Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 220715

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
315 AM EDT Tue May 22 2018


Latest water vapor imagery shows upper level wave/circulation
tracking over northern Lake Michigan, with corresponding mid level
jet (500 MB) of 45 knots tracking through southeast Michigan around
noon. A pool of low level moisture seen coming out of northern
Indiana (see NAM 850-700 MB Theta-E/surface dew pts) looks like it
will be sufficient to generate at least scattered showers and
isolated thunderstorms as MLCapes reach and exceed 500 J/KG toward
the Ohio border (per local probabilistic guidance), as surface winds
flip around to light southwest and surface dew pts climb above 60
degrees south of M-59. The low levels (925 MB) look to remain fairly
saturated/low clouds, but with the surface boundary straddling the
heart of the cwa, and differences in wind direction, probably looking
at highs ranging from 65 (north) to 75 (south). If instability does
ramp up a little more than expected, there is concern for locally
heavy rain as inland inverted surface trough arches back and
hovers/persists this afternoon over central sections of the State, as
good push of dry air does not look to occur until/toward 00z.
However, preference is toward a more muted response such as 00z HIres

Surface ridging building in tonight could set the stage for fog
development, but there is some uncertainty whether low clouds
are going to fully dissipate in a timely fashion.

A significant warmup will occur over the end of the work week, as
pronounced 500 MB upper level ridge over the Mississippi River
Valley slowly advances east, with the ridge axis arriving Friday
morning in a slightly flattened/weakened mode. None-the-less,
strengthening low level southwest winds will advect a lot of warmth
into Lower Michigan, and 850 mb temps of 16+ C will supports temps
well into the 80s on Friday, as frontal boundary looks to be
sufficiently north over the northern Great Lakes.

Height falls over the weekend as upper level low coming out of the
northern Rockies gradually slides into the Western Great Lakes. Bulk
of 12z Euro ensembles keep CWA within the warm sector on Saturday,
supporting temps still in the 80s with good chance of showers and
thunderstorms. Obviously, timing of any thunderstorm complex during
the mid day hours could easily short circuit temps.



Weak low pressure will track across southern Lower Michigan and Lake
Erie today, leading to generally light and variable winds across
Lakes St Clair and Erie. On Lake Huron, light east-northeast winds
will back to the north-northwest during the afternoon and evening as
the low advances into the eastern Great Lakes. High pressure will
expand into the region from the west tonight into Wednesday. This
high will reside over the region through Thursday, providing
generally light and variable winds.


Issued at 1157 PM EDT Mon May 21 2018


Low pressure moving over the south end of Lake Michigan will pull a
warm front into Lower Michigan during the night. The approach of
these features allows MVFR ceiling to increase coverage over SE
Michigan with a transition to IFR/LIFR before sunrise. There remains
a late night low chance of thunderstorms as the low moves through SE
Michigan, however coverage is expected to be too low and timing too
uncertain to include in this forecast issuance. Slow improvement
into MVFR is then expected as the low exits and the wind turns
northwest during afternoon into Tuesday evening.

For DTW... MVFR ceiling will become more firmly established over the
terminal, fall to IFR during the night, and then last through mid
morning. This will be accompanied by scattered showers with an
isolated thunderstorm possible, although timing and coverage need to
be refined in later updates. IFR improves to MVFR as the wind turns
northwest during the afternoon.


* High for ceiling 5000 ft or less.

* Low for late night/early morning thunderstorms.


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



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