Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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108
FXUS63 KDTX 171745
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
145 PM EDT Mon Jul 17 2017


.AVIATION...

Center of surface high pressure now in place over Saginaw Bay is
responsible for a very stable thermodynamic environment. Nothing
more than flat cumulus this afternoon at the top of the boundary
layer. Models suggest low level moisture bleeding southwestward from
the southern Lake Huron basin late tonight, providing moisture for
surface MVFR vsbys in haze. Models also suggest higher moisture
contents now in place over portions of southern Lake Michigan and
western Lower Michigan to drift over southeastern Michigan late
Tuesday morning and Tuesday afternoon. Expecting benign boundary
layer cumulus development again tomorrow.

For DTW...SCT to BKN coverage of boundary layer cumulus this
afternoon thinning out late afternoon. No aviation weather impacts
throughout much of the night. Will see potential increase for MVFR
vsby degradation to MVFR tuesday morning. Boundary layer cumulus
again Tuesday with potential for BKN coverage by the noon hour.

//DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less during the early afternoon.

&&

.PREV DISCUSSION...
Issued at 343 AM EDT Mon Jul 17 2017

DISCUSSION...

Mid/upper level trough axis has passed south of lower MI allowing
the positively tilted ridge to start building into the region. Some
patches of clouds are lingering across the area along with a stratus
shield over southern Ontario back building into eastern lower MI as
anticylonic flow around the departing low pull the low level
moisture back into the area. Overall cloud should diminish today
outside of a possible window of diurnally driven cu. Though the
ridge will build with surface high pressure sliding across the Great
Lakes, low level thermal trough will be squarely overhead today with
850mb temps possibly holding in the single digits through the day
before slowly moderating tonight into Tuesday.  Look for high temps
to hold mainly in the upper 70s today.

Temperatures will rebound quickly Tuesday back to July norms in the
low/mid 80s as the ridge axis passes through lower MI. 850mb temps
will recover back into the mid teens with strong thermal advection
with westerly flow with an added solar component with mostly sunny
conditions as high pressure becomes stacked at the surface and
aloft.

The ridge folding over will be due to a strong wave coming
ashore over the NW conus on Monday. The associated westerly zonal
jet will surge across southern Canada quickly flattening out the
western ridge. Enhancing the jet will be funneling effects between
the strong north/central Canadian Low and strong subtropical ridge
sprawled across the southern conus. The next opportunity for
precipitation will come Wednesday as a wave tracking across southern
Canada pulls a cold front through the Great Lakes. Low confidence in
setup at this time as persistence forecasting brings pessimism.
Forcing looks to lift through the western and northern Great Lakes
on its way into western Quebec. The frontal forcing will wane as it
tracks south and east into the ridge and early indications for a
coupled jet structure will be north of the region as well. Could
possibly see some nocturnal convection upstream with any shortwave
racing through the flow as NAM does show a good 850mb low level jet
develop. This activity diving around the ridge would bring increased
pops to the region but we`re a ways away from getting models to
latch onto that scenario.

The rest of the mid to late week period will be warm with a chance
for convection Thursday as a shortwave passes. The main baroclinic
zone will lie north of the area with only brief reprieves due to
passing shortwaves. Temps through the mid week should stay steadily
in the mid 80s with opportunities for upper 80s depending on cloud
trends and shortwaves. Fast zonal flow pattern will look to break
down over the coming weekend as stronger wave train looks to add
some amplification to the longwave pattern.

MARINE...

A broad area of high pressure will drift across the Great Lakes
today through Tuesday. This will set up ideal marine conditions over
all areas. Some lingering light to moderate north wind over Lake
Huron during the morning will become light and variable by afternoon
with a corresponding decrease in waves. Light south wind will follow
Tuesday as the high drifts eastward. Dry weather will be in place
until a chance of thunderstorms returns with the next cold front
due later Tuesday night through Wednesday.

&&

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

$$

AVIATION.....CB
DISCUSSION...DRK
MARINE.......BT


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at www.weather.gov/detroit.



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