Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 151920

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
320 PM EDT Tue Aug 15 2017


Slow thermodynamic recovery of the boundary layer underway this
afternoon, as southeast Michigan recovers from the remnant latent
heat plume and corresponding subsidence left in the wake of an
earlier mid level wave passage. Adequate low level moisture to
support some renewed diurnal cu growth as this airmass overturns,
with a particular focus from the eastern thumb down through the Ohio
border within a couple regions of enhanced low level troughing/
convergence. It remains within these zones that a low potential for
garden variety level convection could yet emerge under weak
instability through the duration of the peak heating cycle. No more
than isolated coverage given weak underlying forcing and limited
depth to the instability and moisture quality.

Influx of lower theta-e air commences through tonight, as low level
flow turns northeasterly within the eastern flank of expanding high
pressure centered over lake superior. This high will govern
conditions through Wednesday, eventually taking residence across
northern lake huron by late in the day. Retention of shallow low
level moisture may capitalize on a weak gradient and a trend toward
clear skies to support some fog development late tonight. Northern
locales appear better positioned to see some visibility restrictions
around daybreak. A generally dry and stable profile retained through
continued easterly flow will then yield quiet conditions for
Wednesday. Existing airmass will moderate minimally under this
pattern, pointing to a very seasonable mid August day with highs
peaking in the lower 80s.

Consolidated mid level energy will lift from the plains into the
midwest/upper great lakes late this week.  Strong northward moisture
transport will accompany a corresponding deepening of southwest flow
immediately downstream.  This process will lift a warm frontal
boundary toward the region Wednesday night, with latest model
guidance arriving with a consensus mid level entry by early Thursday
morning.  Greater low level jet support will tend to slide from
northern IL into western/northern lower, casting some doubt as to
the rainfall potential along this advancing front with eastward
extent.  However the high degree of moisture advection tied to good
system relative isentropic ascent should provide a solid shot for
rainfall Thursday.  Extent and residence time of warm frontal cloud
debris/showers will likely ultimately dictate the convective
response with the trailing cold front currently forecast to sweep
through Thursday evening.  Brief pre-frontal intrusion of tropical
moisture - lower 70s dewpoints - would accelerate the recovery
process during the afternoon should the early day debris
progressively exit.  Prospects for MLCAPE to reach within the 1000
J/KG range will exist, but with lapse rates remaining somewhat
paltry given the water laden profile.  Deep layer shear appears
sufficient to organize stronger updrafts, but the inherent
uncertainty under this setup certainly supports simply a marginal
risk mention for severe convection at this stage.

As low pressure departs the region on Friday, a few lingering
showers will be possible during the morning before weak ridging
brings drier conditions to the region by afternoon. Model guidance
is now hinting at a stronger wave pushing through the southern Great
Lakes on Saturday, thus a chance of showers and thunderstorms is now
included in the forecast along with increased cloudiness. Following
the passage of the wave, ridging along with surface high pressure
will bring dry and pleasant conditions through Monday. A slow
warming trend will occur during this period with highs in the upper
70s to near 80 on Friday increasing to the mid 80s on Monday.



Moderate northeast flow today will veer to southeasterly by
Wednesday night as low pressure approaches the region from the west.
Fresh SE breeze will then persist through Thursday as low pressure
lifts toward the Straits...gustiness limited by the warm stable
fetch. Thunderstorms will be possible through the day Thursday until
cold frontal passage late Thursday evening. Moderate westerlies fill
in behind the front for the remainder of the week.


Issued at 1226 PM EDT Tue Aug 15 2017


MVFR boundary layer cu will gradually mix up to low VFR during the
afternoon. Wind will become increasingly northeasterly during this
time as high pressure builds across the Great Lakes. Theta-e
gradient invof the Detroit area early this aftn marks the northern
edge of the instability reservoir that has potential to produce a
few showers before sagging south after 21z. Attm, expectation for
development/coverage is too low to warrant inclusion in the

For DTW...With surface high pressure anchored over Ontario,
conditions will be marginally favorable for NE operations -
conditional on wind speed - through the forecast period.


* High for cigs aob 5kft


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



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