Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 181736
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
136 PM EDT Sun Jun 18 2017


.AVIATION...

Cold front slipping through Southeast Michigan this afternoon will
provide a chance for showers and thunderstorms to the Detroit-area
terminals prior to 19Z. Front will then slip east allowing just a
scattered cu field to persist through the afternoon. Gusty west
winds behind the front will continue through this evening, gusting
up to about 30 knots.

For DTW...One more small window of thunderstorm chances will exist
from 18-19Z this afternoon before a cold front slips through the
area and brings dry weather for the remainder of today and tonight.
Winds will turn more to the west behind the front (250-270 degrees),
and will gust between 25 and 30 knots before subsiding this evening.

//DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms 18-19Z this afternoon. Low for thunderstorms
  Monday afternoon and evening.

* Low for cigs below 5000 ft this afternoon. Medium Monday after 14Z.

&&

.PREV DISCUSSION...
Issued at 928 AM EDT Sun Jun 18 2017

UPDATE...

Forecast looks to be on track. Banking on that big inversion/speed
bump in the 12-16 kft layer seen on the 12z DTX sounding to keep
activity at bay and allow for mostly showers as the cold front tracks
through. Otherwise, strong low level jet of 50+ knots is always a
concern, and would not take much to mix down stronger winds to
surface, as gradient winds and mixing alone will be able to support
wind gusts 30 to 35 mph by this afternoon. Based off latest Rap,
looking modest wind shift/frontal passage around 18z.

PREV DISCUSSION...
Issued at 304 AM EDT Sun Jun 18 2017

DISCUSSION...

Area of showers with embedded thunderstorms will continue to lumber
through the forecast area early this morning with main theta-e ridge
in advance of approaching shortwave currently over the upper midwest.
While another large MCS over the central plains/midwest and several
smaller convective clusters east from there have intercepted the
best theta-e air and limited the overall intensity and coverage of
convection over lower Michigan, jet support associated with the
approaching shortwave should lead to at least a maintenance of the
current activity into the morning hours and quite possibly a slight
expansion. Hence, will maintain the basic precipitation forecast as
is with relatively high precip chances into mid morning tapering off
midday into the afternoon before ending mid/late afternoon as upper
trough axis passes through the region.

With area still in the warm sector, temperatures will be warm again
today, especially over the southeast forecast area where highs may
push the mid 80s in some spots. Otherwise, temperatures in/around 80
will be common before cooler air begins to make inroads late today
into this evening.

Overall upper troughing is still expected to expand over the area
into early/mid next week as a steady flow of jet energy feeds into
mean upper trough once this significant shortwave passes east. This
will bring cooler readings with 70s for highs common Monday through
Wednesday and lows falling back into the 50s most locations during
that time frame. While organized convection is not expected in this
time frame, scattered showers and perhaps isolated storms will be
possible under developing upper level cold pool associated with the
deepening upper trough. This will be especially noticeable in the
mid/late afternoon on into early evening during peak heating and
instability.

Slightly better shower/thunderstorm chances appear again late in
the week as upper trough temporarily breaks down and zonal upper
flow allows for better moisture return into the Great Lakes (as well
as temperatures back into the 80s). Several shortwave will track
through area along main belt of upper level westerlies and bring the
chance of periodic scattered showers/storms roughly Wednesday night
into Friday night. By the end of the forecast period next weekend,
upper troughing appears likely to re-expand across area leading to
cooler and generally quieter weather.

MARINE...

A low pressure system will strengthen as it lifts through the Great
Lakes this afternoon. This system will pull a cold front through the
region this afternoon with a chance of showers and thunderstorms in
advance of it. Southwest winds are expected to approach small craft
gusts, but the flow will be predominantly offshore - so waves will
should remain somewhat tempered. The exception will be Saginaw Bay
where longer fetch conditions will become establish behind the front.

HYDROLOGY...

Showers and thunderstorms will continue through this afternoon until
a cold front sweeps through the area. Plenty of moisture in the
atmosphere supports heavy downpours through this period as has been
the case the last day or so. Radar estimates over Midland and Bay
Counties are around 2 inches from Saturday`s activity training over
that area. Activity should be more progressive today with the front
but those areas that experience thunderstorms could see additional
rainfall totals exceeding an inch. This will result in localized
ponding of water and possible short duration flooding in favorable
drainage basins.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 8 PM EDT this evening for LHZ421-422.

Lake St Clair...Small Craft Advisory until 8 PM EDT this evening for LCZ460.

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

$$

AVIATION.....HLO
UPDATE.......SF
DISCUSSION...DG
MARINE.......DRK
HYDROLOGY....DRK


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



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