Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231947
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
347 PM EDT Fri Jun 23 2017

.DISCUSSION...

Redevelopment of showers and a few thunderstorms will continue
through late afternoon before cooler and less humid air arrives
behind the cold front and brings an end to activity by early
evening. Measures of instability will be the main factor to monitor
for convective intensity with this round. Hourly mesoanalysis
indicates MLCAPE around 500 J/kg, which could build toward 1000 J/kg
by late afternoon, while model soundings show a mostly narrow CAPE
profile. There is still some wind in the mid levels, 30-40 kts in
the 700-500 mb layer, which could help with a precip loaded wind
gust around 40 mph. This, along with locally heavy rainfall, will be
the main concerns as PW lingers around 1.7 inches. Mid afternoon
radar trend have shown some tendency for training patterns,
especially south of metro Detroit. Otherwise convective clusters
will have orientation along the moisture gradient and normal to the
westerly mean flow. This and the postfrontal negative theta-e
advection at and below 850 mb will guide activity out of SE Michigan
around 00Z.

A clearing trend with cooler and less humid air will follow the exit
of early evening showers/storms through the overnight and Saturday
morning. A mostly sunny start to the day will help temperatures warm
from lows in the 50s which will lead to a generous cumulus response
during the afternoon. This will occur under cool temperatures aloft
carried in by the upper level trough now over the Midwest which will
bring 500 mb temperatures from around -9 C today to around -18 C
Saturday afternoon and evening. Daytime heating that will lift high
temps into the lower 70s will produce at least scattered convection
over lower Michigan. Upstream observations over the Midwest today
support model output suggesting scattered showers and isolated
thunderstorms as surface dewpoint lingers in the 50s and produces
surface based CAPE around 500 J/kg. A cycle with strong diurnal
dependence will then continue with a diminishing trend Saturday
night and redevelopment Sunday as the next surge of cold advection
aloft moves into the southern Great Lakes. Associated low level
thickness cooling will also limit high temperatures to the upper 60s
most areas and lower 70s around metro Detroit.

By the start of next week, the region will continue to reside in
longwave troughing.  Currently, models have a shortwave moving
across the Great Lakes region which will bring another round of
possible rain and thunderstorms on Monday.  The trough is then
quickly replaced by upper level riding as surface high pressure
begins to build in from the west.  This will bring a break from
precipitation Tuesday and Wednesday before chances for precipitation
increase again to round out the week.  The coolest temperatures in
the extended will come in on Monday as highs struggle to reach 70
degrees.  This will likely only last for a day before temperatures
warm back into the 70s and then push back around 80 by the end of
the week.

&&

.MARINE...

Winds will be out of the west-northwest tonight as a cold front
exits the Central Great Lakes this afternoon. West to northwest flow
will is expected to persist through the weekend as broad low
pressure remains in place over the northern Great Lakes.
Speeds are expected to remain modest, but gusts may just top 20
knots over western Lake Erie both Saturday and Sunday afternoons.

&&

.PREV DISCUSSION...
Issued at 105 PM EDT Fri Jun 23 2017

AVIATION...

Drier air is slowly working into southeast Michigan, as winds shift
to the west/northwest. Still, lingering standing water and
saturated ground will require much of the afternoon to mix
out low clouds, with clear/mostly clear skies then around toward
sunset, persisting overnight. Winds will be light overnight, and
there is some concern fog could develop, especially MBS, but decided
against it with the short night and continued modest dry advection.
Cold air aloft tomorrow should promote a rapid cu up, with scattered
afternoon showers/isolated thunderstorms possible.

For DTW...Borderline MVFR/low vfr cigs to start, slowly lifting and
mixing  out as the afternoon wears on, with mostly clear skies this
evening and tonight. West/northwest winds generally around 10 knots
this afternoon, becoming light this evening and overnight.

//DTW THRESHOLD PROBABILITIES...

* Medium confidence in ceilings aob 5kft this afternoon, then
  again tomorrow afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BT/SP
MARINE.......SF
AVIATION.....SF


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at www.weather.gov/detroit.



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