Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 45 46 47 48 49 50

675
FXUS63 KDTX 011338
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
938 AM EDT SAT OCT 1 2016

.UPDATE...

Water vapor imagery shows the upper low spinning over east central
IN. Next prominent lobe of vorticity was rotating northward just
east of Cincy. Some agreement with the hi-res models with this
lobe rotating east of far southeast lower and then spinning back
to the northwest in the central part of the forecast area this
afternoon. That may focus the showers and a few thunderstorms
mainly north of I-69. The center of the upper low circulation will
spin to the IN/OH/MI corner by 00z. This in itself will be
responsible for additional shower development later this afternoon
for the far south part of the forecast area. Will adjust the pops
slightly to have 50 percent for all areas south of the tri cities
and thumb where likely 60/70 pops will reside.

Areas near ADG and TFF are seeing a little sun this morning! This
clear slot may rotate into parts of metro Detroit before quickly
filling in with cumulus...especially given that the both the Cincy
wave and upper low are moving toward us. This weakness in the
cloud field will help to boost the instability just a bit for the
afternoon.

Also noted this morning is the very moist southeast flow off of
the marine areas, lifting into the Irish Hills area. This has
created areas of drizzle and expect that to last into the early
afternoon until those upper features move closer to the forecast
area.

&&

.PREV DISCUSSION...
Issued at 655 AM EDT Sat OCT 1 2016

AVIATION...

Organized showers will refocus further north today mainly impacting
KMBS and possibly KFNT. From KPTK south expect a persistence of
IFR/LIFR gradually improving to MVFR this afternoon as drier air as
veering SE wind works drier air into the boundary layer. Improvement
will be delayed until late this evening across the north. Carrying
prevailing -RA in the Detroit area as episodes of light showers or
drizzle will be likely for much of the day. Diurnal heating will
support shower and possibly t-storm development by late aftn.
Variable or calm winds tonight combined with abundant boundary layer
moisture will support development of MVFR BR.

For DTW...Wind may hover near noise abatement thresholds early but
the gradient will weaken and turn southeasterly during the morning.

//DTW Threshold Probabilities...

* High for cig aob 5kft

* Low for tstorm impacting KDTW airspace late this aftn.

PREV DISCUSSION...
Issued at 323 AM EDT Sat OCT 1 2016

DISCUSSION...

As of 06Z, the center of the upper low was located along the IN/KY
border, just southwest of Cincinnati OH. This upper low, which has
been nearly stationary for days, will finally eject off to the
northeast over the next couple of days. However, it will continue to
influence the forecast area through the duration of the weekend,
providing periodic rounds of showers. The more persistent mid level
frontal dynamics and feed of deep Atlantic moisture which supported
the rounds of moderate to heavy rainfall over the past three days
has at least weakened as it has been driven into the northern
Great Lakes.

Recent model solutions have slowed the northward progression of the
upper low today. The center of the mid level circulation is now
forecast to be near Fort Wayne, IN by evening as it remains
relatively compact. The associated surface low will slowly drift
north along the IN/IL border while a pseudo occluded frontal feature
nudges into the southern portions of the forecast area this
afternoon.

After a break in the showers during the late evening and early
portion of the overnight, another round of showers is already
spreading across the forecast area from the east. These showers are
associated with ascent along a mid level short wave feature which
has enhanced the fgen along a mid level theta e gradient. Recent hi
res solutions indicate this mid level ascent will quickly push
through the forecast area early this morning, suggesting these more
organized showers will largely occur prior to daybreak. Some brief
mid level descent will then occur which will likely support a lull
in activity later in the morning into the early afternoon, although
ample low level moisture may support some drizzle. An axis of mid
level deformation is expected to become reestablished during the
afternoon from wrn Lake Erie into northern Michigan. This ascent
will overspread the thumb and possibly the nrn Saginaw Valley this
afternoon, providing the potential for some more organized showers
in this region. Farther south, diurnal destabilization, aided by
cooling mid level temps associated with the approaching upper low,
will contribute to scattered showers and thunderstorms.

The upper low will track across Se Mi overnight before lifting into
Ontario on Sunday. The mid level cold pool and associated steep mid
level lapse rates and ample low level moisture will support a chance
for convection tonight through Sunday. Chances may increase on
Sunday given the diurnal destabilization and model indications of
some boundary layer convergence along a remnant sfc trough. There is
also indications in the 00Z model suite that some upper divergence,
courtesy of a jet max rounding the north side of the upper low, will
briefly overspread the area Sunday.

Dry conditions will finally return to the forecast area on Monday as
high pressure expands over the region in the wake of the departing
upper low. Northeast flow ahead of the sfc high will hold Monday
highs in the 60s, much like this weekend. The drier airmass will
support cooler nighttime temps Mon night. Southerly flow will
develop Tues into Wednesday, supporting daytime highs into the 70s.
The next chance for rain will be Thurs and Fri along a cold front
associated with the approach of a long wave trough.

MARINE...

Small craft advisories remain in effect as moderate easterly winds
build significant wave heights to several feet in the nearshore
zones of Lake Huron...especially along the tip of the Thumb. Winds
will gradually diminish and back to northerly by Sunday afternoon as
the stalled low pressure finally lifts out of the area. There is a
chance of waterspouts over area waters throughout this time.

HYDROLOGY...

Around a quarter of an inch of rainfall is possible between forecast
issuance time this morning and this evening. The heaviest rain,
where amounts stand the best chance to exceed a quarter of an inch,
will be north of the I-69 corridor between roughly 2pm and 8pm.
Further south, rain will be considerably less organized with nothing
more than isolated pockets of heavier rain possible during peak
heating.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 AM EDT this morning FOR LHZ421-441-
     442.

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

$$

UPDATE.......RBP
AVIATION.....JVC
DISCUSSION...SC
MARINE.......JVC
HYDROLOGY....JVC


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.