Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221641
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1241 PM EDT Mon Jul 22 2019


.AVIATION...

There is an ongoing push of colder air across Lower Mi along and
behind a mid level trough axis. While there is a region of mid/high
level clouds associated with the mid level trough, diurnal heating
within the cooler low level airmass has led to the development of
sct-bkn cumulus; with bases ranging from 2k ft up to 4k ft. The
growth of the daytime boundary layer will lead to an upward trend in
the bases of the cu during the course of the afternoon.

For DTW...A northerly gradient and increase in the wind speeds with
daytime heating this afternoon will sustain winds around 10 knots
from 350 to 020 degrees. There will be a tendency for wind speeds to
decrease after sunset, although an increasing northerly gradient
will inhibit boundary layer decoupling, thus keeping at least a light
wind into the night.

.DTW THRESHOLD PROBABILITIES...

* Low in ceilings at or below 5000 ft this afternoon.

&&

.PREV DISCUSSION...
Issued at 455 AM EDT Mon Jul 22 2019

Dewpoints have fallen into the upper 50s and low 60s and
temperatures have followed suit as yesterday`s airmass is ushered
east. Mesoanalysis confirms decreasing moisture quality with
westward extent as dewpoints fall into the mid and low 50s over
Wisconsin. Even so, two shortwaves capture attention on channel 9
imagery. The first is directly overhead at press time and has been
sufficient to force disorganized light shower activity within some
remnant low-level moisture south of I-94. This wave and attendant
showers will exit east prior to period 1. The second is a more
robust PV anomaly centered over northern Wisconsin at 07z. A narrow
band of light, high based showers has developed immediately in
advance of this feature and within a narrow corridor of enhanced H5
fgen. As the back edge of this airmass defined by elevated moisture
confined to about 10kft AGL works through Lower Michigan today, chc
pops would be in order were it not for the expectation for this wave
to become increasingly sheared by SWLy flow downstream of the
neutrally tilted trough. As such, suspect diurnal heating will be
insufficient to counter the increasingly dry airmass and waning
larger scale forcing. Nothing more than an isolated/fleeting high-
based shower this aftn with the best chance north and west. Nothing
worth a wx mention in the grids. 850mb temps falling to around 10C
will support highs in the upper 70s to around 80, just short of
average late July values. Expansive surface high pressure anchored
over the Lower Missouri River Valley supported by confluent NW flow
aloft will extend east into Lower Michigan by tonight. Clear skies
and light or calm winds will support temps bottoming out as best
they can in late July. A good night to open the windows as MET/MAV
blend yields upper 40s to mid 50s.

No change in airmass for Tuesday with full insolation allowing temps
to quickly recover from morning lows. Compact shortwave originating
in the high latitudes of Canada currently tracking SSE within
prevailing NW flow regime aloft. Strong consensus among the NWP with
this energy increases confidence in its arrival over Lower MI during
peak heating on Tuesday. Decent lapse rates around 7C/KM and
uninhibited insolation for much of the day will support MLCAPEs of
at least 500 j/kg, greater destabilization potential mitigated by
the cool continental nature of the airmass at the surface.
Nonetheless, respectable dynamic forcing, an H5 cold pool
characterized by temps of -15 to -17C, and Tw zero heights just a
couple thousand feet above the top of the boundary layer will be
supportive of small hail production within stronger cores. A few
gusts of 30-40 mph will also be possible given the dry and well-
mixed nature of the forecast soundings. Broad-brushed high chance
pops along the forecast path of the mid-level wave in favor of
leaning toward other mesoscale convergence signatures (i.e. sea
breeze).

Stagnant longwave ridge over the western US will ensure regional
convective activity finally quiets down and surface high pressure
retains control for the remainder of the week. Resultant abundance
of sunshine will favor gradual moderation of the airmass while the
lack of organized moisture return limits afternoon dewpoints to 60
degrees or less.

MARINE...

The central Great Lakes are between a broad region of high pressure
over the Plains states and low pressure near James Bay through
Tuesday. Moderate northerly wind today builds waves over criteria
for Small Craft Advisory and is reinforced by a cold front that the
James Bay low pulls across Lake Huron tonight into early Tuesday.
Scattered showers are possible trailing the front however the cooler
air establishes unstable conditions over the water to maintain
higher wind and waves across the south third of Lake Huron. High
pressure from the Plains then builds over the Great Lakes Wednesday
and holds through late week.

PREV DISCUSSION...
Issued at 359 AM EDT Mon Jul 22 2019

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 4 PM EDT this afternoon for MIZ048.

     Beach Hazards Statement until 8 PM EDT this evening for MIZ049-055-
     063.

     Lakeshore Flood Advisory until 10 PM EDT this evening for MIZ049-
     055-063.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-
     441>443.

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

$$

AVIATION.....SC
DISCUSSION...JVC
MARINE.......BT


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