Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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045
FXUS63 KDTX 240405
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1205 AM EDT Sat Jun 24 2017


.AVIATION...

Cooler and much drier air has filtered into southeastern Michigan
this evening. Impressive shortwave feature with some linkage to
upper level jet entrance region has resulted in aggressive
altostratus and a tiny amount of virga over southern Lower Michigan
this evening. Cold advection and stability just too tough to
overcome. A ribbon of midlevel moisture will linger back over the
central Great Lakes late tonight keeping altostratus around. This
ribbon of moisture will then result in boundary layer cumulus
development late Saturday morning along with some shower and
isolated thunderstorm potential over the northern cwa Saturday
afternoon.

//DTW THRESHOLD PROBABILITIES...

* Medium confidence in ceilings aob 5kft Saturday afternoon.

&&

.PREV DISCUSSION...
Issued at 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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

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


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at www.weather.gov/detroit.



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