Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
000
FXUS63 KDTX 141938
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
338 PM EDT Mon Aug 14 2017

.DISCUSSION...

Well-defined surface trough has taken shape over western Lower this
afternoon in advance of a shortwave crossing Lake Michigan at press
time. Convergent southerly flow within the trough has begun to yield
a partial coverage of showers that will likely exhibit a modest
increase in coverage over the next few hours. Forcing will sweep
east of the forecast area by 03z providing several hours of
downtime, although a few isolated showers are not out of the
question within the lingering moisture axis during the overnight
hours. Trailing wave over eastern MN/western WI this afternoon is
supporting enhanced cloud cover and light rain showers over the NW
Great Lakes region. This wave will track directly overhead during
the first half of Tuesday, providing adequate uplift for a healthy
coverage of stratocu and another round of showers along the lead
edge of the attendant theta-e gradient. Instability will be greatly
limited by stable mid-levels limiting concerns for thunder. With
virtually no change in resident airmass characteristics other than
ongoing modest advection of slightly higher dewpoints, highs will
fall in the low 80s once again.

Jet digging into the base of the West Coast trough will serve to
eject energy from the 4-corners region Tuesday night into the
northern great Lakes by Wednesday night. Downstream shortwave
ridging is modeled to be on the stronger side. Associated surface
high pressure will be augmented by the lake aggregate yielding high
confidence in dry conditions through Wednesday. Northeast flow will
limit mixing heights in at least the NE third of the CWA limiting
highs to the low to mid 70s while locales along and west of a
Saginaw/Flint/Warren line will all have a chance at 80s as 850mb
temps hold steady in the mid teens.

Low pressure lifting through northern Michigan on Thursday will
bring the next chance for widespread rain and thunderstorms as it
pulls a cold front through SE Michigan. Ahead of the cold front,
southerly flow will advect a very moist airmass northward with dew
points near 70 F and PWATs approaching 2 in. This will bring the
potential for heavy rainfall in any storms that develop on Thursday.
An upper level trough then looks to translate eastward through the
region over the weekend bringing cooler conditions. Surface high
pressure building into the region next weekend will bring mainly dry
conditions. However, isolated showers cannot be ruled out during the
late week period as weak disturbances drop southeastward through the
trough. Highs look to remain in the 70s on Friday and Saturday
before moderating to the lower 80s on Sunday. Lows will range from
the upper 50s to mid 60s Friday through Sunday.

&&

.MARINE...

Weak frontal boundary easing across the region will sustain a low
potential for thunderstorms over Lake Huron and Saginaw Bay through
tonight. The overall gradient will remain weak as this boundary
exits to the south by early Tuesday, replaced by weak high pressure
building back into the upper great lakes. This will sustain
relatively light and variable winds through Tuesday. A modest
increase in easterly winds Tuesday night and Wednesday as the
gradient strengthens. The arrival of a stronger area of low will
then result in a period of more unsettled conditions Wednesday night
and Thursday. South-southeast winds are forecast to strengthen in
advance of an associated warm front during this time, with gusts
potential excedding 20 knots at times. This system will also bring
an increasing potential for thunderstorms. The passage of this
system Thursday night will result in a veering of the winds to the
west by Friday.

&&

.HYDROLOGY...

An increasingly moist and unstable environment will accompany a warm
front into the region Wednesday night and Thursday.  This will lead
to a good chance for showers and thunderstorms during this time.
Widespread rainfall totals of a quarter to three quarters of an inch
are highly probable. Locally higher totals are expected in
thunderstorms considering the high level of moisture that will be
present over a considerable depth of the atmosphere.

&&

.PREV DISCUSSION...
Issued at 121 PM EDT Mon Aug 14 2017

AVIATION...

Gradual increase in coverage of diurnal cu will leave a window for
intermittent BKN conditions through the latter half of the day.
There remains the potential for a shower or thunderstorm to impact
MBS late this afternoon, but greater potential expected to remain
northwest of this area.  Otherwise, passage of a mid level wave will
maintain some higher cloudiness into tonight.  Weak frontal boundary
easing into the region could spark an isolated shower/thunderstorm
overnight, but uncertainty in timing and expectations for a low
coverage will support simply a minor mention.  Light southerly winds
to continue through this evening.

For DTW...Prevalent diurnal cu field will intermittent carry a
ceiling at or below 5000 ft through sunset.  Limited potential for
thunderstorms late tonight and early Tuesday.

//DTW THRESHOLD PROBABILITIES...

* Low in ceilings below 5000 ft this afternoon. Moderate Tuesday.

* Low in thunderstorms Tuesday.


&&

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

$$

DISCUSSION...JVC/JD
MARINE.......MR
HYDROLOGY....MR
AVIATION.....MR


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.