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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
1159 PM EDT Sat Apr 19 2014



A dry east to southeast flow will maintain clear skies below 15k feet
tonight. Little variation in conditions through Sunday...modest
winds veered slightly toward a south-southeast direction.

//Dtw threshold threats...

* none


Previous discussion...issued 341 PM EDT Sat Apr 19 2014

Short term...this evening and tonight

Temperatures over most of the forecast area have warmed into the 50s under
full daytime sunshine. The easterly flow has however led to much
cooler readings along the lakes Erie/Huron shorelines. Lingering surface
ridging associated with departing surface high northeast of the state
and very dry low level air will cause temperatures to quickly drop off into
the 40s following sunset this evening. The cooling will be earlier
and more abrupt over the eastern half of the forecast area as the
ambient easterly flow advances the marine layer well inland.

After a brief period of ideal radiational cooling conditions late
this evening...the low level flow will strengthen as it backs to the
S-southeast overnight and will begin to usher in warmer low level air
toward daybreak sun. The upper wave now rotating across Manitoba and
SW Ontario will break down the ridge over lower Michigan tonight which
will open the door for a little cirrus to spill into Southeast Michigan. These
factors support leaning toward the higher end of MOS guidance for
mins /mainly low to middle 30s/.

Long term...

A very interesting and rare height configuration is in place with
short wavelength high index flow. The first thing that will be
ongoing at the start of the period is heights will be rising due to
some larger oscillation...likely at the hemispheric scale.

Southeastern Michigan will benefit from this large scale ridge
building for Sunday by deflecting the northern plains low pressure
system northward into Canada. Surface ridge and high pressure will
be able to maintain a strong foothold over lower Michigan thanks to
dry and stable air. This will cause an approaching frontal boundary
from this shortwave to hang up north of the County Warning Area by Sunday afternoon.
Various solutions are suggesting a low chance will be possible north
of the Tri Cities Sunday afternoon. Went dry...with forecast
soundings suggesting hydrometeors would fall out of a cloud deck
between 10-15 kft. Suspect much of this activity will be virga.
Conditions on Sunday will be extremely pleasant with temperatures
pushing toward the 70 degree mark.

Shortwave ridging and amplification ahead of the next inbound
shortwave will cause heights to rise regionally on Monday. Trend of
the model solutions alluded to by the previous forecast discussion
along with the latest guidance supports going with a slower timing
of the surface front that will eventually clear southeastern
Michigan Monday evening. Went decidedly drier with the grids for
Monday. Will still carry a chance during the afternoon for areas
south of I 69...but it is a close call on whether to pull them
completely. Regardless...expect the bulk of the day to be nice. In
fact...with drier conditions went considerably warmer too. Highs
Monday in southwesterly well mixed flow will likely push into the
lower 70s. Lapse rates Monday evening still support a thunder
mention...although instability appears it will be too weak/modest to
support a strong thunderstorm risk.

Low pressure is a little slower to push east than originally
forecast which leaves lingering showers over the eastern thumb area
early Wednesday morning. Remainder of Wednesday and first half of
Thursday look to be dry with mostly sunny conditions dominating.
Thursday afternoon...the low pressure setting up to the west over
the northern plains will start to bring in the clouds with weak
chances of showers for the afternoon. Friday looks to the be the
greater chance of getting wet with probability of precipitation a little above 50 percent
to start the day. Chances of showers are anticipated through
Saturday. On Sunday an elongated Canadian high builds over the


Conditions will remain reasonably quiet into tonight as light east
flow...averaging 10 knots or so...continues to filter off of strong
high pressure centered to the north/northeast. Two low pressure
systems will then pass near the area late this weekend into early
next week. The first will track across Ontario on Sunday...dropping
a cold front down into Northern Lake Huron. The front will remain
quasi-stationary over this area until the second low pressure system
draws it southward Monday and Monday night. Stronger north winds are
then possible across the area late Monday night into Tuesday behind
the front as colder air filters back into the area.


DTX watches/warnings/advisories...
Lake Huron...none.
Lake St Clair...none.
Michigan waters of Lake Erie...none.



short term...SC
long term....cb/de

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