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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
1055 PM EDT Wednesday may 27 2015

Update...

Residual instability trailing the surface frontal passage is just
about exhausted by the late evening update. The 00z DTX sounding
illustrated about 1300 j/kg of surface based cape translating into
0-1 km MLCAPE of less than 500 j/kg. This helped spark a few
showers in The Thumb earlier in the evening with the last bit of
support from the upper wave. Now both the wave and front will move
far enough east to bring an end to all rain potential for the rest
of the night.

Plan to leave the mention of patchy fog over south sections where
it rained earlier in the day. Good radiational cooling conditions
will support the possibility as high pressure settles over the
region. There will also be some low level dry air advection Post
front that will keep any fog on the shallow side through middle
Thursday morning.

&&

Aviation...issued 705 PM EDT Wednesday may 27 2015

The cold front will sweep the rest of the way through Southeast Michigan
leaving behind VFR conditions and a decreasing westerly wind over
the terminal corridor for the rest of the night. Surface high
pressure building into region overnight may promote light fog
development toward sunrise. Shallow MVFR restriction appears most
likely based on the character of less humid air behind the front but
also with wet ground contributions at most locations.

For dtw... there remains low potential for a pop-up shower or
thunderstorm through 01-02z as the cold front will be about over
the terminal area. Coverage will be monitored but is expected to
remain too low for a mention in the forecast.

//Dtw threshold probabilities...

* high potential for ceiling at or below 5000 feet during the evening.

* Low potential for additional thunderstorms from 00z to 02z.

&&

Previous discussion...issued 336 PM EDT Wednesday may 27 2015

Short term...through tonight

Surface trough continues to work across Southeast Michigan this
afternoon...with the cold front following behind...still stretched
from about Montana pleasant down towards Kalamazoo at 300 PM. Out ahead
of these features...unstable airmass remains with 18z kdtx radiosonde observation
confirming earlier model estimates with sb cape around 1400 j/kg.
The stronger storms have been aligned along a boundary seen on kdtx
radar imagery that stretched from southern Livingston County
northeastward into St Clair County. Storms...some strong to
severe...will continue the most unstable air will continue to be
located roughly south of a line from Lexington to Howell...with
instability starting to decrease as storms work the atmosphere over
and the cold front begins to work across the area...both happening
by early this evening. Further north across the Saginaw
Valley...cooler and drier air has already begun to arrive with the
front and only expecting isolated light showers over the next few
hours.

Upper trough will continue to work across the western and central
Great Lakes overnight...driving the cold front east. Expecting to
see some deeper layer subsidence set in behind the upper wave and as
surface ridging builds into the southern half of Michigan. This
should allow skies to scatter out and winds to go light. Good
radiational cooling conditions will then promote some patch fog
formation...especially where soils are more saturated from earlier
rainfall. Best potential for fog will therefore be along/south of a
line from Lexington to Howell. Min temperatures will cool a bit from last
night with lower humidity and cooler air arriving behind the
front...with forecast mins in the low 50s to upper 50s.

Long term...

Shortwave ridge and small area of surface high pressure will bring
dry weather on Thursday and Thursday night. While temperatures will
still approach 80 degrees in many locations...relative humidity will
be lower as dew points settle back into the low/middle 50s. Dry weather
will persist into part of Friday...but as shortwave ridge shifts to
the east...mean upper level ridge axis will re-establish over the
eastern Seaboard and leave area within broad southwest upper flow
which will bring a return of warm and humid weather late Friday into
Saturday. This airmass will be shortlived as a vigorous storm system
churns across Canada and drives a strong cold front into the area by
the middle of the upcoming weekend.

Shower and thunderstorm chances will increase notably by Friday
evening into Saturday as Richer Theta-E air funnels back into the
area and shortwave energy/troughing helps to focus the increasingly
unstable airmass ahead of the approaching cold front. Modest middle
level wind field will also aid in organized convective clusters with
a least some potential for a few severe storms by Friday evening.
Thunderstorms chances then continue into Saturday...culminating in a
decent round of convection Saturday afternoon as the cold front
moves through lower Michigan.

A much quieter weather pattern then sets up late this weekend into
the early and middle part of next week as a large area of Canadian high
pressure builds into and through the Great Lakes and northeast
Continental U.S..

In terms of temperatures...widespread 80s can be expected Thursday
and especially Friday...with only areas immediately along the cooler
Great Lakes waters holding in the 70s Thursday. With the cold frontal passage
and scattered to numerous showers and storms over the area...highs
will be capped in the 70s on Saturday...with much cooler air then
bring 60s from Sunday into Monday before a gradual moderation back
into the 70s occurs by middle next week. As the aforementioned surface
high shifts over the area...expect plenty of minimum temperatures in
the 40s early Sunday and Monday mornings.

Marine...

A Small Craft Advisory will continue into this evening over Saginaw
Bay through the tip of The Thumb as southwest flow in advance of a
weak cold front funnels up the Bay and create wind gusts to around
25 knots. Otherwise...most marine areas will see winds around 15
knots...with 20 knot flow. This front will also focus scattered
showers and thunderstorms over parts of the area this afternoon into
this evening...with the highest concentration of convection from
Lake St Clair south to Lake Erie. Dry conditions are expected by
tonight into Thursday as high pressure settles over the area. These
conditions will continue into Friday before the chance of showers
and thunderstorms return late in the day on into Friday night and
Saturday.

&&

DTX watches/warnings/advisories...

Michigan...none.

Lake Huron...none.

Lake St Clair...none.

Michigan waters of Lake Erie...none.

&&

$$

Update.......bt
aviation.....Bt
short term...hlo
long term....dg
marine.......dg



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