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fxus63 kdtx 190353 
afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
1153 PM EDT Wed Sep 18 2019

Aviation...

A cold front in the Midwest sends only high clouds over lower
Michigan tonight as it reaches western Upper Michigan and dissipates
through Thursday. Dry/VFR conditions are also maintained by high
pressure centered over Quebec that continues to extend westward into
the central Great Lakes tonight. The high becomes centered over the
New England states and maintains control of aviation weather in Southeast
Michigan through Thursday evening.

Dtw threshold probabilities...

* none

&&

Previous discussion...
issued at 333 PM EDT Wed Sep 18 2019

Discussion...

Mid-day GOES-east satellite imagery depicts a wide swath of clear air
across Southeast Michigan. A few cirrus bands have streamed into the northern
thumb from Southern Lake Huron as a line of altostratus advects
eastward across Southern Lake Michigan along a low amplitude
shortwave. Quiescent conditions today are attributed to high
pressure centered over the mouth of the St Lawrence River which has
acted to stabilize the column with neutral moisture advection. Have
maintained zero pops today/tonight as evening precipitable water values should hold
below 1.00 in the presence of a mid-upper level ridging and weak
flow. Above 400 mb, forecast soundings depict a layer of saturation
wrt ice that will support some high cloud coverage overnight
providing only slight lw radiative insolation. Limited adjustments
made with today's forecast as temps have been on track Post-morning
update. Highs are expected to approach or just cross the 80 degree
mark with overnight lows in the upper 50s /several degrees above
climatological norms/.

These last few days of astronomical Summer will continue the warmer-
than-normal trend as the thermal ridge remains in place on Thursday
and most of Friday. 500 mb heights around 587 dam will persist with 800 mb
temps around 17 c allowing for highs around 80 with mainly clear
skies and ample low-level dry air in place as 900 mb dewpoint
depressions exceed 30 c. The only chance for any precip in the short
term forecast period is Friday afternoon when the sfc-800 mb layer
becomes nearly saturated across the west-central County Warning Area border. This is
partially due to low-level S/SW flow and surface dewpoints creeping
back into the low-mid 60s. If precip does occur, it will be very
shallow due to broad model consensus of a persistent cap at 800 mb and
weak forcing. Currently the NAM/sref/nmm are part of the select few
solutions to generate any qpf, and given the low confidence, have
included just a small area of slgt chc pops Friday afternoon.

Energetic upper level flow over Canada this weekend will suppress
the northern extent of the ridge in place over the Great Lakes while
folding it eastward as well. This will nudge a stalled front,
extending from northern Ontario SW through WI, closer to lower Michigan.
On Saturday a shortwave lifting up the front will usher in warmer
and more humid air but the best forcing will still be back to the
west thus we will have a chance of showers and thunderstorms but
most activity will be west and north. Longwave trough and pv Max
will then release from the northern plains through northern Michigan on
Sunday pulling a cold front through lower Michigan. This will bring a
higher chance of thunderstorms Sunday afternoon/evening along or
ahead of the front. Can't rule out a few severe storms but at this
point the best forcing will not be over the area and the soundings
look warm aloft eating into any potential cape. GFS has good shear
but weak cape for Sunday. As the front stalls south of the state
line, another short wave and surface low looks to ripple along it
for Monday keeping chances of storms in the forecast.

Marine...

High pressure anchored just east of the region will maintain lighter
winds and low wave action through the late week period. Modest late
day easterly winds will turn southeasterly tonight. Winds then veer
to southerly Thursday, prevailing from this direction to finish the
week.

&&

DTX watches/warnings/advisories...

Michigan...none.
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.

&&

$$

Aviation.....Bt
discussion...kk/dk

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