Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 190351
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1151 PM EDT Wed Apr 18 2018


.AVIATION...

Light snow within fgen forcing will settle south/southeast through
the area early in the forecast, affecting KPTK south through 07z to
08z or so. MVFR cigs will transition to lower VFR and then scatter
out on Thursday morning as subsidence sets in within an increasingly
gusty northwest flow. Peak gusts should push 25 knots during best
afternoon boundary layer mixing, and aside from a period of sct-bkn
diurnal cu, generally expect clearing skies Thursday afternoon into
evening.

For DTW...Light snow will be possible within fgen forcing through
roughly 08z with MVFR cigs holding on overnight before scattering
out Thursday morning. Winds will become northwest behind this system
with gusts nearing 25 knots midday Thursday.

/DTW THRESHOLD PROBABILITIES...

* High for ceilings aob 5000 ft tonight, medium early Thursday
  morning.

* Low confidence in exceeding crosswind threshold tomorrow.

&&

.PREV DISCUSSION...
Issued at 324 PM EDT Wed Apr 18 2018

DISCUSSION...
Compact mid level closed wave over eastern Iowa will track quickly
eastward across far southern lower Michigan overnight. In the
process the wave will weaken and open as it encounters and gets
absorbed into another mid level trough rotating down through the
eastern Great Lakes. Deep moisture is limited with this system and
will become more limited through the night as a surface low
associate with this wave over southern Indiana begins to initiate
convection to the south.  This will cut into moisture feed into
lower Michigan and also cut down on qpf amounts. Colder and drier
air advecting into the lower levels from the northeast will also
reduce amounts.  Looking for around a quarter inch qpf along the
Ohio border to a trace or few hundreths across northern Saginaw
Valley and Thumb. Precip this evening will start off as rain as
surface temperatures this afternoon climb into the upper 30s to
lower 40s. Thermo profile quickly goes below freezing above the
surface but stays within -10c up to about 700mb where moisture depth
for the most part ends. Dewpoints in the 20s will also rapidly lower
boundary temps from wet bulbing to the point where rain will mix
with snow around sunset then become all snow from north to south as
the night goes on. Any accumulations will be less then an inch with
best shot of accumulations along the Irish Hills across
livingston/Oakland counties and eastern tier of Thumb. Here temps
should reach freezing before precip end before daybreak. Other
locations that have best chance for accumulatlons will be Lenawee
and Monroe where duration and qpf will be longer and higher. To
reiterate, precipitation will be light to very light with this event
and any accumulations will be less then an inch and mostly on grassy
and elevated surfaces.

For Thursday, winds will increase rapidly in the morning from the
north as surface gradient becomes tight between incoming High
pressure and departing low to the east.  Weak surface trough and
flow off of Lake Huron may produce scattered lake effect snow/rain
showers during the morning from the Thumb into the northern metro
Detroit area. Skies will clear from west to east in the afternoon as
flow becomes northwest. Highs Thursday will still only reach into
the 40s but feel like the 30s from 15 to 25 mph gusty winds.

Large high pressure will move into the Great Lakes for the end of
the week bringing clear skies, lighter winds but still cold nights
Thursday and Friday with lows in the 20s and 30s.  Highs Friday will
be much better then of late in the upper 40s to low 50s but still
well below normal.

A prolonged stretch of calm, dry conditions will continue into the
weekend and early next week as an upper ridge and surface high
pressure slowly migrate east over the region. Other than some
passing high clouds across the southern half of the CWA on Saturday,
mainly sunny skies are expected through Monday. A relatively cool
air mass will gradually moderate during this timeframe allowing
highs to rise into the 50s over the weekend before reaching the 60s
early next week. The next chance for precipitation then looks to
return during the middle part of next week as a shortwave drops
through the region.

MARINE...

Low pressure tracking through the Ohio Valley this evening, with
strong northwest winds developing behind the low late tonight into
tomorrow. Wind gusts of 25 to 30 knots will be common over Lake
Huron, with brief gusts to low end gales possible over the southern
Lake Huron basin early Thursday evening.

Large high pressure will expand across the region on Friday and will
persist across the region through the weekend, resulting in light
and variable winds.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 PM EDT Friday for LHZ421-441>443.

     Small Craft Advisory until 4 PM EDT Thursday for LHZ422.

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

$$

AVIATION.....DG
DISCUSSION...DRC/JD
MARINE.......SF


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