National Weather Service United States Department of Commerce

Forecast commentary -

Cold front associated with the wave digging through the Great Lakes is progressing south this
morning and will clear through Michigan this morning. The inverted surface trough sending moisture
northward that is aiding showers and some patchy fog early this morning will be shunted east by this
front. Throughout today the upper level low across the central Appalachians will pivot northward and
begin to get absorbed by the trough currently tracking through the Great Lakes. This consolidation
will result in the wave slowing down slightly over the central Great Lakes as it pivots over to the
eastern Great Lakes tonight and then well east by tomorrow. Anticipate that scattered showers will
come to an end for much of the area with clearing conditions by late morning with incoming
subsidence and dry air. Slowing of the wave will allow the trailing PV to graze eastern Michigan.
Combine that with the northerly flow and moisture boost off of Lake Huron and eastern portions of
the Thumb will some extended rain chances through afternoon. There will be gusty winds behind the
front as well with gusts up to 30 mph possible throughout the afternoon.

Cold pool with temperatures at 850mb around 0C will bring temperatures down a little further today
into the low to mid 50s for the inland areas. Temperatures in the 40s across portions of the Thumb
where northerly flow off of Lake Huron will keep things cooler. Clearing conditions overnight will
allow for good radiational cooling to occur with temperatures around freezing in the low to mid 30s.

Shortwave ridge will build over Michigan on Thursday and bring a brief break from precipitation.
Plenty of sunshine will allow temperatures to rebound back into the lower 60s and upper 50s. Quick
return to wet conditions with another upper trough digging through the Great Lakes on Friday. Cold
front will accompany this system and result in increased rain chances for Friday morning and
afternoon along the front. Vorticity max and upper jet will rotate through the base of the trough
keeping rain chances going Friday evening into Saturday. The quality of moisture available to this
system is not great. Expecting QPF amounts around a tenth of an inch, which will be more tied to the
vorticity max than along the cold front. Cold pool associated with this trough and persistent
northwest flow will result moderating high temperatures in low to mid 50s through the weekend.

Upper ridge and surface high building in on Sunday will dominate the weather into early next week.
Full insolation with warm southerly flow will allow temperatures to increase into the 60s by Monday
and 70s by Tuesday. Some locations across the far Lower Michigan may even reach 80 degrees on

. . posted at 341 AM EDT Wed Apr 25 2018

Should see blossoming radar coverage early this evening ( supported by latest hrrr/rap/12z NAM )
over the central Great Lakes, as sharp northern stream trough tracks into the western Great Lakes,
interacting with moisture in place ( 12z DTX indicated pw value of 0.92 inches/184 percent of normal
), as surface dew pts are also climbing to around 50 degrees at press time.

Consolidating of upper level PV at base of trough will lead to slowing down of the PV anomaly as it
tracks through Lower Michigan tomorrow morning. 12z UKMET/Euro remain slower and farther south
compared to GFS/nam, but still should have enough forward momentum to clear southeast Michigan by
early evening, with post wave subsidence and drying taking place to clear skies out for Wednesday
night. With an added boost from Lake Huron, as 850 mb temps slip below zero tomorrow, appears
showers are likely for eastern Thumb region during the day.

Favorable radiating conditions Wednesday night, with mins predominately in the 30-35 degree range.

Good shortwave ridging on Thursday ahead of next trough will support sunshine and temperatures back
around normal, lower 60s, with very light westerly wind advertised.

A chance for rain showers returns on Friday as an upper trough and cold front push through from west
to east. Depth of moisture is not looking particularly impressive with this system, so it's possible
just a few sprinkles will result Friday afternoon. High temps Friday look to reach about 60 degrees
before cold advection takes over. 500 mb vort max pushing in behind the front will wrap around the
trough and help it linger over the eastern Great Lakes through the first half of the weekend.
Northwest flow and cold pool aloft ( 850 mb temps falling to around -5 C ) will limit Saturday highs
to the mid 50s.

By Sunday, the upper trough will move out and strong ridging through the column will arrive. Dry
conditions and clear skies will prevail through the early week. Full late April insolation and
thermal ridge over the region will allow high temps to rise from the mid to upper 50s on Sunday to
the lower 70s by Tuesday.

. . posted at 313 PM EDT Tue Apr 24 2018