Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 172257

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 PM EDT Mon Jul 17 2017


Other than a chance of ~5SM br late tonight due to calm conditions
associated with surface ridge, expect VFR cigs/vsbys throughout the
forecast. Light south to southwest flow will develop on Tuesday as
the high pressure center shifts east of the region. The only clouds
will be few-sct cumulus early this evening and again with daytime
heating on Tuesday.


* None.


Issued at 322 PM EDT Mon Jul 17 2017


Main story for this week is warmer temperatures and more humid
conditions starting on Tuesday and a return to periodic shower and
thunderstorm chances starting early Wednesday.

Upper ridge will fold over Michigan late today and tonight, placing
the center of surface high pressure overhead. Deep-layer subsidence
will promote good radiational cooling conditions, allowing
temperatures to fall back into the mid 50s to low 60s once again. A
few patches of shallow fog or light haze will again be possible as
well, especially west of Lake St Clair and Lake Erie.

High pressure will remain in control over southern Michigan on
Tuesday as the center shifts into the eastern Great Lakes. Upper
ridge will flatten as a large upper trough progresses through
central Canada. This will push a cold front down into the northern
Great Lakes tomorrow. Increasing southwest flow over Lower Michigan
in advance of the front will help boost temperatures and sfc-H850
dewpoints. Max temps look to top out in the mid-80s under partly
cloudy skies.

The frontal boundary will continue to drop southward through the
Central Great Lakes Tuesday night and Wednesday as the Canadian
trough moves slowly east. Smaller shortwaves will meanwhile be
steered across the region (and over the front) between the trough
and an expansive ridge extending over much of the southern CONUS.
This will bring a chance for showers and thunderstorms to Southeast
Michigan on Wednesday. Early day timing of the front over the
northern portion of the forecast area and clouds over the south will
likely limit any severe threat.

Rain showers and thunderstorms will remain a possibility throughout
Thursday as the GFS and ECMWF bring a weak warm front through
southern Michigan through the morning and afternoon hours.
Additional precipitation chances will be possible Friday and into
the weekend, however, confidence is low as to the when and where, as
there are major disagreement between model runs. The GEM and ECMWF
set up a frontal boundary across Central Michigan which would
provide rain and thunderstorm chances late Friday into Saturday. The
GFS holds off on rain chances until Saturday afternoon into Sunday
morning as it pushes a weak low pressure system pushes east from
Iowa into Michigan. The ECMWF model run also picks up on this weak
low pressure system, which increases confidence slightly regarding
precipitation during the mid-Saturday to early-Sunday timeframe. The
GEM develops the same low pressure, however it is delayed compared
to the other two model runs, bringing it through Michigan Sunday
into Monday. Overall, rain and thunderstorm chances will exist for
the second half of the week. PoP values will remain between 20 - 40
percent through Thursday, increasing to 40 - 60 percent Friday into
Saturday, as confidence is slightly higher during those days.


A broad area of high pressure will drift across the Great Lakes
through Tuesday. No significant weather impacts to marine interests
are expected. Light and variable winds late today will transition to
weak southerly on Tuesday. Dry weather will be in place until a
chance of thunderstorms returns with a weak frontal boundary due
Wednesday morning. Another chance of showers and thunderstorms will
exist late Thursday.


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



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