Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 191656
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1256 PM EDT Mon Jun 19 2017


.AVIATION...

Diurnal heating, combined with passing weak shortwave, will lead to
extensive diurnal cu and increase in shower activity.  Lightning is
also on the increase along the lead edge of the shortwave and will
effect mainly the first couple hours of the tafs.  Diurnal showers
will continue the rest of the afternoon before diminishing with lost
of daytime heating.  Generally broken mid level deck over night
through Tuesday morning.  Winds will remain wsw through taf period
diminishing somewhat overnight to around 10kts but will increase again
Tuesday and become gusty shortly after sunrise.


For DTW...Broken MVFR/lower VFR ceilings this afternoon as shower
activity increases.  Scattered thunder possible for the first
several hours of taf period along the lead edge of the shortwave.
After the passage expect just scattered showers diminishing around
sunset.  WSW winds around 15 knots will diminish slightly tonight
before increasing again around sunrise Tuesday and becoming gusty to
around 25 knots.  Sct-bkn vfr tonight and Tuesday with a slight
chance of late diurnal light showers.


//DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms 17z-01z

* Medium for cigs aob 5000 ft this afternoon.

&&

.PREV DISCUSSION...
Issued at 948 AM EDT Mon Jun 19 2017

UPDATE...

No substantive changes to forecast reasoning this morning. Diurnal cu
development is already underway over western and northern Lower with
radar returns popping up over Wisconsin. Cloud and shower coverage
will increase during late morning with SCT/NUM coverage over the CWA
during peak heating. Nudged pops upward across the board given
observational evidence and strong support by 12z HRRR. Highest pops
across the eastern third of the CWA where favorable overlap of
diurnal heating/forcing is expected. Fresh grids/ZFP have been sent.

PREV DISCUSSION...
Issued at 335 AM EDT Mon Jun 19 2017

DISCUSSION...

An upper level trough has set up over the Great Lakes and will hold
through mid week while several shortwaves track through it. In
addition, a trailing surface trough extending back from the strong
surface low now over eastern Ontario, will linger over the region
with a few troughs rotating around it. Though not an idea setup for
severe weather, should be enough support for scattered showers and
isolated thunderstorms.

First opportunity for precipitation will come this afternoon as a
surface trough swings through during the afternoon hours with weak
mid level energy moving in aloft. Post cold frontal airmass is
notably cooler (70s) and drier (mid 50 dewpoints) than the previous
few day, but still enough boundary layer forcing to produce some
showers. Cooler air advecting in aloft with 850mb temps falling to
around 10C today will produce healthy low level lapse rates in
addition to around 500 J/kg of CAPE during peak heating. Lack of
shear (sub 20 knots) will prevent storms from organizing but any
rapidly developing updrafts could produce some small hail as
freezing heights fall to around 700-750mb.

Thermal trough slides over on Tuesday with 850mb temps falling
further to around 8C. Stronger shortwave drops through the trough
across lower MI again during peak heating in the afternoon. Models
advertise slightly lower CAPE (sub 500 J/kg) but higher bulk shear
values (model average around 30 knots) as 50 knot flow aloft sinks
lower in the column to around 10kft. Expect a decent coverage of
showers with the compact wave overhead, but should again result in
scattered to possibly numerous coverage with brief heavy showers and
small hail possible. With coldest airmass overhead, expect highs to
fall slightly further into the low-mid 70 range Tuesday.

Heights start to increase on Wednesday as the next jet max relocates
over the northern plains. This will bring about more westerly flow
and help temperatures start to rebound back into the upper 70s. High
pressure will slide across the region as well which will keep the
area dry through the day. Precip chances do return on Thursday as a
warm front tries to lift, and possibly settle, over the area. This
combined with any shortwave activity could lead to periodic chances
for showers and thunderstorms through the end of the week. Better
return flow from the southwest will help temps rise back into the
80s as well.

MARINE...

An upper level trough will build across the region during the first
part of week, bringing scattered showers and possibly a few storms.
This activity will be focus mainly during the afternoon and early
evening hours during peak daytime heating. Winds during the period
will generally be light and westerly. However, a bit of an uptick in
wind gusts can be expected late Tuesday into Tuesday night as a
shortwave trough sweeps through area around the base of the slowly
exiting upper level trough. No headlines are anticipated at this
time.

&&

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

$$

AVIATION.....DRC
UPDATE.......JVC
DISCUSSION...DRK
MARINE.......DG


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at www.weather.gov/detroit.



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