Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 291740
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
140 PM EDT SUN MAY 29 2016


.AVIATION...

An approaching cold front will be a focusing mechanism for showers
and thunderstorms this afternoon. CU field has developed in advance
of the front over western and central lower Michigan but has been
restricted further east due to lingering cirrus thus far. The front
will swing through this afternoon and exit into Ontario by this
evening. Though hires models mostly agree there will be some
convection along the front, none are too keen on widespread develop
as shallow moisture and low level cap appear to keep storms in
check. None the less, with storms in and around southeast MI,
included a three hour window of VCTS for all sites. Some stronger
storms may become severe with strong winds and large hail. Best
chance for storms appears to be north of PTK in the thumb,but all
sites have some risk of seeing a storm or two. Afternoon winds will
gust to around 20 knots with deep diurnal mixing and will once again
drop off around sunset. After the front passes, drier air will try
to clear the skies tonight through Monday.

FOR DTW...Showers and thunderstorms are just beginning to initiate
over central lower Michigan so it will be a few hours before
reaching the terminal. Best window for possible activity will be
from about 20-23Z. Should see mostly VFR conditions outside of any
cells that track near the terminal. Skies will try to clear out
overnight as drier air advects in behind the front.

//DTW Threshold Probabilities...

* Low for ceilings at or below 5000 FT outside of thunderstorm
  activity.

* Low for thunderstorms affecting DTW/D21 airspace today.

&&

.PREV DISCUSSION...
Issued at 1026 AM EDT Sun May 29 2016

UPDATE...

Warm sector destabilization is underway across Lower Michigan
ahead of a sfc cold front, moving into western Lake Michigan as of
14Z. Se Mi currently resides on the western edge of a dense high
cloud deck. These clouds will slide to the east very slowly today.
There will still be adequate afternoon destabilization west of
this cloud deck, which will advect into the forecast area under
good ssw flow today. There are however a few obstacles to
overcome in order to achieve deep convection today. First off,
large scale ascent via the mid level height falls, upper jet
support and convergence along the sfc front will not be terribly
strong. There is an axis of low level moisture extending from nrn
Indiana into Se Mi. Model soundings however suggest this moisture
is shallow, so there is a concern that diurnal mixing may reduce
boundary layer moisture to such a degree as to hinder deep
convection. The 12Z DTX sounding also showed some capping in the
900 to 800mb layer, which may also inhibit deep convective
initiation this afternoon. Given these factors, just chance type
pops for afternoon showers/thunderstorms will be maintained in the
forecast. Various hi res solutions suggest the most probable
locations for thunderstorm development will be across the thumb
into Port Huron in the 19Z to 23Z time frame.

If deep convection can materialize, strong to severe storms will
still be a concern. Despite rather marginal deep layer shear of 25
to 30 knots, if 0-1km MLCAPE can reach 1k to 1500 j/kg, model
soundings indicate somewhat good cape density, supportive of gusty
winds and hail. The degree of mid level dry air and steep low
level lapse rates would also support strong convective downbursts.
For these reasons all of Se Mi remains in a marginal risk for
severe storms this afternoon and early evening. A special 18Z DTX
sounding is being planned to better asses afternoon convective
potential.

PREV DISCUSSION...
Issued at 257 AM EDT Sun May 29 2016

DISCUSSION...

A weak cold front will progress west to east through lower Michigan
late today as a vigorous shortwave lifts from the upper Mississippi
Valley into the northern Great Lakes. A surface trough will precede
this front during the afternoon/early evening hours, providing focus
for scattered convection as moderately unstable conditions develop
within the warm/humid airmass that has overspread the region during
the past few days.

Mid level WSW flow in the 25 to 30 knot range will provide enough
bulk shear to allow for at least minimal convective organization
within the unstable warm sector. Generally expect a few multi-
cellular clusters with overall convective coverage remaining rather
scattered. Timing of the pre-frontal trough actually suggests most
convective initiation will occur over the area during the mid to
late afternoon with this activity then being swept east out of lower
Michigan by 00z or so. During this 4 or 5 hour window, expect a few
storms to at least approach severe limits with isolated large hail
and/or damaging wind gusts. This seems most likely over the Thumb
region where lake breeze convergence will most likely enhance the
updrafts that form along passing trough axis.

Several quiet days will follow as high pressure builds across the
central Great Lakes early in the upcoming week in the wake of this
cold front. While temperatures will still climb into the 80s in most
locations during this time frame, humidity levels will be lower as
the dew point temperatures in the lower/mid 60s of late will be
replaced by readings in the mid/upper 50s. This will also allow for
cooler overnight temperatures in the 50s to around 60.

Warm/humid conditions will briefly build back into the region during
the middle of the week as upper level heights build in advance of
the next shortwave trough as it eject slowly ENE along the US and
Canadian border region. This system will bring an increased chance
of showers and a few thunderstorms from Wednesday into Thursday
before the cold front associated with this upper level trough moves
through the region and brings a cooler/drier weather pattern heading
into next weekend as upper trough becomes established over the
Great Lakes late in this forecast period. Temperatures of 70 to 75
by day and 50 to 55 by night will become common from Friday on into
the weekend.

MARINE...

Areas of fog...potentially dense...will remain possible over Lake
Huron into this afternoon before south winds increasing to 10 to 15
kts ahead of a cold front allows any fog to mix out. The front will
push across the region late this afternoon and evening as low
pressure tracks across Ontario. Showers and thunderstorms will be
possible as the front slides through a warm and humid airmass...with
a few storms becoming strong or possibly even severe during the
afternoon and evening. The biggest threats will be damaging wind
gusts to 50 kts and hail to 1" in diameter. Light westerly flow and
dry weather are expected behind the front for Memorial Day.

&&

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

$$

AVIATION.....DRK
UPDATE.......SC
DISCUSSION...DG
MARINE.......HLO


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