal airmass will
filter into the area by midweek and may persist through the end of
the forecast period.


Ideal boating conditions can be expected this weekend as a weak
pressure gradient will persist across the Great Lakes. Southerly
winds will gradual increase Sun night into Monday ahead of a cold
front approaching the western Great Lakes. Strong over lake
stability should hold gusts below 20 knots over the lakes. The front
is forecast to traverse the region late Monday night into
Tuesday...leading to a veering of the winds toward the west-northwest and a
good chance of showers and thunderstorms.


DTX watches/warnings/advisories...
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.


short term...sf
long term....SC

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